MXPA00011396A - Water-reducible coating composition for providing corrosion protection. - Google Patents

Abstract

The present invention describes a water-reducible, chromium-free coating composition for providing corrosion protection to a substrate, such as a metal substrate. The deposited coating film is corrosion-resistant and for coated articles which are threaded, e.g., steel fasteners, the coating provides a non-thread-filling coating. The coating composition contains particulate metal, such as particulate zinc or aluminum. Although substituents can be separately packaged, the composition is virtually always a one-package coating composition. The composition is water-based, and also contains organic liquid of low ebullition. The composition contains water-reducible organofunctional silane, particularly an epoxy functional silane, as a binding agent. The composition has highly desirable, extended shelf life. The composition can be easily applied in the usual manner, such as dip-drain or dip-spin technique, and readily cures at elevated temperature.

Description

COMPOSITION OF REDUCED COATING IN WATER TO PROVIDE PROTECTION AGAINST CORROSION BACKGROUND OF THE INVENTION A variety of coating compositions containing chromium are known. at least substantially resin free to protect ferrous substrates. Those containing particulate metal are of special interest.

Representative coatings of this type that were initially developed could be very simple, such as compositions containing essentially chromic acid and particulate metal in an alcohol medium as described in the U.A. No 3,687,738 A further development of particular effectiveness for providing a corrosion-resistant coating on metal substrates was the more complex composition as shown in the U.S. Patent. No. 3,907,608. The composition 2o comprised chromic acid, or equivalent, a particulate metal of mainly zinc or aluminum, humectant and a liquid medium comprising higher boiling organic liquid water. The composition had very desirable coating characteristics when 5 included a viscosity modifier such as a water soluble cellulose ether, as described in the U.S. Patent. A. No. 3, 940,280. The coating could be especially useful as an internal coating. In this way it has been taught to use said more complex coating composition as an internal coating on ferrous surfaces. The reverse is then provided with an upper silicate coating, as described in US Pat. No. 4,365,003. Another top coating that could be used is a weldable primer, most notably a zinc-rich primer, which can typically be applied prior to electrical resistance welding of the substrate, as discussed in U.S. Pat. No. 3,940,280 mentioned above. It has been known that when the coating compositions could contain the particulate metal as untreated aluminum flake, said flake may be unstable in water-based coating compositions. In such water-based coating compositions, the conventional aluminum flake will react with water in the composition to form hydrogen gas. One approach to avoid this problem has been to coat the aluminum flake. One of these coatings is an acrylic coating formed by reacting mono-ethylenically unsaturated silane with acrylic monomers having amine hydroxyl or epoxy groups, as described in the U.S. Patent. No. 4,312,886. However, these products are specialty items made to provide a glamorous good looking coating and have not found wide acceptance. Another approach to improving the coating composition was to consider the chromic acid constituent. As taught in the U.S. Patent. Do not 10 4,266,975 this constituent can be partially replaced by boric acid component. However, some chromic acid is retained as a constituent. For coating compositions for, - providing corrosion resistance to metal substrates, whose compositions are of the particular type referred to as "wash primers", have conventionally contained zinc chromate pigment. Efforts have been made with these primers to provide 20 chromium-free anti-corrosion primers, thus reducing potential contamination problems. It has been proposed, as described in the U.S. Patent, A. No. 4,098,749, a coating composition containing a butyral resin of 25 polyvinyl, an organofunctional silane, a borate or - ^ - »Tt? FraTÉ * i-k- - - composed of polyphosphate and phosphoric acid. The composition may contain a metal powder as an optional ingredient and usually a phenolic resin. Said compositions, however, are not suitable as replacements for the complex compositions discussed above of powdery metal and chromium-providing substance, due in part to their resin content. The preparation of compositions has been proposed 10 of coating containing hydrolyzed organotrihydrocarbonoxy silane and a particulate metal. These compositions, such as are described in the patent of E.U.A. No. 4,218,354, can provide protection against corrosion to a coated substrate. Without However, the silanes used are not reducible in water. Rather they react with water and can easily form a gel, unless the reaction occurs in the presence of organic liquid. The compositions, in this way, may have limited utility.

More recently, it has been taught in the U.S. Patent. No. 5,868,819 that composition substituents which are epoxy functional silanes, and which are reducible in water, may be useful in forming compositions for coating metal substrates. The C. compositions are based on a variety of ingredients ? ^^^^ ta to provide a chromium free system. As mentioned above, the corrosion resistant coatings can be combinations of lower coatings and upper coatings. The top coatings can be solder-based, solvent-based zinc-rich primers. For top coatings, such as these zinc-rich primers, it has been proposed, as described in the U.S. Patent. No. 4,476,260, improve the corrosion resistance of the primer by formulating a primer to contain zinc pigment, a thermoplastic or thermosetting resin, an organosilane, and optionally aluminum trihydrate with one or more dispersing agents. These compositions, however, are not suitable as replacements for the complete lower coating compositions, and would be useful in the combination of coatings as the zinc-rich topcoat. Therefore, it would be desirable to provide a coating composition that could have wide acceptance of complex lower coating compositions. It would be further desirable to provide such compositions, which avoid the problems of contamination associated with the hexavalent chromium containing compositions, as well as to avoid compositions that are solvent based.

SUMMARY OF THE INVENTION The present invention provides a water-reducible coating composition, generally referred to herein as a waterborne coating composition, having highly desirable characteristics such as providing a coating that offers desirable corrosion resistance. on coated steel parts. In addition to the corrosion resistance, the deposited film has desirable coating adhesion on the substrate. For small, threaded parts, such as threaded fasteners, the cladding can be a non-threaded cladding. The composition is free of chromium as well as being reducible in water. The coating application equipment in this way can be easily cleaned and the cleaning liquid can be disposed of easily and economically. The coating composition of the present invention can virtually always be easily a composition of a package, thereby providing ease of preparation, storage and transport as well as use. The composition lends itself to prolonged storage stability and offers improved flexibility in choice of ingredients to prepare a more economical and efficient composition. In one aspect, the invention is directed to a water-reducible, chromium-free and stable coating composition for application to, and heat curing on, a substrate to provide corrosion protection thereto, which composition comprises: (A) water in an amount that supplies from about 20 to about 70 weight percent of the coating composition; (B) boiling organic liquid: (C) particulate metal; (D) water-reducing, organofunctional, silane binder containing alkoxy groups, whose binder contributes from about 30 to about 20 weight percent of the weight of the total composition; and (E) wetting agent; and with the proviso that the coating composition has a molar ratio of water to alkoxy silane groups greater than 4.5: 1. In another aspect, the invention is directed to the above-noted coating composition which additionally contains one or more of boric acid component typically and / or corrosion inhibiting substituent. Another aspect of the invention is directed to a coated substrate, protected with a corrosion-resistant, chromium-free coating, of the film deposited and cured from the coating composition described herein. In another aspect, the invention is directed to a method for preparing a coated substrate resistant to corrosion by applying the coating composition described herein to the substrate in an amount to provide at least about 500 milligrams per 0.0929 square meters of coating on the substrate. after curing the composition applied on the substrate at a temperature of about 343SC (650SF) for a time of at least about 5 minutes. In a still further aspect, the invention is directed to preparing the coating composition by pre-mixing silane binder with aqueous medium, or organic liquid, or both aqueous medium and organic liquid, and then using the resulting premix in subsequent processing comprising mixing metal in particles to provide the final coating composition.

