Comparative Research on Properties of Trivalent and Hexavalent Passive Film on Galvanized steel

摘要

The anticorrosive performances of various kinds of conversion films including hexavalent and trivalent chromium passivation were studied on galvanized steel. The hexavalent and trivalent passivations showed similar protection tendency in the corrosion tests, but the hexavalent passivation had slightly better results than trivalent one. It was found the difference in the corrosion resistance given by the two films was attributed to the difference of their morphology and thickness by SEM test, for the hexavalent film was denser, smoother and thicker. Using EDS and XRD experiments, it was found that the hexavalent and trivalent passive films had the same chemical element but different components. Considering the environmental protection, the trivalent passivation will have better developing prospect in the near future.