Synergistic effect of hydrophobic film and porous MAO membrane containing alkynol inhibitor for enhanced corrosion resistance of magnesium alloy

Magnesium and magnesium alloys have important applications in aviation, electronic devices, medical equipment, and automotive industries, while the corrosion is a common and real problem that must be solved for these applications. In this paper, a novel and effective anti-corrosive composite coating on AZ31 Mg alloys was prepared by the combination of micro-arc oxidation (MAO) layer, corrosion inhibitor and hydrophobic wax film technologies. And among these, the MAO treated micro- and nanopores as the container of corrosion inhibitor and the solid hydrophobic wax as the multifunctional sealing isolating agent. The morphology and phase composition of the resulting composite coatings were investigated by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively, indicating the successful synthesis of the organic-inorganic composite coating. The potentiodynamic polarization and electrochemical impedance spectroscopy measurements showed that compared with the MAO membrane covered Mg alloys, the organic-inorganic composite coating has superior corrosion resistance with the a lower corrosion current (5.764 × 10−9 A/cm2) and a higher protection efficiency (99.7%) after immersion in 3.5 wt% NaCl solution, attributing to the synergistic effect of effective inhibition of inhibitor and the physical barrier ability of hydrophobic film and MAO membrane. This simple and low cost strategy to fabricate organic-inorganic composite anticorrosion coatings would have promising applications in the corrosion protection of the light metals and their alloys.