A multi-component corrosion inhibitor mixture for film-forming binders for the protection of metal substrates

Abstract

The present invention relates to a multi-component corrosion inhibitor mixture for film-forming binders for the protection of metal substrates. The corrosion inhibitor composition according to the present invention comprises at least two metal polycarboxylate salts and at least one metallic non-lithium phosphate salt. Furthermore, the corrosion protection coating for a metallic surface according to the present invention comprises the corrosion inhibitor composition according to the present invention.

Description

Field of invention

[0001] The present invention generally relates to corrosion inhibitors for use with film-forming binders for the protection of metallic surfaces. BACKGROUND

[0002] Many metals are susceptible to corrosion, especially when exposed to harsh environments such as those found around vehicles, including aircraft, marine vehicles, and land vehicles. This corrosion can include galvanic corrosion on the surface of the metals, particularly in the presence of an electrolyte such as salt water. To combat corrosion, paints, primers, or other film-forming binders can be used to coat metallic surfaces and help prevent them from being exposed to the elements. These binders may contain corrosion inhibitors that, in some formulations, can react with the surface of the metal to inhibit corrosion, including galvanic corrosion.However, these chemicals must be designed to inhibit corrosion rather than promote it, which is sometimes a difficult task and may require intensive experimentation to determine their effectiveness on specific metal substrates.

[0003] It is known to incorporate corrosion inhibitor mixtures into film-forming binders, see US patents Nos. 10,351,715 and 10,889,723, both of which are hereby incorporated by reference. SUMMARY OF THE INVENTION

[0004] The present invention, in at least one embodiment, is generally directed to a novel multi-component corrosion inhibitor, sometimes for use with a film-forming binder. The multi-component corrosion inhibitor comprises at least three metallic salt components.

[0005] At least one of the at least three metallic salt components can be lithium-free. The lithium-free metallic salt can be a phosphate salt. The phosphate salt can be nickel phosphate or magnesium phosphate.

[0006] One of the at least three metallic salt components can be a non-phosphate lithium salt.

[0007] The multi-component corrosion inhibitor can comprise four metallic salt components, for example: two metal polycarboxylate salts, preferably a zinc citrate and a zinc oxalate, a nickel salt, preferably nickel oxalate, and a nickel phosphate. In this embodiment, a non-phosphate lithium salt can replace the nickel phosphate.

[0008] In an alternative embodiment, the at least three metallic salt components include zinc citrate, zinc oxalate, and magnesium phosphate. In this embodiment, a non-phosphate lithium salt can replace the magnesium phosphate.

[0009] The above, as well as further tasks, features and advantages of the various embodiments of the present invention, will become clear from the following detailed description. DESCRIPTION OF THE PREFERRED FORM(S)

[0010] In a broad embodiment, the multi-component corrosion inhibitor composition of the present invention comprises at least two metal polycarboxylate salts and at least one non-lithium metallic salt. In some embodiments, the at least two metal polycarboxylate salts are selected from the anion group consisting of citrates and oxalates. In some embodiments, both carboxylate salts are zinc carboxylates, one a citrate and one an oxalate. In some embodiments, the third metal salt is a nickel oxalate, nickel phosphate, or magnesium phosphate, and is preferably magnesium phosphate. An additional fourth metal salt may be present if the third metal salt is a nickel oxalate. The fourth metal salt may be selected from the group containing a non-lithium metallic phosphate, in some embodiments a nickel phosphate.

[0011] Example A, a three-part inhibitor, comprising and in some embodiments consisting of, or in other embodiments essentially consisting of: Zinc citrate. Zinc citrate (C 12 H 10 O 14 Zinc (Zn3) is a zinc salt of citric acid, readily soluble in water, and used in dental and pharmaceutical products. Zinc oxalate (ZnC2O4) is a white crystalline powder at room temperature and can be used to treat metals.

[0012] Magnesium phosphate. Magnesium phosphate (Mg3(PO4)2) is used as a muscle relaxant.

[0013] Example B is a four-part inhibitor comprising, or in some embodiments consisting of, or in other embodiments essentially consisting of: Zinc citrate and zinc oxalates as indicated above; Nickel oxalate (C2NiO2). Nickel oxalate is a light green powder that is insoluble in water and can be used in the production of metals. Nickel phosphate (Ni3(PO4)2) is a paramagnetic, light green solid that is insoluble in water and is used in the electroplating of metals.

[0014] All of the above ingredients can be purchased from chemical suppliers or produced in a laboratory using known reactions. All are powders at room temperature and safe to handle.

[0015] In some embodiments, each of the multi-component corrosion inhibitor combinations specified herein can be mixed into a film-forming binder for use on a metallic substrate, including an aluminum alloy substrate. In some embodiments, the multi-component corrosion inhibitor combination can be mixed into a curable binder prior to curing, and in some embodiments, the curable binder is a polymer, including an amine epoxy compound. The corrosion inhibitor combination can be mixed into the binder in a weight ratio of 10% to 90% (10%–65%).