DESCRIPTION OF THE PREFERRED MODALITIES The coating composition described herein, when prepared in final form for application to a substrate, will usually be referred to herein simply as the "coating composition" or "final coating composition", however , can also be called a "water-reducible coating composition". To supply the liquid medium, sometimes referred to herein as the "aqueous medium", of the coating composition, water will always be used in combination with organic liquid. It is contemplated that the composition can be infinitely dilutable with water. Because of this, the composition will generally be referred to herein as a water-based coating composition, although it will be understood that some organic liquid is present. Water is present in the composition in an amount of at least about 20, and usually not more than about 70 weight percent, weight of total base composition. The use of less than about 20 weight percent water may be inefficient to provide ease of composition formulation, while more than about 70 weight percent water is inefficient to provide a composition that is easy to apply. While it will be understood that the composition is easily dilutable, it is preferred by efficiency and economy that the composition contain water in an amount of about 25, and more generally from about 30, to about 60 weight percent, total weight basis Of composition. The organic liquid of the liquid medium of coating composition is a low boiling organic liquid, although some high boiling organic liquids may be present, so that the liquid medium may include mixtures of the above. It was previously considered that the compositions serving should contain high boiling organic liquid as an important ingredient. This was described in U.S. Patent No. 5,868,819. Suitable coating compositions can also be produced containing low boiling organic liquid, while retaining desirable compositional characteristics, such as composition stability. The low boiling organic liquids have a boiling point at atmospheric pressure of less than about 100 ° C, and are preferably soluble in water. These may be represented by acetone, or low molecular weight alcohols such as methanol, ethanol, n-propyl alcohol and isopropyl alcohol, and further include ketones boiling below 100 ° C, such as water-soluble ketones, v.gr ,, methyl ethyl ketone. Generally, the organic liquid will be present in an amount of from about 1 to about 30 weight percent, the total weight basis of the composition. The presence of this organic liquid, particularly in amounts greater than 10 about 10 weight percent, e.g., at 15 to 25 weight percent, may improve the corrosion resistance of the coating, but the use of more than about 30 weight percent may be rendered non-economic . Preferably, for economy more easily 15 of composition preparation, the acetone will supply the low boiling organic liquid and will be present in an amount between about 1 and about 10 weight percent of the total composition. It should be understood that the organic liquid is 2o typically provides the composition as a separate component, but that part of all the liquid can be introduced otherwise. When the metal particles have been prepared as metal flake in organic liquid medium, the resulting particulate metal can 25 be in the form of pasta. When said metal shaped Éa? > If the paste is used, it may provide some portion of all the organic liquid to the coating composition. For example, the aluminum flake paste can be 25 weight percent dipropylene glycol, a high boiling organic liquid, and easily contribute one weight percent of said glycol to the total composition. To contribute aluminum to particles, the use of aluminum flake paste can be economical. Theref by economics, those compositions containing aluminum flake may typically have a liquid medium in combination that includes high boiling organic liquid. In general, representative high boiling organic liquids contain carbon, oxygen and hydrogen. They may have at least one oxygen-containing constituent which may be hydroxyl, or oxo, or a low molecular weight ether group, ie, a d-C4 ether group. Since the dispersibility in water and preferably the water solubility is sought, the high molecular weight polymer hydrocarbons are not particularly suitable, and advantageously the hydrocarbons they serve contain less than about 15 carbon atoms and have a molecular weight of 400 or less. Particular hydrocarbons that may be present as an elevated boiling organic liquid include tri- and tetraethylene glycol, di- and tri-propylene glycol, the monomethyl, dimethyl and ethyl ethers of these glycols, low molecular weight liquid polypropylene glycols, as well as alcohol of diacetone, the low molecular weight ethers of diethylene glycol and mixtures thereof. For economy, ease of composition preparation and for reduced volatile constituents in the composition, the Dipropylene glycol is the preferred high boiling organic liquid and is preferably present in an amount between about 1 to about 10 weight percent of the total composition, When the organic liquid is a mixture of organic liquid of When boiling with high boiling organic liquid, said mixture may be represented by acetone plus dipropylene glycol. The particulate metal of the coating composition, in general, can be any pigment 2nd metal such as finely divided aluminum, manganese, cadmium, nickel, stainless steel, tin, ferrous alloys, magnesium or zinc. The particulate metal is more particularly zinc powder or zinc flake or aluminum powder or aluminum flake. The particulate metal 25 can be a mixture of any of the above, as well > üÉiáíiBij i? ritMttH «_ how to understand alloys and intermetallic mixtures of them. The flake can be mixed with powdered metal powder, but typically with only minor amounts of powder. The metal powders typically have particle size such that all particles pass 100 mesh and a larger amount pass 325 mesh ("mesh" as used herein in the US Standard Strainer Series). Dusts are usually spherical in opposition to the characteristic 10 flake sheet. When zinc particulate with aluminum is combined in the composition, aluminum may be present in a much smaller amount, e.g. , from as little as about 2 to about 5 weight percent, 15 of the particulate metal, and still provide a glossy appearance coating. Usually aluminum will contribute at least about 10 weight percent of the particulate metal. In this way, frequently, the weight ratio of aluminum to zinc in Said combination is at least about 1: 9. On the other hand, by economics, aluminum will advantageously not contribute more than about 50 weight percent of the total zinc and aluminum, so that the weight ratio of aluminum to zinc can reach 1: 1. The particulate metal content of the coating composition • MM will not exceed more than about 35 percent by weight of the weight of the total composition to maintain the best coating appearance, but will usually contribute at least about 10 percent by weight to consistently achieve a coating appearance desirable bright. Advantageously, when aluminum is present, and especially when it is present without other particulate metal, aluminum will provide from about 1.5 to about 35 weight percent of the total weight of the composition. Typically, when the particulate zinc is present in the composition, it will provide from about 10 to about 35 weight percent of the total composition weight. As discussed above, especially when the metal has been prepared in a flake form in a liquid medium, the metal can build with some liquid in a smaller amount, eg, dipropylene glycol or mineral spirits, or some liquid still in amount. vestigial, The particulate metals that contribute to the liquid are usually used as pastes, and these grazes can be used directly with other compositional ingredients. However, it should be understood that the particulate metals can also be used in dry form in the coating composition. In addition to particulate metal, another necessary ingredient in the water-reducible coating composition is silane. By the use of the term "silane" herein, or by using the term "silane binding agent" is meant an organofunctional silane, reducible in water. To be reducible in water, the silane must be easily dilutable with water and preferably completely dilutable with water. The useful silane is not one in which the silane must have a cosolvent present when it is reduced with water, so as to prevent gelation during the reduction of water, or to prevent the formation of a precipitate. For example, silanes such as the organotrihydro-carbonyl silanes of the U.S. Patent,. No. 4,218,354, as represented by methyltriethoxy silane, are not useful herein since they must be mixed with a cosolvent and water, e.g., ethylene glycol monoethyl ether and water. For these silanes, the silane and water react so that without the cosolvent, rapid gelation would be typical. In this regard, the silanes which are useful herein are water-reducible, non-gelling silanes. Useful silanes, however, can be reactable with water so long as said reaction does not proceed rapidly to gelation or precipitate formation. Combining with water then provides dilution of silane water, and the subsequent ease of mixing with other coating composition ingredients, without intermediate, deleterious activity, e.g., precipitate formation or composition gelation or both. In the appropriate silanes, organofunctionality can be represented by vinyl, e.g., as in vinyltrimethoxysilane, or methacryloxy, such as in methacryloxypropyl-thioxysilane, and amino, as in 3-amino-propyltrinnetoxysilane, but is preferably functional epoxy for improved coating as well as composition stability. The agent usually contains functionality of -Si (OCH3) 3, or functionality -Si) 2CH3) 3 or -Si (OCH2CH2CH3) 3. The silanes used hitherto have usually been employed as surface treatment agents. It was unexpected to find that, in the compositions of the present invention, they would serve as binders. Because of this, they are often referred to herein as silane binders. They can also serve to stabilize the coating bath against autogenous, harmful reaction. The silane appears to agglutinate and passivate the particulate metal so that the bathing stability of the coating composition is improved. In addition, in the applied coating, the coating adhesion and the corrosion resistance are improved. To provide these characteristics, the silane will contribute from about 3 weight percent to about 20 weight percent of the total weight of composition. Less than about 3 weight percent of the silane will be insufficient to desirably improve the bath stability as well as the coating adhesion. On the other hand, more than about 20 weight percent of the silane will not be economical. In general, for improved bath stability accompanied by desirable economy, the silane will contribute from about 5 weight percent to about 12 weight percent of the total weight of composition. The sol itself is advantageously easily dispersible in aqueous medium, and is preferably soluble in said medium. Preferably, the useful silane is an epoxy functional silane such as beta- (3,4-epoxycyclohexy-1) and i-trimethoxy-silane, 4 (trimethoxysilyl) butane-1,2-epoxide or gamma-glycidoxypropyl-p-methoxysilane epoxide. The silane will be present in an amount relative to water to provide a molar ratio of water, to the alkoxy groups present in the silane atom, greater than 4.5: 1. A ratio that is not greater than 4.5: 1 can provide a