PURPOSE: To develop a corrosion-resisting hydrophilic film-forming agent causing no effusion of sexivalent Cr and exercising its effects for a long period by further adding polyhydric alcohol and saccharides to a hydrophilic metallic surface-treating agent for a chromium-acrylic acid polymer-fluoride-silica-type Al material.
CONSTITUTION: As the forming agent for forming a film combining superior hydrophilic property with corrosion resistance onto the Al-type metal, an aqueous solution containing the following is used: trivalent Cr compounds such as chromium hydroxide, chromium sulfate, etc., and Cr compounds of sexivalent Cr etc., such as CrO3, by 2W20g/l expressed in terms of CrO3 (where sexivalent Cr>1g/l); water-soluble acrylic acid polymers, by 2W20g/l as a solid; fluorides such as hydrofluoric acid etc., by 0.1W5g/l expressed in terms of F; phosphoric acid such as orthophosphoric acid etc., by 0.1W50g/l expressed in terms of P43-; powdered silica so that the ratio of silica to the total solid is 0.2W0.8; and further, water-soluble reducing agents such as polyhydric alcohol, saccharides, etc., by 0.2W50g/l. In this way, the corrosion-resisting hydrophilic film-forming agent free from effusion of noxious CrO3 and exercising its effects over a long period can be obtained.
ISOBE MASASHI
ENDO MARIKO
