Corrosion-inhibiting coating for metallic substrates comprising a brittle aluminum alloy and a binder

Abstract

Corrosion-inhibiting coating for metallic substrates comprising a brittle aluminum alloy and a binder. Composition of a corrosion-inhibiting coating for a metallic substrate, the coating composition comprising a film-forming binder and powdered aluminum alloy particles. The aluminum alloy comprises silicon in an amount of 1% to 30% by weight, as well as one or more elements, selected from a first group, which includes an element enhancing embrittlement and / or an element enhancing electrochemical anodizing.

Description

Title of the invention: Corrosion-inhibiting coating for metallic substrates comprising a brittle aluminum alloy and a binder Scope of the invention

[0001] The present invention relates to coatings, including corrosion-inhibiting coatings for metallic substrates. Technological background

[0002] Paints and other coatings are often applied to metallic substrates in order to prevent corrosion of these substrates and also to protect them against degradation.

[0003] These paints and other coatings sometimes contain metallic particles such as aluminum or aluminum alloy particles, magnesium or zinc particles, the particles being designed to help prevent, by acting as a sacrificial anode, galvanic corrosion of the metallic substrate.

[0004] Aluminum alloy particles are used in corrosion inhibitor compounds, which aluminum alloy particles sometimes contain up to 5 to 6% of elements or ingredients other than aluminum. Summary and details of the invention

[0005] U.S. Patent No. 11,739,395 was recently issued and discloses an aluminum alloy containing embrittling elements selected from the group consisting of silicon in an amount of 1 to 30 wt% and / or germanium. This patent claims a method for creating an aluminum powder comprising mixing and melting aluminum with an embrittling element or a combination of embrittling elements. The alloy is cooled, cut into small pieces, which are crushed. The crushed pieces are pulverized and ground to a size of less than 200 microns (for reference, a human hair has a diameter of approximately 50 microns).

[0006] U.S. patent 11,739,395 also describes the use of activators consisting of tin, indium, gallium, and bismuth, mixed with aluminum and embrittling elements. These alloys make it possible to control narrow particle size distributions dlO less than or equal to the value of d50 less 50% of d50 and d90 less than or equal to the value of d50 plus 50% of d50 (i.e., dlO - 5 microns, d50 equal to 10 microns, and d90 equal to 15 microns), as well as powder sizes at least as small as 4 microns in diameter.

[0007] The present invention aims to provide corrosion-inhibiting coatings for metallic substrates that use one or more of the alloys described in U.S. Patent 11,739,395. Collectively, these alloys will be referred to as "high embrittlement" aluminum alloys.

[0008] These alloys include at least the following aluminum alloys: aluminum alloys that are both brittle (elongation less than 1%) and electroactive (in some embodiments, electrical potential less than 0.900 volts relative to a saturated calomel electrode, efficiency greater than 70% and high current density); aluminum alloys with 1-30% (preferably 10-30% by weight of silicon); alloys with these percentages of silicon and either germanium or gallium as additional embrittling elements; alloys with these percentages of silicon with less than 1% each of one or more of the following activation elements (making the alloy more anodic): indium, gallium, tin and bismuth.

[0009] The powdered particles of any of the aforementioned alloys are considered to be particles whose longest diameter is less than or equal to 300 microns, and preferably less than or equal to 200 microns, and preferably still between 10 nanometers and 30 microns.

[0010] In embodiments of the present invention, one or more types of highly embrittling powder particles are incorporated by mixing into a binder to form a corrosion-inhibiting coating on a metallic substrate. In embodiments of the present invention, the corrosion-inhibiting compounds are used on an aluminum alloy substrate that is part of an aircraft.

[0011] The present invention therefore relates to a corrosion-inhibiting coating composition for a metallic substrate, the coating composition comprising: - a film-forming binder; and, - aluminum alloy powder particles, the aluminum alloy containing silicon in the quantity of 1% to 30% by weight as well as one or more elements chosen from a first group, the first group comprising: an element enhancing embrittlement and / or an element enhancing electrochemical anodizing.