coating composition that is thick and difficult to produce and use. Advantageously, this ratio will be greater than about 5: 1 and preferably for better ease of preparation of coating composition will be higher than around 6: 1. For this molar ratio, the moles of alkoxy groups are such groups having the formula as described above with reference to the silane functionality, e.g., the formula 3 -. These may also sometimes be referred to herein as carbonxy or hydrocarbonoxy groups, for the purpose of assisting the dispersion of particulate metal., a dispersing agent is added, i.e., surfactant, which serves as a "wetting agent" or "humidifier", as those terms are used herein. These wetting agents or mixtures of appropriate wetting agents can include nonionic agents such as the alkyl phenol polyethoxy nonionic adducts, for example. Compounds representative of these agents are described more specifically in the examples. Also, anionic wetting agents can be used, and these are very advantageously controlled foam anionic wetting agents. These wetting agents or mixture of wetting agents are useful, they can include anionic agents such as organic phosphate esters, as well as the diester sulfosuccinates as represented by sodium bistridecyl sulfusuccinate. The amount of said wetting agent is typically present in an amount of about 0.01 to about 3 weight percent of the total coating composition. The necessary ingredients of coating composition are the ingredients discussed above, ie, water, low boiling organic liquid, particulate metal, silane binding agent and wetting agent. It is contemplated that the coating composition may also contain additional ingredients, e.g., the above-mentioned high boiling organic liquid. As additional ingredients, the coating composition may also contain what is usually referred to herein as a "boric acid component," or "boron-containing compound." For the "component" or for the "compound", as the terms are used herein, it is convenient to use rotoboronic acid, 2o commercially available as "boric acid", although it is also possible to use various products obtained by heating and dehydrating orthoboric acid , such as metaboric acid, tetraboric acid and boron oxide. In addition, usually only as a minor amount, even when it may be more, salts may be used, e.g., Q ^^ up to 40 percent by weight or more of the boric acid component can be supplied as borax, zinc borate or the like. The boric acid component must be present in an amount of at least about 0.1 weight percent to provide demonstrable improvement of the corrosion resistance characteristic of the coating. This component may be present in an amount of up to about 10 weight percent or more of the composition. Advantageously, for efficient corrosion resistance, the composition will contain from about 0.2 to about 5 weight percent boric acid component, with from about 0.4 to about 0.8 weight percent being preferred. It is contemplated that the composition may contain a pH modifier, which is capable of adjusting the pH of the final composition. Usually, the composition, without pH modifier, will be at a pH within the range of about and to about 7.5. At a pH greater than about 7.5, the resulting coating will demonstrate a detrimental lack of adhesion on a coated substrate. It will be understood that as the coating composition is produced, particularly in one or more stages where the composition has some, but less than all of the ingredients, the pH at a particular stage may be less than 6. However, when it produces the complete coating composition, and especially after it is aged, whose aging will be discussed below, then the composition will achieve the required pH. When a modifier is used, the pH modifier is generally selected from alkali metal oxides and hydroxides, with lithium and sodium as the preferred alkali metals for improved coating integrity; or, it is selected from oxides and hydroxides usually from the metals belonging to Groups IIA and IIB in the Periodic Table, which compounds are soluble in aqueous solution, such as strontium, calcium, barium, magnesium, zinc and cadmium. The pH modifier can also be another compound, eg. , a carbonate or nitrate of the above metals. The coating composition may also contain thickener. It had previously been considered that the thickener was an important ingredient, as discussed in the U.S. Patent. No. 5,868,819, However, it has now been found that useful coating compositions containing no thickener can be produced, and the desirable characteristics of coating composition such as storage stability, however, can be achieved. For the present invention, the thickener in this manner is an optional substituent. The thickener, when present, can contribute an amount between about 0.01 to about 2.0 weight percent thickener, the total weight basis of the composition. This thickener can be a water-soluble cellulose ether, including thickeners "Cellosize" (registered trademark). Suitable thickeners include the hydroxyethylcellulose ethers, methylcellulose, methylhydroxypropylcellulose, ethylhydroxyethylcellulose, methyl ethylcellulose or mixtures of these substances. Even when the cellulose ester needs to be soluble in water to increase the thickening of the coating composition, it does not need to be soluble in the organic liquid When the thickener is present, less than about 0.02 weight percent of the thickener will be insufficient to impart the advantageous composition thickness, while more than about 2 weight percent of the thickener in the composition may lead to high viscosities that provide compositions that They are hard to work. Preferably, for the best thickening without harmful high viscosity, the total composition will contain from about 0.1 to about 1.2 weight percent thickener. It will be understood that even when the use of a cellulosic thickener is contemplated, and in this way the thickener can be referred to herein as a cellulosic thickener, something throughout the thickener can be another thickener ingredient. These other thickeners include xanthan gum, association thickeners, such as urethane-association thickeners and urethane-free non-ionic association thickeners, which are typically opaque, high boiling liquids, v.gr, boiling above 100%. . Other suitable thickeners include modified clays such as highly beneficiated hectorite clay and organically modified and activated smectite clay, even when not preferred. When thickener is used. it is usually the last ingredient added to the formulation. The coating composition may also contain additional ingredients in addition to those already enumerated above. These other ingredients may include phosphates. It should be understood that substituents containing phosphorus, even in a slightly soluble or insoluble form, may be present, v. Gr, as a pigment such as ferrophos. Additional ingredients will often be substances that may include inorganic salts, often employed in the metal coating art to impart some corrosion resistance or improvement in corrosion resistance. Materials include calcium nitrate, dibasic ammonium phosphate, calcium sulfonate, 1-nitropropane lithium carbonate (also useful as a pH modifier), or the like, and, if used, these are more commonly used in the composition of coating in a total combined amount of about 0.1 to about 2 weight percent. More than about 2 weight percent of said additional ingredient can be used when it is present for a combination of uses, such as lithium carbonate used as a corrosion inhibitor and also as a pH adjusting agent. More typically, the coating composition is free of these additional ingredients. As mentioned above, the composition must be free of chromium, which may also be referred to herein as "chromium free". Being free of chromium it is implied that the composition preferably does not contain chromium ion, e.g., as trivalent or hexavalent chromium, said chromium including ion as could be contributed by chromic acid or dichromate salts. If any hexavalent chromium is present, it advantageously should not exceed vestigial amounts, e.g., be present to provide less than 0.1 milligram of chromium per 0.0929 square meters of coating, for better environmental significance. It should be understood that the composition may contain chromium in a non-soluble form, such as for example metallic chromium contributed as part of a particulate metal that could be in the form of an alloy or present as an intermetallic mixture. When the compositions that are described herein as resin-free, such are preferably resin-free except for vestigial amounts of resin, but these may include minor amounts of resin, such as a small percentage by weight, v, g . , 1 to 3 weight percent of resin. By "resin" is meant generally polymeric, synthetic resins, which are typically used as binders in paint systems, but are not intended to include any thickener, when present or including the silane binder. The coating composition can be formulated in a variety of procedures. For example, as an alternative to directly using the silane binder in a concentrated form, the silane can be used as a more dilute premix of the silane, such as the silane mixed with a diluent, e.g., a diluent selected from starting from the substituents that provide the liquid medium of coating composition, such as water, or water plus boric acid component, or water plus low boiling organic liquid including acetone. The resulting most dilute silane-containing mixture, which contains as little as 10 weight percent, up to as much as 90 weight percent or more, of silane, may be mixed with other compositional ingredients. Additionally, it is contemplated that the binder of silane can initially be mixed together with any of the other necessary ingredients of the composition. Therefore, the silane in a liquid form, such as in a diluent, can be mixed with other composition ingredients that are in solid or liquid form. However, it will almost always be present in any composition before particulate metal is added to that composition. As a further example of the method of preparing coating composition, a precursor mixture could be prepared from the organic liquid. which may be present together with wetting agent, while metal particulate is also included. This precursor mixture, which will be referred to herein as the "precursor mixture", will typically contain from about 25 to about 40 parts by weight of organic liquid, from about 4 to about 8 parts by weight of wetting agent and a remainder of metal in particles, base 100 parts by weight of the precursor mixture. At 100 parts by weight of this precursor mixture, sufficient silane binder may be added, preferably diluted with water, so that in a more dilute premix discussed above, from about 3 to about 20 weight percent of the agent is provided. , weight basis of the final coating composition. After the addition of the silane binder, the composition can be further diluted to contain up to about 70 weight percent aqueous medium, final weight basis of the coating composition, packaging concepts, as well as formulation considerations for how the coating composition is prepared, they can be taken into consideration when the ingredients of the composition are put together. In this way, it is contemplated that less of all the coating composition ingredients may be present in other composition premixes. These may include, for example, wetting agent, or wetting agent plus boric acid component, or aqueous medium plus boric acid component.

