LOW SLUDGING COMPOSITION AND PROCESS FOR TREATING ALUMINUM AND ITS ALLOYS

摘要

A highly corrosion-resistant, strongly paint-adherent conversion coating is formed on the surface of aluminiferous metal substrates by contacting such surfaces for 0.5 to 60 seconds with a sludging-free water-based surface treatment bath that has a pH of 1.5 to 4.0 and contains a zirconium compound, phosphoric acid compound, oxidizing agent, and a compound that is a source of hydrogen fluoride (in a quantity that produces a concentration of from 0.0001 to 0.2 g/L HF in the treatment bath). This contact is preferably followed by a water rinse and drying.