[0012] The following optional characteristics of the composition according to the invention, to be taken individually or in combination, may be mentioned as follows:

[0013] - silicon in the aluminum alloy represents 10% to 30% by weight and the The first group comprises 0.01% to 0.50% by weight of tin and 0.005% to 0.05% by weight of indium; and / or

[0014] the ductility of the alloy is less than 1%; and / or

[0015] the alloy is zinc-free; and / or

[0016] the alloy comprises up to 5% zinc by weight; and / or

[0017] the first group consists of tin, indium, germanium, gallium and magnesium, the element chosen or each of the elements chosen being in the quantity of 0.01% to 0.50% by weight.

[0018] - the binder comprises: a hardenable organic or inorganic binder; and / or

[0019] a resin; and / or

[0020] a polymer binder.

[0021] - the binder comprises:

[0022] a film-forming resin selected from the group consisting of epoxy resins, polyesters, polyacrylates, polyurethanes, polyethers, polyaspartic esters, isocyanates, mercapto functional resins, amine functional resins, amide functional resins, imide functional resins, acetoacetate resins, functional fluorinated resins, alkyd resins and their mixtures.

[0023] - the composition further comprises: a hardening agent; or a hardening agent hardening, the hardening agent from a group including hydroxy functional resins, including isocyanates and isocyanurates.

[0024] - the film-forming binder of the coating composition is chosen from the group consisting of polyacrylates, polyurethanes, polyimides, epoxide-derived polymers, isocyanate-derived polymers, and uncured prepolymers or monomers of said polymers; or

[0025] the film-forming binder is chosen from the group consisting of inorganic polymers derived from silanes, siloxanes and silicones; or

[0026] the binder consists of a resin and a hardening agent.

[0027] - the particles have longest dimensions between 1 and 200 microns.

[0028] - half of the particles are between 5 and 20 microns, and / or characterized by the fact that 10% of the particles are less than 5 microns, 50% of the particles are less than 10 microns and 90% of the particles are less than 15 microns.

[0029] - at least part of the particles have a diameter of 4 microns or more.

[0030] - the particles are: coated with a semiconductor coating and / or an oxide metallic; or

[0031] passivated by a conversion coating; or

[0032] treated with a saline solution of titanium and zirconium salts before being added to the binder; or

[0033] coated with a semiconductor corrosion inhibitor derived from a solution consisting essentially of an acidic aqueous solution of about 0.01 to 22 parts of a trivalent chromium compound, about 0.01 to 12 parts of hexafluorozirconate, and about 0.01 to 12 parts of at least one fluorocarbon selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates, of about 0.00 to 12 parts of at least one divalent zinc compound; or

[0034] coated with a semiconductor corrosion inhibitor derived from a solution consisting essentially of an acidic aqueous solution of about 0.01 to 22 parts of a trivalent chromium compound, about 0.01 to 12 parts of hexafluorozirconate, about 0.01 to 12 parts of at least one fluorocarbon selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates, about 0.00 to 12 parts of at least one divalent zinc compound and further comprising up to 5 parts by weight of a corrosion inhibitor.

[0035] - the particles are coated:

[0036] of a semiconductor coating derived from a molybdate solution; or

[0037] of an aqueous solution consisting essentially of trivalent chromium compounds, hexafluoro zirconates and at least one fluorocarbon selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluoro titanates; or

[0038] of a coating derived from a corrosion-resistant aqueous composition having a pH in the range of about 2.8 to 4.0 at temperatures in the range of about 49°C to 93.33°C, the coating composition of particles consisting essentially, in parts by weight per liter of water, of about 20 to 70 parts of potassium hexafluorozirconate, 15 to 92 parts of chromium sulfate (basic), and 0.0 part to about 1.5 parts of potassium tetrafluoroborate.

[0039] - the solution from which the semiconductor corrosion inhibitor is derived includes a stabilizing compound.

[0040] - the composition further comprises a corrosion inhibitor.

[0041] - the corrosion inhibitor is an inorganic or organic compound.

[0042] - the corrosion inhibitor is a lithium salt, the lithium salt being chosen from the inorganic and organic lithium salts which have a solubility constant in water at 25°C in the range of 1x10 11 to 5x102.

