Preparation and study of a molybdate passivation film on zinc alloy

Abstract

Molybdate passivation film was prepared on the surface of Zn-Fe alloy coating by chemical passivation treatment, and compared with unpassivation and conventional tungstate passivation film. The surface leveling of molybdate passivation film is the best, and tungstate surface still has a few protrusions. Salt spray test shows that the white rust time after passivation by sodium molybdate is up to 127 h, which is much longer than the unpassivation time. After passivation, the corrosion current density of the two passivated surfaces decreased significantly, and the molybdate passivated surface was 0.815 × 10−2 μA cm−2, tungstate passivated surface was 1.653 × 10−2 μA cm−2, and the unpassivated surface was 2.187 × 10−2μA cm−2.EIS experiment showed that the corrosion current density of the two passivated surfaces decreased significantly. Molybdate passivation has the highest resistance Rp 3582.9 Ω ·cm2.