Patent ID: 6719852
Filing Date: 2004-04-13
Classification: C23C,Y10T

Abstract:
A processing solution for forming a hexavalent chromium free, corrosion resistant trivalent chromate conversion film on zinc or zinc alloy plating layers, which comprises:a silicon compound; trivalent chromium and oxalic acid in a molar ratio ranging from 0.5/1 to 1.5/1, wherein the trivalent chromium is present in the form of a water-soluble complex with oxalic acid; and cobalt ions, which are stably present in the processing solution without causing any precipitation due to formation of a hardly soluble metal salt with oxalic acid; wherein the solution reacts with zinc when bringing it into contact with the zinc or zinc alloy plating to form a hexavalent chromium free, corrosion resistant, trivalent chromate conversion film containing zinc, trivalent chromium, cobalt, oxalic acid and SiO2 on the plating.