[0043] - the corrosion inhibitor comprises a zinc salt of 2,5-dhnercapto-l,3,4- thiadiazole (DMTD), the zinc salt of DMTD being the zinc salt of 2,5-dimercapto-l,3,4-thiadiazole (VII) and a lithium salt having a solubility in water in the range of 0.01 to 120 g / L at 20°C, selected from the group consisting of lithium carbonate, lithium phosphate, lithium bicarbonate, lithium tetraborate and lithium oxalate.

[0044] - the corrosion inhibitor comprises: an effective amount of a synergistic mixture of metallic polycarboxylates; or

[0045] a combination of lithium phosphate with metal polycarboxylate compounds; or

[0046] an organic corrosion inhibitor selected from the group consisting of benzimidazole, benzothiazole, benzoxazole, diphenyl triazole, benzotriazole and tolylazole.

[0047] - the coating composition comprises powdered alloy particles having a chemical composition of AlxSi, where x is an amount of Si from 10 to 30 percent by weight, and any of the binders as defined above.

[0048] - the coating composition comprises powdered alloy particles having a chemical composition of Al20Si0.05Sn0.02In and any of the binders as defined above.

[0049] - the coating composition comprises powdered alloy particles having a chemical composition of AlxSiySnzIn, where x is an amount of Si from 10 to 30 percent by weight, y is an amount of Sn from 0.01 to 0.50 percent by weight, and z is an amount of In from 0.005 to 0.05 percent by weight. A. Binders

[0050] The binders of the present invention may comprise one or a mixture of the following: curable organic or inorganic compositions, resins and resins with curing agents, polymers and the like.

[0051] Binders can be in one part, with curing by moisture / air or UV. Binders can be in two parts, such as a resin and a curing agent (hardener), curing, for example, by cross-linking. Binders can be in three parts.

[0052] Binders include all binders mentioned below. This is only a partial list of binders that can be used with the highly embrittling powder particles according to the invention.

[0053] Binders can also be greases, oils, waxes, lubricants, sealants, adhesives, gels, elastomers, cold sprays and brush application binders.

[0054] In embodiments, the coating compositions may comprise 20 to 95% by weight of the non-volatile film-forming binder, 10 to 70% of coated or uncoated powder particles, and 0.0 to 40% of corrosion inhibitors, all these percentages being by weight. The powder may be placed in the binder in an uncoated state or may be coated before being mixed with the binder.

[0055] In addition to the high-embritability aluminum powder, whether coated or not, placed in the binder, other ingredients may be mixed into the binder / powder mixture. These other ingredients may include at least corrosion inhibitors.

[0056] Corrosion inhibitors generally act on the metallic substrate; here, in certain embodiments, an aluminum alloy substrate such as The aluminum alloy is part of an aircraft. Corrosion inhibitors generally act independently of the aluminum powder or in synergy with it to reduce corrosion of the aluminum substrate.

[0057] At this stage, the Applicant requests the reader to note the use of the word "coating." It is sometimes used to describe the corrosion-inhibiting coating applied to the aluminum substrate, that is, a corrosion-inhibiting coating comprising at least one binder and a high-embrittle aluminum alloy powder. We also use the term "coating" to describe a coating (encasement) on the powder particle itself, which is created during a powder processing procedure before the powder is mixed with the binder. The context will enable the reader to determine whether the term coating refers to the processing of the aluminum powder or to the mixing of the powder and binder.

[0058] The Applicant also requests the reader to note that the powder is an aluminum alloy and that the preferred metallic substrate to which the corrosion-inhibiting coating is applied is also an aluminum alloy. However, the powder is one of the specific aluminum alloys described herein as having high embrittlement properties, whereas the metallic substrate can be any aluminum alloy, such as those commonly found in aircraft construction and aircraft parts.

[0059] B - Coatings on high embrittlement aluminium alloy particles.

[0060] When powders are coated, they are coated to improve protection against galvanic corrosion of the metallic substrate. In other words, the coatings on the highly embrittling aluminum powders presented here can, in certain embodiments, improve their ability to protect the underlying metallic substrate against galvanic corrosion.

[0061] These coatings may include semiconducting coatings, such as metal oxides. They may be coatings derived from acidic aqueous solutions containing trivalent chromium. They may also be coatings derived from titanium zirconate salts or molybdate solutions. Finally, they may be conversion coatings that passivate the surface of aluminum alloy particles. These coatings will be described in more detail below.

