Composition and method for non-chromate coating of aluminum
First Claim
1. An aqueous acidic solution which is effective in forming a dried in place non-chromate conversion coating on the surface of aluminum or alloys thereof, consisting essentially of:
- (a) from greater than 10 to about 16 grams per liter of a polymer selected from the group consisting of polyacrylic acid and homopolymers thereof;
(b) from greater than 12 to about 19 grams per liter dihydro-hexafluozirconic acid; and
(c) from about 0.17 to about 0.3 grams per liter hydrofluoric acid wherein the ratio of a;
b;
c is in the range of about 0.84 to about 0.89;
1;
up to about 0.02.
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Abstract
A chromate and phosphate free composition and method for forming a dried in place conversion coating for aluminum and aluminum alloys. The method entails the application of the composition to aluminum or aluminum alloys and allowing the composition to dry in place. The composition is an acidic aqueous solution preferably containing more than 8 grams per liter dihydro-hexafluozirconaic acid, more than 10 grams per liter polyacrylic acid and more than 0.17 grams per liter hydrofluoric acid in a ratio of 1:0.84:0.014. The solution forms a dried in place conversion coating having a weight of from 6 to 25 milligrams per square foot in treatment (contact and drying) times as short as 2 seconds.
55 Citations
9 Claims
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1. An aqueous acidic solution which is effective in forming a dried in place non-chromate conversion coating on the surface of aluminum or alloys thereof, consisting essentially of:
-
(a) from greater than 10 to about 16 grams per liter of a polymer selected from the group consisting of polyacrylic acid and homopolymers thereof; (b) from greater than 12 to about 19 grams per liter dihydro-hexafluozirconic acid; and (c) from about 0.17 to about 0.3 grams per liter hydrofluoric acid wherein the ratio of a;
b;
c is in the range of about 0.84 to about 0.89;
1;
up to about 0.02. - View Dependent Claims (2, 3, 4)
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5. A method of forming a conversion coating on the surface of aluminum or alloys thereof, comprising:
- applying to said surface an aqueous acidic solution consisting essentially of;
(a) from greater than 10 to about 16 grams per liter of a polymer selected from the group consisting of polyacrylic acid and homopolymers thereof; (b) from greater than 12 to about 19 grams per liter dihydro-hexafluozirconic acid; and (c) from about 0.17 to about 0.26 grams per liter hydrofluoric acid; and
allowing said solution to dry on said surface in a length of time sufficient to form a conversion coating weighing from about 6 to about 25 milligrams per square foot wherein the ratio of a;
b;
c of said solution is in the range of about 0.84 to about 0.89;
1;
about 0.013 to about 0.014. - View Dependent Claims (6, 7, 8, 9)
- applying to said surface an aqueous acidic solution consisting essentially of;
Specification