Patent ID: 6620263
Filing Date: 2003-09-16
Classification: C23C

Abstract:
An aqueous liquid working composition for forming a phosphate conversion coating on a metal surface by spontaneous chemical reaction upon contact with said metal surface, said aqueous liquid working composition comprising water and the following components:(A) dissolved phosphate anions that have a concentration in the working composition within a range from about 1.5 g/l to about 4.5 g/l; (B) dissolved zinc cations that have a concentration in the working composition that is within a range from about 0.60 g/l to about 1.30 g/l; (C) dissolved manganese(II) cations that have a concentration in the working composition that is within a range from about 0.35 g/l to about 0.55 g/l; (D) at least one of: (i) dissolved nickel(II) cations that have a concentration in the working composition within a range from about 0.10 g/l to about 1.5 g/l; and (ii) dissolved copper cations that have a concentration in the working composition that is within a range from about 0.0011 g/l to about 0.025 g/l; (E) dissolved fluoride-containing anions that have a stoichiometric equivalent as fluoride in the working composition that is within a range from about 0.45 g/l to about 0.80 g/l; (F) dissolved nitrate ions that have a concentration in the working composition of from about 3.5 g/l to about 8.8 g/l.; and (G) dissolved accelerator consisting of at least one substance, at the specified concentration in the working composition, selected from the group consisting of: (i) about 0.3 g/l to about 4 g/l of chlorate ions; (ii) about 0.01 g/l to about 0.2 g/l of nitrite ions; (iii) about 0.05 g/l to about 2 g/l of m-nitrobenzene sulphonate ions; (iv) about 0.05 g/l to about 2 g/l of m-nitrobenzoate ions; (v) about 0.05 g/l to about 2 g/l of p-nitrophenol; (vi) about 0.005 g/l to about 0.15 g/l of hydrogen peroxide in free or bound form; (vii) about 0.1 g/l to about 10 g/l of hydroxylamine in free or bound form; and (viii) about 0.1 g/l to about 10 g/l of reducing sugar; wherein said aqueous liquid working composition has a Free Acid value within a range from about âˆ’0.5 points to about 1.20 points.