PASSIVATION OF GALVANIZED STEEL BY TRIVALENT CHROME

Passivation treatment technology for hot-dip galvanized steel using a trivalent chrome or a trivalent chrome with acrylic resin had been developed.The effects of the concentration,pH,time and temperature of passivation on the corrosion resistance of passivation film were studied.The best technology of the treatment was acquired by CrO3 being reduced,HNO3 as passivation oxidizer,H2SO4 and HBO3 as additives.In addition,with Cr2(SO4)3 and NaH2PO3 as complexing agents,H2SO4 and HBO3 as additives,adding the ratio of acrylic resin to H2O 1∶3,a best passivation film was formed.The time to white rust emergence on the hot-dip galvanized steel surface was delayed by passivation treatments using a trivalent chrome or a trivalent chrome with acrylic resin,and corrosion resistance of the film treated by the later was better.