MX2007016154A - Anti-corrosion pigments coming from dust of an electic arc furnace and containing sacrificial calcium - Google Patents

Abstract

An anticorrosion ferrite-based pigment, derived from a hydrometallurgical purification process of EAF dust. EAF dust is generated in an electric arc furnace for carbon steel production by processing scrap metal, direct reduced iron and/or pre-reduced hematite, and using CaO-rich slag;from a condensation reaction of metals vapours of Fe, or Zn and of Mn, Mg, Si and/or Al, and suspended CaO particles and oxygen. The pigment contains a non-toxic amount of lead, and includes condensed metal oxides, comprising ferrites MOFe2θ3, M being Zn, Fe, Mn and Mg, and combinations thereof. The condensed oxides have ferrite structures preserved from the EAF dust, and form aggregates thereof. The pigment includes CaO entrapped by the ferrite structures and being partially available to react with humid air and/or water to protect the substrate against corrosion. The pigments are coated or uncoated. They are used for antifouling or paint formulations.

Description

ANTI-CORROSION PIGMENTS THAT COME FROM THE DUST OF AN ELECTRIC ARCH OVEN AND THAT CONTAIN SACRIFICE CALCIUM FIELD OF THE INVENTION The present invention relates in general to the field of treatment of milled steel powder. More particularly, the invention relates to pigments produced from a process of hydrometallurgical separation of dust produced by electric arc furnaces in steel mills. These pigments are ferrite and / or magnetite type pigments used as anti-corrosive agents in punctures, primers and other coatings.

BACKGROUND OF THE ART Electric arc furnace powder (EAF), also known by the name of K061, is classified as a hazardous material because it contains high concentrations of soluble heavy metals such as cadmium, zinc, chromium and lead, but in particular lead. More specifically, EAF dust usually contains more than the accepted values in leachates for lead and on occasion cadmium and chromium and therefore does not meet the limits specified by the TCLP (Characteristic Toxicity of the Main Procedure) and as One result, the solid is a dangerous substance. This powder also comprises spinel compounds, especially magnetite (Fe304) and various ferrites (MOFe2C03). Those spinel compounds as well as contaminants appear in the form of agglomerates and aggregates. At first sight, the dust is brown and an observer, even with the help of a magnifying glass, will not notice the presence of black spheres of magnetite, even if certain black spheres can reach a diameter of 150 μm. The brown ferrite contained in the powder is ultrafine, and as a pigment, it coats the larger magnetite particles by adsorption. As the name suggests, EAF dust is produced in electric arc furnaces. In this process, the furnace is loaded with material such as metal fragment or pre-reduced metals, the electrodes are diminished and activated, and a molten combination is rapidly formed within the vessel. The slags - which include CaO and MgO in some cases - float on top. Often, secondary amounts of fragments are loaded into the container once the initial fusion combination has been formed. The raw materials used as the iron source may be selected from a variety of reduced or mined sources of minerals or a combination thereof. It is often preferable to load the furnace with direct reduced iron (DRI) - also known as sponge iron, pre-reduced iron and highly metallized iron - to, for example, increase productivity, improve total thermal efficiency, reduce certain contaminants and lower emission charges. DRI can be produced by a number of processes such as solid state reduction processes employing hot reduction gases, or solid carbonaceous reducers similar to carbon. In the MIDREX process, as described for example, in U.S. Patent No. 4,046,557 (BEGGS), hot reducing gas is used that consists mainly of CO and H2, which is generated by the continuous catalytic removal of a hydrocarbon. The reducing gas flows countercurrent to particulate metal oxides (eg, iron oxide), within a container, to produce a metallized product (i.e., DRI). Alternatively, and where energy cost is required, the DRI can be produced using carbon as the reducing agent. Such a process is described, for example, in U.S. Patent No. 6,129,777 (FUGI et al.). The DRI is highly metallized, contains less metal impurity components such as trap elements, the sources of which may include elements Cu, Sn, Zn, Pb, Sb, Bi, As, Cr, Ni, Mo and V. DRI is often used as a material concentrated in electric arc furnaces, when the metal fragment containing high amounts of trap elements is fed into the furnace. Another pre-reduced source of iron are pre-reduced pellets of hematite. Hematite is the mineral form of iron (III) oxide Fe203, and can be pre-reduced by a number of techniques before it is loaded into the EAF container, usually in the form of pellets. In most EAF, in addition to the pre-reduced hematite or DRI, a slag-forming material is fed into the EAF vessel at certain points in the melting process. The slag formed from these materials can perform a number of functions, such as providing a continuous functionally molten oxide phase of the surface of the steel to be treated, capturing and retaining the non-metallic material present in the steel (e.g. aluminum), being non-oxidizing or reduced with respect to steel, control the sulfur content of the steel, promoting the formation of a stable arc, protecting the steel from contact with the atmosphere and providing thermal insulation. These slag-forming materials can include CaO calcium oxide in one or a variety of forms-such as burnt lime, dolomite and limestone, among others-which are thus capable of forming a CaO-rich slag. The lime in particular increases the basicity as part of the slag-forming material. Depending on the source of iron (slag, DRI, pre-reduced hematite, iron ore, etc.), the material that forms slag and the operating conditions of the EAF, a variety of different steel products, can be produced. It also follows that, that a wide range of powder products can be produced from different EAF steel constructions. In this way, the different powders have different compositions, properties, toxicities and potential uses. In this sense, of interest are the EAF powders produced from the production of carbon steel using metal fragments, DRI and / or pre-reduced hematite as raw materials, and using a CaO rich slag. Of particular interest is the EAF powder produced from DRI or pre-reduced hematite, with or without metal fragments as well, whose properties and potential utility have not been adequately sought or optimized, especially in relation to producing anticorrosive ferrite pigments. In the EAF process, the temperatures inside the EAF vessel and between the arcs vary in space and time and also depend on which raw materials are melted down. The molten combination contains molten iron, zinc, as well as trap elements, etc. The EAF vessel is the site of a complex multi-component, multi-phase system. It is desirable to achieve and maintain a high temperature, but it is important to keep in mind that each compound in the system has a different melting temperature (FT) and evaporation temperature (ET), some of which are, for example, at atmospheric pressure : Pb FT = 327C, ET = 1740C; Zn FT = 420C, ET = 908C; Mg FT = 650C, ET = 1107C; Mn FT = 1245C, ET = 2097C; Fe FT = 1535C, ET = 3000-3500C; Fe203 FT = 540C; CaO FT = 2570C. In such a multiple phase and multiple component reaction, there is inevitably a proportion of certain metals and compounds that are vaporized and suspended above the molten combination and slag in the upper portion of the container. These metallic vapors either condense and fall back into the molten slag layer combination, or flow out of the main vessel through an exhaust pipe. These metal vapors exiting through the exhaust pipe condense or sublimate with the hollow space or against the internal walls of the exhaust pipe to form the EAF dust, which is collected and stored for disposal or attempted recycling. There is a variety of treatment processes to process this EAF powder. Most of the EAF powder treatment processes in the prior art have as their main objective to recover or remove the heavy metals in an "aggressive" manner, attacking the crystallographic structure of the ferrite spinels. The known processes are also not specifically directed to the EAF powder produced from EAF, to the DRI process, pre-reduced hematite and / or metal fragments and to the use of CaO-rich slags. Also known in the prior art, it is European Patent No. 0 853 648 (ROUX et al.), Equivalent to US Patent No. 6,022,406, which describes a hydrometallurgical process of EAF powder treatment with the primary purpose of producing pigments This process comprises a step of magnetic separation of the powder into two fractions, a fraction containing less magnetic elements, and the other fraction containing non-magnetic elements, as well as steps of treating those two fractions to obtain zinc ferrite pigments. ROUX et al., Also describes the remarkable and essential step of calcining the material at a temperature of 450 ° C to 650 ° C. The process described also has the effect of attacking the crystallographic structure of spinels other than zinc ferrite spinel, and in this sense, it is also an aggressive process. This process thus significantly modifies the structure, as well as the physical and chemical interactions found in the EAF dust. Also known in the art are ferrite pigments, which include particular calcium phases, which provide anti-corrosive properties to the pigment, most of which use a calcination method. In general, calcination is the process of heating a substance at a high temperature, but below its melting temperature, to bring about thermal decomposition or a transition phase in its physical or chemical composition. U.S. Patent No. 3,904,421 (SHIMIZU et al.) Discloses anti-corrosion pigments for paints containing at least 5% oxide of calcium oxide phase-iron oxide 2CaO.Fe203. This phase, which could appear to have a structure similar to ferrite, is produced by calcining iron oxide and a calcium compound at high temperatures. This phase allows hydration reactions and the release of calcium hydroxide to maintain a basic pH and protect against corrosion of a metallic substrate. This is a mechanism that can help in the prevention of corrosion, but is limited in that the calcination reactions are required to produce the pigment. US Patent No. 4,225,352 (MARINO et al.) Also describes this 2CaO.Fe203 phase derived from calcination for having anticorrosion properties, but is used at a high concentration of 25% or more in aqueous paint formulations. In this case, the phase is used due to its low solubility in aqueous solutions to prevent the gelling of the paint during storage. U.S. Patent No. 4,211,656 (HUND et al.), Discloses a pigment so-called "active", produced by calcining a metal oxide such as CaO and an iron oxide F03 at a temperature range from 400 ° C to 600 ° C. It was found that this temperature range reduces the corrosion intensity of a coated substrate with a paint containing the resulting pigments. In this way, the products of the calcinations are not defined, but for the calcination temperature and reactants by which they are produced, and for their resistance to corrosion, in accordance with the Thompson corrosion test. It can be appreciated that certain pigments containing calcium iron ferrites or zinc ferrites are known in the art, and are almost exclusively produced by a calcination method. Much work has been faithful to polish the calcination conditions - such as temperature range, reagent compositions - to produce ferrite pigments for certain purposes, and a plethora of patents are directed to such calcination methods. These pigments and processes are limited by calcination, which is a high-temperature, aggressive process that results in physical and / or chemical modifications. However, the methods for recycling EAF powder to extract potential advantageous pigment products have not been fully developed, and there is currently a huge potential to improve and discover new pigments derived from EAF powder. There is currently a need for pigments derived from EAF powder. Particularly, there is a need for a selected EAF powder treatment process that allows a non-aggressive and efficient recovery of the different ferrites and magnetites present in the powder, as well as, allowing decontamination of the powder, to produce economical and safe pigments. that the anticorrosive properties present, distinguishing the structures and some advantages over the prior art.

SUMMARY OF THE INVENTION The present invention responds to the needs mentioned above, by providing pigments derived from EAF powder. Accordingly, the present invention provides an anti-corrosion ferrite based pigment for use in a paint for coating a substrate, the pigment to be derived from a hydrometallurgical purification process of the EAF powder. The EAF powder is generated in an electric arc furnace or the like, for processing carbon steel from source materials including metal fragments, and using a CaO-based slag. The EAF powder is produced from a condensation reaction of metal vapors of Fe, Zn and metals chosen from the group consisting of Mn, Mg, Si and Al, and suspended CaO-based particles and oxygen. The pigment contains a non-toxic amount of lead, and comprises fused metal oxides. The condensed metal oxides include a plurality of different ferrites of the general formula: MOFe203 M includes Zn, Fe, Mn, Mg and complexes thereof, for the different ferrites. The ferrites have ferrite or ferrite-like structures substantially preserved from the EAF powder and aggregates of said ferrite or ferrite-like structures are formed. The pigment also includes CaO trapped by the ferrite or ferrite-like structures and being at least partially available to react with moist air and / or water to protect the substrate from corrosion. In a preferred embodiment of the present invention, a first portion of the CaO is physically trapped with the ferrite or ferrite-like structure and a second portion of the CaO is physically trapped with the aggregates. The second portion of CaO is available as a sacrificial calcium source to react with moist air and / or water to produce Ca (OH) 2 and locally increase the pH, preferably to 12 or higher. Preferably, sacrificial calcium further activates the formation of at least one hydroxide protecting phase. The protective hydroxide phase preferably includes Zn (OH) 2, amorphous calcium hydroxide, protlandite, and / or calcium-zinc hydroxide phases such as one having a crystallographic phase of CaZn2 (OH) 6 hydrate. In another preferred embodiment of the present invention, the pigment contains from about 4 to 12% by weight of calcium. In still another embodiment of the present invention, the pigment further comprises a coating of the aggregates, said coating being based on calcium-zinc and deposited in the pigment to increase the amount of sacrificing calcium therein. The present invention further provides a use of the above pigment as an additive in paint, primer coat or coating formulations to produce an anticorrosive formulation.

The present invention further provides a use of the above pigment as an additive in an antifouling formulation for preferably antifouling against selected organisms.