[0016] In some embodiments, the curable binder is one part; in some embodiments, the binder is two parts, one side resin and one side curing agent (hardener), wherein the inhibitor combination can be mixed into one or both sides.

[0017] Metal particles, in some embodiments metal particles between 1 and 200 micrometers (in some embodiments 1-70 micrometers) as their longest dimension, may be added to the coating to provide additional protection for a metal substrate if the metal particles are more anodic than the metal substrate onto which the coating composition is applied. In this way, the metal particles can act as sacrificial anodes. The metal particles may be coated aluminum alloy particles. With regard to metal particles, coated or uncoated, as well as film-forming binders, see the following documents, all of which are incorporated herein by reference: U.S. Patent No. 8,262,938; U.S. Patent No. 8,277,688; U.S. Patent No. 9,243,333; U.S. Patent No. 9,243,150; U.S. Patent Application Publication No. 2012 / 0025142. and PCT application no. US2018 / 066843.In some embodiments, the metal particles are high-silicon aluminum with 20% silicon, 0.05% tin, and 0.02% indium (by weight). In some embodiments, the coated or uncoated particles may be an aluminum alloy containing zinc and indium.

[0018] The metal particles can be coated with a semiconducting corrosion-inhibiting coating.

[0019] The semiconducting corrosion-inhibiting coating can be provided by a semiconducting corrosion-inhibiting oxide on the nanometer scale, wherein the oxide is derived from an acidic aqueous solution consisting essentially, by weight, of: 0.01 to 22 parts of a trivalent chromium compound, of 0.01 to 12 parts of a hexafluorozirconate, of 0.01 to 12 parts of at least one fluorine compound selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates.

[0020] In one embodiment, the coating composition is curable below 120 °C and comprises a film-forming resin, a curing agent for the film-forming resin, and a four-part corrosion inhibitor mixture comprising zinc citrate, a zinc oxalate salt, a nickel oxalate salt, and a nickel phosphate salt. In another embodiment, the inhibitor mixture comprises three parts: two zinc components and magnesium phosphate.

[0021] The film-forming binder can be a resin and can be selected from the group consisting of epoxy resins, polyesters, polyacrylates, polyurethanes, polyethers, polyaspartic acid esters, polysiloxanes, isocyanates, mercapto-functional resins, amine-functional resins, amide-functional resins, imide-functional resins, silane-containing resins, polysiloxanes, acetoacetate resins, functionally fluorinated resins, alkyd resins and mixtures thereof.

[0022] The following corrosion inhibitor coatings were produced in the following combinations. Each coating (mixtures of 3 and 4 parts) was produced by combining (brushing) the mixtures in an amine epoxy binder at a loading rate of 20-80% by volume, to a thickness of approximately 1-3 mil on a clean 3" x 6" aluminum 2024 alloy substrate, which was then allowed to dry. Step 1: Dissolving the resin. Epon 1001 F resin 40% MAK (methylamyl ketone): 60% Epon 1001 F (wt.%) Step 2: Creating the binder. 83.3 grams MAK: Epon, mixed with 4.21 grams Ethacure 2000 (amine hardener) for the binder. Step 3: Mixing the inhibitors Example A: Take 2 mol zinc oxalate or 60 wt% of the inhibitor mixture (25-75%), 1 mol zinc citrate or 25% (25-75%), and 1 mol magnesium phosphate 15% (5-30%). In the three-part mixture, a non-phosphate lithium salt can replace the magnesium phosphate. Or Example B: Take 2 mol zinc oxalate and 1 mol zinc citrate: (the same weight percentages as stated above), 1 mol nickel oxalate 7.5% (5-30%): 1 mol nickel phosphate 7.5% (5-30%). In the four-part mixture, a non-phosphate lithium salt can replace the nickel phosphate. Mix and combine until a homogeneous powder forms. Step 4: Creating the coating

[0023] Take 10g of TCP (trichrome)-passivated aluminum alloy (AlZnIn) particles, 1-70 micrometers longest dimension, add 4 grams of inhibitor mixture, add 12 grams of binder mixture and place this in a shear mixer under vacuum for 2 minutes at 1500 rpm or until thoroughly mixed.

[0024] Initial Open Cell Potential (OCP) and potentiodynamic polarization tests were performed (Gamry Instruments Potentiostat Model # Reference 620) and it was shown that the inhibitor combinations were successful in preventing corrosion compared to a non-inhibitor control and proved advantageous compared to several inhibitor combinations, some of which contained lithium salt.

[0025] Standard salt spray tests confirmed the effectiveness of the inhibitor mixtures listed herein on aluminium alloy substrates.

