Enhanced Corrosion Resistance of AZ31B Magnesium Alloy by Cooperation of Rare Earth Cerium and Stannate Conversion Coating

摘要

The optimal conditions for formation of single stannate or cerium conversion coatings formed onAZ31B magnesium were selected through orthogonal experiment analysis, and then anticorrosivecomposite film on AZ31B magnesium alloy by a combination process of rare earth cerium andstannate was investigated for the first time by Tafel polarization and electrochemical impedancespectroscopy (EIS). The film formed by single rare earth cerium or stannate can correspondingly retardthe corrosion of AZ31B alloy. However, combination of rare earth cerium and stannate furtherenhances the corrosion resistance clearly; the composite coating has much higher corrosive resistancethan that by each single component. Additionally, the corrosion resistance of the composite filmincreases with increasing immersion time. A comparison of SEM and XRD results further indicatesthat the composite coating shows multilayer film composed of cerium oxide compound, magnesiumstannate compounds and magnesium hydroxide.