BRIEF DESCRIPTION OF THE FIGURES The characteristics of the present invention will be better understood by reading in detail the detailed description, while referring to the attached drawings in which: Figure 1 is a flow diagram of the process according to a first variant Suitable for producing first grade ferrite pigments. Figure 2 is a flow chart of the process according to a second suitable variant for producing ferrite pigments of the second degree. Figure 3 is a flow diagram of the process according to a third suitable variant to produce ferrite pigments of the third degree. Figure 4 is a flow diagram of the process according to a fourth suitable variant to produce ferrite pigments of the fourth degree. Figure 5 is a flow diagram of the process showing a fifth and a sixth variants suitable for producing magnetite pigments of the first and second grades. Figure 6 is a flow chart of the process according to a seventh variant suitable for producing ferrite / magnetite pigments. Figure 7 is a graph showing the extraction values for calcium, chromium, zinc and lead against time, and the use of a hydraulic impeller. Figure 8 is a series of graphs representing the variation of zeta potential, pH and conductivity against the concentration of sodium metaphosphate for a partially washed powder suspension. Figure 9 is a graph showing the extraction values for calcium, chromium, zinc and lead against time, and the use of a high cut impeller. Figures 10 to 13 are graphs showing the granulometric distribution of the first fraction (ferrite fraction) after one or two passes in the grinder. Figure 14 is a photo of ferrite pigments taken with an AFM microscope after wet grinding by abrasion, showing the state of agglomeration and the fine size of the constituent ferrite fragments. Figures 15A and 15B respectively, are an X-ray powder diffraction graph of the spinels, in the EAF chimney dust and electron microscope photographs of the chimney dust sweep. Figure 16 is a Dispersive System Analysis of a calcium ferrite phase of the pigment, including a fluorescence plot and a scanning electron microscope (SEM) photograph thereof. Figure 17 is a Dispersive System Analysis of a zincite phase of the pigment, including a fluorescence graph and a scanning electron microscope photograph thereof (SEM). Figure 18 is a representation of a pigment layer that covers a metal substrate, against corrosion through a mechanism of chemical activity. Figure 19 is an X-ray powder diffraction graph comparing active ferrite, passive ferrite, frankinite and zinc hydroxide hydrate and calcium. Figures 20A, 20B and 20C are, respectively, representations of the spinel unit cell, a three-dimensional trace of multiple component spinel bonuses, and a representation of the crystalline structure of portlandite (brucite isotope). Figure 21 is a graph showing DTA and TGA analysis of the active ferrite pigment. Figure 22 is a graph showing the DTA traces of different hydroxides.

Figure 23 is an X-ray powder diffraction graph comparing franklinite, portlandite and the active ferrite pigment. Figures 24A to 24C are SEM photographs of the zinc-based precipitate. Figure 26 is a SEM photograph of the pigment coated at a pH of 9. Figure 27 is a SEM photograph of the pigment coated at a pH of 9, showing a prismatic tubular crystal. Figure 28 is a SEM photograph of the pigment coated at a pH of 9, showing a pigment sphere. Figure 29 is a SEM photograph of the pigment coated at a pH of 9, showing a small pigment sphere. Figure 30 is a SEM photograph of the pigment coated at a pH of 9, showing a structure similar to a columnar bar. Figure 31 is an X-ray powder diffraction graph of the pigment coated at a pH of 9. Figure 32 is a SEM photograph of the coated pigment at a pH of 12.6, showing ground glassy rhombohedral crystals. Figure 33 is a SEM photograph approach of the coated pigment of Figure 32. Figure 34 is a SEM photograph of the pigment coated at a pH of 12.6, showing a small pigment sphere. Figure 35 is a SEM photograph of the pigment coated at a pH of 12.6, showing two small pigment spheres. Figure 36 is a SEM photograph of the micronized pigment of Figure 35. Figure 37 is a SEM photograph of an uncoated pigment of the third degree. Figure 38A is an X-ray powder diffraction graph of the pigment coated at a pH of 12.6. Figure 38B is a graph showing DTA and TGA analysis of the pigment of Figure 38A. Figures 39A to 39E are photographs of plates covered with TiO in which discovered organisms are present. Figure 40 is a photograph of a plate covered with an anti-crypto formulation containing the active pigment, in which only one type of algae is present.

DESCRIPTION OF PREFERRED PIGMENTS AND PROCESSES OF THE INVENTION The present invention relates to an anticorrosive ferite pigment from a metallurgical powder purification process of EAF. The pigment is produced from a selected source using a particular type of process. The pigment is therefore given with unique structures and advantageous properties to combat corrosion. Subsequently, the production processes, structures, properties, grades and uses of these new pigments will be described. 1) Production of the EAF powder The pigments according to the present invention are derived from a selected EAF dust hydrometallurgical purification process. Table 1 shows typical EAF powder chemical compositions that come from three different steel mills. These compositions show, for example, high concentrations of certain heavy metals.

TABLE 1: EAF POWDER CHEMICAL ANALYSIS THAT COMES FROM TWO DIFFERENT STEERING FACTORIES IN THE PROVINCE OF QUEBEC, CANADA It should be noted that depending on the source of the powder, different variants of the hydrometallurgical process are preferable. On the one hand, EAF dust coming from an electric arc furnace using DRI or pre-reduced hematite as an important raw material source of iron, will contain low amounts of heavy metals, in particular, lead, and will require even less harsh treatment. to drive and purify the pigments based on ferrite.

On the other hand, the dust that comes from EAF of an electric arc furnace that uses a high amount of metal fragments, possibly including galvanized metals, will contain relatively high amounts of heavy metals and zinc compounds, and will be subjected to other favored processes to isolate the desired pigments. Mostly considering the variants of different processes and the pigments derived from these, they will be exposed later below. The selected iron source is fed into the electric arc furnace and is produced during the steel production process that occurs in this EAF powder. This EAF powder is produced from a vapor condensation reaction of Fe metal and metals chosen from the group consisting of Zn, Mn, Mg, Si and Al, and suspended CaO particles and oxygen. The EAF powder also contains a plurality of other compounds, some of which must be removed due to toxicity and others, which act as an inert filler material. The system in the EAF vessel is complex. In particular, some metals are gaseous, while other compounds are in a solid state still suspended with metallic vapors. An important one of these suspended solid compounds is CaO calcium oxide, which has a preferably high melting temperature of about 2570 ° C. The CaO can be provided in the form of lime. Part of the lime is in the form of suspended lime dust, which is mixed in the interspace above the molten combination with the metallic vapors. The metal vapors mainly include Fe, Zn, Mg, Mn, Al and Si, as well as some undesirable elements, such as Pb and other heavy metals. The metal vapors of the CaO powder flow from the container through an exhaust pipe, while they are cooled and condensed. This condensation produces EAF powder, which itself, includes a variety of compounds that have a variety of structural characteristics. It should be noted that the specific properties that include anti-corrosion properties of ferrite pigments produced from EAF powder by hydrometallurgical processes, are dependent on the composition of the pure EAF powder itself and the steps of processes to separate, leach and isolate the desired pigments. It should be noted that a person skilled in the art will be able to use a similar powder or powder source resulting from a similar metal vapor condensation reaction to derive a ferrite pigment of condensed metal oxides with anti-corrosion properties by a similar hydrometallurgical process. depend on the content and availability of calcium.

Depending on the origin of the EAF chimney dust, various concentrations of heavy metals, calcium oxides and spinels are present in the pure powder. This depends on the hematite, metal fragment and other quantities of reagents and origins, as well as the operating conditions of steel mills and production demands. 1. 1) From DRI or pre-reduced hematite iron sources A selected EAF powder is generated in an electric arc furnace or similar, to process direct reduced iron (DRI) or pre-reduced hematite. Preferably, the DRI is produced in a MIDREX style process, which is described in the "BACKGROUND" section, or in an analogous process. The pre-reduced hematite or other similar starting material can also be used. EAF dust that comes from steel mills that use primarily metal fragments and pre-reduced hematite, tend to contain less lead and other toxic compounds, and therefore, require some less aggressive treatment steps to remove them. Table 2 shows the partial composition of EAF powder produced by a steelmaker using mainly metal fragments and pre-reduced hematite.

TABLE 2: CHEMENSE POWDER CHEMICAL ANALYSIS, COMPOSITION WITH METALLIC FRAGMENTS AND PRE-REDUCED HEMATITE 1. 2) From iron sources of metal fragments As mentioned above, ferrite-based pigments can also be made from EAF powder that comes from furnaces that produce carbon steel, which use metal fragments as their primary source of iron. The metal fragments can be galvanized or not. Since these EAF powders have a relatively high concentration of heavy metals, the additional processing steps are referenced to sufficiently leach the heavy metals and provide the pigment in accordance with the common toxicity limits. As will be described in detail below, this EAF powder is subjected to acidic leaching, preferably, with nitric acid. After the lead is selectively precipitated from the leachate, the latter is re-deposited as a coating on the ferrite-based pigment to produce a coated pigment having excellent and surprising anti-corrosion properties. 2) Production of the Pigments Once the selected EAF powder is procured, it is metallurgically processed to provide the pigments of the present invention. In general terms, the hydrometallurgical process is for the treatment of agglomerates containing EAF dust of small ferrite particles and larger magnetite particles, the coatings of ferrite particles by adsorption of the larger magnetite particles, the powder also It contains calcium oxide, zinc oxide and a toxic amount of leachable lead, together with minor elements are selected from the group consisting of Mg, Cr, Cu, Cd, V and chlorides. Reviewing widely, the process includes a first treatment and a second treatment. The first treatment includes washing, decanting, separating and adding an anionic surfactant, magnetic separation and selection, thereby converting the pure EAF powder into separate ferrite and magnetite fractions having a certain size distribution. The second treatment involves several stages of leaching to further purify the fractions to provide the desired pigments. Additional grinding steps may also be preferred to obtain the desired properties. With reference to Figure 1, which shows a first variant of the process, the first treatment, which is performed in a tank (10), comprises the steps of: a) washing the EAF powder (12) in water to dissolve the soluble salts, metals and simple oxides contained in the powder, the washing step being carried out with an alkaline pH which is preferably greater than 12; b) decanting the solution from step a) to obtain a supernatant liquid (14) containing the dissolved salts, metals and simple oxides and a suspension (16) containing ferrites and magnetites, a non-toxic amount of leachable lead and an amount Reduced calcium; c) separating the suspension (16) and the supernatant liquid; and d) adding to the suspension obtained in step c) an anionic surfactant (18), preferably a phosphate and more preferably sodium metaphosphate, to disperse the ferrite particles adsorbed on the magnetite particles. It is worth mentioning that another anionic surfactant known in the art and having the same effect of dispersing the adsorbed ferrite particles is within the scope of the present invention. Preferably, the sequence of steps a) to c) is carried out more than once before adding the anionic surfactant. Note that stages a) to c) are not shown in the figures. Steps a) to d) are carried out in the tank (10) shown in each of figures 1 to 6. After the first treatment, the suspension (16) of step d) is sent to further stages of the process to produce pigments selected from the group consisting of ferrite pigments, magnetite pigments and ferrite / magnetite pigments. The treatment of the suspension (16) will vary depending on the degree of ferrite or magnetite to be produced. The production of each of these grades according to the process of the invention will be described in more detail later. It should also be understood that although the preferred pigments of the present invention are those that are based on ferrite, the hydrometallurgical process also provides other pigments, in particular those which are based on magnetite. The magnetite-based pigments will also be described hereinafter, as they may have advantageous and surprising properties and be of commercial interest. It was found that the use of an anionic surfactant increases the efficiency and quality of the additional separation steps such as sieving and separation of the ferrite / magnetite by a magnetic © separator. Steps a) to c) also allow the decontamination of the powder by leaching salts, metals and simple oxides such as lead oxide. This selective solubilization is due to the alkaline pH solution, which is preferably greater than 12, resulting from the first wash, and the second optional washing, with water. This alkalinity promotes the solubilization of PbO and, with the addition of surfactant, allows the product to pass the test established by the TCLP, which regulates hazardous materials standards. Advantageously, the process of the invention also allows the separation of ferrites from the magnetites without degrading the crystallographic structure of the spinels, to produce magnetite and / or ferrite pigments of different grades, whose different compositions have commercial values. The process also allows the decontamination of EAF dust by hydrometallurgical means while maintaining the most stable families of intact spinels. The solution obtained in step a) described above has a positive zeta potential, and the anionic surfactant is preferably added in a concentration sufficient to reduce the zeta potential up to or near the isoelectric point, and more preferably up to the isoelectric point. The anionic surfactant is preferably a phosphate or an equivalent thereof. More preferably, sodium metaphosphate is used as a surfactant. More will be said of said considerations of the role of the anionic surfactant hereinafter. Step e) of treating the suspension preferably comprises the step of magnetically separating the suspension into a first fraction composed essentially of brown ferrites and a second fraction composed essentially of black magnetite, the first fraction being less magnetic than the second fraction. The magnetic separation is preferably carried out with a magnetic field in the range of 400 to 700 gauss, more preferably around 550 gauss. The processing steps include several stages of selection, leaching, washing and grinding, which depend on the pigment to be produced. In general, the leaching stages fall under the second treatment, which will be discussed here later. Four grades of ferrite pigments, two degrees of magnetite pigments and a degree of ferrite / magnetite pigments are produced in the pilot run. The ferrite pigments are produced in accordance with the first, second, third and fourth variants of the processes shown in Figures 1 to 4; the magnetite pigments are produced in accordance with the fifth and sixth variants shown in Figure 5; and the ferrite / magnetite pigments are produced in accordance with the seventh variant of the process shown in Figure 6. More of these grades will be discussed later. 2. 1) Treatment of the first fraction to produce pigments based on ferrite The treatment step of the first fraction preferably comprises the steps of: - removing from the first fraction, particles having a grain size of 20 μm or more, to obtain a first refined fraction; - leaching the first fraction refined with a solvent, to obtain a leached suspension; - separating the leached suspension into a solid fraction containing ferrite pigments and a liquid fraction containing constituents of the first fraction soluble in the solvent; and - drying the solid fraction to obtain dried ferrite pigments. According to a first variant, the solvent is water and the ferrite pigments obtained are ferrite pigments of a first degree. According to a second variant, the solvent is sulfuric acid, the leaching is carried out at a pH of 0.5 to 3 and the ferrite pigments obtained are ferrite pigments of a second degree. According to a third variant, the solvent is nitric acid, the leaching is carried out at a pH of up to 3, and the ferrite pigments obtained are ferrite pigments of a third degree. According to a fourth variant, the process further comprises the step of wet grinding the solid fraction to obtain a fourth grade of pigments having a finer average grain size and a lower concentration of lead compared to the third grade ferrite . Part of the novelty of the process for all grades of pigment lies in an initial treatment of the EAF powder with water with the addition of an anionic surfactant. This surfactant increases the efficiency and quality of the separation of the ferrite / magnetite by the magnetic separator. This initial treatment also allows the decontamination of the dust by leaching salts, metals and simple oxides such as lead oxide. This selective solubilization is due to the alkaline solution of pH > 12 resulting from the first wash (first mixed) and rinse (second mixed) with water (Table 3). This alkalinity promotes the solubilization of PbO and allows the product to pass the test established by the TCLP, which regulates hazardous materials standards (Table 4).

