WO2025154062A1

WO2025154062A1 - Corrosion protective formulations

Info

Publication number: WO2025154062A1
Application number: PCT/IL2025/050049
Authority: WO
Inventors: Roi PERETZ; Galit VERED PARVARI; Jonathan WOLF ABRAMCZYK; Tomer HILLEL; Hagai HADAS
Original assignee: Coreteel Technologies Ltd
Current assignee: Coreteel Technologies Ltd
Priority date: 2024-01-17
Filing date: 2025-01-15
Publication date: 2025-07-24
Anticipated expiration: 2026-07-17

Abstract

The present disclosure concerns formulations for protecting metal surfaces from corrosion. More specifically, this disclosure concerns liquid formulations that form one or more layers of protection against corrosion on metallic surfaces, the formulation comprising at least one first antioxidant, at least one metal ion complexating agent, and optionally at least one second antioxidant.

Description

Corrosion protective formulations

TECHNOLOGICAL FIELD

The present disclosure concerns formulations for protecting metal surfaces from corrosion. More specifically, this disclosure concerns formulations that form one or more layers of protection against corrosion on metallic surfaces.

BACKGROUND ART

References considered to be relevant as background to the presently disclosed subject matter are listed below:

- US 3,547,710

- JP 2002/105393

- US 8,926,867

Jaramillo et a!.. Progress in Organic Coatings 2019, 135, 191-204

Ghazi et al., Journal of Bio- and Tribo-Corrosion 2022, 8, 31

Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.

BACKGROUND

Metal surfaces, typically iron or simple steel alloys (e.g. carbon steels), are known to be prone to oxidation processes upon exposure to various environmental conditions. In many cases, this oxidation leads to corrosion of the metal. Metals are commonly used in engineering structures which may be constantly exposed to harsh environmental conditions. While expected to maintain their structural integrity over long periods, even exposure to milder conditions can cause corrosion, which leads to structural and mechanical degradation. Depending on the metal and the conditions in which it was exposed, chemical reactions with various species in the environment (such as water, oxygen-containing molecules, etc.) may lead to irreversible structural and mechanical damage to the engineering element. A prime example of a chemical product of such a reaction is “red rust”, Fe2C>3 and its hydrates, which is not strongly bound to its parent metal bulk and not only leads to eventual mass loss as it detaches, but is also permeable to further corrosion promoting species and therefore enables the corrosion process to proceed further into the base metal.

However, not all metal oxides are detrimental to the protection of the base metal. In some cases such metal oxides are considered, with or without additional elements (such as hydrogen or others) in various possible compound stoichiometries, to be protective oxides since they are both relatively strongly bound to the parent metal and are relatively impermeable to many corrosion promoting species. Thus, the presence of protective oxides can assist in slowing down the rate of corrosion processes and/or reducing the extent of corrosion-induced damage. A notable example of a protective oxide in aluminum is alumina, AI2O3; similarly, protective oxides in ferrous metals and their alloys are a series of oxyhydroxides, such as goethite (a-FeOOH) and lepidocrocite (y-FeOOH). These latter are found in weathering steels (such as Cor-ten), which are intrinsically alloyed to promote the formation of such oxides. Another alloying technique is used to create stainless steels, in which alloying metals (often chromium) within the steel undergo oxidation to create protective oxides (such as chromium oxides).

While stainless steel and weathering steel enable higher resistance to corrosive conditions, such steels are significantly more expensive than simpler carbon steels, and hence have drawbacks for large scale engineering uses. Furthermore, the type of environment in which they can be set might be limited by the presence of various chemical species, such as chlorides (seashore or marine environments) in the case of many weathering steels.

Other than alloying, various means to minimize the corrosive oxidation of metal surfaces have been suggested and used. One example is coating the surface of the metal with one or more topcoats, for example paint layers, that can form a barrier against various corrosion-inducing environmental species. However, maintaining the integrity of such paint layers is difficult, especially over time and challenging environmental conditions. Once damaged, for example locally scratched, eroded or peeled, the protection of the underlying metal surface is significantly hampered. Further, the application of these topcoats typically requires a tedious process of surface preparation that involves the removal of previous coating layers and oxide layers (which may require mechanical abrasion such as sand-blasting, and/or chemical abrasion such as the use of strong acids), applying of several coats of paint (usually also requiring priming the surface before painting) - all of which are lengthy and costly processes, which need to be repeated periodically.

Another technique, which is typically locally applied over small surfaces which have already been at least partially corroded, is the use of “rust converters”. Rust converters are formulations that convert certain iron oxides into other chemical species. Such converters typically have a limited protection effect as these may not sufficiently penetrate the entire corrosion layer. Further, as rust converted products may be permeable to various corrosion-inducing species and susceptible to being washed-off or abraded-off the surface, their application on engineering structures, such as structural frames, roofing, cladding boards, etc., which are constantly exposed to high humidity, fog, rain, snow or marine conditions, often proves insufficient to provide effective protection from continued corrosion. Hence, such formulations are often used as a basic layer applied to small surface regions, onto which additional paint or barrier layers need to be applied in order to provide longer-term protection from further or continued corrosion. Moreover, such formulations often contain harmful and/or toxic materials as their main components, such as strong acids, which are detrimental to the environment and unsuitable for prolonged human exposure, e.g. by personnel applying these materials on a daily basis.

Other, more complex treatments, including galvanizing or electroplating, typically require specialized equipment and utilization of often toxic and/or carcinogenic components, and in some cases require considerable energy investment, such as heating. Many of these treatments are highly expensive.

It would therefore be beneficial to provide formulations that can form an effective protective layer on metal surfaces, which do not require prior substantial surface preparation, provide surface protection for a prolonged period of time even upon exposure to corrosive conditions, and are environmentally and personnel friendly.

GENERAL DESCRIPTION

The present disclosure provides liquid formulations which are based on synergistic combinations of components, predominantly environmentally friendly components. The formulations are tailored to be easily applied onto metal surfaces in a variety of standard technique applications, without the requirement for prior, intensive surface preparation. The components of the formulations, when combined in the manner disclosed herein, were surprisingly found to provide synergistic activity for significant reduction of the corroding oxidative processes and provide effective building of a protective barrier layer against corrosion on metal surfaces, primarily ferrous metals. The formulations create protective layers which effectively hinder the diffusion of corrosion promoting species (CPS) towards the base metal, and/or considerably reduce the rate at which these CPS further corrode the metal, even when applied to surfaces which have already undergone oxidative corrosion, without the need to fully remove previously existing corrosion layers before applying the liquid formulations of this disclosure.

While in typical rust converters strong acids are used for decomposing metal oxides, such as red rust, and to release iron ions from the surface, the present formulation utilizes environmentally friendly mild components.

Thus, by a first of its aspects, the present disclosure provides a liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises at least one first antioxidant and at least one metal ion complexating agent, the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20.

By another aspect, the present disclosure provides a liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises at least one first antioxidant, at least one second antioxidant, at least one metal ion complexating agent, the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20, and the weight ratio between the at least one first antioxidant and the second antioxidant ranges between about 10: 1 and about 1 : 10, the at least one first antioxidant and at least one second antioxidant differing in standard reduction potentials by at least about 20 mV.

The formulations of this disclosure are designed for application over metal surfaces, e.g. pure metals or metal alloys. The metals are typically those used for engineering purposes, e.g. structural metals and metal alloys. The metal can be, for example, a ferrous metal or ferrous alloy, aluminum or aluminum alloys, nickel alloys, magnesium alloys, etc.

According to some embodiments, the metal surface is a ferrous metal surface. The term ferrous metal(s) means to denote iron (Fe) or iron-based alloys, typically alloys for which iron is the predominant component. The term means to encompass pure iron, crude iron, wrought iron, cast steel, carbon steel, or any iron-based alloy.

According to some other embodiments, the metal surface is an aluminum metal surface. The term aluminum metal(s) means to denote aluminum (Al) or aluminum-based alloys, typically alloys for which aluminum is the predominant component.

As noted, exposure of metal surfaces to various conditions can result in structural or mechanical degradation due to the formation of various oxides on the surface. Within the context of the present disclosure, the term corrosion promoting species (CPS) will be used to denote various chemicals which enhance the rate and/or severity of this degradation, and these include, but are not limited to, water (either by direct contact with the fluid or by humidity), ions (such as chlorides), electrolytes, acids, bases, sulfur oxides, and various forms of oxygen or reactive oxygen species. The term reactive oxygen species (ROS) means to denote atoms or molecules containing at least one oxygen atom in a form which renders them highly reactive in chemical reactions, particularly oxidation of metals, metal oxides and salts, and/or organic molecules. ROS may include, but are not limited to, singlet molecular oxygen, superoxide anions and radicals, hydroxyl radicals, alkoxyl radicals, peroxyl radicals, peroxides (such as hydrogen or hydrogen or alkyl peroxides), and nitrous oxide.

