| abstract |
A coating composition comprising an aqueous mixture containing acid-stable particles and one or more fluoroacids. The amount of the acid-stable particles in the coating composition is from 0.005% to 8% by weight on a dry weight basis. The acid-stable particles can be selected from aluminum-modified silica particles, nonaluminum-modified silica particles, and organic particles selected from anionically stabilized polymer dispersion particles. The invention is also directed to a coating on a metal substrate. The coating contains acid-stable particles attached to the metal substrate through a metal-oxide matrix. The metal-oxide matrix comprises a metal selected from titanium, zirconium, silicon, hafnium, boron, aluminum, germanium, or tin. |