TABLE 3 WATER ANALYSIS First Treatment TABLE 4 RESULTS OF TCLP All the pigment grades have been obtained by a substantially similar treatment, the processes differ in the specific leaching stage that gives the pigments their desired chemical and surface characteristics. In many cases, the specific coating also gives the pigments even greater specific properties for more particular markets.

Ferrite pigments First grade (Fl) The ferrite pigment of the first grade was produced with the help of a solution containing an optimum concentration of surfactant, the concentration being a function of the isoelectric point of the powder to be treated, and with a leaching referred to above as the second treatment only with water. The first grade ferrite pigment contains a high amount of lead that could not be easily leached under normal pH conditions. After ten months and many agitations in water, this pigment showed no leaching of heavy metals (Table 5) and is comparable to the second and third grade pigments compared later. Heavy metals, with the exception of 8% zinc in the resistant form of zincite, were present and stabilized in the structure of certain ferrites and spinels.

TABLE 5: ANALYSIS OF AQUEOUS LIXIVIATE OF 10 MONTHS The different stages of acid leaching of the process leave solid ferrites of different compositions and, as experience has shown, ferrites rich in Ca were less stable to leaching than zinc ferrites or other ferrites that represent complex oxides of Ca, Fe , Zn, Mn, Mg, Ni, Cr, etc. The resistant ferrites left after leaching, which constitute the pigment, gave the pigment a high thermal stability and resistance to leaching, which are a function of the ionic stoichiometry and the type and quality of the crystalline composite structures. On the other hand, the ferrite pigments of the first grade demonstrated high resistance to corrosion as demonstrated to the dew (fog) with salt tests, allowing the coated metal plates to resist corrosion for more than 1500 hours in a fog of salt, which is equal to or greater than that of all other pigments, including those of commercial grade used in the tests. The first degree ferrite pigment owes its resistance to corrosion (salt fog) to CaO, which is sacrificed as Ca (OH) 2 and / or to the resulting alkaline viscosity (soapy appearance) associated with Ca (OH) and the high alkalinity of the pigment.Second grade ferrite pigment (F2) The ferrite pigment of the second grade was produced in the same way as the first grade ferrite, except that the second treatment was carried out with sulfuric acid. The preparation stages of the second grade pigments were identical to those used for the ferrite pigments of the first degree, in addition to the surfactant that occurs after the first wash but before the magnetic separation. For the second-grade pigments, leaching using sulfuric acid at a pH between 0.5 and 3, allowed the preservation of a certain amount of hydrated calcium sulfate, the solubilization of all the zinc in the form of zincite (ZnO) and the stabilization of the lead as a solid sulfate. Using this treatment, effluents rich in zinc sulphate, are an adequate form of compound to be recycled directly again in an electrolysis process, to recover the value of zinc. The calcium sulfates generated by leaching are not dangerous in anticorrosive paints. Calcium sulfate is often used as a filler with pigments used in paints and is often desirable as a pigment additive. This pigment did not require wet grinding by abrasion, nor did it require a second magnetic separation and a second sieving after acid leaching. The pigment was filtered to obtain a permissible soluble salt concentration of 0.3 g / 1 mg, and then dried and micronized. Consequently, the ferrite pigments of the second degree allowed the preservation of a calcium fraction, the transformation of lead oxide and lead sulphate (which is very stable) and the solubilization of zinc oxide in zinc sulfate. These characteristics of the second grade pigment make this pigment an excellent colorant as well as a corrosion resistant pigment.

Third grade ferrite pigment (F3) The ferrite pigment of the third degree was produced in the same way as the first grade ferrite, except that the second treatment was made with nitric acid. Leaching with nitric acid allowed the preferential removal of lead and other heavy metals due to the oxidizing property of the acid. The leaching was carried out at a pH between 0 and 3, which allowed the elimination of certain families of ferrite, as a function of pH, to minimize the total lead in the pigment and to give a pigment with a particular signature with respect to its composition , structure and surface characteristics. As an example, between a pH of 3 and 1.5, the ferrites exhibited a zeta surface potential which is positive, but this potential turned negative at a pH < 1.5. This characteristic load influenced the acceptable requirements and their associated mechanisms. The different ferrites obtained from these leaching showed high heat resistance capacities, which are very valuable pigment properties. This leaching also minimizes the difference between the colors of the pigment and allowed a delta of variation of approximately 0.5 for pigments of different dust origins (Table 6). The properties were equal or superior to that of the pigments currently recognized in the industrial market. This degree of pigment showed greater resistance to corrosion depending on the coating used and also presented a thermal stability since it preserves its color dye at temperatures exceeding 300 to 400 ° C.

TABLE 6: VARIATION OF PIGMENTS OF FERRITAS HS4 (THIRD DEGREE) OF THE SIDERÚRGICA FACTORY 1 This thermal resistance is a requirement for plastics, spray paints and ceramics.

Fourth grade ferrite pigment (F4) The fourth degree ferrite pigment was produced in the same way as the third grade ferrite pigment, with the addition of a wet grinding step. This pigment can be used in concrete as a cement additive that increases the fluidity and compressive strength of concrete. This pigment had a granulometry finer than that of the third degree, the ferrite pigment and the ferrite / magnetite pigment. The ferrite pigments of the first, second, third and fourth grades have applications in anticorrosive paints. The third degree can be used in plastic and powder paints due to its thermal resistance. This pigment can also be used as a cement additive, slimming agent and additive in high performance concrete. The main difference between the second and third grade ferrite pigments lies in their surface properties. 2. 2) Treatment of the second fraction to produce pigments based on magnetite The treatment step of the second fraction preferably comprises the step of sieving at 6 μm to obtain a first finer fraction with particles having a grain size of 6 μm or less, and a coarser fraction with particles having a grain size greater than 6 μm. In that case, the process preferably further comprises the steps of: grinding the coarsest fraction, and removing the particles having a grain size greater than 40 μm from the coarser ground fraction and returning those particles for further grinding, and a second finer fraction having particles with a grain size of less than 6 μm, resulting in the thickest fraction containing particles having a grain size of between 40 and 6 μm. According to a fifth variant of the process, the thickest fraction is preferably wet crushed by abrasion to achieve an average grain size of about 0.3 μm. The crushed product is subsequently filtered and dried to obtain a first degree magnetite pigment. According to a sixth variant, the first and second finer fractions, which contain particles of less than 6 μm, are purified by suspending the residual contaminants contained therein with an anionic surfactant, to obtain a purified magnetic fraction. The purified fraction is subsequently decanted, wet crushed by abrasion, filtered and dried, to obtain a magnetite pigment of a second degree.

Magnetite pigments First grade (Ml) The first grade magnetite pigment was produced by grinding the magnetite fraction obtained from the magnetic separation with a ball mill. The crushed fraction was passed through a sieve of between 38 and 6 μm, wet crushed by abrasion to obtain as a result an average grain size of approximately 0.3 μm. The pigment was then filtered, coated with an organic, dried and micronized coating.

Second degree magnetite pigments (M2) The second degree magnetite pigment was obtained by sieving the magnetic fraction, which had already been subjected to grinding in a ball mill, 6 μm. This fraction was purified by placing the silica, carbonate and residual ferrite contaminants in suspension, with the help of an anionic dispersing surfactant. More particularly, this pigment grade of magnetite was obtained by sieving at 6 μm the magnetic fraction of the magnetic separation and the fractions of less than 6 μm originating from the screening of the coarse magnetite after its trituration in a ball mill. This fraction, which contained a concentration of magnetite, was purified by placing the silica carbonate and residual ferrite contaminants in suspension with the aid of a surfactant. Two successive treatments of surfactant addition were required, followed by decanting the magnetite and separating the suspension, to obtain a properly black product, which was subjected to wet grinding by abrasion to achieve a desired granulometry. The solid was finally filtered with an organic additive, dried and micronized. This purification step is similar to that of the first powder treatment. The ferrites and contaminants were put in suspension, and the magnetite was decanted. A rough non-pigmented magnetite was also produced. This was obtained after grinding by abrasion of the thicker magnetite fraction of 30. The abrasion cleans the surface of the magnetite spheres by abrading the white coating of calcium and silicate initially present. This stage improves the black color of the spheres and eliminates magnetites that are less resistant to abrasion. The product of 70 and 30 μm can be used as an organic pigment in photocopy processing. The commercial niche of this solid depends on its granulometry, morphology, resistance to friction and magnetic properties. 2. 3) Production of magnetite / ferrite pigments According to a seventh variant of the invention, which does not involve magnetic separation, the process preferably comprises the steps of: - removing from the suspension obtained in step d) particles having a grain size of 60 μm or less, to obtain a refined suspension; leaching the refined suspension in nitric acid at a pH of about 3, to obtain a suspension leached with or without a controlled amount of ZnO, which retards the setting of the concrete; - separating the leached suspension into a solid fraction containing a mixture of ferrite and magnetite pigments and a liquid fraction containing nitric acid-soluble constituents; and - drying the solid fraction to obtain dry pigments containing the mixture of ferrite and magnetite. The pigments obtained with this variant are suitable for use in concrete formulations to retard the setting of concrete or to color the same. All seven variants described above preferably comprise the steps of: coating the pigments with an inorganic and / or organic coating; and - micronizing the coated pigments.