These premixes can be formed with liquid which may or may not include aqueous medium, or may or may not include organic liquid. A representative premix will be discussed more particularly below with respect to packaging. It is contemplated that a premix can be mixed with the aforementioned precursor mixture of organic liquid, wetting agent and particulate metal. Premixes may be resin-free. Premixtures, free of resin, may sometimes be referred to below as convenient as a "premixed premix." It will be understood that the aforementioned precursor mixture, as well as the various premixes, is often contemplated as separate packages, such as for storage or shipping, or both, Still considering storage stability, the preferred composition is always a package formulation of all the coating composition ingredients, However, it will be understood that, as mentioned above, a precursor mixture, containing the ingredients of particulate metal, organic liquid and wetting agent, can be prepared and packaged separately. Other ingredients may also be available as a package of premixed ingredients, e.g., silane binding agent, or one or both of humectant and boric acid component, which could all be in a liquid medium. This package could constitute one of the possible premixes mentioned above. This package, when the humectant and boric acid is present may or may not be present, may contain said ingredients in the following hundred by weight, all based on 100 percent total package weight: about 15 to about 60 percent of silane, 0 to about 10 percent (typically about 2 to about 6 percent) of boric acid component, 0 to about 5 percent corrosion inhibitor, about 10 to about 30 percent wetting agent, 0 to approximately 15 percent thickness and a remainder, v.gr. , about 20 to about 30 percent liquid, such as organic liquid. The package may have enough water added thereto to provide as much as about 50 or more, but more usually up to 30 weight percent aqueous medium, based on the weight of a packet containing water. It will be understood that the final coating composition, as well as separate pre-blended packages, can be prepared in concentrated form. In this way, even when the water will be present in the coating composition in an amount of about 20 weight percent, the packing formulation discussed immediately below could even with as little as 5 to less than 20 percent water . Then, the package would be mixed with additional water to provide up to as much as about 70 weight percent water in the final coating composition. When aluminum particulates will be used in the coating composition, and especially when both particulate zinc and particulate aluminum will be used, a variant of the above packing considerations may be used. It is more preferred to use said combination of zinc and aluminum and to start with a mixture, susceptible to packing, of about 10 to 15 percent wetting agent, about 2 to 5 percent boric acid component, about 15 to 35 percent. one hundred percent silane binder and one aqueous medium residue to provide a total weight of 100 percent by weight. In this mixture, metal can then be dispersed into particles, usually as a flake, e.g., zinc flake. Additional aqueous medium can be added, whereby the resulting metal containing dispersion can contain about 25 to 45 weight percent of the particulate metal and as much as about 40 to about 60 weight percent aqueous medium., both based on the total weight of the resulting metal containing dispersion. Typically, an additional pack precursor mixture is then prepared separately to introduce the particulate aluminum to the final coating composition. This particulate aluminum will generally be aluminum flake, but it should be understood that other flake metals, e.g. , zinc scale, may be present with the aluminum in this precursor mixture. This additional package may contain from about 20 to about 35 weight percent (typically from about 25 to about 30 weight percent) of silane binder, from about 20 to about 35 weight percent (typically from about 20 to about 35 weight percent). about 25 to about 30 weight percent) of organic liquid, and about 30 to about 50 weight percent (typically about 35 to about 45 weight percent) of particulate aluminum, e.g. , aluminum in the form of flake, to provide 100 percent in total weight for this additional package. Then, usually, from about 5 weight percent to about 20 weight percent of this additional package is combined with from about 80 to about 95 weight percent of the above-described metal-containing dispersion to prepare, typically, a final coating composition of particulate zinc plus aluminum flake. Even when made as a package formulation, the final coating composition has highly desirable storage stability. This conforms to the silane binding ability to protect the particulate metal from deleterious reaction with other compositional ingredients during prolonged storage. This extended shelf stability was unexpected, due to the recognized reaction problems of particulate metal in water reducible systems, e.g., gasification of aqueous compositions containing particulate zinc. However, even after storage as a single package, the compositions of the present invention can be unpacked, prepared for coating application as by strong agitation, then easily applied. The resulting coatings can have the desirable corrosion resistance, and often the other coating characteristics, of the applied coatings of freshly prepared compositions. When a bath of the coating composition has been prepared, it has been found desirable to age this mixture. Aging can help provide better coating performance. Usually, the aging of the mixture will be for at least 1 hour, and advantageously for at least about 2 hours to about 7 days, or more. Aging for less than 1 hour may be insufficient to develop desirable bathing characteristics, while aging longer than 7 days may be uneconomic. The final coating composition, either freshly prepared or after storage, may be applied through various techniques, such as immersion techniques, including immersion drainage and immersion spinning processes. When the parts are compatible therewith, the coating can be applied by curtain coating, brush coating or roller coating and including combinations of the above. It is also contemplated to use spray technique as well as combinations, e.g., spraying and spinning and brush and brush techniques. Coated articles that are at an elevated temperature can be coated, often without extensive cooling, by a process such as immersion spinning, immersion drainage or spray coating.

