Processing solution for forming hexavalent chromium free, black conversion film on zinc or zinc alloy plating layers, and method for forming hexavalent chromium free, black conversion film on zinc or zinc alloy plating layers

摘要

It is an object of the present invention to provide a processing solution used for forming a hexavalent chromium free, black conversion film, which is applied onto the surface of zinc or zinc alloy plating layers, and which has corrosion resistance identical to or higher than that achieved by the conventional hexavalent chromium-containing conversion film.