MULTI-COMPONENT CORROSION INHIBITOR MIXTURE FOR FILM-FORMING BINDERS INTENDED TO PROTECT METALLIC SUBSTRATES

Abstract

MULTI-COMPONENT CORROSION INHIBITOR MIXTURE FOR FILM-FORMING BINDERS INTENDED TO PROTECT METALLIC SUBSTRATES. A corrosion inhibitor composition comprises at least two metal polycarboxylate salts and at least one non-lithium metal phosphate salt. The metal polycarboxylate salts may be citrates and / or oxalates. The non-lithium metal phosphate salts may be nickel phosphate or aluminum phosphate.

Description

Title of the invention: MULTI-COMPONENT CORROSION INHIBITOR MIXTURE FOR FILM-FORMING BINDERS INTENDED TO PROTECT METALLIC SUBSTRATES FIELD OF THE INVENTION

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

[0002] Many metals are susceptible to corrosion, particularly when exposed to harsh environments such as those found around vehicles, including aircraft, marine, and land vehicles. This corrosion can include galvanic corrosion on the surface of metals, especially 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 metal surfaces and help prevent their exposure to weathering. These binders may contain corrosion-inhibiting compositions which, in some embodiments, can react with the metal surface to inhibit corrosion, including galvanic corrosion.However, these chemicals must be designed to inhibit, not promote, corrosion, which is sometimes a difficult task and may require extensive experimentation to determine effectiveness on certain metallic substrates.

[0003] It is known to put corrosion-inhibiting mixtures into film-forming binders, see U.S. patents no. 10,351,715 and 10,889,723, both incorporated by reference to the present description. Summary of the invention

[0004] The present invention, in at least one embodiment, generally relates to a novel multi-component corrosion inhibitor, sometimes intended 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 metal salt components may be lithium-free. The lithium-free metal salt may be a phosphate salt. The phosphate salt may be nickel phosphate or magnesium phosphate.

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

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

[0008] In another embodiment, the at least three metallic components comprise zinc citrate, zinc oxalate, and magnesium phosphate. In this embodiment, the magnesium phosphate may be replaced by a non-phosphate lithium salt.

[0009] The invention relates to a corrosion inhibitor composition, characterized in that it comprises at least two metal polycarboxylate salts and at least one non-lithium metal phosphate salt.

[0010] According to one embodiment, the at least two metal polycarboxylate salts are chosen from an anion group comprising citrates and oxalates.

[0011] According to one embodiment, the at least two metal polycarboxylate salts comprise zinc citrate and zinc oxalate.

[0012] According to one embodiment, the composition further comprises at least one nickel salt.

[0013] According to one embodiment, at least one nickel salt is chosen from the group comprising: nickel oxalate and nickel phosphate.

[0014] According to one embodiment, at least one non-lithium metallic phosphate salt is chosen from the group comprising nickel phosphate and magnesium phosphate.

[0015] According to one embodiment, the nickel salt is nickel oxalate and the composition further comprises a fourth salt, the fourth salt being nickel phosphate.

[0016] According to one embodiment, the composition consists essentially of, by weight of inhibitory composition, zinc oxalate 25-75%, zinc citrate 25-75%, nickel oxalate 5-30% and nickel phosphate 5-30%.

[0017] According to one embodiment, the non-lithium metallic phosphate salt is magnesium phosphate.

[0018] According to one embodiment, the composition consists essentially of, by weight of inhibitory composition, zinc oxalate 25-75%, zinc citrate 25-75% and magnesium phosphate 5-30%.

[0019] Another object of the invention is a corrosion protection coating for a metallic surface, characterized in that the corrosion protection coating comprises any of the corrosion-inhibiting compositions as described above and a binder.

[0020] According to one embodiment, the binder comprises a resin selected from one or more of the following: epoxy resins, polyesters, polyacrylates, polyurethanes, polyethers, polyaspartic esters, polysiloxanes, isocyanates, functional resins mercapto, amine functional resins, amide functional resins, imide functional resins, silane-containing resins, polysiloxanes, acetoacetate resins, functional fluorinated resins, alkyd resins and their mixtures.

[0021] According to one embodiment, the binder is a film-forming binder.

[0022] According to one embodiment, the corrosion protection coating present in the form of a paint, primer, grease, oil, gel, wax, elastomer, sealant and / or gasket.