The protected substrate can be any substrate, e.g., ceramic substrate or the like, but is more particularly a metal substrate such as zinc or iron, e.g., steel substrate, an important consideration being that any of said Substrates support the thermal cure conditions for the coating. By a "zinc" substrate is meant a substrate of zinc or zinc alloy, or a metal such as steel coated with zinc or zinc alloy, as well as a substrate containing zinc in intermetallic mixture. Also, the substrate iron may be in alloy or intermetallic mixing form. Especially when these are metal substrates, which are more usually ferrous substrates, these can be pretreated, eg, by chromate or phosphate treatment, before the application of the lower coating. In this way, the substrate can be pretreated to have, for example, a coating of iron phosphate in an amount of about 50 to about 100 mg / 0.0929 square meters or a coating of zinc phosphate in an amount of about 200. to approximately 2,000 mg / 0.0929 m2. After the application of the coating composition to the substrate, it is preferred for better corrosion resistance to heat cure the applied coating subsequently. However, the volatile coating substances can initially simply evaporate from the applied coating, e.g., drying prior to curing. The cooling after drying can be eliminated. The temperature for said drying, which may also be referred to as procured, may be within the range of about 38SC (100aF) to not substantially greater than about 121SC (250BF). The drying times can be of the order of about 2 to about 25 minutes. For substrates containing applied coating composition, subsequent curing of the composition on the substrate will usually be curing in a hot air oven, alth other methods of curing, eg, infrared baking and induction curing can be used. The coating composition will be thermally cured at an elevated temperature, e.g., of the order of about 232SC (4509F), but usually higher, of furnace air temperature. Curing typically will provide a substrate temperature, usually as a peak metal temperature, of at least about 232 ° C (450 ° F). Furnace air temperatures may be higher, such as of the order of 343 ° C (650 ° F), but for economy, the substrate temperature need not exceed about 232eC (4509F). Curing, such as in a hot air convection oven, can be carried out for several minutes. Even th curing times may be less than 5 minutes, they are more typically in the order of about 10 to about 40 minutes. It is to be understood that curing times and temperatures can be effected when more than one coating is applied or when a higher heat-cured coating is used subsequently. Thus, cured shorter time and lower temperature can be used when it will apply one or more additional coatings or a top coat that proceeds through a high temperature bake to a longer cure time. Also, when more than one thermally curable coating or topcoat is applied to be applied, the first coating, or lower coating, may only need to be dried, as discussed above. The curing can then proceed after the application of a second coating, or of a thermally cured top coat. The resulting weight of the coating on the metal substrate can vary to a considerable degree, ... J¡2 = rlf but will always be present in an amount that supplies more than 500 mg / 0.0929 m2 of coatingA smaller amount will not lead to desirably improved corrosion resistance. Advantageously, a coating of more than about 1,000 mg / 0.929 m2 of coated substrate will be present for better corrosion resistance while more typically between about 2,000 to 5,000 mg / 0.929 m2 of coating will be present. In this coating, it will generally be present from about 400 mg / 0.29 square meters to about 4,500 mg / 0.929 square meters of particulate metal. prior to use, the coated substrate may be coated in a superior form, eg, with a silica substance. The term "silica substance", as used herein for the top coating, is intended to include both silicates and colloidal silicas. Colloidal silicas include both those that are solvent-based as well as aqueous systems, with colloidal silicas based on water being more advantageous for economy. As is typical, these colloidal silicas may include additional ingredients, e.g., thickeners such as, for example, up to about 5 weight percent of a water soluble cellulose ether discussed above. Also, a smaller amount, v, gr. 20 to 40 weight percent and usually a minor amount of the colloidal silicas may be replaced by colloidal alumina. In general, the use of the colloidal silicas will provide heavier top coatings of silica on the substrate materials with the bottom coating. It is contemplated to use colloidal silicas containing up to 50 weight percent solids, but typically much more concentrated silicas will be diluted, for example, when spray application of the top coat will be used. When the upper coating silica substance is silicate, it may be organic or inorganic. Useful organic silicates include alkyl silicates, e.g., ethyl, propyl, butyl and polyethyl silicates, as well as alcosyl silicates such as monoethyl silicate ethylene glycol. More generally by economics, the organic silicate is ethyl silicate. Advantageously, the inorganic silicates are used for better economy and performance of corrosion resistance. These are typically used as aqueous solutions, but solvent-based dispersions can also be used. When used herein with reference to silicates, the term "solution" is intended include true solutions and hydrosols. The preferred inorganic silicates are the aqueous silicates which are the water soluble silicates, including sodium, potassium, lithium and sodium / lithium combinations, as well as other related combinations. With reference to sodium silicate as representative, the molar ratios of Si02 to Na20 generally vary between 1: 1 and 4'1. For better efficiency and economy, an aqueous-based sodium silicate is preferred as the silica substance. The use of silica substance as a top coating has been described in the U.S. Patent. No. 4,365,003, the disclosure of which is incorporated herein by reference. Other ingredients may be present in the top coating composition of silica substance, e.g., wetting and coloring agents, and the composition may contain chromium substituents if desired, but may be free of chromium as defined in what foregoing to provide a completely chromium free coating. Substances that may be present may also include thickening agents and dispersants as well as pH adjusting agents, but all of these ingredients will typically not add more than about 5 weight percent, and usually less, of the coating composition.