Ferrite / magnetite (FM) pigments The ferrite / magnetite pigment suitable as a colorant for concrete was produced with nitric acid at a pH of 3 but without magnetic separation. The suspension of the first treatment was subjected to the following steps: sieving at 6 μm, leaching in nitric acid, filtration to reduce its soluble salt content, and drying in an instant dryer, producing a coarse pigment composed of agglomerates having a size of medium grain of 5 μm. Sifting allowed the removal of coarser contaminants including silica, carbon and other fragments. After this, the suspension containing a magnetic charge is subjected to leaching with nitric acid at a pH of 3 to remove the zincite, since the zincite delays the setting of the cement. The product was filtered to reduce its content of soluble gas, after which the drying in an instant dryer or by evaporation gave the pigment a granulometry with an average of approximately 5 μm. For this degree of pigments, the initial pilot process was greatly simplified, which translates into reduced production costs. Because its granulometry is very large, the pigment can not be used as an additive in cement, to produce high performance concrete. For all grades of pigments, either ferrite pigments, magnetite pigments or ferrite / magnetite pigments, at the end of the treatment, an organic additive was provided for the finished product to standardize the surface charges, to facilitate the incorporation of the dry pigment in paint resins, and to give the desired fluidity for handling. However, it is noteworthy that the coating step is optional for the process. 3) Detailed description of the preferred variants of the hydrometallurgical process As noted above, a variant of pigments can be derived from the hydrometallurgical process described herein. Although ferrite-based pigments for use in anticorrosive paints are a preferred product of certain process variants, other variants can produce other pigments. Preferred variants of the processes described hereinabove are thus directed to magnetite-based or ferrite-based pigments, some of which are described here above. More specifically, the process for treating EAF powder according to the invention is a hydrometallurgical process for the treatment of electric arc furnace dust (EAF) from steel mills which contains agglomerates of small ferrite particles and large particles of magnetite, coating the ferrite particles by adsorption the larger magnetite particles, also containing calcium powder and a toxic amount of leachable lead together with minor elements selected from the group consisting of Mg, Cr, Cu, Cd, V and chlorides. Ferrites represent a family of complexes of compounds represented chemically by the major elements Ca, Fe, Zn, Mg, which are the major and important elements in this process together with minor elements selected from the group consisting of manganese, chromium, copper, cadmium, lead, vanadium and chlorides. Most elements are represented as oxides; either complex oxides such as ferrites or simple oxides represented by PbO, ZnO, CaO, some other salts and metals are also present. This process also applies to EAF powder with a low zinc content generated from the use of pre-reduced iron ore granules or hematite. The process steps according to the different preferred variants of the process are illustrated in figures 1 to 6, for the different grades of pigment. They show a batch hydrometallurgical process without atmospheric emissions. The powder suspension of the first washing stage consists essentially of ferrite (65-75%), magnetites (20-28%), zincite (ZnO) and litharge (PbO) (8%), CaO / Ca (OH) 2 (5-12%) and variable concentrations of silica and carbon. A difference between the process of the invention and the prior art of the EAF powder treatment processes resides in the fact that the profitability of the present process is not a function of the concentration of zinc and the EAF powder. One of those steel mills that will be observed in the example uses an EAF feed of at least 50% pre-reduced hematite, with 50% iron fragments of different grades. Depending on the production required, the percentage of hematite and iron fragments may vary. For this steel factory, the average zinc concentration of the powder is close to 9% compared to 16-22% for dust generated from feeds composed of iron fragments only. Table 1 shows two clinical analyzes of EAF dust from two steel mills in Quebec, which were used to test the process. The optimization and characterization of the pilot test trial were carried out: • leading to physicochemical analysis: chemical analysis, granulometric distribution tests, and identification of the chemical phases by x-ray diffraction and electron microscopy, etc .; • optimization of the performance efficiency in different stations by measuring the volume and concentration (g / 1) of the suspension, the weights of its solid fractions, and the processing time; the pH and electrical conductivity of the liquids was also measured, etc.; • note the pH and electrical conductivity of liquids; • Evaluate the pigments noting the specifications of solid color, moisture, oil absorption capacity, dispersion quality, and salt fog tests, etc. 3. 1 First treatment: example The process comprises the first treatment which consists essentially of washing and rinsing the EAF powder to reduce the amount of soluble calcium and lead, to later facilitate the additional treatment of the powder to produce commercial grade pigments.

Washing and first stirring The EAF powder was washed with water under stirring provided by a hydrofoil impeller with a rotation speed of about 350 rpm in a tank. The height of the fluid level and the diameter of the tank had a ratio of 1: 1. The tank's agitation system also comprised four deflectors, which acted as static agitators. The concentration of the suspension was 16%.

The tests were made with batches of 10, 20 and 30 kg of powder per 60 liters of liquid, corresponding to solids concentrations of 16, 32 and 48%, respectively. Washing provided: an aqueous solution of alkaline pH > 12; • a solution of soluble salts, heavy metals and simple oxides under alkaline conditions (see Table 2) (this chemical charge was the liquid that was eliminated by decanting and pumping the supernatant liquid); • the beginning of the degradation of the ferrite particles that are weakly bound (Figure 7); • the dissolution of CaO and some calcium ferrites in soluble calcium and CaOH, and the dissociation of lead oxide; • the transformation of the abundant CaO fraction into CaOH2 and the dissolution of lead oxide; • It is worth mentioning that further agitation with other types of cutting agitators can result in unfavorable high concentrations of Ca and Pb in the liquid, which could impede subsequent treatment steps. • The duration of the agitation was 60 minutes and was followed by a decantation period of 60 minutes and a liquid separation supernatant. Given the high specific weights of the ferrites and magnetites, the decantation of the solids in suspension was used instead of the filtration.

Rinse and second agitation The wash suspension was rinsed with water.

The water is preferable: • to recover the metals and alkaline water of pH 12 from the interstitial water in the 20 liters of residual pulp of the first mixture; and • to continue the leaching of calcium, lead and zinc into the dust. The rinsing was carried out during a period of 60 minutes, followed by a decanting and recovery of 60 minutes of supernatant fluid.

Addition of the surfactant The addition of a surfactant had several objectives in the process. First, it reduces the positive charge of the fine particles of the pulp represented by a 32 mV zeta to reach the isoelectric point (zeta of 0 mV) for the system (suspension). This reduction of the charge of the chemical phases of the system facilitated the fractionation of the compositions. Additional details on the effect of the surfactant on the charge of the chemical phases are given in the section entitled "Magnetic separation" hereinafter. Second, when a phosphate such as sodium metaphosphate was used, the surfactant temporarily confined the CaO from the ferrites by coating the surface of the particles with phosphate. Also, the surfactant was able to convert the calcium already in solution into calcium phosphate, which was insoluble in the solution and was concentrated with the solids. It is also believed that some of the lead in the solution is also precipitated in the form of lead phosphate or in the form of a calcium and lead phosphate phase. These deductions are supported by the titration of the suspension with sodium metaphosphate, which is the preferred surfactant (Figure 8). The conditions of the tests whose results are shown in Figure 8 were: 5% solids in a 240 ml suspension; titration with sodium metaphosphate of 3.6% (w / w) (22 ml of the solution was used); zeta potential calculated using a lower average volume; S.G. 4g / cc. The graph that shows Zeta against the Concentration of Tensoactivo, shows the reduction of the positive charge towards the isoelectric point. The graph that shows the Conductivity versus the Tensoactive Concentration represents the concentration of ions in the supernatant liquid, which decreases wthe addition of the surfactant. After the addition of the surfactant, the agitation was summarized to standardize the state of the mixture and the feed of the magnetic separator which was fed at a flow rate of 1 l / min. The suspension was fed into the magnetic separator while stirring, so as to keep the homogeneous suspension in its content of magnetite and ferrite through the tank. After the stirring step and the two decanting stages, the alkaline solutions of the effluents (80 liters) were used in the treatment of the effluent. The alkaline liquid was mixed wthe acid effluents of the second treatment, which will be better described later to neutralize the acidity and to promote the precipitation of the metals in solution. The first treatment (washing) of the crude EAF powder, which generated an alkaline solution, also promoted the solubilization of the soluble salts in simple lead and zinc oxides at a concentration that meets the government standards of the TCLP test, and the rules Government on hazardous materials. In other words, the leaching of the powder does not exceed the TCLP standard (Table 3) and is thus not considered contaminated, nor subject to the rules of hazardous materials.

The role of agitation in the first treatment The agitation tests were carried out under varying times of 15 to 60 minutes, using a hydrophoyl impeller. The granulometry resulting from the solid fraction of the suspension was obtained by means of a granulometer that can measure at the nanometer scale according to the parameters of number, surface and volume (Figure 7). The corresponding granulometric variation after 60 minutes indicated an acceptable size, with a mean of approximately 0.6 μm for the solid. This diameter was further reduced during the leaching of the second treatment. With other impellents, which have higher cut levels, the resulting granulometry was very fine to optimize the first treatment. Other agitation tests were performed, in which the supernatant fluid was analyzed after the filtration for its content of lead and calcium, and the results are presented in Table 6, and in Figure 9. The chemical concentrations resulting from the test with the hydrophoyl impellant they indicated a stable concentration for a stirring time of 60 min. The stirring time represented a maximum for the extraction of calcium, and a saturation plateau for the value of the lead.

For the other impellers, the elemental concentrations were too high, and thus were not optimized.

TABLE 7 LEACHING EAF DUST DURING THE FIRST TREATMENT AT VARIABLE TIMES Test # 1: 10 kg on the 1T system of the pilot plant AAS analysis results After the first treatment, which was carried out in the tank (10) of Figures 1 to 6, the suspension (16) is sent to the magnetic separation (20) to separate the magnetite particles and the ferrite particles, as in Figures 1 to 5, which show the first to sixth variants; or is sent to the screen (30) and subsequently to the second treatment (40), as in Figure 6 which shows the seventh variant, to finally produce a ferrite and magnetite pigment suitable for use as a colorant for concrete.

The first to the sixth variants, which relate to the production of ferrite pigments (Figures 1 to 4) and the production of magnetite pigments (Figure 5), will now be described in greater detail with reference to Figures 1 to 5. For each of these variants, as widely described, and the suspension (16) of the first treatment was subjected to a magnetic separation (20) to obtain a ferrite fraction (24) and a fraction of magnetite (26). Both of these fractions (24 and 26) were subjected, respectively, to a sieving (30 or 300). Referring to Figures 1 to 4, the fraction of refined ferrite (34) of the screen (30) was further subjected to a second treatment (40) depending on the degree of the ferrite pigments produced. In the case of the third and fourth variants (Figures 3 and 4), the second treatment was preceded by at least one of the following stages: decanting (60), crushing (50 or 55) and magnetic separation (200). After the second treatment (40), the suspension (46) obtained was subjected to filtration (70), and subsequently to the typical process steps used in the field of pigment production, such as drying (90), coating (80) and micronization (100). The filtration step (70) produces water that will be recycled (72). It is also worth mentioning that in the first and third variants of the process, the second treatment was preferably followed by a second magnetic separation (200, 220) used to separate the fraction of magnetite (202, 222) that remained in the suspension (46 ) of the ferrite fraction (206, 226). The ferrite fraction (206, 226) was sent back to the ferrite production line to produce ferrite pigments, while the magnetite fraction (202, 222) was sent to the magnetite production line. Referring to Figure 5, the magnetic fraction (26) of the magnetic separation (20) was sent, preferably with magnetic particles (202, 212, 222) of the other process steps, to a first screening (30) at 150 μm . Fraction (38) of less than 150 μm was sent to a ball mill (500) and then to a second sieve (300) to obtain a first finer fraction (304) with particles having a grain size of 6 μm or less; and a coarser fraction (306) with particles having a grain size greater than 6 μm. The thickest fraction (306) was then ground and sieved at 40 μm (those stages are not shown in Figure 5) to finally obtain a coarser fraction containing particles having a grain size between 40 and 6 μm.

The thickest fraction (306) was crushed wet by abrasion (50) to achieve an average grain size of approximately 0.3 μm. This was subsequently subjected to the typical process steps used in the field of pigment production, such as drying (90), coating (80) and micronization (100). The finer fractions (304) were purified by suspending (600) the residual contaminants contained therein with an anionic surfactant (802), to obtain a purified magnetic fraction (602).

Magnetic Separation (20) The magnetic separation stage (20) produces the first fraction (24) that contains in a larger portion of ferrite particles and the second fraction (26) that contains in a larger portion magnetite particles. In the raw EAF powder, the black magnetite is never apparent or visible to the naked eye, although the magnetite is large and rough compared to the other components of the powder. This phenomenon is explained by the adsorption of the ferrites to the surface of the magnetites. In the raw powder, the ferrites are positive and the magnetite is negative, which produces an electrostatic attraction between these two chemical phases. This charge can be measured with a device called "Electroacoustic Sonic Amplitude (ESA)", which allows the calculation of the zeta potential of the particles in aqueous medium, and the indirect and qualitative evaluation of the surface charge of the particles. The results indicate that the ferrites have a positive charge with a zeta of +27 mV, while the magnetites are slightly negative and have a zeta of -3 mV, which corresponds to the charge values for the natural magnetites. Also, because the ferrites have a particle size less than 1 μm, they will coat the large rough surface of the magnetite. This rough surface of the magnetite surfaces seems to be produced by the deposition of phases of calcium compositions and others that can be removed by abrasion. These factors make it difficult to separate the ferrites from the magnetites. Laboratory experience teaches us that without a surfactant, it is possible to obtain a fraction concentrated in magnetite, but this fraction is brown and not black, and has a large proportion of ferrites trapped with concentrated magnetite. In the process of the present invention, by adding an anionic surfactant (preferably sodium metaphosphate), the positive charge of the ferrites is neutralized and can be inverted to achieve negative charges with an intensity of -40 to -160 mV, and lower. The addition of surfactant increases the surface charges of the fine ferrites, decreases the cohesion or attraction between the ferrites and magnetites, produces a stronger repulsion between the ferrite particles and keeps those ferrites in suspension. The coarse magnetic fraction, which has a very small surface area, is not greatly affected by the addition of surfactant. The granulometry and the mass of the magnetites allow the decantation of the magnetite with the ferrite in suspension. This procedure substantially improves the results of magnetic separation and sieving. The condition at the isoelectric point is preferable to optimize magnetic separation and sieving (see next section), while controlling the concentration of lead in the solid.