[0062] US patents 8,277,688 and 9,243,150 describe a semiconductor coating that can be applied to the aluminum alloy powders described herein. The Applicant applies these coatings to the high-embrittleness aluminum alloy powders described herein. The coatings are derived from trivalent chromium compounds. The powder coating or "pigment" is described as a coating corrosion inhibitor because it helps prevent the aluminum powder from corroding and therefore from no longer being able to act as a sacrificial anode.

[0063] In embodiments, the semiconductor coating is obtained by treating the powder in an acidic aqueous solution of about 0.01 to 22 parts by weight of a trivalent chromium compound, about 0.01 to 12 parts by weight of hexafluorozirconate, about 0.01 to 12 parts by weight of at least one fluorocarbon selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates, about 0.00 to 12 parts by weight of at least one divalent zinc compound.

[0064] In another example, the semiconducting coating on the high embrittlement alloy can be derived from an acidic aqueous solution consisting essentially of about 0.01 to 22 parts by weight of a trivalent chromium compound, about 0.01 to 12 parts by weight of a hexafluorozirconate, about 0.01 to 12 parts by weight of at least one fluorocarbon selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates.

[0065] In another example, the semiconductor coating can be derived from an acidic aqueous solution consisting essentially of about 0.01 to 22 parts by weight of a trivalent chromium compound, about 0.01 to 12 parts by weight of a hexafluorozirconate, about 0.01 to 12 parts by weight of at least one fluorocarbon selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates and about 0.01 to 12 parts by weight of at least one divalent zinc compound.

[0066] In another example, the semiconductor coating can be derived from an acidic aqueous solution consisting essentially of about 0.01 to 22 parts by weight of a trivalent chromium compound, about 0.01 to 12 parts by weight of a hexafluorozirconate, 0.01 to 12 parts by weight of at least one fluorocarbon selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates, about 0.00 to 12 parts by weight of at least one divalent zinc compound, and about 0.01 to 5 parts by weight of a water-soluble organic corrosion inhibitor.

[0067] In another example, the semiconductor coating can be derived from an acidic aqueous solution consisting essentially of about 0.01 to 22 parts by weight of a trivalent chromium compound, about 0.01 to 12 parts by weight of a hexafluorozirconate, about 0.00 to 12 parts by weight of at least one divalent zinc compound, effective amounts of at least one stabilizing compound selected from the group consisting of polyhydroxy compounds, carboxylic compounds and mixtures of polyhydroxy and carboxylic compounds, and 0.00 to 5 parts by weight of a water-soluble organic corrosion inhibitor.

[0068] For the purposes of this application, whenever a range for a component specified herein is from 0.00 to a given quantity, that component is optional.

[0069] The powder coating composition can also be derived essentially from an acidic aqueous solution consisting essentially of about 0.01 to 22 parts by weight of a trivalent chromium compound, about 0.01 to 12 parts by weight of hexafluorozirconate, about 0.01 to 12 parts by weight of at least one fluorocarbon selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates and about 0.0 to 5 parts by weight of a water-soluble corrosion inhibitor.

[0070] The powder coatings described above are generally called trichrome-based coatings (TCP or trichrome passivation). Initial tests with 20% Si, 0.05% tin and 0.02% indium by weight (the remainder being pure aluminum or about 99% purity) revealed that they worked well with the TCP coating, compared with low-silicon aluminum alloys of the prior art (less than 5% Si).

[0071] Semiconductor coatings for the high-embrittleness aluminum alloy powders presented herein, which may be called molybdate-based coatings, are described below. These coatings are described in US patent 17 / 655,298.

[0072] The molybdate solution is capable of reacting with the alloy particles in an uncoated state.

[0073] The molybdate solution is aqueous and comprises a molybdate and at least one of a permanganate and a hexafluorozirconate.

[0074] Molybdate, permanganate, and hexafluorozirconate are selected from the group comprising potassium molybdate, potassium permanganate, and potassium hexafluorozirconate. Each of the components molybdate, permanganate, and hexafluorozirconate present in the molybdate solution is generally present in a molar range from 0.001 to 0.50 moles per liter of the molybdate solution. The coating has a thickness between 1 nanometer and 3 microns.