In order to provide improved stability of coupled coating composition with increased coating integrity. The top coating of silica substance can be applied by any of the various techniques described above for use with the coating composition, such as immersion techniques including dip-dipping and dip-spinning processes, by any method of For coating, the top layer must be present in an amount greater than about 50 mg / 0.929 m2 of coated substrate. By economy, the top coating weights for cured top coatings shall not exceed approximately 2,000 mg / 0.929 m2. 15 coated substrate. This scale is for the top coating of cured silica substance. Preferably, for better coating efficiency and economy of top coating of silica substance, the top coating is a silicate 20 inorganic that provides from about 200 to about 800 mg / 0.929 m2 of top coat of cured silicate. For the curing of the top coating of silica substance, it is typical to select the 25 curing conditions in accordance with the substance of Maüüá ÉMMhi particular silica used. For colloidal silicas, air drying may be sufficient; but for efficiency, curing at elevated temperature for all silica substances is preferred. Curing at elevated temperature may be preceded by drying, such as air drying. Independently of the above drying, a lower curing temperature, v.gr .. of the order of about 66aC (150aF) to about 149aC (3002F), will be useful for the colloidal silica and 10 organic silicates. For inorganic silicates, curing typically occurs at a temperature in the range of about 149aC (300aF) to about 2609C (500aF). In general, curing temperatures range from about 66aC (150aF) to about 15 427SC (800aF) or higher, such as peak metal temperatures, may be useful. At higher temperatures, curing times can be as fast as about 10 minutes, even when longer curing times, up to about 20 minutes, are longer. 20 usual. Also, the articles can be coated in a superior manner with the higher coating of silica substance while the articles are at elevated temperature, such as from the curing of the water-reducible coating composition. This 25 could be done by spray coating or It is also drained by immersion, that is, an immersion of the article at elevated temperature towards the top coating composition, which can provide rapid cooling of the article. Upon removal of the top coating composition, the article may be drained. Some or all of the top coating cure may be achieved by the operation. Before use, the substrate coated with the coating of the water reducible coating composition may also be coated. up further with any other suitable topcoat, i.e., a paint or primer, including electrocoat primers and weldable primers, such as zinc-rich primers that can typically be applied prior to electrical resistance welding. For example, it has already been shown in the U.S. Patent. No. 3,671,331 that a top coating of a primer containing an electrically conductive particulate pigment, such as zinc, is highly useful for a metal substrate that is first coated with another coating composition. Other top-coat paints may contain pigment in a binder or may be non-pigmented, e.g., generally cellulose lacquers, resin varnishes and oleoresin varnishes. as for example tung oil varnish. The paints can be reduced with solvent or can be reduced in water, eg, latexes or water soluble resins, including modified or soluble alkyds, or the paints can have reactive solvents such as in polyesters or polyurethanes. Additional suitable paints that may be used include oil paints, including phenolic resin paints, solvent reduced alkyls, epoxies, acrylics, vinyl, including polyvinyl butyral, and oil-wax type liners such as linseed oil paints. paraffin wax Of particular interest, the substrate coated with the coating from the water-reducible coating composition can form a particularly suitable substrate for paint deposition by electrocoating. The electrodeposition of film forming materials is well known and may include electrocoating of simply a film-forming material in a bath or such a bath which may contain one or more pigments, metal particles, drying oils, dyes, spreaders and the like, and the bath can be a dispersion or ostensible solution and the like. Some of the well-known resinous materials useful as film-forming materials include polyester resins. alkyd resins, acrylate resins, hydrocarbon resins and epoxy resins, and said materials may be reacted with other monomers and / or organic polymers including hydrocarbons such as ethylene glycol, monohydric alcohols, ethers and ketones. Also of interest are polycarboxylic acid resins which can be solubilized with polyfunctional amino compounds and include drying oils-modified polybasic acids, esters or anhydrides which can be further reacted with divinylbenzene for example or acrylic acid and esters as well as vinyl monomers polymerizable. In addition, the substances of interest are the anodically deposited film-forming materials. However, the broad scope to which the electrodeposition of film-forming materials relates, includes the deposition of said materials on anodic or cathode substrates, and by means of various techniques for passage of current through a bath. After electrodeposition and removal of the coated substrate from the bath, curing of the film-forming materials can be performed. The curing time and temperature will depend on the film-forming materials present, but is typically an air cure at room temperature or a forced cure at a temperature of up to 260SC (500aF) and for times up to 60 minutes., at lower temperatures. An additional top coating of special interest is a coating applied by rapid cooling coating. In this way the substrate coated with the coating from the water-reducible coating composition can proceed to a coating by rapid cooling, eg, following thermal cure of the water-reducible coating, as mentioned above , for higher coatings of silica substance. This rapid quenching of articles at elevated temperature by bringing them into contact with an aqueous resin solution has been discussed in Japanese Patent Application No. 53-14746. Suitable resin solutions include alkyd, epoxy, melamine and urea resins. For this, it has also been taught, for example in the U.S. Patent. No. 4,555,445, that the appropriate topcoat compositions can be pigmented dispersions or emulsions. These may include copolymer dispersions in liquid medium as well as aqueous emulsions and dispersions of appropriate waxes. The articles may receive top coating in these compositions, the articles of which are at elevated temperature such as after the curing of the water reducible coating applied, by methods including a dip-dipping or a spray coating operation. By means of said fast cooling coating operation, all the curing of the upper coating can be achieved without additional heating. The fast cooling coating with solutions, emulsions and polymer dispersions, and with heated baths, has also been discussed in the U.S. Patent. No. 5,283,280. Another top coating of particular interest is the autodeposited coating. The autodeposition of coatings provides a latex-based coating film on metal articles, without external voltage applied in the process. In the patent of E.U.A. No. 3,592,699, it is taught to apply a coating from a bath of appropriate polymer latex, oxidizing agent, fluoride ion and acid sufficient to maintain a pH of about 2.5 to 3.5, Formulated as said acidic composition, the bath can use dissolution of metal as a driving force for coating deposition. More recently, the Patent of E.U.A. No. 5,300,323 has taught a pretreatment of zinc surface with a solution of aqueous hydrogen fluoride containing an additive such as boric acid. This can help to deny the formation of tiny holes during the autodeposition coating. Before coating, it is in most cases advisable to remove foreign matter from the substrate surface, such as by thorough cleaning and degreasing. Degreasing can be achieved with known agents, for example, with agents containing sodium metasilicate, caustic soda, carbon tetrachloride, tricoloroethylene and the like. Commercial alkaline cleaning compositions that combine washing and mild abrasive treatments can be used for cleaning, v.gr ,, an aqueous cleaning solution of trisodium phosphate-sodium hydroxide. In addition to cleaning, the substrate can be subjected to cleaning plus chemical attack, or cleaning plus shot blasting. The following examples show ways in which the invention can be practiced, but should not be considered as limiting the invention. In the examples, the following procedures have been used: PREPARING TEST PANELS Unless specifically described otherwise, the test panels are low carbon, cold rolled steel panels. Steel panels can be prepared for coating by first dipping in a cleaning solution. A metal cleaning solution may contain 155.52 grams, per 3,785 liters of water, of a mixture of 25 weight percent tripotassium phosphate and 75 weight percent potassium hydroxide. This alkaline bath is maintained at a temperature of about 55aC to 82aC (150aF to 180aF). Following the cleaning solution, the panels can be rubbed with a cleaning pad, which is a fibrous, porous pad of synthetic fiber impregnated with an abrasive. Next, the rubbed panels are rinsed with water and again immersed in cleaning solution. After removal of the solution, the panels are rinsed with running water and preferably dried.

