Chromium-Free Passivation Process for Zinc Coating

A chromium-free colorful passivation technology for zinc coating was developed. Thus the beautiful rainbow-color-like passivation film was obtained on the zinc coating by properly controlling the passivation condition in the presence of major raw material molybdate and a synergistic inhibitor. The optimized passivation process was established, and the corrosion resistance of the molybdate conversion coating was investigated by means of electrochemical techniques using chromate conversion coating and zinc coating as the comparisons. It was found that the chromium-free passivation process based on the molybdate could be used to effectively increase the corrosion resistance of the zinc coating.