[0026] The corrosion inhibitor composition can be mixed with a binder to form a coating, primer, grease, oils, gel, wax, elastomer, sealant, gasket or sealing material.

[0027] The binder compositions disclosed herein are particularly useful in coatings and primers for application on aircraft surfaces, including exterior and interior surfaces, including those comprising an aluminium alloy.

[0028] The preceding description includes numerous details for explanatory purposes, to ensure a thorough understanding of the embodiments. However, it will be clear to those skilled in the art that these specific details are not necessary. In other cases, well-known structures and components are shown in the form of a clock diagram so as not to impair understanding.

[0029] The embodiments described above are intended to be examples only. Modifications, alterations, and variations may be made by those skilled in the art to specific embodiments. The scope of the claims should not be limited to the specific embodiments given in the examples, but should be interpreted in the broadest way that is consistent with the overall description. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 2018 / 066843

[0017]

Claims

[1] A corrosion inhibitor composition comprising at least two metal polycarboxylate salts and at least one metallic non-lithium phosphate salt. [2] The composition according to claim 1, wherein the at least two metal polycarboxylate salts are selected from an anion group comprising citrates and oxalates. [3] The composition according to claim 2, wherein the at least two metal polycarboxylate salts comprise zinc citrate and zinc oxalate. [4] The composition according to one or more of claims 1 to 3, which further comprises at least one nickel salt. [5] The composition according to claim 4, wherein the at least one nickel salt is selected from the group comprising: nickel oxalate and nickel phosphate. [6] The composition according to one or more of claims 1 to 5, wherein the at least one metallic non-lithium phosphate salt is selected from the group comprising: nickel phosphate and magnesium phosphate. [7] The composition according to claim 5, wherein the nickel salt is nickel oxalate and the composition further comprises a fourth salt, wherein the fourth salt is nickel phosphate. [8] The composition according to claim 7, which essentially consists of zinc oxalate 25-75%, zinc citrate 25-75%, nickel oxalate 5-30% and nickel phosphate 5-30%, based on the weight of the inhibitor composition. [9] The composition according to claim 6, if this depends on one of several of claims 1 to 3, wherein the metallic non-lithium phosphate salt is magnesium phosphate. [10] The composition according to claim 9, which essentially consists of zinc oxalate 25-75%, zinc citrate 25-75%, and magnesium phosphate 5-30%, based on the weight of the inhibitor composition. [11] A corrosion protection coating for a metallic surface, wherein the corrosion protection coating comprises one of the corrosion inhibitor compositions according to one or more of claims 1 to 10 and a binder. [12] The corrosion protection coating according to claim 11, wherein the binder comprises a resin selected from one or more of the following: epoxy resins, polyesters, polyacrylates, polyurethanes, polyethers, polyaspartic esters, polysiloxanes, isocyanates, mercapto-functional resins, amine-functional resins, amide-functional resins, imide-functional resins, silane-containing resins, polysiloxanes, acetoacetate resins, functionally fluorinated resins, alkyd resins and mixtures thereof. [13] The corrosion protection coating according to claim 11 or 12, wherein the binder is a film-forming binder. [14] The corrosion protection coating according to one of several of claims 11 to 13 in the form of a paint, a primer, a grease, an oil, a gel, a wax, an elastomer, a sealant or a gasket. [15] The corrosion protection coating according to one of several of claims 11 to 14, which further comprises coated or uncoated metal particles. [16] The corrosion protection coating according to claim 15, wherein the metal particles are aluminium alloy particles. [17] The corrosion protection coating according to one or more of claims 15 to 16, wherein the metal particles are coated and the coating is a semi-conductive corrosion-inhibiting coating. [18] The corrosion protection coating according to claim 16, wherein the semiconducting corrosion-inhibiting coating is a semiconducting corrosion-inhibiting oxide on the nanometer scale, wherein the oxide is derived from an acidic aqueous solution consisting substantially, in parts by weight, of 0.01 to 22 parts of a trivalent chromium compound, from 0.01 to 12 parts of a hexafluorozirconate, from 0.01 to 12 parts of at least one fluorine compound selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates. [19] The corrosion protection coating according to one or more of claims 11 to 18, wherein the metallic surface comprises an aluminium alloy surface. [20] A method for protecting an aluminium alloy comprising at least part of a surface of an aircraft, the method comprising: Coating the surface with a corrosion protection coating according to one or more of claims 11 to 19. [21] A method for producing a corrosion protection coating according to one or more of claims 11 to 19, wherein the method comprises: Mixing a corrosion inhibitor composition according to one or more of claims 1 to 10 with the binder. [22] The method according to claim 21, which further comprises the step of mixing the metal particles according to one or more of claims 15 to 18 with the corrosion inhibitor composition and the binder.