The formulation is based on synergistic combinations of antioxidants and metal ion complexating agents, that promote the formation of a protective layer against corrosion on the surface of the metal. An antioxidant is a chemical species that reacts with ROS to produce less reactive species, or interferes with, or slows redox reactions by other mechanistic routes, such as reacting with intermediates or by-products of the oxidation process. Such interference or rate reduction of the oxidation process slows or prevents ROS from reacting with the metal in a manner destructive to the metal. Compared to the metal ion complexating agents, as will also be elaborated hereinbelow, the antioxidant has a significantly reduced capability of complexating with metal ions.

For example, within the context of the present disclosure when applying onto ferrous metals, antioxidants interfere in the redox reaction between iron and molecular oxygen and/or other ROS in the presence of water and/or other CPS. Further, depending on the formulation, the combination of antioxidant(s) and metal ion complexating agent promote decomposition of non-protective iron oxides and their hydrates, thereby rendering iron ions (Fell and Felll) available for further chemical reactions, such as complexation into an organic layer (such as tannate-Fe complexes) over the metal surface, which reduces the diffusion rate of incoming CPS. Further, the presence of the antioxidant(s) and metal ion complexating agent may promote the formation of protective oxides, for example by reducing the activation energy barrier for their formation.

In the context of the present disclosure, the term protective oxide will refer to a stable metal oxide, including oxyhydroxides, with varying degrees of hydration and stoichiometries, formed onto the surface of the metal, and is substantially impermeable to CPSs.

For aluminum metals, and more importantly for ferrous metals and alloys thereof, of the above-described mechanisms are of importance for protection against corrosion especially in challenging corrosive environments (such as those containing chlorides), for example the formation of a layer which serves as a barrier to reduce the diffusion of these CPS towards the underlying metal surface.

Applicant has surprisingly found that a synergistic activity for forming a protective layer over a metal surface can be obtained when combining at least one first antioxidant with at least one metal ion complexating agent (and, at times, also with a second antioxidant) at defined ratios.

In the context of the presently disclosed formulations, synergy (or synergism) refers to improved performance (as compared with the performance/or activity of each component alone) in one or more, typically two or more of the following characteristics of the metal surface due to application of the formulation: (i) reduced weight loss of the metal, (ii) reduced variability in weight loss (e.g. smaller standard deviation across multiple samples or test areas), (iii) reduced number of sites per surface area in which damaging corrosion has developed following a given exposure time, (iv) reduced surface area percentage which displays damaging corrosion products, and/or (v) reduced pitting, corrosion penetration and/or advance into the bulk of the metal.

According to some embodiments, the synergy provides improved performance in any combination of two or more of said characteristics.

Without wishing to be bound by theory, the synergism permits the occurrence of several reactions, occurring substantially in parallel after application of the formulation onto the metal surface. One of these reactions is the release of metal ions from the metal’s surface or from already existing metal oxides on the surface. These metal ions (e.g. iron ions) can be complexated with the one or more metal ion complexating agents. The soluble complexation products can be removed from the surface, thus exposing more of the metal surface to the antioxidants in the formulation, now continuing the same reactions or other reactions. The water insoluble complexation products can settle over time as a protective layer onto the surface, building up a diffusion-reducing barrier against diffusion of CPS towards the bulk metal. Furthermore, these insoluble complexation products can create, on their own or in combination with other components in the liquid formulation, a barrier layer which reduces the diffusion of the antioxidants away from the surface. This enables maintaining a substantive concentration of antioxidants on or near the surface to prolong their contact with the surface and prevent their washing off.

Another reaction is the catalytic conversion of the metal ions and/or oxides, in the presence of ROS, into species such as oxides and/or oxyhydroxides, that, without wishing to be bound by theory, may serve as protective oxides.

According to some embodiments, the at least one first antioxidant is selected from ascorbic acid, ascorbic acid derivatives (such as methyl-13-(2-(3,4-dihydroxy-5-oxo-2,5- dihydrofuran-2-yl)-2-hydroxyethoxy)propanoate), glutathione, carotenoids, terpenes, curcuminoids, saponins and steroids, bio-molecules and other chemical species with pi- conjugation along an aromatic and/or poly-ene molecular structure, and/or chemical species which enable high stabilization of radicals formed at sites prone to homolytic cleavage of chemical bonds.

According to some other embodiments, the at least one first antioxidant is selected from ascorbic acid, ascorbic acid derivatives (such as methyl-13-(2-(3,4-dihydroxy-5- oxo-2, 5 -dihydrofuran-2-yl)-2-hydroxy ethoxy jpropanoate), 6-hydroxy-2, 5,7,8- tetramethylchroman-2-carboxylic acid, carotenoids, terpenes, curcuminoids, and salts or combinations thereof.

By some embodiments, the at least one first antioxidant is ascorbic acid, an ascorbic acid derivative (such as methyl-13-(2-(3,4-dihydroxy-5-oxo-2,5-dihydrofuran- 2-yl)-2-hydroxy ethoxy jpropanoate), or a salt thereof.

According to some embodiments, the formulation comprises at least about 0.3 wt% of said at least one first antioxidant.

By some embodiments, the formulation comprises between about 0.3 wt% and about 20 wt% of said at least one first antioxidant, for example between about 1 wt% and about 15 wt% of said at least one first antioxidant, between about 1 wt% and about 13 wt% of said at least one first antioxidant, or between about 1 wt% and about 10 wt% of said at least one first antioxidant. According to some embodiments, the formulation comprises between about 2 wt% and about 15 wt% of said at least one first antioxidant, for example between about 3 wt% and about 15 wt% of said at least one first antioxidant, between about 3 wt% and about 13 wt% of said at least one first antioxidant, or between about 5 wt% and about 10 wt% of said at least one first antioxidant. The inventors have found that, in some cases, concentrations higher than 20 wt% of the first antioxidant may lead to decrease in the formulation’s protective capabilities.

The formulation comprises at least one metal ion complexating agent (interchangeably referred to herein in the abbreviated form complexating agent), that reacts with one or more of the metal ions or metal oxides to form a sediment layer onto the metal surface. The complexating agent is chosen to be highly reactive to the metal ion or metal oxide, thereby forming the sediment layer in a relatively short timeframe after application of the formulation onto the metal surface. The sediment layer serves as a preliminary diffusion hindering layer to CPS, thereby reducing the CPS diffusion rate towards the metal surface. Further, the sediment layer can also function to physically entrap the first and/or second antioxidants and possibly sacrificial antioxidants, and hold them in proximity to the metal surface. While the complexating agent may have some antioxidant activity, it is noted that within the scope of the present disclosure, the complexating agent has significantly lower antioxidant activity as compared to the first antioxidant, while having increased complexating capabilities to ionic metal species or neutral metal surfaces.

According to some embodiments, the at least one complexing agent can be selected from polyethers (including crown ethers), polyvinyl alcohols, polysaccharides, polyamines, polyureas, polyvinyl alcohols, acrylates, polyepoxides, polysulfones, polystyrenes, polyesters, polyamides, polyphenols, and/or small chelating molecules (possibly functionalized to assist in the formation of a bound macro-sized layer), such as aminopolycarboxylates (e.g. EDTA), iminodisuccinic acid (IDS), S,S-ethylenediamine- N,N'-disuccinic acid (EDDS), L-Glutamic acid N,N-diacetic acids (GLDA), methylglycinediacetic acid (MGDA), nitrilotriacetic acid (NTA), polyaspartic acids, any suitable salt or derivative thereof, and any combinations thereof.

According to some embodiments, the at least one complexing agent is selected from polyphenols. Polyphenols are organic compounds having a plurality of phenolic hydroxyl groups, such as flavonoids (including flavones, flavonols, flavanols, flavanones, isoflavones, proanthocyanidins, anthocyanins), phenolic acids, phenolcarboxylic acids, lignans, etc.

According to some embodiments, the polyphenols are selected from tannins and pseudo-tannins. Tannins are polyphenolic compounds, typically macromolecules, having one or more types of phenolic compound as a repeating unit in their structure. Tannins are usually derived and/or isolated from natural sources, e.g. fruit, seeds, leaves, tree barks, etc., and can complex with various organic and non-organic compounds due to their relatively large number of hydroxyl and/or carboxyl moi eties.

According to some embodiments, the tannins are selected from hydrolysable tannins, phlorotannins, condensed tannins, phlobatannins, and mixtures thereof.

According to some other embodiments, the tannins are selected from hydrolysable tannins, condensed tannins or any mixture thereof.

By some embodiments, the polyphenols are selected from ellagic, gallic, and condensed tannins, and mixtures thereof.

By some embodiments, the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranges between about 10:1 and about 1:10. According to other embodiments, the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranges between about 10:1 and about 1:1. By some other embodiments, the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranges between about 10:1 and about 2:1.

