Technology of environment-friendly chemical conversion coating for magnesium alloy

The surface morphologies,phase structures and corrosion resistance of the stannate conversion coating on AZ91D magnesium alloy gained from an environment-friendly conversion process were investigated by using SEM,XRD and salt immersion test.The results show that the conversion coating consisted of α phase,β phase and MgSnO3·3H2O.The silvery white coating composed of sphere-like particle layer formed uniform right on the under layer,with uniformand level surface.The environment-friendly chromium-free process was more effective to improve the corrosion resistance of magnesium alloys than that of the traditional DOW7 process.