New sealing treatment of microarc oxidation coating

Silanisation treatment was proposed as a new approach for sealing treatment of microarc oxidation (MAO) coating on Mg alloy AZ91D. The morphologies of the Mg alloy surfaces after MAO with or without silanisation sealing treatment were characterised by scanning electron microscopy. The results demonstrated that quite a few structural defects, including microcracks and micropores, could be observed after MAO treatment, while most of them were able to be well sealed after silanisation treatment. Moreover, the corrosion resistance performances of the Mg alloy after surface treatments were evaluated by potentiodynamic polarisation curves and electrochemical impedance spectroscopy. The results showed that the corrosion current density of the AZ91D Mg alloy combining MAO and silanisation treatment was decreased by five orders of magnitude comparing with the untreated blank substrate, which demonstrates sharply increasing anticorrosive performances of the alloy.