[0075] The molybdate solution is an aqueous solution and includes a pH adjusting agent and / or a buffer. The pH of the molybdate solution is generally adjusted to between 2 and 4 or between 9 and 11. The coating is generally free of chromium and / or lithium.

[0076] A method for manufacturing the coated high-embrittle powder may include the steps of: mixing the molybdate or TCP solution; and adding the metal particles to the mixed molybdate or TCP solution. The mixed solution is capable of receiving the metal particles immediately after mixing the said molybdate solution, but TCP may require some time before it can be used.

[0077] The coating method may further include at least one of the following steps: cleaning the metal particles before adding them to the solution; agitating or stirring the mixture of metal particles and solution for a period of time; allowing the solution to settle; rinsing the wet coated particles; and drying the coated particles.

[0078] The steps for mixing the molybdate solution for use in the powder coating may include the following steps: supplying a quantity of deionized water; adding powdered components of the molybdate solution to the deionized water; and mixing the powdered components of the molybdate solution with the deionized water. The powdered components may be selected from the group comprising: potassium molybdate, potassium permanganate, and potassium hexafluorozirconate.

[0079] The coatings described above can be called molybdate-based powder coatings.

[0080] In addition to the above, there are semiconducting coatings on aluminum particles derived from titanium zirconate salts. A chemical conversion coating on an aluminum alloy (whose chemical composition consists of Mg 2.2%–2.8%, Si 0.25%, Cu 0.1%, Zn 0.1%, Mn 0.1%, Fe 0.4%, Cr 0.15%–0.35%, and the remainder being Al) was used as a solution for coating the metal particles. The chemical conversion coating was prepared using K₂ZrF₆ and K₂TiF₆ as the main salts, KMnO₄ as the oxidant, and NaF as the accelerator. The same process is proposed by the applicant company for the high embrittlement powder. The results showed that the prepared conversion coating consisted mainly of A1F3.3H2O, A12O3, MnO2 and TiO2, and that it exhibited good corrosion resistance.

[0081] The conversion treatment solution consisted of KMnO4: 2-4 g L-1, NaF: 0.1 g L-1, K2ZrF6: 0.25-0.75 g L-1, and K2TiF6: 1-1.5 g L-1. The pH was approximately 2, the treatment temperature was in the range of 70 to 80 °C, and the treatment time was approximately 5 minutes. The treatment solution consisted of NiSO4·6H2O: 1.2 g L-1 and NaF: 0.6 g L-1. The treatment time was approximately 30 minutes, and the treatment temperature was ambient temperature. After the conversion treatment, the samples were treated in boiling water for approximately 30 minutes, then immersed in fluorosilane (FAS-17: 2 g, isopropanol: 180 g, H2O: 18 g) at room temperature for approximately 24 h. The samples were then oven-dried at 120 °C for approximately 30 minutes. The duration and / or temperature of the Treatment times may be extended for the processing of highly embrittled powders. See https: / / www.mdpi.com / 2079-6412Z8 / ll / 397.

[0082] This conversion coating can be used on powder with high embrittlement.

[0083] C. Corrosion inhibitors to be mixed in the binder / powder mixture.

[0084] The applicant requests the reader to note that corrosion inhibitors can be used both in the formulation for coating the powder particles before the coated powder particles are placed in the binder and that corrosion inhibitors can also be placed in the binder / powder mixture. The role of the former is primarily to slow down corrosion, as they act as a sacrificial anode. The role of the latter is to protect the surface of the aluminum substrate. We will examine below the role of corrosion inhibitors to be mixed in the binder / powder mixture.

[0085] Any corrosion-resistant coatings may further include a corrosion inhibitor. The corrosion inhibitor may be ionic or organic.

[0086] The corrosion-resistant coating may comprise at least one corrosion inhibitor selected from the group comprising: a lithium salt, an organic or inorganic lithium salt, lithium phosphate, lithium carbonate, at least one metal polycarboxylate, magnesium-containing materials, metallic magnesium particles, a magnesium alloy, magnesium oxide, magnesium oxyaminophosphate salts, magnesium carbonate and magnesium hydroxide, magnesium citrate, magnesium oxalate, zinc citrate, zinc oxalate, and a combination thereof. In some embodiments, the corrosion inhibitor does not contain lithium. The corrosion inhibitor comprises, in some embodiments, lithium-free synergistic combinations of metal oxalates, metal picrates, metal succinates, metal tartrates, and metal adipates.Some of these can be found in U.S. Patent US8,628,689, incorporated herein by reference, as well as in U.S. Patent US10,351,715.