[0023] According to one embodiment, the corrosion protection coating further comprises coated or uncoated metallic particles.

[0024] According to one embodiment, the metallic particles are aluminum alloy particles.

[0025] According to one embodiment, the metallic particles are coated and the coating is a semiconductor corrosion inhibitor coating.

[0026] According to one embodiment, the semiconductor corrosion inhibitor coating is a semiconductor corrosion inhibitor oxide, on the nanometer scale, the oxide being derived from an acidic aqueous solution consisting essentially of, by weight parts, :

[0027] from 0.01 to 22 parts of a trivalent chromium compound,

[0028] from 0.01 to 12 parts of a hexafluorozirconate,

[0029] from 0.01 to 12 parts of at least one fluorinated compound selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates.

[0030] According to one embodiment, the corrosion protection coating is applied to a metallic surface, and the metallic surface comprises an aluminum alloy surface.

[0031] Another object of the invention is a method for protecting an aluminum alloy comprising at least a portion of an aircraft surface, characterized in that the method comprises:

[0032] coat the surface with a corrosion protection coating as described above.

[0033] Another object of the invention is a method for manufacturing a corrosion protection coating as described above, characterized in that the method comprises:

[0034] mix a corrosion inhibitor composition as described above with the binder.

[0035] According to one embodiment, the process includes the additional step of mixing the metallic particles as described above with the corrosion inhibitor composition and the binder.

[0036] The aforementioned objectives, features and advantages, as well as other objectives, features and advantages of the various embodiments of the present invention, will become clear from the detailed written description that follows.

[0037] DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0038] In a general embodiment, the multi-component corrosion inhibitor composition of the present invention comprises at least two metal polycarboxylate salts and at least one non-lithium metal salt.

[0039] In embodiments, the at least two metal polycarboxylate salts are chosen from the anion group consisting of citrates and oxalates.

[0040] In some embodiments, the two carboxylate salts are zinc carboxylates, one being a citrate and the other an oxalate.

[0041] In embodiments, the third metal salt is nickel oxalate, nickel phosphate or magnesium phosphate, and preferably is magnesium phosphate.

[0042] A fourth additional metal salt may be present if the third metal salt is a nickel oxalate.

[0043] The fourth metal salt can be chosen from the group containing a non-lithium metal phosphate, in some embodiments a nickel phosphate.

[0044] Example A, a three-part inhibitor comprising, and in certain embodiments consisting of, or in other embodiments consisting essentially of:

[0045] Zinc citrate. Zinc citrate (Ci2HioOi4Zn3) is a zinc salt of citric acid, it is slightly soluble in water and is used in dental and pharmaceutical products.

[0046] Zinc oxalate. Zinc oxalate (ZnC2O4) is a white crystalline powder at room temperature and can be used to treat metals.

[0047] Magnesium phosphate. Magnesium phosphate (Mg3(PO4)2) is used as a muscle relaxant.

[0048] Example B is a four-part inhibitor comprising, or in some embodiments consisting of, or in other embodiments consisting essentially of

[0049] zinc citrate and zinc oxalates described above;

[0050] Nickel oxalate (C2NiO2) Nickel oxalate is a light green powder which is insoluble in water and which can be used in the manufacture of metals.

[0051] Nickel phosphate (Ni3(PO4)2) is a light green, paramagnetic solid, insoluble in water and used in the electroplating of metals.

[0052] All of the above ingredients can be purchased from chemical suppliers or manufactured in the laboratory by known reactions. All are powders at room temperature and can be handled safely.

[0053] In embodiments, any one of the multi-component corrosion inhibitor combinations presented herein can be incorporated by mixing into a film-forming binder for use on a metallic substrate comprising an aluminum alloy substrate.

[0054] In some embodiments, the multi-component corrosion inhibitor combination can be incorporated by mixing into a curable binder prior to curing, and in some embodiments, the curable binder is a polymer, comprising an epoxy amine.

[0055] The corrosion inhibitor combination can be incorporated by mixing into the binder in a weight ratio of 10% to 90% (preferably 10% to 65%).

[0056] In some embodiments, the curable binder is in one part; in other embodiments, the binder is in two parts, a resin part and a curing agent (hardener) part; the inhibitor combination can be incorporated by mixing into one or both parts.

