Composition and method for coating metal surfaces
AssigneeUnion Carbide Corporation
InventorJames W. Davis
Life of this patent
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Abstract
This application is concerned with the treatment of metal surfaces with stable solutions of hexavalent chromium, trivalent chromium, phosphoric acid, polyacrylic acid and water dispersible acrylic emulsion polymer to enhance the corrosion resistance and paint adhesion properties of the metal; the coating uniquely having generally universal utility under a wide variety of paint systems and paint types.
Claims13
The method of making a stable aqueous composition for coating metal surfaces to enhance the corrosion resistance and paint adhesion properties thereof, said composition containing, as the coating forming ingredients:
- hexavalent chromium, trivalent chromium, phosphoric acid, polyacrylic acid, and an acrylic emulsion polymer, and said method comprising:
- (1) forming an aqueous solution of the chromium trioxide and the phosphoric acid;
- (2) reducing about 40 to 60% of the hexavalent chromium to trivalent chromium under conditions adapted to completely dissolve all of the reaction products;
- (3) adding the polyacrylic acid to the partially reduced chromium solution under conditions adapted to insure complete interaction of the reactants present;
- and
- (4) adding the acrylic emulsion polymer to the partially reduced chromium polyacrylic acid solution.
The method of making a stable aqueous composition for coating metal surfaces to enhance the corrosion resistance and paint adhesion properties thereof and which comprises:
- (a) dissolving about 41.5 grams chromium trioxide and about 14.5 grams phosphoric acid (100% H.sub.3 PO.sub.4) in about 250 to 300 ml water;
- (b) adding about 4.4 grams formaldehyde (100% HCHO) under conditions adapted to prevent boilover;
- (c) maintaining the reactants at about 180.degree.-190.degree. F. for sufficient time to effect completion of the partial reduction of the chromium, to eliminate any unreacted formaldehyde and to insure the complete dissolution of the resulting reaction products;
- (d) diluting the resulting solution with about 300-350 ml water;
- (e) adding thereto about 76 grams of a polyacrylic acid solution (25% solids weight/volume) in a manner adapted to complete the reaction between the phosphoric acid and chromium values and the polyacrylic acid;
- (f) bringing the total solution volume to about 800 ml with added water;
- and
- (g) thereafter, adding 160 grams of acrylic emulsion polymer dispersion (containing about 46-47% solids weight/volume) diluted to 200 ml with water, to the partially reduced chromium-polyacrylic acid solution.
A stable aqueous solution for coating metal surfaces to enhance their corrosion resistance and paint adhesion properties, said solution containing:
- (a) about 10 parts by weight of chromium trioxide, about 40-55% of which has been reduced to the trivalent state;
- (b) about 3 to 4 parts by weight of phosphoric acid (100% H.sub.3 PO.sub.4);
- (c) about 4 to 5 parts by weight of polyacrylic acid;
- (d) about 17 to 20 parts by weight of acrylic emulsion polymer solids:
- and
- (e) water to make from about 200 to 4000 parts by weight of solution.
A stable aqueous solution for coating metal surfaces to enhance their corrosion resistance and paint adhesion properties, said solution having a pH between about 1 and 2 and containing:
- (a) about 8.3 grams of chromium trioxide, about 46-50% of which has been reduced to the trivalent state;
- (b) about 2.9 grams of phosphoric acid (100% H.sub.3 PO.sub.4);
- (c) about 3.8 grams of polyacrylic acid;
- (d) about 14.9 grams of acrylic emulsion polymer solids;
- and
- (e) water to make from about 200 ml to 4 liters of solution.
Dependencies are inferred from the claim text.