[0087] The corrosion inhibitor may comprise a zinc salt of 2,5-dimercapto-1,3,4-thiadiazole (DMTD), the zinc salt of DMTD being the zinc salt of 2,5-dimercapto-1,3,4-thiadiazole (VII), and a lithium salt having a solubility in water in the range of 0.01 to 120 g / L at 20°C, selected from the group consisting of lithium carbonate, lithium phosphate, lithium bicarbonate, lithium tetraborate, and lithium oxalate. See WO2023135326.

[0088] The corrosion inhibitor comprises, in embodiments, a combination of lithium phosphate with metal polycarboxylate compounds, as indicated in US patent 10,889,723.

[0089] The corrosion inhibitor may be an organic corrosion inhibitor selected from the group consisting of benzimidazole, benzothiazole, benzoxazole, diphenyl triazole, benzotriazole, and tolylazole. These are described in US patent 9,243,150.

[0090] Corrosion inhibitors may include zinc and magnesium phosphates, individually or in mixture, up to 50% by weight of the final coating composition, with or without any of the polycarboxylates listed above or with or without any of the lithium salts listed above.

[0091] The following embodiments describe the incorporation of metal carboxylate salts into chromium-free conversion coatings in the binder / powder mixture for the purpose of increasing corrosion resistance. The compositions of the inhibitory salts are described as follows. The anions include polycarboxylates selected from linear and branched aliphatic molecules such as oxalate, citrate, tartrate, succinate, malonate, and adipate, and the like. The cations include zinc, magnesium, manganese, calcium, strontium, zirconium, scandium, yttrium, lanthanum, and other lanthanides such as cerium, praseodymium, neodymium, samarium, europium, and gadolinium. The choice of flag and cation will influence solubility in water as well as reactivity with other chemicals involved in the conversion coating solution and / or the metallic substrate.

[0092] Metal carboxylate salts are added to the chromium-free conversion coating in amounts ranging from approximately 0.5 to 5.0 grams per liter and may be added individually or in combination with other inhibitors. Carboxylate inhibitors may be mixed with other carboxylate inhibitors using the same cation. For example, but without limitation, zinc oxalate and zinc malonate may be mixed, or they may be mixed with different cations with the same or different anions. As another example, but without limitation, cerium oxalate and zinc oxalate or cerium oxalate and zinc malonate may be mixed.Carboxylate inhibitors can also be combined with soluble inorganic salts having the same cation, such as zinc oxalate and zinc sulfate, or they can be mixed with different cations with different anions, such as zinc oxalate and lithium phosphate.

[0093] Inhibitors can also be mixed in different molar ratios to achieve maximum synergistic performance. This can range, but is not limited to, from relatively low concentrations of a few milligrams per liter to concentrations beyond the supersaturation point for the carboxylate inhibitor, which can no longer dissolve in solution.

[0094] These relate more specifically to synergistic combinations of metal polycarboxylates and methods of treating the metal to improve its corrosion resistance. The method consists of applying to the metal surface a chromium-free conversion coating comprising an effective amount of a synergistic mixture of metal carboxylates, more precisely, but without limitation, a synergistic mixture of corrosion inhibitors, consisting of at least two different metal carboxylates, such as polycarboxylic acids selected from linear and branched aliphatic molecules like oxalate, succinate, and adipate, and aromatic molecules like phthalate, mellitate, and trimellitate, and the like. These are specific examples of certain molecules. Many other polycarboxylic acids can be used to prepare the synergistic combination.

[0095] The cations of metal carboxylates are identified in the periodic table and include, for example, but without limitation, elements selected from: Group Ia – lithium, potassium, and sodium; Group Ia – magnesium, calcium, strontium, and barium; Group IIIb – scandium, yttrium, lanthanum, and other lanthanides; Group IVb – titanium and zirconium; Group Vb – vanadium and niobium; Group VIb – chromium and molybdenum; Group VIIIb – manganese; Group VIII – iron, cobalt, and nickel; Group Ib – copper; Group Ib – zinc; Group IIIa – aluminum; and Group Va – bismuth. See US20230136068.