Evaluation of the results The magnetic separation in aqueous medium was carried out with a drum for which a magnetic field was generated by means of an electromagnet with a maximum power of approximately 1200 gauss. The suspension (16), which had a solconcentration of 16% and a surfactant mass concentration ranging from 0.1% to 1.3%, was used in the separation. Magnetic separators are well known and do not need further description. The suspension (16) was fed with a flow rate of 1 l / min. To detach the magnetic fraction from the drum, an additional flow of water was added (22) of 1.4 l / min, totaling 150 liters of liquid (to be recycled) with a concentration of 3% solids to be recovered by decanting (60) and sieving (30). The maximum fraction of magnetite recovered in the pulp varied from one company to another according to its production. However, the maximum fraction recovered was of the order of 15 to 20% for the producer using a pre-reduced magnetite mineral and between 8 and 10% for the producer using only iron fragments. The quality of the separation was evaluated qualitatively under the microscope observing the color, which distinguishes magnetite from carbon. The color was also used to evaluate the quality of the magnetic separation. Table 7 compares the three color components, according to the HunterLab color scale, for the raw powder for separation, and for the separated and sieved ferrite and magnetite fractions. The "L" parameter of 0.00 corresponds to a black standard used to calibrate the apparatus, while the value of 100.00 is associated with the white standard. The parameter "L" indicated a pale tone for the fractions obtained without the addition of surfactant, and that, consequently, only contained a concentration of magnetite still coated with brown ferrites. On the contrary, with the addition of surfactant, the fraction of magnetite was of a blacker tone according to the optical apparatus and also according to the observed with the naked eye.

TABLE 8 COLOR COMPARISON FOR EAF, FERRITE AND MAGNETITE DUST, SEPARATED FOR MAGNETIC SEPARATION (MSP) The efficiency of the magnetic separation is supported by the mass values of the amount of ferrite trapped by the magnetite. The weights of the fractions indicate that without the addition of surfactant, the ferrite trapped by the magnetite reached a maximum. On the other hand, with the addition of a surfactant, the amount of ferrite decreased (Table 9). The adsorption of the surfactant preferably occurred on the fine fraction of a solid and thus in this case, on the ferrites. The magnetites, which are thicker, experienced a change in charge that is less significant and thus there is less effect on the mobility of this phase.

TABLE 9 QUANTITY OF TRAPPED FERRITAS FOR MAGNETITE AS A FUNCTION OF THE TENSOACTIVE Another indication of the separation efficiency is provided by the results of the magnetite recovery tests obtained from the rough fraction > 20 μm after sieving the non-magnetic fraction. This ferrite fraction comprises rough contaminants (ie, carbon) and magnetite with a lower amount of fine silica and carbonate or calcium phases. The magnetite was not separated in the first magnetic separation since it was coated with silica and calcium phases. The amount trapped varied with the amount and concentration of the surfactant added. For a separation without surfactant, 197 g of rough magnetite were recovered. The same fraction after adding the surfactant resulted in a recovery of 221 g, or 11% more magnetite recovered. This result is explained by the fact that the surfactant is more efficient in the dispersion of the particles, and thus the finer contaminants of larger magnetite spheroids; Coal has no influence on separation. For the process according to this document, it is preferable to use the surfactant in accordance with a specific dosage, to produce two fractions (24 and 26) which are suitable for suitable products for commercial applications, as will be explained in further details below. : Screening (300 or 30) The screening of the ferrite fraction (24) or the magnetic fraction (26) is essential to produce ferrite pigments or magnetic pigments that have a commercial value, because it allows the physical separation of large agglomerates and certain contaminants that accompany the ferrites and magnetites. All particles or agglomerated substances of more than 20 μm with or without magnetic susceptibility, they can be separated. The carbon and even metal fragments of partially fused residues are separated by sieving. In addition, to improve the separation of the ferrites and magnetites in the first treatment and the magnetic separation, the addition of surfactants prevents the obstruction of the sieves and capable of sieving with openings of 20 to 6 μm. The blockage is caused by portlandite, a calcium hydroxide Ca (OH) 2, which is produced from lime in the raw EAF powder. The portlandite in solution and in suspension is deposited in the walls of the containers and, in particular, in the mesh of the sieve, thus sealing the last one. Using an appropriate active surface (sodium metaphosphate), the calcium in solution is precipitated in the form of calcium phosphate. This precipitation is associated with the decrease in conductivity observed during the addition of the surfactant and this decrease continues after reaching the isoelectric point, achieving in some cases, a minimum of conductivity (Figure 9). These screening tests show that most of the active surface concentration is increased, most of the solution approaches a minimum of conductivity and less obstruction of the sieves is observed. Also, the internal walls of tanks, screens and other equipment can be easily cleaned, simply by rinsing them with water. If the addition of a surfactant is not used, the portlandite which adheres to the surfaces and screen mesh can be cleaned with an aqueous acidic solution. The concentration of the surfactant that provides the minimum conductivity is not preferred because such as a concentration of sodium metaphosphate interferes with the leachate leading into the pulp. The addition of the surface active provides the isoelectric point is sufficient to double the suspension flow rate in the sieves from 4 ml / min to 7 or 8 l / min and thus increases the filtration capacity. The addition of the surface active decreases the number of cleanings required for a 10 kg tank using a 20 μm sieve by a factor of three. In addition to the suspension, a flow of water for sieving (32) is used to facilitate sieving. In the first to third variant, the hardened screened fraction (36) emitted from the first screening (30) is subjected to a separation (210) used to separate the fraction of magnetite (212) remaining in the ferrite fraction (24). ). The magnetite fraction (212) is sent to the magnetite production line, as shown in Figure 5.

Wet crushing or crushing by wear (50) This wet crushing can be achieved with silica sand and zirconium beads or other materials with a spherical morphology and sufficient hardness to resist abrasion. The results provided are obtained with the zirconium perlillas with a granulometry range of 0.4 to 0.6 mm in a horizontal mill, with horizontal type discs. The conditions of crushing and results are presented in table 10.

Table 10: CONDITIONS OF WET CRUSHING AND RESULTS FOR FERRITAS 1. Wet Grinding Conditions for Ferrites 2. Results of wet crushing for Ferrites The goal of this grinding is to break large aggregates of more than 5 to 20 μm to provide the ferrite pigment particles of a restricted range of granulometry, more specifically, a bell curve distribution with an average of about 0.3 μm . The granulometric distribution after wet milling ensures that the fraction of rough aggregates in the powder are removed and transferred in the fine granulometry range. The diameter obtained (on the surface) is 0.25 to 0.28 μm, with a desired bell curve distribution for the pigments. The results are illustrated in figures 10, 11, 12 and 13. Figures 11 and 12 illustrate the granulometric distributions for suspensions after one or two steps in the mill. For more aggressive leaching processes, as for the second grade ferrite pigment, the suspension does not require grinding, the granulometric average is already closed for or adjusted under 0.8 μm. Normally, the first grade ferrite pigment requires grinding to obtain adequate dispersion. Also, some powders may contain enough aggregates around 20 μm to require the use of a wet grind. For cement additives, wet grinding is necessarily because, by decreasing the granulometry, it increases the contact surface between the particles, and generates new surfaces for a more efficient leaching in the second treatment (40). The ferrite pigment particles, even after grinding, are still aggregates of fine nanoscale particles. Figure 14 (AFM microscope) confirms the state of agglomeration and the fine size of the perlillas or constituent fragments. 3. Second Treatment (40) of the ferrite fraction: example The goal of the second treatment (40) is to leach the heavy metals still in the suspension, to remove the less stable ferrites and provide certain surface characteristics required of the pigments (intensity) potential sign and zeta), to improve the compatibility of the pigment in paints, plastics and concrete. The chemical composition of the pigment spinels resulting from the second treatment (40) are represented by the chemical compositions provided in Table 11. These pigments represent several ferrites or spinels that differ slightly rich in iron, zinc, magnesium and manganese and contain the Al elements. , Yes, Pb, NI, Cr etc., as minor components. All minor components are stabilized in the spinel structure and the lead adheres to the leached criterion of the TCLP and the standards and expectations used for the manufacture of paint, of which the most rigorous imposes a maximum concentration of 500 ppm of lead in paint. .

TABLE 11: CHEMICAL COMPOSITION VARIATIONS OF FERRITE PIGMENTS AS A pH FUNCTION As an example, the effect of the second treatment is illustrated in Table 11 by the variation of lead for the different third grade pigment leached at different pHs with nitric acid. The most important variations are the concentrations of lead and zeta for the different pigments. The sign of the relative charge represented by the zeta potential in aqueous medium is particularly important, changing the last from +40 mV for the first degree to -9 to 11 mV for the pigment leached at a pH of 1.5 to 0.5. This parameter is important for the behavior of the pigment and also influences the pigment properties and the coating mechanism, or even the type of coating it can accept, if required.

Conditions of the second treatment (40) A pulp of 8 to 10% solids in 55 liters of water was acidified with 6 N nitric acid at the desired pH by continuous addition of acid over a period of 30 min. The pH was maintained for 60 minutes, adding sporadically the acid while stirring the pulp. Decanting was preferred and the supernatant liquid was removed. • In the first variant, water (37) was simply used as the leaching agent. In the second variant, sulfuric acid (42) was used and in the third variant, nitric acid (43) was used as the leaching agent. 3. 3) Production of ferrite / magnetite pigments (seventh variant): Example Referring to Figure 6, and according to the seventh variant used to produce the ferrite / magnetite pigment, the suspension (16) of the first treatment (10) does not was subjected to the separation of magnetite. The suspension was instead subjected to sieving at 60 μm or less. The thickest fraction (31) was separated into magnetic (216) and lower magnetic (218) fractions, by magnetic separation (220), and these fractions could be used in other parts of the process. The finest fraction referred to herein as the refined suspension (33) was subjected to the second leaching treatment (40) with nitric acid (43) at a pH of about 3, to obtain a leached suspension (48) without or a controlled amount of ZnO, which retards the setting of concrete. The leached suspension (48) was separated into a solid fraction (74) containing a mixture of ferrite and magnetite pigments and a liguid fraction (72) containing nitric acid-soluble constituents. The solid fraction (74) was then dried (90) to obtain dry pigments containing a mixture of ferrite and magnetite. 4) Characteristics and Pigment Properties of Pigments Ferrite-based and magnetite-based pigments produced by the processes described in this document above, have certain characteristics and pigment properties, some of which are measured and tabulated. 4. 1) Characteristics of ferrite-based pigments Of particular interest are the ferrite-based pigments produced by the processes described above and have anticorrosion applications. These ferrite-based pigments can be used in paint formulation to coat a substrate, in particular a substrate exposed to corrosion, to protect it from the corrosive effects of moisture, water and penetration ions. The ferrite-based pigments are formed from a condensation reaction of Fe metal vapors with other metal vapors present in the EAF vessel, which includes metal vapors Zn, Mn and Mg are involved in the reaction. This condensation reaction provides EAF powder with a particular composition of ferrites, magnetites, contaminants and, varied oxides and metals which are treated in accordance with the hydrometallurgical process described hereinbefore. It is with this process that the ferrite-based pigment is isolated from the selected EAF powder in a "non-aggressive" manner, thus being able to retain certain properties that may otherwise be destroyed or modified. The ferrite-based pigment thus contains a non-toxic amount of lead, as the latter is leached out of the EAF powder. The pigment also includes oxides of condensed metal. These oxides comprise a diverse array of ferrites, which are formed by condensation reactions and which include zinc ferrites, magnetite (iron ferrites), calcium ferrites, magnesium ferrites, manganese ferrites, and also minor amounts of other ferrites based on metal. The general formula of ferrites is MOFe203, where M is one or more of the aforementioned metals. Of course, other metals can form any ferrite in complexes, as well as other compounds. A general formula for a multiple metal ferrite in the form of a complex, for example, is (MnxZnyFe? -? - y) Fe204. It will be noted that ferrite-based pigment ferrites may include magnetites. The degree to which magnetite is present depends mainly on the magnetic separation stage of the hydrometallurgical process. Thus, pigments based on non-magnetic ferrite can be obtained instead of the magnetic field is also able to magnetically remove the magnetic fraction of the fraction of non-magnetic ferrite. Preferably, the pigment based on ferrite contains ferrites based on Zn, which could also include ferrites Mn.Zn. These ferrites are in fact preserved from the EAF powder, which contains a plurality of Ferrites to Zn and Mn. The condensed metal oxides, thus include ferrite or ferrite-like structures, substantially preserved from the EAF powder. These structures form ferrite aggregates and ferrite-like structures of varying size. The aggregates may also contain filler materials of virtually inert compounds, which are often found in pigments for use in pairs. As mentioned above, the granulometry of the pigments can be calibrated by several stages of grinding to bring the size of the aggregate to the desired average. The size and shape of the aggregate are also influenced by the specific leaching stages and pH level used for purification of the pigment product in the second treatment. This will be described in detail later. The pigment based on ferrite also includes CaO trapped by ferrite or ferrite-like structures. This CaO is at least partially available to react with moist air and / or water to protect the substrate against corrosion. The trapped CaO is a result of the suspended CaO particles that become associated with the condensation metals in the formation of phenomena where the ferrite or ferrite-like structures come together, in part due to the action of CaO. Thus, CaO is trapped by being both associated between the ferrite structures to help form the agglomerates (so called "first portion") and associated with the same ferrite structure (so called "second portion"). CaO trapped is not, however, all permanently guanically or physically fixed in certain states, but is rather partially available to react with moist air or water. More specifically, the CaO that holds the agglomerates together is more readily available for reactions. These pigments react with water, moist air and / or oxidizing conditions to liberate or provide CaO which is trapped within the aggregates formed of nanoparticles of ferrites also within the ferrite lattice. CaO exhibits an exothermic reaction with water and is a vision as the first compound reacts when it has a higher energy state. The primary reaction is as follows: CaO + H20 >; Ca (OH) 2 This reaction has the immediate effect of locally increasing the pH on the surface of the pigment. This reaction also has the effect of causing other chemical reactions. As the pH conditions change and the CaO within the aggregates is reduced, a variety of physical and chemical phenomena can occur. Thus, the CAO that is initially available for this provoked reaction can be called "sacrificed calcium". The first portion of CaO is more readily available to act as sacrificed calcium. However, the second portion of CaO may become more available when the first reaction is reduced, the former thus replenishing the sacrificed calcium. This is particularly advantageous for providing the pigment with long-lasting anti-corrosion properties. The sacrificed calcium can also cause the formation of a variety of protective hydroxide phases, depending on the calcium concentration and the composition of the ferrites, aggregates and pigment fillers. Preferably, the protective hydroxide phase comprises Zn (OH) 2, which can be observed in the form of a precipitate. In some of the salt spray tests, a white film precipitate comprising Zn (OH) 2 is observed. Of course, depending on the other reactions and the degree of the corrosive environment and the resulting iron oxides present, the precipitate may be orange. A precipitate is observed that occurs in a film that covers the metal substrate. This type of corrosion protection can be characterized as "self-healing", as the exposed metal surface is coated and "heated" by a physical layer of Zn (OH) 2 for protection. Also preferably, the protective hydroxide phase comprises one selected from phases of amorphous calcium hydroxide and portlandite. Portlandite is the crystalline form of calcium hydroxide which is identified by X-ray diffraction. Preferably also, the protective hydroxide phase comprises a zinc and calcium hydroxide. A plurality of phases of zinc and calcium hydroxide are possible, but a preferable one is a crystallographic phase having a crystal structure analogous to that of the hydrate CaZn2 (OH) 6. In addition, the protective hydroxide phase may comprise an iron-calcium-zinc hydroxide. A preferred one of such phases is Fe (CaZn) 2 (OH) hydrate which is in all probability of being present in the measured diffraction spectra. In some cases, such as for Zn (OH) 2, the hydroxide phase forms a physical protective layer on the metal substrate to help physically protect the metal substrate from penetration ions, water and oxygen.

