Multipurpose surface functionalization on AZ31 magnesium alloys by atomic layer deposition: Tailoring the corrosion resistance and electrical performance

An environmentally friendly atomic layer deposition (ALD) method with excellent atomic scale roughness controllability is developed to fabricate a highly conformal, corrosion preventive and conducting Al doped ZnO (AZO) film on a plasma electrolytic oxidation (PEO) layer coated AZ31 magnesium alloy. Compared with the insulated PEO coated magnesium alloy, the electrical conductivity of the composite coating increases to 25 S m^-1, and in the meantime the anticorrosion performance of the PEO/AZO coating is greatly improved compared to the bare Mg alloy. The enhanced electrical properties of the composite coating are due to the abundant oxygen deficiency in the AZO film generated during the ALD process. The improvement of the corrosion resistance is attributed to the changes in the bond angle and the distance between the surface coating molecule and adsorbent H₂O molecule. As a result, the hydrophilic surface of PEO changes to the hydrophobic surface of AZO, providing a novel process to protect the surface of the magnesium alloy. It is believed that this technique may provide a novel and controllable strategy to expand the practical applications of magnesium alloys.