[0096] D. Other ingredients for the binder / powder mixture

[0097] Surfactants, wetting agents, antifoams, or adhesion promoters may be used as required. When the binder is a resin and the curing agent is a hardening agent, an accelerator may be used. E. Charge of the binder / powder mixture

[0098] The binder / powder mixture may comprise, by non-volatile weight of the film-forming composition: 20-95% binder; 10-70% coated particles; and 0.0-40% corrosion inhibitor. Optionally, 0.0 to 5.0 parts, and preferably 0.1 to 1.5 parts, of at least one wetting agent or surfactant and approximately 0.0 to 5.0 parts of a solvent such as water or an organic solvent.

[0099] F. Uses of the new corrosion inhibitor compound

[0100] Use of the new corrosion-inhibiting coating compositions described herein.

[0101] The new corrosion-inhibiting coatings can be used on aluminum alloys whose surface can be pretreated before the coating is applied. For example, the aluminum alloy substrate can be pretreated with conversion coatings known in the prior art, can be anodized, or can be treated to increase the adhesion of the binder to the surface of the aluminum alloy.

[0102] The new corrosion-inhibiting coatings can be used as a primer or paint on the exterior or interior of an aluminum or aluminum alloy surface or part of an aircraft.

[0103] Although the invention has been described with reference to specific embodiments, this description should not be interpreted in a restrictive manner. Various modifications of the described embodiments, as well as other embodiments of the invention, will be apparent to those skilled in the art by referring to the description of the invention.

Claims

Demands

1. Corrosion inhibitor coating composition for a metallic substrate, the coating composition comprising: - a film-forming binder; and, - powdered aluminum alloy particles, the aluminum alloy containing silicon in the amount of 1% to 30% by weight as well as one or more elements selected from a first group, the first group comprising: an element enhancing embrittlement and / or an element enhancing electrochemical anodizing.

2. Coating composition according to claim 1, characterized in that: the silicon in the aluminum alloy represents from 10% to 30% by weight and the first group comprises from 0.01% to 0.50% by weight of tin and from 0.005% to 0.05% by weight of indium; and / or the ductility of the alloy is less than 1%; and / or the alloy is free of zinc; and / or the alloy comprises up to 5% by weight of zinc; and / or the first group consists of tin, indium, germanium, gallium and magnesium, the chosen element or each of the chosen elements being in the amount of 0.01% to 0.50% by weight.

3. Coating composition according to any one of claims 1 or 2, characterized in that the binder comprises: a sand-cured organic or inorganic binder; and / or a resin; and / or a polymer binder.

4. Coating composition according to any one of claims 1 or 2, characterized in that the binder comprises: a film-forming resin selected from the group consisting of epoxy resins, polyesters, polyacrylates, polyurethanes, polyethers, polyaspartic esters, isocyanates, mercapto functional resins, amine functional resins, amide functional resins, imide functional resins, acetoacetate resins, functional fluorinated resins, alkyd resins and mixtures thereof.

5. A coating composition according to claim 4, characterized in that it further comprises: a curing agent; or a curing agent, the curing agent being derived from a group including hydroxy functional resins, including isocyanates and isocyanurates.

6. Coating composition according to any one of claims 1 or 3, characterized in that: the film-forming binder of the coating composition is selected from the group consisting of polyacrylates, polyurethanes, polyimides, epoxy-derived polymers, isocyanate-derived polymers, and uncured prepolymers or monomers of said polymers; or the film-forming binder is selected from the group consisting of inorganic polymers derived from silanes, siloxanes and silicones; or the binder consists of a resin and a curing agent.

7. Coating composition according to any one of claims 1 to 6, characterized in that the particles have longest dimensions between 1 and 200 microns.

8. Coating composition according to claim 7, characterized in that half of the particles are between 5 and 20 microns, and / or characterized in that 10% of the particles are less than 5 microns, 50% of the particles are less than 10 microns and 90% of the particles are less than 15 microns.

