Composition and Processes of a Dry-In-Place Trivalent Chromium Corrosion-Resistant Coating for Use on Metal Surfaces
First Claim
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1. A composition for coating or touching-up or both coating and touching-up a metal surface, said composition comprising water and:
- (A) from about 4.5 millimoles per kilogram to about 27 millimoles per kilogram of a component of fluorometallate anions and mixtures of fluorometallate anions, each of said anions comprising;
(i) at least four fluorine atoms; and
(ii) at least one atom of an element selected from the group consisting of titanium, zirconium, hafnium, silicon, aluminum, and boron, and, optionally, one or both of(iii) at least one ionizable hydrogen atom; and
(iv) at least one oxygen atom;
(B) from about 3.8 g/l to about 46 g/l of trivalent chromium cations;
said composition being substantially free of hexavalent chromium.
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Abstract
Corrosion resistant coatings are formed on aluminum by contacting with aqueous solutions containing trivalent chromium ions and fluorometallate ions, the solutions being substantially free of hexavalent chromium. Trivalent chromium films formed on the aluminum surface when tested in 5% NaCl salt spray chamber showed corrosion resistance in excess of 168 hours. Trivalent chromium coated aluminum also serves as an effective base for paint primers.
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Citations
18 Claims
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1. A composition for coating or touching-up or both coating and touching-up a metal surface, said composition comprising water and:
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(A) from about 4.5 millimoles per kilogram to about 27 millimoles per kilogram of a component of fluorometallate anions and mixtures of fluorometallate anions, each of said anions comprising; (i) at least four fluorine atoms; and (ii) at least one atom of an element selected from the group consisting of titanium, zirconium, hafnium, silicon, aluminum, and boron, and, optionally, one or both of (iii) at least one ionizable hydrogen atom; and (iv) at least one oxygen atom; (B) from about 3.8 g/l to about 46 g/l of trivalent chromium cations; said composition being substantially free of hexavalent chromium. - View Dependent Claims (2, 3, 4, 5, 6, 11, 12, 13, 14, 15, 16, 17, 18)
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7. A composition for coating or touching-up or both coating and touching-up a metal surface, said composition being made by mixing together a first mass of water and at least the following components:
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(A) a second mass of at least one water-soluble source of fluorometallate anions to provide in the composition from about 4.5 to about 27 mM/kg of the fluorometallate anions and mixtures thereof, each of said anions comprising; (i) at least four fluorine atoms; and (ii) at least one atom of an element selected from the group consisting of titanium, zirconium, hafnium, silicon, aluminum, and boron, and, optionally, one or both of (iii) at least one ionizable hydrogen atom; and (iv) at least one oxygen atom; (B) a third mass of a component to provide the composition with from about 3.8 g/l to about 46 g/l of trivalent chromium cations; wherein the composition comprises less than 0.04 wt % hexavalent chromium cations and the trivalent chromium cations are not oxidized to hexavalent chromium during coating or touching-up. - View Dependent Claims (8, 9, 10)
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Specification