Patent ID: 8257510

Claim:
A process for forming non-halogen containing trivalent chromium coatings on metal substrates comprising the steps of: (a) preparing a solution comprising 0.25 to 4.0 atomic % of a metal compound selected from the group consisting of zirconium, titanium, hafnium, and mixtures thereof, a source of trivalent chromium, a chelating agent and polyhydroxy alcohol; (b) heating the solution to a temperature of between 40-80° C. to form a polymer gel with entrapped trivalent chromium and a metal selected from the group consisting of zirconium, titanium, hafnium, and mixtures thereof; (c) controlling the pH of the polymer gel between 6.0-8.0; (d) contacting the metal substrate with the polymer gel at a temperature of between 10-80° C. to form a single layer conversion coating on the substrate wherein the single layer conversion coating consists of a non-halogen containing trivalent chromium conversion coating.