9. Coating composition according to any one of claims 7 or 8, characterized in that at least a portion of the particles have a diameter of 4 microns or more.

10. A coating composition according to any one of claims 1 to 9 characterized in that the particles are: coated with a semiconductor coating and / or a metal oxide; or passivated by a conversion coating; or treated with a saline solution of titanium and zirconium salts before being added to the binder; or coated with a semiconductor corrosion inhibitor derived from a solution consisting essentially of an acidic aqueous solution of about 0.01 to 22 parts of a trivalent chromium compound, about 0.01 to 12 parts of hexafluorozirconate, about 0.01 to 12 parts of at least one fluorocarbon selected from the group consisting of tetrafluoroborates, hexafluorosilicates, and hexafluorotitanates, and about 0.00 to 12 parts of at least one divalent zinc compound; or coated with a semiconductor corrosion inhibitor derived from a solution consisting essentially of an acidic aqueous solution of about 0.01 to 22 parts of a trivalent chromium compound, about 0.01 to 12 parts of hexafluorozirconate, about 0.01 to 12 parts of at least one fluorocarbon selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates, about 0.00 to 12 parts of at least one divalent zinc compound and further comprising up to 5 parts by weight of a corrosion inhibitor.

11. Coating composition according to any one of claims 1 to 9, characterized in that the particles are coated: with a semiconducting coating derived from a molybdate solution; or with an aqueous solution consisting essentially of trivalent chromium compounds, hexafluoro zirconates and at least one fluorocarbon selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluoro titanates; or a coating derived from a corrosion-resistant aqueous composition having a pH in the range of about 2.8 to 4.0 at temperatures in the range of about 49°C to 93.33°C, the coating composition of particles consisting essentially, in parts by weight per liter of water, of about 20 to 70 parts of potassium hexafluorozirconate, 15 to 92 parts of chromium sulfate (basic), and 0.0 part to about 1.5 parts of potassium tetrafluoroborate.

12. Coating composition according to any one of claims 10 or 11, characterized in that the solution from which the semiconductor corrosion inhibitor is derived comprises a stabilizing compound.

13. Coating composition according to any one of claims 1 to 12, characterized in that it further comprises a corrosion inhibitor.

14. Coating composition according to claim 13, characterized in that the corrosion inhibitor is an inorganic or organic compound.

15. Coating composition according to claim 13, characterized in that the corrosion inhibitor is a lithium salt, the lithium salt being selected from inorganic lithium salts and organics which have a solubility constant in water at 25°C in the range of 1x10 11 to 5x102.

16. Coating composition according to claim 14, characterized in that the corrosion inhibitor comprises a zinc salt of 2,5-dimercapto-l,3,4-thiadiazole (DMTD), the zinc salt of DMTD being the zinc salt of 2,5-dimercapto-l,3,4-thiadiazole (VII) and a lithium salt having a solubility in water in the range of 0.01 to 120 g / L at 20°C, selected from the group consisting of lithium carbonate, lithium phosphate, lithium bicarbonate, lithium tetraborate and lithium oxalate.

17. Coating composition according to claim 13, characterized in that the corrosion inhibitor comprises: an effective amount of a synergistic mixture of metal polycarboxylates; or a combination of lithium phosphate with metal polycarboxylate compounds; or an organic corrosion inhibitor selected from the group consisting of benzimidazole, benzothiazole, benzoxazole, diphenyl triazole, benzotriazole and tolylazole.

18. Coating composition according to claim 1, characterized in that it comprises powdered alloy particles having a chemical composition of AlxSi, where x is an amount of Si from 10 to 30 percent by weight, and any of the binders as defined in any one of claims 3 to 6.

19. Coating composition according to claim 1, characterized in that it comprises powdered alloy particles having a chemical composition of Al20Si0.05Sn0.02In and any of the binders as defined in any one of claims 3 to 6.

20. Coating composition according to claim 1, characterized in that it comprises powdered alloy particles having a chemical composition of AlxSiySnzIn, where x is an amount of Si from 10 to 30 percent by weight, y is an amount of Sn from 0.01 to 0.50 percent by weight, and z is an amount of In from 0.005 to 0.05 percent by weight.