By some embodiments, the weight percent ratio (w/w) between said at least one first antioxidant and said at least one metal ion complexating agent in the formulation is about 10:1, 9.5:1, 9:1, 8.5:1, 8:1, 7.5:1, 7:1, 6.5:1, 6:1, 5.5:1, 5:1, 4.5:1, 4:1, 3.5:1, 3:1, 2.5:1, 2:1, 1.5:1, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, 1:10.5, 1:11, 1:11.5, 1:12, 1:12.5, 1:13, 1:13.5, 1:14, 1:14.5, 1:15, 1:15.5, 1:16, 1:16.5, 1:17, 1:17.5, 1:18, 1:18.5, 1:19, 1:19.5, or even 1:20.

According to some embodiments, the formulation comprises at least 0.1 wt% of said at least one complexing agent. By some other embodiments, the formulation comprises between about 0.1 wt% and about 5 wt% of the at least one complexing agent. By further embodiments, the formulation comprises between about 0.1 wt% and about 3.5 wt% of said at least one ion complexating agent. By some further embodiments, the formulation comprises between about 0.3 wt% and about 3.5 wt% of said at least one ion complexating agent.

It is noted that in other systems, such as in weathering steels, the formation of such protective oxides may take years and decades, depending on the environmental conditions to which the surface is exposed. The presently disclosed formulations were found to surprisingly promote rapid formation of potentially protective oxides due to the synergistic activity of the first antioxidant and the ion complexating agent, and at times also with a second antioxidant. These combinations in the formulations of this disclosure not only promote rapid formation of the potentially protective oxides, but also prolongs the residence of the antioxidants on the surface of the metal, thereby prolonging the capability of the formulation to create protective oxides on the surface.

In the formulations of this disclosure, the second antioxidant is selected to have a higher standard reduction potential than that of the first antioxidant, e.g. at least about 20 mV higher. According to some embodiments, the formulation comprises at least one second antioxidant, typically the first antioxidant and second antioxidant differing in standard reduction potentials by at least about 20 mV, e.g. at least about 50 mV, at least about 100 mV, at least about 150 mV, at least about 200 mV, at least about 250 mV, at least about 300 mV, or even higher.

According to other embodiments, the difference in reduction potentials between the first antioxidant and the second antioxidant ranges between about 20mV and about IV.

The term reduction potential refers to the one-electron transfer standard potential, as used in the field of electrochemistry.

Applicant has surprisingly found that, in addition to combining the first antioxidant with the ion complexating agent, the incorporation of such a second antioxidant can have a significant contribution to the effectivity of the formation of protective oxide/s. Without wishing to be bound by theory, this occurs due to differing reaction kinetics of these two antioxidants with ROS, as the second antioxidant reacts more readily with ROS. Thus, the second antioxidant can provide improved conditions (such as a low concentration of ROS) for the action of the first antioxidant, which reacts to obtain surface protection - such as the conversion of the metal oxides into protective oxides. Due to the differences in their reduction potential, the first antioxidant can also function to restore the second antioxidant over time, thereby effectively rendering the formerly reacted second antioxidant available for new reactions with additional ROS. Hence, a further synergistic relationship can be obtained - the second antioxidant prolongs the active lifetime of the first antioxidant (thereby increasing it capacity to form protective oxides onto the metal surface), while the first antioxidant also functions to regenerate the second antioxidant - thereby freeing the second antioxidant to further react with additional ROS. This is one type of a synergistic relationship leading to increased protection performance.

According to some embodiments, the second antioxidant is selected from uric acid, oxalic acid, cyanuric acid, hydroquinone, tocopherols, carotenoids, terpenes, curcuminoids, saponins and steroids, bio-molecules and other chemical species with pi- conjugation along an aromatic and/or polyene molecular structure, and/or chemical species which enable high stabilization of radicals formed at sites prone to homolytic cleavage of chemical bonds, provided that the first antioxidant is different from the second antioxidant.

According to some embodiments, the at least one first antioxidant is selected from ascorbic acid, glutathione, and salts or combinations thereof.

By some preferred embodiments, the at least one first antioxidant is ascorbic acid, an ascorbic acid derivative (such as methyl-13-(2-(3,4-dihydroxy-5-oxo-2,5- dihydrofuran-2-yl)-2-hydroxyethoxy)propanoate), and salts or combinations thereof.

According to other embodiments, the at least one second antioxidant is selected from uric acid, oxalic acid, cyanuric acid, hydroquinone, tocopherols (including water soluble derivatives such as 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox™)), carotenoids (e.g. beta carotene, lutein, astaxanthin), terpenes, curcuminoids (e.g. curcumin), saponins and steroids (such as estradiol and estriol), bio-molecules (such as bilirubin) and other chemical species with pi-conjugation along an aromatic and/or poly-ene molecular structure, and/or chemical species which enable high stabilization of radicals formed at sites prone to homolytic cleavage of chemical bonds).

Non limiting exemplary flavonoids are flavones, flavonols, flavanols, flavanones, isoflavones, proanthocyanidins, anthocyanins, etc. By some preferred embodiments, the at least one second antioxidant is selected from uric acid, oxalic acid, cyanuric acid, hydroquinone, tocopherols, and salts or combinations thereof.

According to some embodiments, the weight ratio between said at least one first antioxidant and said at least one second antioxidant in the formulation ranges between about 10: 1 and about 1 :10. According to other embodiments, the weight ratio (w/w) between said at least one first antioxidant and said at least one second antioxidant in the formulation ranges between about 4: 1 and about 1 :4.

By some embodiments, the weight ratio (w/w) between said at least one first antioxidant and said at least one second antioxidant in the formulation is about 10: 1, 9.5: 1, 9: 1, 8.5: 1, 8: 1, 7.5: 1, 7: 1, 6.5: 1, 6: 1, 5.5: 1, 5: 1, 4.5: 1, 4: 1, 3.5: 1, 3: 1, 2.5: 1, 2:1, 1.5: 1, 1 : 1, 1 : 1.5, 1 :2, 1 :2.5, 1 :3, 1 :3.5, 1 :4, 1 :4.5, 1 :5, 1 :5.5, 1 :6, 1 :6.5, 1 :7, 1 :7.5, 1 :8, 1 :8.5, 1 :9, 1 :9.5, or about 1 : 10.

By some other embodiments, the formulation comprises said at least one second antioxidant in a concentration of at least 0.1 wt%. According to other embodiments, the formulation comprises said at least one second antioxidant at a concentration ranging between about 0.1 wt% and about 10 wt%, e.g. between about 2 wt% and about 10 wt%.

According to some embodiments, the liquid formulation has a pH of at least about 0.5, e.g. between about 1 and 9, depending on the acidity of the antioxidants, and/or presence of other acidic species in the formulation. By some embodiments, the pH of the liquid formulation is between about 1 and about 6. According to other embodiments, the pH of the liquid formulation is between about 2 and about 6. According to some other embodiments, the pH of the liquid formulation is between about 3 and about 6. According to yet other embodiments, the pH of the liquid formulation is between about 4 and about 6.

By other embodiments, the pH of the liquid formulation is between about 5 and about 9. By further embodiments, the pH of the liquid formulation is between about 6 and about 9.

According to some embodiments, the formulation further comprises at least one sacrificial antioxidant. The sacrificial antioxidant is an antioxidant having higher/increased reaction kinetics with ROS compared to at least the first antioxidant. According to some embodiments, the sacrificial antioxidant has a higher/increased reaction kinetics with the ROS compared to that of the second antioxidant. Without wishing to be bound by theory, the sacrificial antioxidant is utilized to function at the application site (towards ROS after the formula has been applied onto the surface), and/or to prolong the lifetime and performance of a formula when stored and/or transported prior to being applied on its target metal surface.

According to some embodiments, the sacrificial antioxidant is selected from uric acid, glutathione, carotenoids, terpenes, curcuminoids, saponins and steroids, biomolecules and other chemical species with pi -conjugation along an aromatic and/or polyene molecular structure, and/or chemical species which enable high stabilization of radicals formed at sites prone to homolytic cleavage of chemical bonds, given that the sacrificial antioxidant is different from the first antioxidant and from the second antioxidant.

In some embodiments, the sacrificial antioxidant can be an inorganic component, such as particles consisting of or comprising zinc, copper, manganese and/or selenium. Ions of these or other metals may also be included into the formulation, as salts or as ion pairs of carrier organic molecules (e.g. anionic polymers).

By some embodiments, the weight ratio between said sacrificial antioxidant and said at least one first antioxidant ranges between about 1 : 100 and 100: 1. By other embodiments, the weight ratio between said sacrificial antioxidant and said at least one first antioxidant ranges between about 1 : 100 and 1 :50, or even between 1 : 100 and 1 : 10.

By some other embodiments, the weight ratio between said sacrificial antioxidant and said at least one second antioxidant ranges between about 1: 100 and 100: 1. By other embodiments, the weight ratio between said sacrificial antioxidant and said at least one second antioxidant ranges between about 1 : 100 and 1 :50, or even between 1 : 100 and 1 : 10.

By some further embodiments, when comprising said at least one sacrificial antioxidant, such sacrificial antioxidant is present in the formulation at a concentration of at least 0.1 wt%.