APPLICATION OF COATING TO TEST PARTS AND COATING WEIGHT Unless otherwise described in the examples, the cleaned parts are typically coated by immersion in the coating composition, the excess composition thereof is removed and drained, sometimes with a gentle stirring action, and then baked immediately or air-dried at room temperature or precured at modest temperature until the coating is dry to the touch and then baked. Baking and precuring continue in a hot air convection oven at temperatures and with times as specified in the examples. The coating weights for panels, generally expressed as weight per unit surface area, are typically determined by selecting a panel of known surface area and weighing it before coating. After the panel has been coated, it is weighed again and the coating weight per selected unit of surface area, almost always presented as milligrams per 0.0929 square meters (mg / 0.0929 m2, is taken to a direct calculation.

COATING ADHESION TEST This test is conducted by manually pressing a strip of tape coated with a pressure sensitive adhesive against the coated surface of the test panel, which tape is then quickly removed. The coating evaluates qualitatively in accordance with the amount of coating removed by the adhesive on the tape, compared to the condition of a conventional test panel.

CORROSION RESISTANCE TEST (ASTM B117) AND CLASSIFICATION The corrosion resistance of coated parts is measured by the conventional salt spray (fog) test for ASTM B-117 paints and varnishes. In this test, the parts are placed in a chamber maintained at a constant temperature where they are exposed to a fine mist (fog) of a 5 percent salt solution for specified periods of time, rinsed in water and dried. The extent of corrosion of the test parts can be expressed as a percent of red rust.

EXAMPLE 1 To 18.9 parts by weight of deionized water, 3 parts by weight of gamma-glycidoxypropyltrimethoxysilane and 0.6 part by weight of orthoboric acid are mixed with moderate stirring as mixing continues. After the mixing is continued for 3 hours, an additional 29.2 parts by weight of deionized water and a wetting mixture containing 1.5 parts by weight of a nonionic, nonionic ("nen") nonylphenol humectant having an molecular weight of 396 and a specific gravity of 1.0298 at 20 / 20sC and 1.5 parts? n weight of a nenw having a molecular weight of 616 and a specific gravity of 1.057 at 20 / 20sC. To this mixture are then added 2 additional parts by weight of the aforementioned silane, 4.1 parts by weight of acetone and 0.7 parts by weight of 1-nitropropane. To this mixture 35.2 parts by weight of zinc flake paste are added. Zinc in flake form had a particle thickness of approximately 0.1 to 0.5 microns and a longer dimension of discrete particles of approximately 80 microns. The sum of all these ingredients is then ground for about 3 hours using a Cowles dissolver operating at approximately 960 revolutions per minute (rpm). To the resulting milled mixture, is then added, while stirring is continued for 1 hour, 0.4 part by weight of sodium bistridecyl sulfosuccinate anionic surfactant and mixing then further continued overnight to prepare a test coating bath. This bath is aged for 6 days and then 2.9 parts by weight of additional gamma-glycidoxypropyltrimethoxysilane is added, with mixing. This resulting coating composition had a molar ratio of water to alkoxy silane groups of 26.7: 1. Clean test panels of 7.62 x 12.70 cm (3 x 5 inches) as described above were then coated in the manner also described above, the panels being separated from the coating composition at a rate of 7.62 centimeters. (3 inches) per minute. Each panel is precured for 10 minutes at a furnace air temperature of 66aC (1502F) and cured for 30 minutes at a furnace air temperature of 316aC (600F), all in the manner as described above. All the resulting panels had a gray, smooth coating of attractive appearance. A representative panel was then subjected to the corrosion resistance test described above. After 96 hours of testing, the panel was removed from the test. The panel exhibited no visible red rust. Another panel having a coating weight for the panel, determined as described above, of 2.408 mg / 0.929 m2 was then subjected to the coating adhesion test described above. The panel was found to have acceptable coating adhesion. For shelf stability test, the resulting coating composition was stored for 8 days at room temperature in a covered container. This totaled 14 days of aging for the test coating composition when the 6 days of aging mentioned above are added. After these additional 8 days, the bath stability was checked by visual inspection and by shaking, as well as by panel coating. The bath stability was found to be acceptable during both visual inspection and agitation. In addition, a coated panel having a coating weight of 2,121 mg / 0.0929 m2, determined in the manner described above, and subjected to the coating adhesion test also described above, exhibited desirable coating adhesion.

EXAMPLE 2 The preparation of coating composition of Example 1 was repeated, except that, as an initial change, the humectant mixture contained 0.7 part by weight of the molecular weight humectant of 396 and 0.9 parts by weight of the 616 molecular weight humectant A subsequent change was the use of 32.4 parts by weight of dry zinc flake, instead of zinc paste. Finally, after the 6-day aging, together with the addition of 2.9 parts by weight of hydroxypropylmethylcellulose thickener as an optional ingredient, The resulting coating composition had a molar ratio of water to alkoxy silane groups of 29: 1. Clean test panels of 7.62 x 12.7 cm (3 x 5 inches) as described above were then coated by pouring coating composition onto the panels and then pulling down a pull bar downwardly wound with wire on the face of the panel. coated panel to provide a uniform coating. Each panel was pre-heated for 10 minutes at an oven temperature of 66SC (150aF) and cured for 30 minutes at an oven air temperature of 3169C (600eF), all in the manner described above. All the resulting panels had a gray, smooth, attractive appearance coating. A representative panel was then subjected to the coating adhesion test described above. It was found that the panel exhibits acceptable coating adhesion. For shelf stability test, the bath was stored for approximately 21 days at room temperature in a covered container. After 21 days, the stability of the bath was checked by visual inspection and by shaking, as well as by paneling. It was found that the bath stability is acceptable both in visual inspection and agitation. In addition, a coated panel subjected to the corrosion resistance test described above exhibited corrosion resistance comparable to freshly prepared bath coatings. In addition, a coated panel subjected to the test of ^^^^^^ coating adhesion was found to exhibit desirable coating adhesion.

