Investigation of the surface modification of magnesium particles with stannate on the corrosion resistance of a Mg-rich epoxy coating on AZ91D magnesium alloy

Abstract A stannate bath was used to pretreat Mg particles in an Mg-rich primer (MRP) coated on the AZ91D magnesium alloy. The duration of the stannate treatment and its effects on the MRP were investigated. After about 20 min of stannate treatment, a protective film of Mg stannate was formed on the surface of the Mg particles and could decrease the corrosion rate of pure Mg. In the first stage, the Mg stannate film reduced the reaction rate of pure Mg particles, prolonging the lifetime of the MRP. In addition, the stannate treatment caused the formation of compact corrosion products in the MRP, improving the barrier effect of the primer. Finally, a protective film consisting of Mg stannate was formed on the AZ91D substrate. The protective film could reduce the corrosion rate of the AZ91D alloy, improving the protective performance of the MRP.