According to some embodiments, the liquid formulation comprises at least one carrier liquid, which permits application of the antioxidants onto the surface of the metal. One or more of the antioxidants can be fully soluble in the carrier liquid, but it is also possible for one or more of the antioxidants, or the complexating agent, to be non- or partially soluble in the carrier liquid. In such cases, dispersants or emulsifiers may be added to the liquid formulation. According to some embodiments, the carrier liquid is water. According to other embodiments, the carrier liquid is an aqueous liquid, e.g. a mixture of water and alcohol (typically ethanol or isopropanol), a mixture of water and short-chain polyols (ethylene glycol, poly(ethylene glycol), etc.), and others. By some other embodiments, the liquid carrier can be a colloidal solution. By other embodiments the liquid can be a low-viscosity gel.

Depending on the desired application method, the viscosity of the liquid formulation can be modified by adding one or more viscosity modifying agents. The viscosity modifying agent functions to increase or decrease the viscosity of the carrier liquid.

By some embodiments, the formulation comprises at least one gelling agent. The gelling agent is an agent that is capable of adjusting the viscosity of carrier to a desired viscosity. Typically the gelling agent also forms thin films when applied onto the metal surface, thereby increasing the residence time of the formulation onto the metal surface. The gelling agents are capable of forming a 3 -dimensional network, for example a viscoelastic network of polymeric chains, capturing at least the antioxidants and complexating agents within the structure of the network. Such capturing assists in maintaining high concentrations of the active components and prolongs the contact time of the antioxidants and the complexating agents with the metal surface and, as a consequence, increases the protection efficiency and/or lifetime of the formulation. Further, the gelling agent can function to increase the stability of the formulation (e.g. prevent sedimentation of components during storage), thereby increasing the shelf-life of the formulations.

The gelling agent may be selected from water-soluble or colloidal water-soluble or partially water soluble polymers, such as cellulose ethers (e.g. hydroxy ethyl cellulose, methyl cellulose, hydroxypropylmethyl cellulose), polyvinylalcohol, polyquatemium-10, guar gum, hydroxypropyl guar gum, xanthan gums, gellans, Aloe vera gel, amla, carrageenan, oat flour, starch and modified starch, gelatin, ghatty gum, gum Arabic, inulin, Konjac gum, locust bean gum, fenugreek, marshmallow root, pectin and modified pectin, solagum, tragacanth gum, etc.

The gelling agent can be selected from one or more polymers, such as acrylic acid/ethyl acrylate copolymers, carboxyvinyl polymers (Carbopol® resins), polyalkenyl polyether cross-linked acrylic acid polymer, hydrophobically modified crosslinked acrylic acid polymers, and others.

According to some embodiments, the gelling agent may be selected from xanthan, gellan, sodium alginate, pectin, low and high methoxy pectins, chitosan, polyvinyl alcohols, and mixtures thereof.

According to some embodiments, the formulation comprises said at least one gelling agent in a concentration ranging between about 0.01 wt% and about 5 wt%.

According to some embodiments, the formulation has a viscosity of between about 0.5 and 2000 mPa-sec. According to some other embodiments, the formulation has a viscosity of between about 500 and 2000 mPa-sec. According to yet other embodiments, the formulation has a viscosity of between about 0.5 and 1000 mPa-sec. The viscosity can be tailored according to the specific application method or use of the formulation, e.g. spraying, dipping, smearing, etc.

In order to further elongate the contact time of the antioxidants with the surface of the metal, the formulation may, by some embodiments, comprise at least one surface fixating component, for example a hydrophobic resin. The surface fixating component is typically one or more polymers forming, after application and curing, a matrix or coating film onto the surface of the metal to minimize removal of the antioxidants from the surface (due to wetting or brushing for example). In some embodiments the fixating component is hydrophobic, to facilitate the coating’s resistance to wetting. Furthermore, this fixating component may further contribute to the protection of the surface by forming a barrier to CPS.

According to some embodiments, the fixating component is selected from polysiloxanes and/or silicone polymers, vinyl acetates, epoxy polymers, polyethers, alkyds, acrylates, aromatic polymers (such as parylene or styrene), polyureas, polyamides, plastics, polyether aryl ketones (such as PEEK) and other organic polymers, as well as co-polymers and/or mixtures thereof.

By some embodiments, the formulation comprises at least 5 wt% of fixating components, e.g. between about 5 wt% and about 80 wt% of said fixating components, between about 10 wt% and about 70 wt% of said fixating components, between about 15 wt% and about 60 wt% of said fixating components, or even between about 20 wt% and about 55 wt% of said fixating components. According to some embodiments, the formulation further comprises at least one functional additive selected from surfactants, emulsifiers, dispersants, defoamers, surface binding agents, antimicrobial agents, biocides, binders, colorants, odorants, odormasking agents, UV-stabilizers, flame retardants, appearance enhancing components (such as for sheen or other optical effects), mechanical reinforcing additives and others.

The formulations of this disclosure are intended for application onto a variety of metal objects, including large scale structural elements that are exposed to various environmental and industrial conditions, including aggressive and abrasive environments. In order to provide mechanical reinforcement to the formulations once applied onto the surface to be treated, the formulation can, by some embodiments, comprise at least one mechanical reinforcing additive (e.g. as a functional additive). The mechanical reinforcing additive means to denote a component that increases the mechanical stability and/or resistivity to abrasion or impact of the protective layer formed once applied onto the metal surface.

By some embodiments, the mechanical reinforcing additive is a water insoluble particulate additive. Once the formulation is applied onto the surface to be treated, the particulate additives become embedded within the film formed by the gelling agent and/or the fixating components, and/or the sedimented ion/complexation agent pair network, and increase the abrasion/impact resistance of the layer formed on the surface.

According to some embodiments, the particulate additive is selected from ceramic particles, mineral particles, metal particles, elastomer particles, organic polymers particles, composite material particles, and combinations thereof. For example, the particulate additive can be selected from aluminum hydroxides of various types (e.g. aluminum trihydroxide), kaolin, metal particles (e.g. zinc, copper, titanium, etc.), metal oxides (e.g. iron oxide, aluminum oxide, zinc oxide, titanium oxide, mica), metal nitrides, metal carbides, inorganic carbides, graphites and functionalized graphites, ceramics and mixtures thereof.

By other embodiments, the mechanical reinforcing additive is a polymeric additive, such as an elastomer (e.g. polyureas, polyurethanes, latex, acrylics, etcf with or without thermoplastic reinforcements (such as PEEK) to increase flexibility of the protective layer. By another aspect, there is provided a liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and 10 wt%; and at least one metal ion complexating agent in an amount of between about 0.3 wt% and about 3.5 wt%; the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 2: 1.

By a further aspect, there is provided a liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and 10 wt%; and at least one metal ion complexating agent in an amount of between about 0.3 wt% and about 3.5 wt%; the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :3.5.

By another aspect, the disclosure provides a liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and about 10 wt%, selected from ascorbic acid, glutathione, 6-hydroxy-2,5,7,8-tetramethylchroman-2- carboxylic acid, carotenoids, terpenes, curcuminoids, and combinations thereof; and at least one metal ion complexating agent in an amount of between about 0.3 wt% and 3.5 wt%, selected from poly ethers, polyvinyl alcohols, polysaccharides, polyamines, polyureas, polyvinyl alcohols, acrylates, polyepoxides, polysulfones, polystyrenes, polyesters, polyamides, polyphenols, aminopolycarboxylates (e.g. EDTA), iminodisuccinic acid (IDS), S,S-ethylenediamine-N,N'-disuccinic acid (EDDS), L- glutamic acid N,N-di acetic acids (GLDA), methylglycinediacetic acid (MGDA), nitrilotriacetic acid (NTA), polyaspartic acids, and any suitable salt or derivative thereof, and any combinations thereof; the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :2. By another aspect, the disclosure provides a liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and about 10 wt%, selected from ascorbic acid, glutathione, 6-hydroxy-2,5,7,8-tetramethylchroman-2- carboxylic acid, carotenoids, terpenes, curcuminoids, and combinations thereof; and at least one metal ion complexating agent in an amount of between about 0.3 wt% and about 3.5 wt%, selected from polyphenols; the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :2.

By another aspect, the disclosure provides a liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and about 10 wt%, selected from ascorbic acid, glutathione, 6-hydroxy-2,5,7,8-tetramethylchroman-2- carboxylic acid, carotenoids, terpenes, curcuminoids, and combinations thereof; and at least one metal ion complexating agent in an amount of between about 0.3 wt% and 3.5 wt%, selected from polyphenols; the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 3.5: 1.

By another aspect, the disclosure provides a liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and about 10 wt%, selected from ascorbic acid, an ascorbic acid derivative, and a salt thereof; and at least one metal ion complexating agent in an amount of between about 0.3 wt% and 3.5 wt%, selected from polyphenols; the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :2.