[0057] Metallic particles, in certain embodiments of 1 to 200 microns (in other embodiments of 1 to 70 microns), of the largest dimension, may be added to the coating to enhance the protection of a metallic substrate, when the metallic particles are more anodic than the metallic substrate to which the coating composition is applied. In this way, the metallic particles can act as sacrificial anodes. The metallic particles may be coated aluminum alloy particles.For the metallic particles, coated or uncoated, and the film-forming binders, see the following documents, all incorporated into this description 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 International Patent Cooperation Treaty Application No. US2018 / 066843. In some embodiments, the metallic particles are high-silicon aluminum, with 20% silicon, 0.05% tin, and 0.02% indium (weight percentages). In some embodiments, the coated or uncoated particles may be an aluminum alloy containing zinc and indium.

[0058] The metallic particles can be coated with a semiconductor corrosion inhibitor coating.

[0059] The semiconductor corrosion-inhibiting coating can be provided by a semiconductor corrosion-inhibiting oxide, on the nanometer scale, the oxide being derived from an acidic aqueous solution consisting essentially of, by weight parts,

[0060] from 0.01 to 22 parts of a trivalent chromium compound,

[0061] from 0.01 to 12 parts of a hexafluorozirconate,

[0062] from 0.01 to 12 parts of at least one fluorinated compound selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates.

[0063] 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, zinc oxalate, nickel oxalate, and nickel phosphate salt. In another embodiment, the inhibitor mixture comprises three parts: the two zinc components and magnesium phosphate.

[0064] The film-forming binder may be a resin and may be selected from the group consisting of 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, functional fluorinated resins, alkyd resins and mixtures thereof.

[0065] The following corrosion-inhibiting coatings were prepared in the following combinations. One coating of each (3-part and 4-part mixture) was prepared by combining the mixtures in an epoxy amine binder at a 20-80% by volume filler before curing (by brushing) to a thickness of approximately 1-3 mil on a clean 3" x 6" 2024 aluminum alloy substrate and allowing it to dry.

[0066] Step 1: Solvation of the resin.

[0067] Epon 1001 F Resin

[0068] 40% MAC (methyl amyl ketone): 60% Epon 1001F (% by weight)

[0069] Step 2: Binder preparation.

[0070] Mix 83.3 grams of MAC:Epon with 4.21 grams of Ethacure 2000 (amine-based hardener) for the binder.

[0071] Step 3: Mixing the inhibitors

[0072] Example A: Take 2 moles of zinc oxalate or 60% by weight of a mixture of inhibitors (25-75%), 1 mole of zinc citrate or 25% (25-75%), and 1 mole of magnesium phosphate 15% (5-30%). In the three-part mixture, the magnesium phosphate may be replaced by a non-phosphate lithium salt.

[0073] or,

[0074] Example B: Take 2 moles of zinc oxalate and 1 mole of zinc citrate (same weight percentages as above), 1 mole of 7.5% (5-30%) nickel oxalate, and 1 mole of 7.5% (5-30%) nickel phosphate. In the four-part mixture, the nickel phosphate can be replaced by a non-phosphate lithium salt.

[0075] Tumble and mix until a homogeneous powder is obtained.

[0076] Step 4: Coating preparation

[0077] Take 10 g of TCP (trichrome) passivated aluminium alloy (AlZnln) particles of 1 to 70 microns in the longest dimension, add 4 g of inhibitor mixture, add 12 g of binder mixture and finish in a vacuum shear mixer for 2 minutes at 1500 rpm or until everything is well mixed.

[0078] Initial open cell potential (OCP) and potentiodynamic polarization tests were performed (Gamry Instruments potentiostat model # reference 620) and the inhibitor combinations proved effective in preventing corrosion compared to a control without inhibitor and were compared favorably to several inhibitor combinations, some of which included lithium salt.

[0079] Standard salt spray tests have confirmed the effectiveness of the example inhibitor mixtures presented here on aluminium alloy substrates.

[0080] The corrosion-inhibiting composition can be mixed with a binder to form a paint, primer, grease, oil, gel, wax, elastomer, sealant, gasket or sealing material.

[0081] The binder compositions disclosed herein are particularly useful in paints and primers intended to be applied to aircraft surfaces, including exterior and interior surfaces, including those made of an aluminum alloy.

