In Vitro Corrosion and Antibacterial Performance of Micro-Arc Oxidation Coating on AZ31 Magnesium Alloy: Effects of Tannic Acid

Abstract

A micro-arc oxidation (MAO) coating was deposited with phytic acid (PA) and tannic acid (TA) on the AZ31 Mg alloy. The surface morphologies and chemical compositions were investigated using field-emission scanning electron microscopy, X-ray photoelectron spectrometry, Fourier transform infrared and X-ray diffractometry. Plate counting method was employed to confirm the antibacterial effect of the TA. The corrosion resistance of the coating was measured using electrochemical and hydrogen evolution tests. The results indicated that the thicker TA-MAO coating had smaller pores, no micro-cracks compared to the MAO coating, which possessed a good corrosion resistance and antibacterial activity in Hank’s solution. The molecular recognition effect of TA was discussed. TA also could be used as a stabilizing agent of the hydroxyapatite (HA) precipitate during the immersion. Additionally, the corrosion mechanism for the TA-MAO coating was proposed.