By another aspect, the disclosure provides a liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and about 10 wt%, selected from ascorbic acid, an ascorbic acid derivative, and a salt thereof; at least one metal ion complexating agent in an amount of between about 0.3 wt% and 3.5 wt%, selected from polyphenols; and and between about 1 wt% and about 10 wt% of at least one second antioxidant; the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1:2.

By yet another aspect, the disclosure provides a liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and 10 wt%; at least one second antioxidant in an amount of between about 0.3 wt% and 10 wt%, provided that the second antioxidant is different from the first antioxidant; and at least one metal ion complexating agent in an amount of between about 0.3 wt% and about 3.5 wt%; the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20, the weight ratio between the first and second antioxidant ranges between about 10: 1 and about 1 : 10, and the at least one first antioxidant and at least one second antioxidant differing in standard reduction potentials by at least about 20 mV.

By yet another aspect, the disclosure provides a liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and 10 wt%, selected from ascorbic acid, glutathione, carotenoids, terpenes, curcuminoids, and combinations thereof; at least one second antioxidant in an amount of between about 0.3 wt% and 10 wt%, selected from uric acid, oxalic acid, cyanuric acid, hydroquinone, glutathione, tocopherols, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid, carotenoids, terpenes, curcuminoids, and combinations thereof, provided that the second antioxidant is different from the first antioxidant, the at least one first antioxidant and at least one second antioxidant differing in standard reduction potentials by at least about 20 mV; and at least one metal ion complexating agent in an amount of between about 0.3 wt% and about 3.5 wt%, selected from polyethers, polyvinyl alcohols, polysaccharides, polyamines, polyureas, polyvinyl alcohols, acrylates, polyepoxides, polysulfones, polystyrenes, polyesters, polyamides, polyphenols, aminopolycarboxylates (e.g. EDTA), iminodisuccinic acid (IDS), S,S-ethylenediamine-N,N'-disuccinic acid (EDDS), L- Glutamic acid N,N-di acetic acids (GLDA), methylglycinediacetic acid (MGDA), nitrilotriacetic acid (NTA), polyaspartic acids, any suitable salt or derivative thereof, and any combinations thereof; the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20, and the weight ratio between the first and second antioxidant ranges between about 10: 1 and about 1 : 10.

Depending on the volume of formulation to be used, it is sometimes desired to store the formulation in a concentrated form, and dilute it to a suitable volume prior to use. Hence, by another one of its aspects, the present disclosure provides a concentrate formulation, readily dilutable by one or more dilution liquids, the concentrate formulation comprises at least one first antioxidant and at least one metal ion complexating agent, the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20.

By some embodiments, the weight ratio between the at least one first antioxidant and the metal ion complexating agent in the concentrate ranges between about 10: 1 and about 1 : 10. According to other embodiments, the weight ratio between the at least one first antioxidant and the metal ion complexating agent in the concentrate ranges between about 10: 1 and about 1 : 1. According to some other embodiments, the weight ratio between the at least one first antioxidant and the metal ion complexating agent in the concentrate ranges between about 10: 1 and about 2: 1.

According to some embodiments, the concentrate further comprises at least one second antioxidant, as defined above. According to such embodiments, the weight ratio (w/w) between said at least one first antioxidant and said at least one second antioxidant in the concentrate ranges between about 10: 1 and about 1 : 10.

As noted, the concentrate is formulated to be readily dilutable by one or more dilution liquids. According to some embodiments, the dilution liquid is the same as the carrier liquid, for example both the carrier liquid and the dilution liquid can be water.

By other embodiments, the dilution liquid is different from said carrier liquid, for example organic solvents such as ethanol, or aqueous organic solutions such as solvated or dispersed polymer solutions, etc. In some embodiments the dilution liquid comprises at least one of gelling agents, resins, mechanical property enhancing additives, etc.

In some embodiments, the concentrate does not include a carrier liquid.

According to some embodiments, the concentrate formulation further comprises at least one sacrificial antioxidant, as described hereinabove.

By some embodiments, the weight ratio between said sacrificial antioxidant and said at least one first antioxidant ranges between about 1 : 100 and about 100: 1.

By some other embodiments, the weight ratio between said sacrificial antioxidant and said at least one second antioxidant ranges between about 1 : 100 and about 100: 1.

By some embodiments, the concentrate formulation comprises at least one gelling agent, as described above.

By some embodiments, the concentrate formulation comprises at least one hydrophobic component, for example a hydrophobic resin, as described above.

By some embodiments, the concentrate formulation comprises at least one fixating component, as described above.

According to some embodiments, the concentrate formulation further comprises at least one functional additive selected from surfactants, emulsifiers, dispersants, defoamers, surface binding agents, antimicrobial agents, biocides, binders, colorants, odorants, odor-masking agents, UV-stabilizers, flame retardants, appearance enhancing components (such as for sheen or other optical effects), and others.

According to some embodiments, the concentrate formulation comprises at least one mechanical reinforcing additive, as described above.

The formulations of this disclosure can also be provided in a kit form, namely a first part comprising some of the formulation ingredients, and a second part that comprises the rest of the formulation’s ingredients.

Hence, according to another aspect, there is provided a kit for preparing a liquid formulation for forming a protective layer against oxidative corrosion on a metal surface, the kit comprises a first container comprising a first liquid composition that comprises a first carrier liquid and at least one first antioxidant, and a second container comprising a second composition (typically in liquid form) that comprises at least one metal ion complexating agent, the first liquid composition and the second composition forming the liquid formulation of this disclosure upon mixing.

According to some embodiments, the second composition is in liquid form and comprises a second liquid carrier. According to such embodiments, the first carrier liquid is identical to the second carrier liquid, for example, water. According to other such embodiments, the first and second carrier liquids are different from one another.

According to some embodiments, the kit is configured to provide a weight ratio between said at least one first antioxidant and said at least one metal ion complexating agent, once the first liquid composition and the second liquid composition are mixed, that ranges between about 10: 1 and about 1 :20.

According to some embodiments, the first solution, the second solution, or both the first and second solutions comprise one or more additional components of the formulation, as defined hereinabove. By some embodiments, the additional components can be selected from at least one second antioxidant, at least one sacrificial antioxidant, at least one gelling agent, at least one hydrophobic component (e.g. a hydrophobic resin), at least one fixating component, at least one particulate additive, and combinations thereof.

According to some embodiments, the first composition, the second composition, or both the first and second compositions comprise at least one functional additive selected from surfactants, emulsifiers, dispersants, defoamers, surface binding agents, antimicrobial agents, biocides, binders, colorants, odorants, odor-masking agents, UV- stabilizers, flame retardants, appearance enhancing components (such as or sheen or other optical effects), and others.

The first and second containers can be stand-alone containers, each containing a defined volume of the first and second compositions, respectively, such that once the volumes of the first and second containers are mixed, the weight ratio between said at least one first antioxidant and said at least one metal ion complexating agent ranges between about 10: 1 and about 1 :20.

Alternatively, the first and second containers may be associated with one another, such as to permit mixing of the first and second compositions in order to obtain the formulation upon user demand.

According to some embodiments, the kit further comprises means for application of the formulation onto the surface to be treated. By another aspect, there is provided a kit for preparing a liquid formulation for forming an oxidation protective layer on a metal surface, the kit comprises a first container comprising a first liquid composition that comprises a first carrier liquid, at least one first antioxidant and at least one metal ion complexating agent, and a second container comprising a second composition that comprises at least one second antioxidant, the first liquid composition and the second composition forming a liquid formulation according to this disclosure upon mixing.

In such aspects, the first and second containers have each a defined volume of the first and second compositions, respectively, such that once the volumes of the first and second containers are mixed, said the weight ratio between said at least one first antioxidant and said at least one metal ion complexating agent ranges between about 10: 1 and about 1 :20 and the weight ratio between the first and second antioxidant ranges between about 10: 1 and about 1 : 10. According to some embodiments, the at least one first antioxidant and at least one second antioxidant differing in standard reduction potentials by at least about 20 mV.

By another one of its aspects, the present disclosure provides a liquid formulation for forming a top coating protective layer against oxidation corrosion on a metal surface, the liquid formulation comprising at least one first antioxidant and at least one metal ion complexating agent, the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20.

The liquid formulation for forming a top coating can further comprise at least one second antioxidant, e.g. such that the at least one first antioxidant and at least one second antioxidant differing in reduction potentials by at least 20m V, typically such that the weight ratio between the first and second antioxidant ranges between about 10: 1 and about 1 : 10.

According to some embodiments, the liquid formulation for forming a top coating oxidation protective layer (z.e. a topcoat formulation) is suitable for application onto the surface to be treated by spraying, brushing or dipping, and functions also as a topcoat onto said metal surface. According to such embodiments, the liquid formulation has a viscosity of between about 0.5 and 2000 mPa sec.

By another aspect, the present disclosure provides a primer liquid composition for forming an oxidation protective layer on a metal surface, the primer liquid composition comprising at least one first antioxidant and at least one metal ion complexating agent, the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20.

