Trivalent chromate solution for aluminum or aluminum alloy and method for forming corrosion-resistant film on aluminum or aluminum alloy surface using the same

摘要

The object of the present invention is to provide a method for forming a coating on the surface of an aluminium or aluminium alloy using a trivalent chromate solution which dose not contain any harmful hexavalent chromium, in which the coating has an excellent corrosion resistance and adhesion with paints. The present invention provides a hexavalent chromium free trivalent chromate solution for an aluminium or aluminium alloy, in which the concentration of a trivalent chromium is in the range of from 0.01 to 100 g/L, the concentration of a metal selected from the group consisting of zinc, cobalt, nickel and a combination thereof is in the range of from 0.01 to 100 g/L and the concentration of a fluorine is in the range of from 0.01 to 50 g/L.