The ferrite-based pigment does not contain only a first portion of CaO that is initially available for immediate reactions with water, but also contains a second portion of CaO trapped within the ferrite or ferrite-like structures. This second portion of CaO is much less available as sacrificed calcium, being trapped inside the ferrites. However, when it is protected against corrosion, it is advantageous to allow the protection to be sustained for a time. This can be achieved by providing anticorrosion agents with different availabilities. It has been found that the pigment based on ferrite according to the invention is extremely useful on protected metal substrates for long periods of time. Some CaO is already available by reacting with water, while the second portion, that is, the CAO trapped within the ferrite structures, is available by reacting at a lower rate and in the case when the first portion of CAO reacts is has leached Thus, however, the protective hydroxide may be leached or otherwise reduced for a time, more reactions proceed and allow more hydroxides to be formed to re-supply the protective layer on the metal surface. It will be noted that it is advantageous to produce the pigment based on ferrite of the present invention using an anionic surfactant in step c) of the hydrometallurgical process. As described above, the surfactant sequesters some calcium, thereby helping to avoid loss during washing and the subsequent magnetic separation and sieving of separation phases. As a result, the ferrite pigments produced from such EAF powders by the process described herein contain a significant amount of calcium, at least part of which is available as sacrificed calcium. Depending on the origin of the EAF chimney dust, various concentrations of heavy metals, calcium oxides and spinels (as shown in Figure 15A) are present in crude powder. This depends on hematite, metal fragment and other qualities and origins of reaction, as well as the conditions that operate the metal smelting and production demands. Figure 15B generally shows the morphology and texture of the powder by SEM. Figure 16 shows the isolated calcium ferrites as observed by an Electronic Scanning Microscope (SEM), and Figure 17, by comparison shows the zincite phase seen by an SEM. Calcium ferrite particles originate as large spherical agglomerates in which a variety of ferrite families are present. Figures 16 and 17 also show a Fluorescence Dispersive System Analysis, el. which exhibits the varied components present in the particular phases. Active ferrite pigments, which contain calcium ferrites, as well as other calcium phases, exhibit a pigment resistance to corrosion. On the other hand, magnetite and ferrite pigments derived from EAF dust that contain more significant amounts of lead and other toxic compounds contain a decreased amount of calcium (due to leaching) and exhibit a more passive resistance to corrosion. Preferably, the anti-corrosion pigments undergo wet grinding, and the passive ferrite pigments additionally undergo leaching, advantageously with nitric acid.

Chemical activity of ferrite pigment Active ferrite pigments are exceptional inhibitors of corrosion. An active ferrite pigment includes any ferrite pigment of such a degree that it contains at least calcium available as sacrificed calcium to react with air and / or water to form protective calcium phases, and more specifically for the first grade ferrite pigment described in this document. An active ferrite pigment advantageously contains at least 4% calcium by weight. These ferrite pigments with at least 4% by weight of calcium contain sacrificed calcium, and thus exhibit chemically active anti-corrosion characteristics. The active ferrite pigments preferably contain about 10% by weight of calcium and preferably still 14% by weight of calcium or more. Table 12 shows the partial chemical analysis of a first degree ferrite pigment. The calcium concentration is 4.4% by weight.

TABLE 12. CHEMICAL ANALYSIS OF THE PIGMENT OF AN ACTIVE FERRITE PIGMENT Calcium is present in the form of several phases associated with ferrite structures. Calcium can be physically trapped within, guimically integrated within or associated around or between the spinal structure of the ferrites. The calcium phases include a variety of calcium ferrites, portlandite, calcium oxide, among others, and are crystalline or amorphous. The concentration of calcium in the active anti-corrosion ferrite pigment varies mainly in accordance with the source of crude EAF powder and the hardness and number of leaching stages, which usually depend on the amount of heavy metals that can be removed from the suspension. The calcium initially present in the crude powder is sequestered by the anionic surfactant and retained through subsequent separation processing steps, to be presented in the ferrite pigment product. Ferrite particles, which have certain crystal structures, comprise and are associated with elements that include iron, zinc and calcium, as well as different phases of it. Reactions between a pigment that contains ferrite particles and that penetrate ions due to moisture and oxygen, include chemical and electrochemical reactions. At least some of the calcium present in the active ferrite pigment is available as sacrificial calcium that is available for chemical reactions to form protective calcium phases. The protective phases advantageously take the form of a protective layer and include oxides and / or calcium hydroxides combined with other metals, and preferably exhibit a crystallographic structure. Sacrificial calcium is associated with ferrites to be available for chemical reactions, particularly in aqueous air to form protective phases. Sacrificial calcium associated with ferrite particles are available for chemical reactions that produce calcium phases associated with ferrite particles. For example, calcium oxide (CaO), which is present in the ferrite pigment and keeps the calcium ferrite agglomerates together, is transformed into calcium hydroxide (Ca (OH) 2) by penetrants. As a result, the calcium ferrite agglomerates are not held together and the calcium becomes available to dissolve the ferrites and / or change phases. In a preferred embodiment of the active ferrites, as shown in Figure 18, sacrificial calcium reacts with zinc and hydroxide ions to produce a calcium-zinc-hydroxide layer of hydroxides including CaZn2 (OH) 6 and others. The protective layers at least partially coat the ferrite particles are formed by sacrificial calcium which reacts with penetration ions and pigment components, and allows the pigment layer containing the ferrite particles to protect a metal substrate coated also in an active way An advantage of these chemically active ferrite pigments is that the reactions involving sacrificial calcium come from an alkaline pH, preferably at a pH > 12. Soluble components that include sacrificial calcium are released and facilitate a basic constant pH in the pigment paint coating. Notably, calcium hydroxide formation reactions raise the pH. This constant basic pH has the advantageous applications in the field of antifouling, in which the scaling rates decrease at higher pH.

Characteristics of the protective hydroxide phases The protective phases produced by the corrosion during the ferrite resistant to reactions are characterized in various forms.

A) Chemical activity Some of the pigments based on ferrite contain sufficiently significant amounts of calcium to be called "active pigments". Active ferrite pigments contain about 4% calcium and are particularly common in resisting corrosion. To characterize some of these protective hydroxide phases of pigments based on ferrite, X-ray diffraction, SEM. Techniques of Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) are used. More particularly, using calcium-zinc-hydroxide hydrate (CaZn (OH)) as a crystallographic reference, the active and passive ferrite pigments are compared. Figure 19, an X-ray powder diffraction graph, shows that the active ferrite pigments contain calcium at least partially complexed in a crystallographic form analogous to the crystallographic structure of CaZn2 (OH) 6. The spinels exhibit an array of subtle differences in prism structures and component processing (shown in Figures 20A, 20B and 20C). The CaZn2 (OH) 6 hydrate exhibits certain characteristics due to its crystallographic structure, and the active ferrite pigments contain complex formation exhibiting similar crystallographic characteristics. In Figure 19, many of the characterization peaks of the active ferrite pigment correspond to characteristic peaks of hydrate CaZn2 (OH) 6, while the passive ferrite pigment lacks such peaks. In fact, the passive ferrite pigment seems to lack any of the crystallographic similarities for hydrate CaZn2 (OH) 6. On the other hand, the active ferrite pigments contain calcium in crystallographic form, which is more specifically analogous to the hydrate CaZn2 (OH) 6- In addition, Figure 21 shows Thermal Analysis Differential (DTA) and Thermogravimetric Analysis (TGA) resulting from the pigment degradation of active ferrites according to the present invention. The DTA curve shows that the endothermic peaks occur around 100 | C and 180 ° C. The peaks represent such phenomenon as water desorption, phase transitions and crystallizations. The TGA curve shows a significant loss of weight between approximately 160 ° C and 215 ° C. The combined diffraction, DTA and TGA results provide a particular characteristic ferrite showing the decomposition, phase response and / or crystal response for heating. The DTA characteristic of other hydroxides are well known in the art and examples of these can be seen in Figure 22. Of course, the DTA and TGA characterizations are in addition to other forms of identification of the compound. In addition, some of Ca (OH) 2 present in the ferrite pimento exhibits crystalline structure. Ca (OH) 2 that exhibits a crystalline structure is referred to as portlandite, an isotope of brucite. The crystal structure is shown in Figure 20C. This structure is also characterized by an X-ray diffraction analysis of the ferrite pigment, shown in Figure 23. This figure also shows that franklinite (Zn, Fe, Mn) (Fe, Mn) 204, is present in this pigment. of active ferrite. The chemically active ferrite pigments, with the general characteristics TA and TGA for a certain temperature range defined in Figure 21 and containing the calcium phases characterized in the analysis of X-ray diffraction, calcium content and other components that reacts with penetration ions. The reactions advantageously maintain a constant basic pH in the coating. The specific action depends on the calcium concentration, as well as the varied reactions between the components of the pigment and penetration ions. With respect to the aforementioned zinc based containing the protective hydroxide phase Zn (0H) 2. Figures 24A, 24B and 24C show the morphology of the precipitate, while Table 13 shows the respective compositions of the different structures.

TABLE 13: COMPOUNDS OF PRECIPITATES BASED ON ZINC B) Electrochemical Activity Ferrite pigments derived from EAF powder also exhibit electrochemical activity in response to penetration ions and the action of the cathode of a substrate covered in paint. In the prior art, chromate pigments (cathodic reaction) and phosphate pigments (anodic reaction) have been used to protect a substrate by electrochemical action. A process of passivation of iron (substrate) by chromate is one that is known in the art, the passivation reactions of which result in a Fe (OH) 2 or 2Cr00H barrier. More grades of ferrite pigment described in this document exhibit some level of electrochemical action. In particular second, third and fourth grade ferrite pigments emphasize this protection mechanism. It can be a process of chemical anticorrosion protection. The calcium that undergoes electrochemical reactions is that it is not sacrificed, and it is transformed into hydroxides such as portlandite Ca (OH2), while other components of the pigment form compounds such as ZnO zincite, zinc hydroxide, iron (II) hydroxide (OH) ) 2, and other hydrated ferrites such as, for example, hydrate Fe (ZnCa) (OH) 8. A protective barrier is mainly formed in and associated with the substrate, which protects against corrosion and additional ion penetration. This barrier composed of calcium phases and other phases can be crystalline and amorphous. Preferably, the first grade of the active pigments have both the first and second portions of CaO, which confer long-lasting anticorrosion properties. In particular, this provides the required strength of an anti-fouling pigment. The chemically active grade can offer a prolonged resistance to corrosion if compared to the coating grades, as the latter depends much more on the hydroxides present in the coating layer.

C) Passive protection Passive ferrite pigments contain less than 4% by weight of calcium and offer protection primarily by providing a physical barrier to the environment instead of a reactive layer associated with ferrite particles or the substrate. Table 14 shows the partial chemical analysis of a fifth grade ferrite pigment. The calcium concentration is 0.68% by weight. The passive ferrite pigments are chemically inert and form a protective barrier in a packaged layer. The second, third and fourth degree ferrite pigments described herein are also used as passive anti-corrosion pigments.