The primer liquid composition can further comprise at least one second antioxidant, such that the at least one first antioxidant and at least one second antioxidant differing in reduction potentials by at least 20m V, typically such that the weight ratio between the first and second antioxidant ranges between about 10: 1 and about 1 : 10.

According to some embodiments, the primer liquid formulation is suitable for application onto the surface to be treated by spraying, brushing or dipping, and functions as a basic layer onto which other layers may be applied, such as protective layers, sealing layers, and/or paint layers.

According to such embodiments, the liquid formulation has a viscosity of between about 0.5 and 2000 mPa- sec.

By another one of its aspects, the present disclosure provides a process for preparing a liquid formulation for forming a protective layer against oxidative corrosion on a metal surface as described herein, the process comprises mixing at least one first antioxidant and at least one metal ion complexating agent in a carrier liquid, thereby obtaining said liquid formulation.

The process can optionally comprise mixing at least one second antioxidant into said carrier liquid.

By another aspect of this disclosure, there is provided a method for forming a protective layer against oxidative corrosion on a metal surface, comprising applying onto said surface a liquid formulation as described herein.

Application of the liquid formulation onto a surface can be by any suitable technique; by some embodiments, said applying of the liquid formulation onto the ferrous metal surface is carried out by dipping, spraying, brushing, rolling, airless spraying, powder coating, etc.

According to some embodiments, the method further comprises, prior to said applying, washing the surface to remove loose particulate matter, and/or removal of oils and greases and/or other contaminants from the surface. It is noted that when utilizing the formulations of this disclosure, unlike other standard treatment techniques of rusted surfaces such as painting or galvanizing, no aggressive surface pretreatment is required, and typically the pre-existing metal oxide layer needs not be removed prior to application of the formulations, as the formulations are designed to utilize the pre-existing metal oxide as a raw material for formation of more stable, protective oxide layers.

Thus, by some embodiments, the surface to be treated comprises at least one corroded surface portion prior to applying of the formulations.

By another aspect of this disclosure, there is provided a method for forming a protective layer against oxidative corrosion on a metal surface, comprising a first application of a liquid formulation as described herein onto said surface to obtain a coated surface, and at least one subsequent application of said liquid formulation onto said coated surface, said subsequent application being at least 1 minute after said first application.

According to some embodiments, the method comprises two or more subsequent applications, the time interval between the subsequent applications typically being between about 1 minute and 60 days.

According to some embodiments, the method comprises a first application of a liquid formulation as described herein onto said surface to obtain a coated surface, permitting said formulation to dry on said surface, and apply at least one subsequent application of said liquid formulation onto the dried surface.

According to other embodiments, the liquid formulation is applied onto a pretreated metal surface. According to some other embodiments, the liquid formulation is applied onto a partially coated metal surface, having portions of exposed metal surface in which no coating or substantive coating exists.

By another aspect, there is provided a method for forming a layer which provides protection against corrosion on a metal surface, the method comprising:

(a) applying a first liquid composition that comprises a first carrier liquid and at least one first antioxidant onto said metal surface, and

(b) applying a second liquid composition that comprises a second carrier liquid and at least one metal ion complexating agent on top of said first liquid composition, thereby forming a liquid formulation on said metal surface, the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20. By another aspect, there is provided a method for forming a layer which provides protection against corrosion on a metal surface, the method comprising:

(a) applying a first liquid composition that comprises a first carrier liquid and at least one first antioxidant onto said metal surface,

(b) applying a second liquid composition that comprises a second carrier liquid and at least one metal ion complexating agent on top of said first liquid composition, and

(c) applying a third liquid composition that comprises a third carrier liquid and at least one second antioxidant on top of said second liquid composition, thereby forming a liquid formulation on said metal surface, the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20, and weight ratio between the first and second antioxidant ranges between about 10: 1 and about 1 : 10.

(a) applying a first liquid composition that comprises a first carrier liquid, at least one first antioxidant, and at least one metal ion complexating agent onto said metal surface, and

(b) applying a second liquid composition that comprises a second carrier liquid and at least one second antioxidant on top of said first liquid composition, and thereby forming a liquid formulation on said metal surface, the weight ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20, and weight ratio between the first and second antioxidant ranges between about 10: 1 and about 1 : 10.

By another aspect of this disclosure, there is provided a method for forming a layer which provides protection against oxidative corrosion on a metal surface, comprising diluting a concentrate formulation as described herein with a dilution liquid to obtain a liquid formulation as described herein, and applying said liquid formulation onto said surface. By some embodiments, the metal surface onto which the formulations are applied can be treated with at least one topcoat layer. Such topcoat layer(s) may include, but are not limited to, paints, adhesives, and lacquers. In such embodiments, these topcoat(s) may provide further protection to the metal against corrosion, and/or further protection against other types of damage (e.g. mechanical damage, damage from chemical reactions), and/or desired appearance, and/or other functionalities (e.g. adhesion to other objects).

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

As used herein, the term about is meant to encompass deviation of ±10% from the specifically mentioned value of a parameter, such as concentration, temperature, pH, etc.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases "ranging/ranges between" a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween. It should be noted that where various embodiments are described by using a given range, the range is given as such merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as "comprises" and "comprising ' , will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any integer or step or group of integers and steps.

Generally it is noted that the term “ ...at least one... ” as applied to any component of the formulations, processes and/or methods of this disclosure should be read to encompass one, two, three, four, or even more different occurrences of said component in the formulations, processes and/or methods of this disclosure.

It is appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

The processes of the present disclosure involve numerous process steps which may or may not be associated with other common physical-chemical processes so as to achieve the desired result. Unless otherwise indicated, such process steps, if present, may be set in different sequences without affecting the workability of the process and its efficacy in achieving the desired end result.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig- 1 is a metallographic crosscut of a carbon steel sample exposed to 500 hours of salt spray, treated, prior to exposure, with a reference formulation that contained two antioxidants.

Fig- 2 is a metallographic crosscut of a carbon steel sample exposed to 500 hours salt spray, treated, prior to exposure, with a formulation according to this disclosure that contained two antioxidants and a metal ion complexating agent.

Figs. 3A-3B are metallographic crosscuts of carbon steel as received with mill scale (Fig. 3A) and after sand blasting (Fig. 3B), after application of a reference formulation (formulation Ref 1).

Figs. 4A-4B are metallographic crosscuts of carbon steel samples with mill scale and after sand blasting, respectively, after application of a formulation according to an embodiment of this disclosure and several days in a salt-spray chamber.

Fig. 5 is a metallographic crosscut of a sample of Fig. 3 A, after application of a formulation according to another embodiment of this disclosure and several days in a saltspray chamber. Figs. 6A-6B are metallographic crosscuts of carbon steel samples with mill scale and after sand blasting, respectively, after application of a formulation that contained only a first antioxidant, devoid of a second antioxidant and an ion complexating agent.

DETAILED DESCRIPTION OF EMBODIMENTS

Example 1

To demonstrate the corrosion protection efficacy of formulations of this disclosure, an exemplary liquid formulation was applied onto metal test samples. A liquid formulation of this disclosure according to Table 1 was applied onto low carbon steel samples: S 235JR (st37) with mill scale rust grade A SSPC VIS 4, and on corroded surface grade C SSPC VIS 4. The samples were cleaned by high-pressure water jet before application of the tested liquid formulation. They were then coated with a mid-coat of epoxy and then top-coated with polyurethane-based paint.

Table 1: Exemplary test formulation

The samples were then subject to various environmental tests, under the specification of ISO 12944-6 C5 that refers to Coastal aeras with high salinity and industrial aeras with high humidity and aggressive atmosphere. The applied conditions simulate accelerated corrosion conditions.

Table 2: Environmental test results * 1,440 hours in salt spray chamber

** 720 hours in humidity chamber

*** 1,440 hours

As evident from Table 2, the tested samples treated with a formulation according to Table 1, the formulation provides protective performance against rusting sufficient to meet the requirements of common standards. This protection included prevention of surface area corrosion, the formation of blisters, cracking flaking and inhibit corrosion at the scribing site, and other defects while maintaining good adhesion of the topcoat to the surface.

Example 2

To demonstrate the type of synergy that can be obtained by the formulations, combinations of components were examined in a series of formulations, which were applied to mild steel samples which were then exposed to 500 hours in a salt spray chamber and analyzed for their subsequent weight loss. Table 3 presents the results and the mass of components in the formulae, which included, in addition, a carrier liquid, fixating agents and some functional additives - all identical in the examined formulae.

Table 3: %wt loss of metal (500 hours of salt spray)

Note: (+) sign in the average weight loss column denotes decreased loss of weight; i. e. more (+) signs mean less weight loss.