[0082] In the preceding description, for explanatory purposes, numerous details are stated to allow for a thorough understanding of the embodiments. However, it will be obvious to a person skilled in the art that these specific details are not necessary. In other cases, well-known structures and components are represented in the form of a clock diagram so as not to obscure understanding.

[0083] The embodiments described above are given by way of example only. Changes, modifications, and variations may be made to the particular embodiments by those skilled in the art. The scope of the claims shall not be limited by the particular embodiments presented in the examples, but shall be interpreted as broadly as possible in accordance with the description as a whole.

Claims

Demands

1. Corrosion-inhibiting composition, characterized in that it comprises at least two metal polycarboxylate salts and at least one non-lithium metal phosphate salt.

2. Composition according to claim 1, characterized in that the at least two metal polycarboxylate salts are selected from an anion group comprising citrates and oxalates.

3. Composition according to claim 2, characterized in that the at least two metal polycarboxylate salts comprise zinc citrate and zinc oxalate.

4. Composition according to any one of the preceding claims 1 to 3, characterized in that it further comprises at least one nickel salt.

5. Composition according to claim 4, characterized in that at least one nickel salt is selected from the group comprising: nickel oxalate and nickel phosphate.

6. Composition according to any one of the preceding claims 1 to 5, characterized in that said at least one non-lithium metallic phosphate salt is selected from the group comprising nickel phosphate and magnesium phosphate.

7. Composition according to claim 5, characterized in that the nickel salt is nickel oxalate and the composition further comprises a fourth salt, the fourth salt being nickel phosphate.

8. Composition according to claim 7, characterized in that it consists essentially of, by weight of inhibitory composition, zinc oxalate 25-75%, zinc citrate 25-75%, nickel oxalate 5-30% and nickel phosphate 5-30%.

9. Composition according to claim 6, when dependent on any one of claims 1 to 3, characterized in that the non-lithium metallic phosphate salt is magnesium phosphate.

10. Composition of claim 9, characterized in that it consists essentially of, by weight of inhibitory composition, zinc oxalate 25-75%, zinc citrate 25-75% and magnesium phosphate 5-30%.

11. A corrosion protection coating for a metallic surface, characterized in that the protective coating corrosion inhibitor comprises any one of the corrosion-inhibiting compositions according to claims 1 to 10 and a binder.

12. Corrosion protection coating according to claim 11, characterized in that 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, functional fluorinated resins, alkyd resins and mixtures thereof.

13. Corrosion protection coating according to claim 11 or 12, characterized in that the binder is a film-forming binder.

14. Corrosion protection coating according to any one of claims 11 to 13, characterized in that it is in the form of: a paint, a primer, a grease, an oil, a gel, a wax, an elastomer, a sealant and / or a sealant.

15. Corrosion protection coating according to any one of claims 11 to 14, characterized in that it further comprises coated or uncoated metallic particles.

16. Corrosion protection coating according to claim 15, characterized in that the metallic particles are aluminum alloy particles.

17. Corrosion protection coating according to any one of claims 14 to 16, characterized in that the metallic particles are coated and the coating is a semiconductor corrosion inhibitor coating.

18. Corrosion protection coating according to claim 16, characterized in that the semiconductor corrosion inhibitor coating is a semiconductor corrosion inhibitor oxide, on a nanoscale, the oxide being derived from an acidic aqueous solution consisting essentially of, by weight parts, of: 0.01 to 22 parts of a trivalent chromium compound, 0.01 to 12 parts of a hexafluorozirconate, 0.01 to 12 parts of at least one fluorinated compound selected from the group consisting of tetrafluoroborates, hexafluorosilicates and hexafluorotitanates.

19. Corrosion protection coating according to any one of claims 11 to 18 applied to a metallic surface, characterized in that the metallic surface comprises an aluminum alloy surface.

20. A method for protecting an aluminum alloy comprising at least a portion of an aircraft surface, characterized in that the method comprises: coating the surface with a corrosion protection coating according to any one of claims 11 to 19.

21. A method for manufacturing a corrosion protection coating according to any one of claims 11 to 19, characterized in that the method comprises: mixing a corrosion-inhibiting composition according to any one of claims 1 to 10 with the binder.

22. A method according to claim 21, characterized in that it includes the additional step of mixing the metallic particles of claims 15 to 18 with the corrosion-inhibiting composition and the binder.