TABLE 14: CHEMICAL ANALYSIS OF THE PIGMENT OF A PASSIVE FERRITE PIGMENT D) Active / Passive Ferrite Mixtures Active ferrite pigments can be mixed with passive ferrite pigments to form hybrid pigments. The passive ferrite pigments can be coated with calcium phase containing solutions (such as leaching from one of the leachate stages of the process described in this document). The anti-corrosion performance of the ferrite pigments can thus be improved. The hybrid pigments can also be made by mixing passive and active ferrite pigments directly to make the resulting ferrite pigments containing a total calcium concentration of 4% by weight or greater.

Pigment properties of some of the ferrite pigments The pigment properties for the ferrite pigments are shown in Table 15A to 15C along with the commercial pigments recognized as ferrites. These commercial ferrites are obtained by mixing oxides in accordance with a company-specific formulation and then calcination at elevated temperature. The table shows different important quantitative pigment properties such as pH, humidity, "long oil" absorption, pigment dry color, paint color, gloss, dispersion in the Hegman calibration, resin incorporation time TABLE 15A: PIGMENTARY PROPERTIES OF FERRITA PIGMENTS TABLE 15B: PIGMENTARY PROPERTIES OF THIRD DEGREE FERRITE PIGMENTS TABLE 15C: PIGMENTARY PROPERTIES OF FERRITE PIGMENTS OF THE THIRD DEGREE Another advantage of the third-grade ferrite pigment is its color stability at temperatures exceeding 300 ° C. Table 16 shows the color parameters for a ferrite before and after heating to 300 ° C.

TABLE 16: COLOR PARAMETER CORRECTION FOR FERRITE PIGMENT HS4 (THIRD DEGREE) BEFORE AND AFTER HEATING AT 300 ° C Another advantageous property of the pigments according to the present invention is that during the process, the pulp has self-preservative properties.

There is a need to add condoms to a pulp that is left or stored for further processing. This is in contrast to titanium oxide, which can include a condom when stored to prevent it from rotting due to mold, mildew or other causes of putrefaction.

Salt Mist Tests Salt Mist Tests for the pigments for which the properties are presented in the preceding section, are given in Table 17 for exposure times of 500, 1000 and 1500 hours, in a chamber designed for testing of accelerated corrosion.

Cp O Cp O TABLE 17: ACCURATE CORROSION TESTING OF FIBER SALT FOR FERRITAS Coating performance after 1512 hours cp O Cp 4. 2) Characteristics of some of the magnetite pigments Magnetite production uses the same treatment units with the exception of an impact mill and a 6 μm sieve. Normally, magnetite does not require leaching with acid and its surface characteristics are more constant. Two magnetites undergo wet grinding: (1) the magnetite fraction after impact crushing, between 38 and 6 μm and (2) the = 6 μm fraction after purification with the surfactants. In both cases, the particles are also rough or long in diameter to be classified as pigments and require wear. Zirconium perlillas of 0.4 to 0.6 or 0.8 mm are used to achieve an average particle size of 0.3 μm. The initial concentration of the pulp is 350 g / 1 and the grinding is carried out continuously until the desired granulometry is obtained. Purification requires magnetite by placing ferrites and other contaminants such as calcium and silica in suspension. This suspension is achieved with the help of an anionic surfactant such as sodium metaphosphate or saratán. The dosage required to optimize the suspension is obtained after titration of the pulp with the surfactant.

The results for the pigment magnetite properties of the present invention and the competing pigment properties are shown in Tables 18A through 18C.

TABLE 18A: PIGMENTARY PROPERTIES OF MAGNETITE PIGMENTS TABLE 18B: PIGMENTARY PROPERTIES OF PIGMENTS OF MAGNETITE TABLE 18C: PIGMENTARY PROPERTIES OF PIGMENTS OF MAGNETITE The salt fog tests are also represented in this table for the magnetites.

The pigments can also be modified to exhibit active anti-corrosion characteristics. The pigment will be active, when they are coated using leachates selected from the hydrometallurgical process preferably with the liquor of the leached NH03 of the ferrite. At least partially leached contains calcium-zinc base characteristics that can help protect the substrate from corrosion. The calcium in the aggregate leachate associated with the large magnetite pigments, coat and protect them from the substrate. Table 19 shows the partial chemical analysis of a magnetite pigment. The calcium concentration is 1.25% by weight.

TABLE 19: CHEMICAL ANALYSIS OF PIGMENT OF MAGNETITE PIGMENT It will also be noted that the magnetite that arrives from the EAF powder by the hydrometallurgical process has other distinguishable characteristics. As explained above, the EAF powder contains oxides of condensed metal, which includes Fe304, magnetite. The black balls of magnetite in the EAF powder are not only coated by the adsorbed ferrite particles, but also contain some ferrite or other compounds. More specifically, it is observed that the magnetite balls formed in the EAF vessel comprise other compounds, that when the magnetite balls are broken and broken to open them, there is a release of ferrites, calcium oxide and other compounds. Thus, depending on the crushing steps performed on the magnetite, different structures may be available and may be possible. As previously discussed, this phenomenon observed with magnetite on a large scale is reasonably thought to occur below μm in size with the ferrites. Therefore, the ferrites can physically trap the fine powder of calcium oxides in suspension with the metallic vapor, which can constitute the second portion of CaO available for reaction and protection against corrosion. This process is unique and can not be duplicated by a calcination procedure. In addition, physically trapped CaO weakens the crystallographic structure and helps increase the availability of such elements as Zn, Mg, Mn and Fe.

) Formulation of paint containing the ferrite-based or magnetite-based pigment: examples The anti-corrosion potential and advantages of the "active" and "passive" ferrite-based pigments are demonstrated in the following examples. Paints containing different grades of active and passive ferrite pigments, or magnetite pigments in paint formulations are prepared and then compared to various commercially available paints containing anti-corrosion pigments. Examples of an internal latex formulation comprising the ferrite pigment and two epoxy formulation components that integrate the pigment are shown in Tables 20 and 21. Table 22 shows a primer formulation. The pigment, integrated into a paint formulation, is applied to a substrate plate. The plate is an E-plate in cold roll steel, and has a profile of 20 microns. The plate is scraped down the middle to expose the substrate, by means of a "drawn line", and then the sample plate is subjected to salt spray for 15,000, 1000 and 500 hours. The resulting corrosion around the drawn line is then observed and analyzed.

TABLE 20: FORMULATION OF INTERIOR LATEX PAINTING INTEGRA PIGMENTOS TABLE 21: EPOXY FORMULATION OF TWO COMPONENTS THAT INTEGRATE PIGMENTS TABLE 22: PRINT LAYER FORMULATION Photographs are taken and observations made to compare the anticorrosive results (in the salt spray tests) of the inventive ferrite or magnetite pigments and pigments found in the market. It is evident that the anticorrosive ferrite pigments have an equal or greater anticorrosive effect. Also, ferrite pigments are easily added to paint formulations to coat a variety of surfaces.

Example 1 A comparison is made between the pigments found in the prior art and the pigments according to the present invention in a salt spray test. The pigments according to the present invention are the same, but better in the protection of the substrate against the corrosion of salt spray. This is evident from the amount of corrosion holes around the scraped plates. The tests conducted are: - a salt spray test at 1500 hours for a first-grade ferrite pigment, zinc chromate or strontium chromate. - a salt spray test at 1500 hours for a first grade ferrite pigment, zinc chromate and zinc compound. - a salt spray test at 1500 hours for first grade ferrite pigment, as well as for commercially available pigments. - a salt spray test at 1500 hours for a fourth grade ferrite pigment, as well as for commercially available pigments.

Example II A comparison is made between a first-grade pigment according to the present invention and titanium oxide, as well as different mixtures of the first-degree ferrite pigment with titanium oxide. The enhanced inhibition effect on corrosion is worthy of attention, especially at a 50% blend. The tests conducted are: - a 1000-hour salt spray test for a first-grade ferrite pigment at different dilution levels in titanium dioxide. - a 500 hour salt spray test for a first grade ferrite pigment at different dilution levels in titanium dioxide.

EXAMPLE III A comparison is made between the coated and uncoated ferrite pigments. It is apparent that the coated pigments exhibit greater resistance to corrosion. The coating of passive fourth grade pigments increases the amount of calcium in it, and results in improved anti-corrosive properties. The tests conducted are: - a 1000-hour salt spray test for the coated and uncoated fourth-grade ferrite pigment. - a 500 hour salt spray test for a coated and uncoated fourth grade ferrite pigment.

Example IV A similar procedure is performed as in the Example II, but a mixture of different grades of ferrite is used. The results are that the performance of ferrite-based pigments is good or better than the others. The conducted test is: - a 500 hour salt fog test for a mixed ferrite pigment, comprising first and fourth grade ferrite pigments.

Example V A similar procedure is performed as in the Example III, but a magnetite pigment is used. The results are that the performance of pigments based on ferrite is good or better than the others. The conducted test is: - a salt spray test at 1500 hours for magnetite pigments, as well as a commercially available pigment.

Example VI An adhesion test is performed to verify the ability of the pigment containing the formulation to adhere to the metal under certain test conditions. It is noted that the pigment has excellent adhesion properties, it is virtually non-detached from the break in the paint coating along the grooves. By comparison, however Ti02 adheres to a coating of the pigment primer layer, the presence of some breaks along the grooves is observed. The tests conducted are: - a test of adhesion of the ferrite pigment of first grade in metal. - an adhesion test of titanium dioxide above in the primer layer of the ferrite pigment.

Example VII Acidic strength tests are also conducted, and the results show that the ferrite pigment resists acid attacks, as non-metals are exposed. A white line in the middle of the plate is observed and indicates the reactive edge that includes calcium sulfate. The comparison is made for a metal surface coated with a Bayer ™ iron oxide pigment, and it is observed that the latter is not resistant to the acid for sulfuric acid as the ferrite pigment. It is evident from the presence of exposed metal in the Bayer ™ sample. The tests conducted are: - a test of concentrated sulfuric acid in the ferrite pigment. - a test of concentrated sulfuric acid in iron oxide.

Example VIII A formulation containing 10% of the first grade pigment is applied to a plate and a formulation containing 10% of the third degree, pigment coating is applied to another plate. These covered plates are subjected to 500 hours of salt fog and compared to conventional Zn phosphate and Y-805K formulations. It is noted that both formulations containing pigments of the present invention have superior corrosion prevention. 6) Pigments coated with leached solution As mentioned above, it is desirable to coat the ferrite base (or magnetite-based pigments) with an organic and inorganic coating. In particularly preferable when such a coating is used, to employ a leached solution derived from the EAF powder hydrometallurgical purification process. More specifically, the solution containing leachate is produced from the third process variant in the nitric acid leaching stage. When the EAF powder has a low content of CaO and other calcium compounds, for example below about 4% by weight, and has a high zinc concentration of about 30% by weight, this is particularly preferred. The leaching stage of the second treatment can be performed at a pH of 0.5 with nitric acid, which results in a lead concentration of approximately 600 ppm compared to other variants, which provides lead concentrations of approximately 1200 ppm or higher. The ferrite-based pigments obtained from the EAF low-lead powder itself contain low levels of lead, which offers significant advantages since lead is an undesirable element due to its toxicity. These pigments also have high thermal resistance and exhibit other desirable properties for pigments. This pigment can be coated with the leached solution to significantly improve its corrosion resistance. The solution that contains liquid is produced in the following way. The effluent from the leachate treatment is a liquor rich in zinc, calcium, magnesium and manganese with some lower concentration of lead. Lead can be selectively precipitated, either by adding concentrated H2SO4 acid that will make lead sulfate or raise the pH with a base such as sodium hydroxide. By raising the pH to 5.2 the lead is precipitated and the liquid can be filtered with very little addition of metal to coat the pigment or its equivalent suspension. This leached coating increases the calcium content and causes the coating on the surface of the pigment. This phenomenon can be associated with charge attraction between the pigment (negative) and the material is suspension (positive). To make the pigment coated, the pigment slurry or pulp (of, for example, the third or leather grade, or Magnetite M2 after purification) is preferably added to the liquor to provide a concentrated liquid, preferably 10% solid, but also be 20% or 30% depending on the production required and also the efficiency that is expected from the production line. The procedure depends on the size of the finished pigment, characteristic that needs to be reached and the amount of the filler that can be tolerated for optimum corrosion resistance. After starting the coating with lime, the process more often continues to slowly increase the pH with the addition of NaOH and the system is then pushed to the found buffer at a pH of about 6.5 and up to a pH of about 12.6, as the case may be. The resulting coating preferably has surface similarities to the first grade pigment, due to the high presence of calcium and zinc phases. As a result, this coating provides added corrosion-resistant properties and remarkable physical and chemical characteristics. Table 23 shows the composition of the solution at different pH.

