TRIVALENT CHROMIUM PASSIVATION AND PRETREATMENT COMPOSITION AND METHOD FOR ZINC-CONTAINING METALS

摘要

Aqueous compositions useful as pretreatments prior to painting and to prevent the formation of white rust in the uncoated condition include an organopolyphosphonic acid or salt thereof, an organosilane, and a trivalent chromium compound. A method for treating a surface of a zinc-containing metal includes contacting the surface with an aqueous composition including an organopolyphosphonic acid or salt thereof, an organosilane, and a trivalent chromium compound. The composition may also include an agent for reducing hydrophilicity, such as a polyacrylic acid. The aqueous composition has been found to be particularly well-suited for treating a zinc-containing metal to passivate the surface, improve paint adhesion, and/or improve corrosion resistance.