Hydrothermal synthesis of corrosion resistant hydrotalcite conversion coating on AZ91D alloy

MgAl hydrotalcite conversion coating was synthesized in situ on AZ91D alloy by hydrothermal treatment in ammonia nitrate aqueous solution. The structure and property of hydrotalcite conversion coating were investigated by Scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and electrochemical measurements. The results show that the hydrothermally synthesized hydrotalcite conversion coating effectively confers good corrosion resistance on AZ91D alloy. The corrosion current density of treated AZ91D alloy is decreased by one order of magnitude as compared to untreated one. It provides a facile way to synthesize chromium-free conversion coating for the corrosion protection of magnesium-aluminum alloy.