TABLE 22: COMPOSITION OF THE SOLUTION AT DIFFERENT PH The liquor used to coat the ferrite and magnetite pigments of the present invention can also be used to coat other commercially available pigments similar to red iron oxide or natural magnetite and even Ti02 to give them more resistance to corrosion. 6. 1) Characteristics of coated pigments Ferrite-based pigments having less than 4% by weight of calcium are coated with the leached solution, to produce coated pigments, which are then analyzed using various techniques.

A) Coating at pH 9 The complete texture of the coated pigment at a pH of 9 is illustrated by a SEM photo in Figure 26. The coated solid pigment exhibits coated spheres, which are large, as well as some filler material. For the filler, some particles have a regular morphology of crystal-like shapes (octahedral or in columns). Others exhibit a morphology which appears in the form of irregular masses or patches. Figure 27 is an SEM photograph illustrating a prismatic tubular crystal, which appears to have incorporated some small pigment spheres to form an aggregate. Table 24 shows the composition of this particle. The content of Ca is low, while there are relatively high amounts of Mg and Mn. The solid also exhibits a high Zn and Fe content.

TABLE 24: COMPOSITION OF A PIGMENT PARTICLE COVERED Figure 28 is a photograph of SEM illustrating 0.5 μm coated pigment spheres, which are abundant and have a Ca concentration of about 0.6% by weight, relatively lower amounts of Mg and Mn and relatively higher amounts of Zn and Fe. Table 25 shows the composition of this particle.

TABLE 25: COMPOSITION OF A REVERSED PIGMENT SPHERE Figure 29 is a photograph of SEM illustrating a smaller coated pigment sphere of 0.2 μm, which appears to have retained the original pigment composition produced at a pH of 0.5 of the fourth degree. The composition and size may tend to support the conclusion that the grain (or sphere) is not coated or receives a relatively thin coating since the concentrations of Ca, Zn and Fe are closer to the original uncoated grade concentrations. Table 26 shows the composition of this particle.

TABLE 26: COMPOSITION OF A COATED PIGMENT SPHERE Figure 30 is a photograph of SEM illustrating a structure similar to a columnar bar, which is associated with a filler-type material having a corresponding composition high in zinc and low in Ca, with usual amounts of Mg, Mn and Fe. Table 27 shows the composition of this particle.

TABLE 27. COMPOSITION OF A COATED PIGMENT COLUMN The pigment coated at pH 9 was also characterized by X-ray diffraction. Figure 31A is a graph showing the different structures contained in this pigment, including calcium-zinc hydroxide hydrate and franklinite (ie, Ca (Zn ( OH) 3) 2.2H20).

B) Coating at pH 12.5 When the pH of the suspension increases from 9 to 12.6, the resulting pigment shows a significantly different texture and morphology. In Figure 32, which is a photograph of SEM, the morphology is seen to be mostly large rhombichedron-type crystals of 10 to 20 μm in which the most usual spherical-like pigments are bonded or agglomerated. The large number of structures in comparison with the pigments, indicates that at a pH higher than 9, the irregular masses already described for the case of pH 9, maintain the growth and finally incorporate the majority of the pigment material in these tubular crystals. In Figure 33, the frosted structure is viewed from an approach, with the pigment particles of the pigment, attached. After the closest examination, it appears that some of the pigment has been incorporated into the larger crystal. As seen in Table 28, the composition has high values of Ca and Zn with low amounts of Fe, Mg and Mn. This composition could indicate that the analysis represents filler material.

TABLE 28: COMPOSITION OF A GRINDING STRUCTURE COVERED Figure 34 is an SEM photograph illustrating a small coated pigment sphere of approximately 0.1 μm. This sphere contains amounts of Fe, Mg and Mn, which are almost close to those found in a pigment, but are relatively low in Zn and have an increased Ca concentration of 1.5%. Table 29 shows the detailed composition of these small spherical particles.

TABLE 29: COMPOSITION OF A SMALL COATED SPHERE Figure 35 is an SEM photograph illustrating a small coated pigment sphere of about 0.75 to 1.5 μm. Table 30 indicates that the late material that precipitates from the coating liquor is relatively low in zinc (between 14% and 17%), and relatively rich in calcium (between 0.7% and 3%). (These similar results are those shown in Figure 34 and Table 29).

TABLE 30: COMPOSITION OF SMALL LINED SPHERES If the pigment in Figure 35 is micronized, all the large ground glass is crushed and the material exhibits all the properties required for a pigment. This is illustrated in Figure 36, as well as in Table 31. This pigment has a composition completely similar to the initially treated powder, with the exception of heavy metals, which have been removed.

TABLE 31: COMPOSITION OF MICRONIZED PIGMENT For the sake of comparison, the uncoated pigment (third degree) of Figure 37 and Table 30 can be observed, relative to the coated pigment of Figure 36.

TABLE 32: COMPOSITION OF NON-COATED PIGMENT In addition, the coated pigment at pH 12.5 was also characterized by X-ray diffraction. Figure 38A is a graph showing the different structures contained in this pigment, including calcium-zinc hydroxide hydrate and franklinite (i.e. (Zn (OH) 3) 2.2H20). This pigment was also characterized by a DTA and TGA graph, shown in Figure 38B. 7) Applications of pigments Of course, pigments have a variety of applications in a myriad of industries. However, a few preferred uses of the pigments are described below. 7. 1) For ferrite-based pigments Anti-fouling is a domain that involves boarding, pipe maintenance, air conditioning and underwater structures industries. The accumulation of ship-hull bodies and other underwater structures such as docks, breaking walls, underwater instruments, marine defenses and other artificial submerged structures is problematic in marine industries. Combating the accumulation of organisms, whether they are microincrustrators (biofilms) or macroincrustrators (barnacles, limpets, seaweed), usually involves scraping or painting with resistant paints. Bioincrustrators are often susceptible to pH and have difficulty growing in basic environments. The active pigment can thus be used in an anti-fouling paint. A coated surface that a paint containing the active ferrite pigment, could not only protect against air and moisture physically, but could have an alkaline pH due to its activity, and could discharge scale.

Examples Metallic plates were coated with a paint formulation containing first grade ferrite-based pigments. Other metal plates were coated with Ti02 to provide comparative results. All the coated metal plates were submerged in a river at a depth where light access was minimal. Then a microscope was used to observe the surface of the plates more closely. After 98 days, the coated plates were removed and observed. Figures 39A to 39E are close-up views of Ti02-coated plates, and it is evident that several discovered organisms are present in the coating. On the contrary, Figure 40 is a close-up view of the coated plate where the ferrite-based pigment is present in the paint. Only one type of organism similar to algae was observed in the plaque and the discovered organisms were absent. Other applications include anti-corrosion paints for metals and other substrates susceptible to ionic penetration and degradation. 7. 2) For magnetite-based pigments The magnetite pigment has morphological and magnetic properties that allow it to be used in photocopier toners. The magnetite pigment can also be coated and used as a black primer or finish paints for anti-corrosion applications. Although the preferred embodiments for carrying out the invention are described in detail above and are illustrated in the appended figures, the invention is not limited to these preferred embodiments, and many changes and modifications can be made by a person skilled in the art, without leave the structure that has been currently invented.

Claims (38)

1. NOVELTY OF THE INVENTION Having described the present is considered as a novelty, and therefore, the content of the following is claimed as property: CLAIMS 1. An anti-corrosion ferrite-based pigment for use in a paint for coating a substrate, the pigment is derived from a hydrofluorological purification process of EAF powder, characterized in that said EFA powder is generated: in an oven of electric arc or the like, for producing carbon steel by processing source materials chosen from the group comprising metal fragments, direct reduced iron and pre-reduced hematite, and using a CaO rich slag; and of a condensation reaction of metal vapors of Fe, Zn and metals chosen from the group consisting of Mg, Mg, Si and Al, and suspended CaO-based particles and oxygen; the pigment contains a non-toxic amount of lead due to the hydrometallurgical purification process, the pigment comprises: fused metal oxides, comprising a plurality of different ferrites of the general formula MOFe203, wherein M comprises Zn, Fe, Mn, Mg and complexes thereof, for the different ferrites, and having ferrite or ferrite-like structures substantially preserved from the EAF powder, and forming aggregates of said ferrite or ferrite-like structures; and CaO trapped by the ferrite or ferrite-like structures and being at least partially available to react with moist air and / or water to protect the substrate from corrosion.
2. 2. The pigment according to claim 1, characterized in that the source materials comprise metal fragments.
3. 3. The pigment according to claim 1, characterized in that M is mainly Zn and the ferrites are franklinite based.
4. 4. The pigment according to claim 1, characterized in that the pigment has low magnetic activity due to low amounts of Fe30.
5. 5. The pigment according to claim 1, characterized in that the pigment has from about 0.5% < ? up to about 20% by weight of calcium.
6. 6. The pigment according to claim 5, characterized in that the pigment has from about 4% to about 12% by weight of calcium.
7. The pigment according to claim 1, characterized in that the pigment has from about 20% to about 60% by weight Fe.
8. 8. The pigment according to claim 1, characterized in that the pigment has from about 5% up to 40% by weight of Zn.
9. 9. The pigment according to claim 8, characterized in that the pigment has from about 30% to about 35% by weight of Zn.
10. 10. The pigment according to claim 1, characterized in that a first CaO portion is physically trapped within the aggregates.
11. 11. The pigment according to claim 10, characterized in that a second portion of the CaO is physically trapped within the ferrite or ferrite-like structure.
12. The pigment according to claim 11, characterized in that the first CaO portion is available as a sacrifice calcium source to react with moist air and / or water to produce Ca (OH) 2 and locally increase the pH.
13. The pigment according to claim 12, characterized in that the second portion of CaO is inside the aggregates and thus becomes increasingly available once the first portion of CaO is depleted, as a source of sacrificial calcium .
14. 14. The pigment according to claim 12, characterized in that the Ca (0H) 2 locally maintains the pH at or above 12.
15. The pigment according to claim 12, characterized in that the sacrificial calcium also activates the formation of at least, a protective phase of hydroxide.
16. 16. The pigment according to claim 15, characterized in that at least one hydroxide protective phase is selected from amorphous phases of calcium hydroxide and crystalline portlandite.
17. 17. The pigment according to claim 15, characterized in that at least one hydroxide protective phase comprises Zn (OH) 2.
18. 18. The pigment according to claim 15, characterized in that at least one hydroxide protective phase comprises a calcium-zinc hydroxide.
19. 19. The pigment according to claim 18, characterized in that the calcium-zinc hydroxide is a crystallographic phase of CaZn2 (OH) 6 hydrate.
20. 20. The pigment according to claim 15, characterized in that at least one hydroxide protective phase forms a physical protective layer on the metallic substrate.
21. 21. The pigment according to claim 20, characterized in that the protective layer comprises from 25% to 70% by weight of Zn from Zn (OH) 2.
22. 22. The pigment according to claim 20, characterized in that the protective layer comprises from 35% to 55% by weight of Zn from Zn (OH) 2.
23. 23. The pigment according to claim 15, characterized in that at least one hydroxide protective phase has a DTA fingerprint as shown in the graph of Figure 21.
24. 24. The pigment according to claim 15, characterized in that less a protective phase of hydroxide presents a TGA trace as shown in the graph of Figure 21.
25. 25. The pigment according to claim 1, characterized in that it has a granulometry that has a distribution similar to a bell curve with an average between 0.2 μm and 1.2 μm.
26. 26. The pigment according to claim 25, characterized in that it has a granulometry having a distribution similar to a bell curve with an average between 0.3 μm and 0.8 μm.
27. 27. The pigment according to claim 1, characterized in that it also comprises a coating of the aggregates, said coating is based on calcium and / or zinc and deposited in the pigment.
28. 28. The pigment according to claim 27, characterized in that the coating is precipitated as a calcium-zinc hydroxide phase.
29. 29. The pigment according to claim 1, characterized in that the substrate is made of metal susceptible to corrosion.
30. 30. The pigment according to claim 1, characterized in that the pigment has been subjected to leaching with a solvent during the hydrometallurgical purification process.
31. 31. The pigment according to claim 30, characterized in that the solvent is water and the pigment produced is a ferrite pigment of a first degree.
32. 32. The pigment according to claim 30, characterized in that the solvent is sulfuric acid, the leaching is carried out at a pH of 0.5 to 3 and the pigment produced is a ferrite pigment of a second degree.
33. 33. The pigment according to claim 30, characterized in that the solvent is nitric acid, the leaching is carried out at a pH of 0 to 3, and the pigment produced is a third grade ferrite pigment.
34. 34. The pigment according to claim 1, characterized in that said pigment has a thermal color resistivity at about 250 ° C.
35. 35. The pigment according to claim 34, characterized in that said pigment has a thermal color resistivity at about 300 ° C.
36. 36. A use of the pigment as defined in claim 1, as an additive in paint, primer coat or coating formulations, to produce an anticorrosive formulation.
37. 37. A use of the pigment as defined in claim 1, as an additive in an antifouling formulation.
38. 38. The use according to claim 37, wherein the anti-fouling formulation is applied to a partially or completely submerged structure, for anti-fouling against selected organisms.