As can be seen in Table 3, higher concentrations of a first antioxidant have not necessarily led to better protective performance (entries A vs. B). A specific metal ion complexating agent used here provided some degree of protection (entry C), but when it was combined with the first antioxidant this protection improved significantly, both in weight loss and the standard deviation (i.e. reproducibility of the weight loss). The protection was even better when a first and second antioxidants were used together with the metal ion complexating agent - not only in the average weight loss, in which every fraction of weight loss reduction can be significant in real-life applications for protection, but also in the narrower range of performance differences, as expressed in the lower standard deviation values, which is crucial in terms of the applications’ reliability and quality.

Example 3

The effect of the combination of two antioxidants with a metal ion binding agent can also be visualized in metallographic sections, of two carbon steel samples exposed to identical conditions of salt spray, as presented in Figs. 1 and 2 below.

As can be seen from comparing the two crosscuts in Figs. 1-2, the metal sample treated with the formulation which included two antioxidants is considerably more damaged at the surface area - as seen with the significant pitting at the top part of the cross section seen in Fig. 1. This is compared to the sample shown in Fig. 2, which was treated with a formula according to Table 1 above, in which the main difference was the addition of the metal ion complexating agent. As can be seen, the surface of the sample of Fig. 2 is considerably better protected from oxidative corrosion.

Example 4

The synergistic effect between the first antioxidant and the complexating agent, with and without a second antioxidant was also tested for various first and second antioxidants. The formulations were applied to mild steel samples which were then exposed to 1,200 hours in a salt spray chamber and analyzed for their subsequent weight loss. Tables 4-1 to 4-5 present the results and the mass of components in the formulae, which included, in addition, a carrier liquid, fixating agents and some functional additives

- all identical in the examined formulae.

Ref. 1 is a formulation devoid of first antioxidant, second antioxidant and metal ion complexating agent; Ref 2 is a naked sample (i.e. not treated). In Tables 4-2 to 4-5, one of the first and second antioxidants of Table 4-1 were replaced by other antioxidants

- all other components remaining the same.

The weight loss measured for Ref 2 was taken to be 100% weight loss point of reference. All other weight losses are provided as relative to this reference point; for example, if in Ref 2 the weight loss was 10%, and for samples treated with the formulation the weight loss was 2%, the presented relative weight loss for this formulation is 20%. Table 4-1: Weight loss after application of formulations based on ascorbic acid and tannins

Table 4-2: Weight loss after application of formulations, ascorbic acid replaced by different antioxidants Table 4-3: Weight loss after application of formulations, ascorbic acid replaced by different antioxidants, tannins removec

Table 4-4: Weight loss after application of formulations, tocopherol replaced by different antioxidants Table 4-5: Weight loss after application of formulations, tocopherol replaced by different antioxidants, tannins removed

As can be seen from Tables 4-1 to 4-5, the combination of ascorbic acid and tannins provides a strong synergistic effect. Attempts to remove ascorbic acid (the first antioxidant) and replace it with other antioxidants (Table 4-2) resulted in a significant increase in weight loss. Replacing tocopherols (the second antioxidant) by other antioxidants (Table 4-4) showed a slight increase in weight loss, however not as significant as for replacement of ascorbic acid.

For all tested formulations, once tannins (the complexating agent) were removed, an extreme increase in weight loss was observed, comparable to the weight loss values of formulations that did not include active components (e.g. Ref 1 in Table 4-1).

Therefore, it can be seen that the formulations based on the combination of ascorbic acid and tannins provide the best protection out of those tested.

Metallographic crosscuts of carbon steel samples can be seen in Figs. 3A-6B. Samples of carbon steel, as received from production (i.e. with the surface of the metal covered by mill scale, namely an external layer that is formed immediately after casting of the steel, that includes a mixture of various oxides, alloys and impurities), as well as carbon steel samples after preliminary sand-blasting surface cleaning, were used.

In Figs. 3A-3B, the samples were treated with formulation Ref 1 (of Table 4-1), namely with a formulation that did not contain a first antioxidant, a second antioxidant, or a metal ion complexating agent. After treatment, the samples were placed in a salt spray chamber for a few days to permit a protective layer to develop on the surface of the samples. Fig. 3A shows the mill-scale sample, while Fig. 3B shows the sand-blasted sample. As can be seen, for both types of samples, no significant protection layer has developed. Where naturally formed oxides are present, the oxide layer is very thin and typically non-continuous, thereby providing no significant surface protection.

In Figs. 4A-4B, the samples were treated with Formulation 1 (of Table 4-1), and then treated under identical conditions as those of Figs. 3A-3B. As can be seen, for these samples a thick and continuous layer of protective oxides was developed on the surface of the samples. Similar results were obtained for application of Formulation 4 (of Table 4-1), as can be seen in Fig. 5.

The effect of application of Formulation 5 (of Table 4-1) is shown in Figs. 6A- 6B. As can be seen, for a formulation that contained only ascorbic acid (the first antioxidant), a very thin, non-continuous layer of oxides has developed on the surface.

Hence, it was observed that at least the combination of a first antioxidant (in this case ascorbic acid) with the metal ion complexating agent (in this case a mixture of tannins), as well as such a combination together with a second antioxidant (in this case tocopherol), resulted in a thick, continuous protection layer on the surface of the samples. These layers were also found to have a good adherence to the surface of the metal, resulting in a stable system that does not easily detach from the metal surface.

Example 5

The formulation of Table 5 has been found to provide protection against oxidative corrosion when applied to metal surfaces, as disclosed herein.

Table 5: Exemplary formulation according to this disclosure

Example 6 Table 6 provides another example of a formulation that was found to provide protection against oxidative corrosion when applied to metal surfaces, as disclosed herein.

Table 7: Exemplary formulation according to this disclosure

Example 7

Table 7 provides another example of a formulation that was found to provide protection against oxidative corrosion when applied to metal surfaces, as disclosed herein.

Table 7: Exemplary formulation according to this disclosure

Example 8

Table 8 provides another example of a formulation that was found to provide protection against oxidative corrosion when applied to metal surfaces, as disclosed herein.

Table 8: Exemplary formulation according to this disclosure

Claims

CLAIMS:

1. A liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises at least one first antioxidant and at least one metal ion complexating agent, the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20.

2. The liquid formulation of claim 1, wherein the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranges between about 10: 1 and about 1 : 10, optionally between about 10: 1 and about 2: 1.

3. The liquid formulation of claim 1 or 2, wherein the at least one first antioxidant is selected from ascorbic acid, ascorbic acid derivatives, glutathione, carotenoids, terpenes, curcuminoids, and salts or combinations thereof.

4. The liquid formulation of claim 3, wherein the at least one first antioxidant is ascorbic acid.

5. The liquid formulation of any one of claims 1 to 4, wherein said metal ion complexating agent is different from said at least one first antioxidant, the complexing agent being selected from polyethers, polyvinyl alcohols, polysaccharides, polyamines, polyureas, polyvinyl alcohols, acrylates, polyepoxides, polysulfones, polystyrenes, polyesters, polyamides, polyphenols, aminopolycarboxylates, iminodisuccinic acid (IDS), S,S-ethylenediamine-N,N'-disuccinic acid (EDDS), L-Glutamic acid N,N-diacetic acids (GLDA), methylglycinediacetic acid (MGDA), nitrilotriacetic acid (NTA), polyaspartic acids, any suitable salt or derivative thereof, and any combinations thereof.

6. The liquid formulation of claim 5, wherein the at least one metal ion complexating agent is at least one polyphenol.

7. The liquid formulation of claim 6, wherein the at least one polyphenol is selected from tannins and pseudo-tannins.

8. The liquid formulation of claim 7, wherein said tannins are selected from hydrolysable tannins, condensed tannins or any mixture thereof.

9. The liquid formulation of claim 7 or 8, wherein said polyphenols are selected from ellagic, gallic, and condensed tannins, and mixtures thereof.

10. The liquid formulation of any one of claims 1 to 9, wherein the formulation comprises between about 0.3 wt% and about 20 wt% of said at least one first antioxidant, optionally between about 3 wt% and about 15 wt% of said at least one first antioxidant.

11. The liquid formulation of any one of claims 1 to 10, wherein the formulation comprises between about 0.1 wt% and about 5 wt% of said at least one metal ion complexating agent, optionally between about 0.1 wt% and about 3 wt% of said at least one metal ion complexating agent.

12. The liquid formulation of any one of claims 1 to 11, further comprising at least one second antioxidant.

13. The liquid formulation of claim 12, wherein the at least one first antioxidant and at least one second antioxidant differing in standard reduction potentials by at least about 20 mV.

14. The liquid formulation of claim 12 or 13, wherein said at least one second antioxidant is selected from uric acid, oxalic acid, cyanuric acid, hydroquinone, glutathione, tocopherols, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid, carotenoids, terpenes, curcuminoids, and salts or combinations thereof, provided that the second antioxidant is different from the first antioxidant.

15. The liquid formulation of claim 14, wherein the at least one second antioxidant is selected from uric acid, oxalic acid, cyanuric acid, hydroquinone, tocopherols, and salts or combinations thereof.

