Corrosion Resistance and Antibacterial Properties of Ag-Containing MAO Coatings on AZ31 Magnesium Alloy Formed by Microarc Oxidation

Abstract

Silver-containing oxide coatings on AZ31 Mg alloys were fabricated by microarc oxidation (MAO) in -containing sodium silicate -based electrolyte, and their physical and chemical properties were investigated, particularly focusing on corrosion resistance and antibacterial activity. The porous oxide coatings consisting of and MgO formed in both -containing and -free electrolytes and the MAO coatings were composed of a porous outer layer and a dense inner layer. MAO in -containing electrolyte resulted in a thicker oxide coating, especially a thicker fluorine (F)-rich inner layer. Fluorine (F) was rich in the dense inner layer, and Ag was preferentially located close to the coating surface. The potentiodynamic test indicated that Ag-containing MAO coating had a more positive corrosion potential (−1.42 V), lower corrosion current density , and thus higher corrosion resistance compared to Ag-free MAO coatings (−1.53 V, , and , respectively). The electrochemical impedance spectroscopy results revealed that the higher corrosion resistance of Ag-containing MAO coating was due to an order of magnitude higher resistance of the dense inner layer. Ag-containing MAO coating showed an excellent antibacterial activity over 99.9% against two strains of bacteria, Staphylococcus aureus and Escherichia coli.