Corrosion resistant trivalent chromium phosphated chemical conversion coatings

A process for preparing a corrosion-resistant trivalent chromium conversion coating on metal substrates comprises treating the substrates with an acidic aqueous solution, which is free of hexavalent chromium, comprising a water soluble trivalent chromium compound, a water soluble fluoride compound, and an additive comprising at least one organic amino-phosphonic acid compound for improved corrosion resistance properties, wherein the improved corrosion protection is provided by adsorption of phosphonate groups of the organic amino-phosphonic acid compound on a surface of the metal subtrate to form a Metal-O—P covalent bond and subsequent formation of a network hydrophobic layer over any active corrosion site on the metal subtrate.

An article having improved corrosion protection comprises an aluminum substrate, an anodized coating on the aluminum substrate and a seal-coating on the anodized coating, wherein the seal coating comprises trivalent chromium and phosphorous, wherein the improved corrosion protection is provided by adsorption of phosphonate groups of an organic amino-phosphonic acid compound on a surface of the aluminum substrate to form a Al—O—P covalent bond and subsequent formation of a network hydrophobic layer over any active corrosion site on the aluminum substrate.