16. The liquid formulation of any one of claims 11 to 15, wherein the weight percent ratio between the at least one first antioxidant and the second antioxidant ranges between about 10: 1 and about 1 : 10.

17. The liquid formulation of claim 16, wherein the weight percent ratio between the at least one first antioxidant and the second antioxidant ranges between about 4: 1 and about 1 :4.

18. The liquid formulation of any one of claims 11 to 17, wherein the formulation comprises between about 1 wt% and about 10 wt% of said at least one second antioxidant.

19. The liquid formulation of any one of claims 1 to 18, further comprises a carrier liquid.

20. The liquid formulation of claim 19, wherein said carrier liquid is water.

21. The liquid formulation of any one of claims 1 to 20, further comprising at least one gelling agent.

22. The liquid formulation of claim 21, wherein said gelling agent is selected from hydroxyethyl cellulose, methyl cellulose, hydroxypropylmethyl cellulose, polyvinylalcohol, polyquatcmium-10, guar gum, hydroxypropyl guar gum, xanthan gums, gellan, Aloe vera gel, amia, carrageenan, oat flour, starch and modified starch, gelatin, ghatty gum, gum Arabic, inulin, Konjac gum, locust bean gum, fenugreek, marshmallow root, sodium alginate, chitosan, pectin and modified pectin, solagum, tragacanth gum, acrylic acid/ethyl acrylate copolymers, carboxyvinyl polymers, polyalkenyl polyether cross-linked acrylic acid polymer, hydrophobically modified crosslinked acrylic acid polymers, polyvinyl alcohols, and mixtures thereof.

23. The liquid formulation of any one of claims 1 to 22, further comprising at least one fixating agent.

24. The liquid formulation of claim 23, wherein said fixating agent is selected from polysiloxanes and/or silicone polymers, vinyl acetate, epoxy polymers, polyethers, alkides, acrylates, aromatic polymers, polyureas, polyamides, plastics, polyether aryl ketones, and copolymers and/or mixtures thereof.

25. The liquid formulation of claim 23 or 24, comprising at least about 5 wt% of said at least one fixating agent.

26. The liquid formulation of any one of claims 1 to 25, further comprising at least one functional additive selected from surfactants, emulsifiers, dispersants, defoamers, surface binding agents, antimicrobial agents, biocides, viscosifiers, binders, colorants, odorants, odor-masking agents, UV-stabilizers, flame retardants, and appearance enhancing components.

27. The liquid formulation of any one of claims 1 to 26, further comprising at least one mechanical reinforcing additive.

28. The liquid formulation of claim 27, wherein the at least one mechanical reinforcing additive is in particulate form.

29. The liquid formulation of claim 28, wherein said particulate additive is selected from ceramic particles, mineral particles, metal particles, elastomer particles, organic polymers particles, composite material particles and combinations thereof.

30. A liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and 10 wt%; and at least one metal ion complexating agent in an amount of between about 0.3 wt% and about 3.5 wt%; the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 2: 1.

31. A liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and about 10 wt%, selected from ascorbic acid and ascorbic acid derivatives; and at least one metal ion complexating agent in an amount of between about 0.3 wt% and about 3.5 wt%, selected from polyphenols; the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :2.

32. A liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises: at least one first antioxidant in an amount of between about 1 wt% and 10 wt%; at least one second antioxidant in an amount of between about 0.3 wt% and 10 wt%, provided that the second antioxidant is different from the first antioxidant and that the at least one first antioxidant and at least one second antioxidant differing in standard reduction potentials by at least about 20 mV; and at least one metal ion complexating agent in an amount of between about 0.3 wt% and about 3.5 wt%; the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20, and the weight percent ratio between the first and second antioxidant ranges between about 10: 1 and about 1 : 10.

33. A liquid formulation for forming a top coating protective layer against corrosion on a metal surface, the formulation comprises at least one first antioxidant and at least one metal ion complexating agent, the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20.

34. A primer liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises at least one first antioxidant and at least one metal ion complexating agent, the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20.

35. The liquid formulation of claim 33 or the primer liquid formulation of claim 34, further comprising at least one second antioxidant, the at least one first antioxidant and at least one second antioxidant differing in standard reduction potentials by at least about 20 mV.

36. A concentrate formulation, readily dilutable by one or more dilution liquids for obtaining the liquid formulation of any one of claims 1 to 35, the concentrate formulation comprises at least one first antioxidant and at least one metal ion complexating agent, the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20.

37. The concentrate formulation of claim 36, further comprising at least one second antioxidant.

38. The concentrate formulation of claim 37, wherein the at least one first antioxidant and at least one second antioxidant differing in standard reduction potentials by at least about 20 mV.

39. The concentrate formulation of claim 37 or 38, wherein the weight percent ratio between the at least one first antioxidant and the second antioxidant ranges between about 10: 1 and about 1 : 10.

40. The concentrate formulation of any one of claims 36 to 39, comprising at least one carrier liquid.

41. A liquid formulation for forming a protective layer against corrosion on a metal surface, the formulation comprises a concentrate formulation according to any one of claims 36 to 40, diluted in one or more one or more dilution liquids.

42. A kit for preparing a liquid formulation for forming a protective layer against corrosion on a metal surface, the kit comprises a first container comprising a first liquid composition that comprises a first carrier liquid and at least one first antioxidant, and a second container comprising a second composition that comprises at least one metal ion complexating agent, the first liquid composition and the second composition forming a liquid formulation according to any one of claims 1 to 35 upon mixing.

43. The kit of claim 42, wherein the second composition is in liquid form, and comprises a second liquid carrier.

44. The kit of claim 42 or 43, configured to provide a weight percent ratio between said at least one first antioxidant and said at least one metal ion complexating agent, once the first liquid composition and the second composition are mixed, that ranges between about 10: 1 and about 1 :20.

45. The kit of any one of claims 40 to 42, wherein each of said first and second containers contain a defined volume of the first and second compositions, respectively, such that once the volumes of the first and second containers are mixed, said the weight percent ratio between said at least one first antioxidant and said at least one metal ion complexating agent ranges between about 10: 1 and about 1 :20.

46. The kit of any one of claims 40 to 45, further comprising a third container comprising a third composition that comprises at least one second antioxidant.

47. A kit for preparing a liquid formulation for forming a protective layer against corrosion on a metal surface, the kit comprises a first container comprising a first liquid composition that comprises a first carrier liquid, at least one first antioxidant and at least one metal ion complexating agent, and a second container comprising a second composition that comprises at least one second antioxidant, the first liquid composition and the second composition forming a liquid formulation according to any one of claims 1 to 35 upon mixing.

48. A process for preparing a liquid formulation for forming a protective layer against corrosion on a ferrous metal surface of any one of claims 1 to 35, the process comprises mixing at least one first antioxidant and at least one second antioxidant in a carrier liquid, thereby obtaining said liquid formulation.

49. A method for forming a protective layer against corrosion on a metal surface, comprising applying onto said surface a liquid formulation according to any one of claims 1 to 35.

50. The method of claim 49, wherein said applying is carried out by dipping, spraying, brushing, rolling, smearing, airless spraying, or powder coating.

51. The method of claim 49 or 50, further comprising, prior to said applying, washing the surface.

52. A method for forming a protective layer against corrosion on a metal surface, comprising a first application of a liquid formulation according to any one of claims 1 to 35 onto said surface to obtain a coated surface, and at least one subsequent application of said liquid formulation onto said coated surface, said subsequent application being at least 1 minute after said first application.

53. A method for forming a protective layer against corrosion on a metal surface, comprising diluting a concentrate formulation according to any one of claims 36 to 40, a dilution liquid to obtain a liquid formulation according to any one of claims 1 to 35, and applying said liquid formulation onto said surface.

54. A method for forming a protective layer against corrosion on a metal surface, the method comprising:

(a) applying a first liquid composition that comprises a first carrier liquid and at least one first antioxidant and at least one metal ion complexating agent onto said metal surface, and

(b) applying a second liquid composition that comprises a second carrier liquid and at least one second antioxidant onto said first liquid composition, thereby forming a liquid formulation on said metal surface, the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20, and the weight percent ratio between the at least one first antioxidant and the second antioxidant ranging between about 10: 1 and about 1 : 10.

55. A method for forming a layer which provides protection against corrosion on a metal surface, the method comprising:

(c) applying a third liquid composition that comprises a third carrier liquid and at least one second antioxidant on top of said second liquid composition, thereby forming a liquid formulation on said metal surface, the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20, and weight percent ratio between the first and second antioxidant ranges between about 10: 1 and about 1 : 10.

56. A method for forming a layer which provides protection against corrosion on a metal surface, the method comprising:

(b) applying a second liquid composition that comprises a second carrier liquid and at least one second antioxidant on top of said first liquid composition, and thereby forming a liquid formulation on said metal surface, the weight percent ratio between the at least one first antioxidant and the metal ion complexating agent ranging between about 10: 1 and about 1 :20, and weight percent ratio between the first and second antioxidant ranges between about 10: 1 and about 1 : 10.