Claims (1)

1. CLAIMS 1. - A stable and water-reducing coating composition, free of chromium and free of resin for application to, and thermal curing on a substrate to provide corrosion protection thereto, the composition comprising: (A) water in an amount supplied from about 20 to about 70 weight percent of the coating composition; (B) low boiling organic liquid; (C) particulate metal; (D) organofunctional silane binder, water reducible, containing alkoxy groups, whose silane binder contributes from about 3 to about 20 weight percent of the coating composition; and (E) wetting agent; and with the proviso that the coating composition has a molar ratio of water to alkoxy silane groups of more than 4.5: 1. 2. The coating composition according to claim 1, wherein the water is present in an amount greater than about 25 weight percent of the coating composition and the composition has a molar ratio of water to higher alkoxy silane groups. to around 5: 1. 3. The coating composition according to claim 1, wherein the composition has a pH within the range of more than 6 to about 7.5, contains water in an amount greater than about 30 weight percent and has a molar ratio of water to alkoxy silane groups greater than about 6: 1. 4. The coating composition according to claim 1, wherein the organic liquid is present in an amount of from about 1 to about 30 weight percent, weight basis of total composition, and the low boiling organic liquid. it is selected from the group consisting of low molecular weight alcohols, water soluble ketones, acetone and mixtures thereof. 5 - The coating composition according to claim 1, wherein the particulate metal is a metal powder, a metal flake, or a mixture of metal powder and metal flake, the metal powder has particle size such that all powders are more finely divided than 100 mesh, and the particulate metal is one or more of zinc, aluminum, alloys and intermetallic mixtures of zinc or aluminum, and mixtures of the foregoing. 6. The coating composition according to claim 1, wherein the composition contains from about 1.5 to about 35 weight percent particulate flake, total composition weight basis, and is at least substantially free of charge. particulate metal powder 7 - The coating composition according to claim 1, wherein the silane is a silane reducible in water, non-gelation and has organofunctionality of one or more of vinyl, metacploxy, ammo, epoxy or mixtures thereof . 8. The coating composition according to claim 7, wherein the silane is a silane reducible in water, epoxy functional, the silane is one of, or a mixture containing beta- (3,4-epoxycyclohexyl) et il trimethoxy silane, 4 (grimetoxysilyl) butane-1. 2 epoxide, and gamma-glycidoxypropyltrimethoxysilane and the silane is present in an amount of from about 5 to about 15 weight percent, total weight basis of composition. 9. The coating composition according to claim 1, wherein all the ingredients (A), (B), (C), (D), and (E) are present in a package. 10. The coating composition according to claim 1, wherein the composition contains from about 0.01 to about 3 weight percent of the wetting agent, total composition weight basis, and the wetting agent is nonionic wetting agent, anionic wetting agent and wetting agent mixture. 11. The coating composition according to claim 1, which further contains about 0.05 to about 2.0 weight percent thickener, base total weight of composition, and the thickener is selected from the group consisting of cellulosic thickener, xanthan gum, modified clays, association thickeners and their mixtures. 12. The coating composition according to claim 11 containing from about 0.2 to about 1.2 weight percent thickener, and the thickener is cellulosic thickener selected from the group consisting of hydroxyethylcellulose, methylcellulose, methylhydroxypropyl- cellulose, and ilhydroxyethylcellulose, methylethylcellulose, and mixtures thereof. 13. - The coating composition according to claim 1, which further contains from about 0.1 to about 10 weight percent of boric acid component, total weight basis of composition, with the boric acid component being selected from the group which consists of orthoboric acid, metaboric acid, tetraboric acid and boron oxide, as well as mixtures thereof. 14. The coating composition according to claim 1, wherein the composition additionally contains from about 0.1 to about 2.0 weight percent of a corrosion inhibitor, based on the total weight of the composition, with the corrosion inhibitor being selected from the group consisting of calcium nitrate, dibasic ammonium phosphate, calcium sulfonate, 1-nitropropane lithium carbonate, and mixtures thereof, 15. The coating composition according to claim 1, which also contains liquid high boiling organic and the high boiling organic liquid is an oxohydroxy liquid selected from the group consisting of tri- and tetraethylene glycol, di- and tripropylene glycol, the monomethyl, dimethyl and ethyl ethers of these glycols, liquid polypropylene glycols, diacetone alcohol, the low molecular weight ethers of diethylene glycol and mixtures thereof. 16. A coated substrate protected with a corrosion-resistant, chromium-free coating of the coating composition according to claim 1, which contains particulate metal, the coating of which is established on the substrate in an amount that provides about 500 to about 5,000 mg / 0.0929 m2 of cured coating on the substrate, the coating containing the particulate metal in an amount of about 400 to about 4,500 mg / 0.0929 2 of cured coating, the coating of which is thermally cured on the substrate heating at a temperature within the range of about 2049C (400SF) to about 343aC (650aF) for a time of at least about 5 minutes. 17. The coated substrate according to claim 16, wherein the coated substrate is further coated with an upper coating. 18. The coated substrate according to claim 17, wherein the coated substrate is further coated with an upper coating composition substantially free of resin, curable to a water resistant protective coating and containing silica in a liquid medium. , whose top coating is applied in an amount sufficient to provide more than about 50 mg / 0.0929 m2 of substrate coated with silica in cured coating. 19. The coated substrate according to claim 18, wherein the topcoat is cured by heating at a temperature within the range of about 66aC (150SF) to about 538aC (1,000aF) for a time of at least about 10 minutes, the top coating provides substantially no more than about 2,000 mg / 0.0929 m2 of the silica substance in the cured coating, and the top coating provides silica substance of one or more of colloidal silica, organic silicate and inorganic silicate . 20. The coated substrate according to claim 17, wherein the coated substrate is further coated further with a topcoating composition of one or more electrocoat primer, autodeposition coating or topcoat of quickcoat coating. 21. The method for preparing a coated corrosion-resistant substrate protected with a coating of a water-reducing, chromium-free coating composition containing particulate metal, which method comprises applying as the coating composition the coating composition that contains particulate metal according to claim 1, in an amount sufficient to provide, after curing, from about 500 to about 5,000 mg / 0.0929 m2 of cured coating on the coated substrate, and curing the coating composition applied on the substrate at a temperature of up to about 343aC (650SF ) for a time of at least about 5 minutes. 22. The method for preparing the water-reducing, chromium-free coating composition according to claim 1, for applying to, and thermal curing on, a substrate for providing corrosion resistance thereto, which method comprises first preparing a premix by mixing together a mixture comprising silane binder with one or more of organic liquid and water, then mixing particulate metal with the resulting premix.