Preparation and Corrosion Resistance of Trivalent Chromium Passivation Coating on Galvanized Steel

Galvanized steel was passivated with trivalent chromium salt. The effect of passivation conditions on the appearance and corrosion resistance of the passivation coating was investigated, and the optimal condition for trivalent Cr passivation was established. The morphology, composition, crystal structure and corrosion resistance of the passivation coating were analyzed by means of scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction and electrochemical testing. It was found that the passivation coating possessed corrosion resistance comparable to that of hexavalent Cr conversion coating, and was mainly composed of ZnO, FeCr and ZnCrxOy. The smooth and dense passivation coating was able to effectively protect the metal substrate and increase the corrosion resistance.