Inhibition Mechanism of Zinc Chromate in Epoxy Coatings for Magnesium Alloys

By means of electrochemical impedance spectroscopy (EIS), dynamic potential polarization, open circuit potential monitoring and XPS, the corrosion protection mechanism of zinc chromate in epoxy coatings for magnesium alloys was studied. The experimental results showed that zinc chromate antirust pigment could be uniformly dispersed in the coatings and improved the shielding effect of the coatings as well as the adhesion force between coating and magnesium substrate. In 3%NaCl solution, zinc chromate was an anodic type corrosion inhibitor. On the surface of the magnesium alloy, passive film was formed by anodic passivation effects of the chromate ions, and thus inhibited the anodic corrosion process and resulted in a positive shift of corrosion potential and an euhacement of anodic polarization of the coated sample.