EFFECT OF APPLIED VOLTAGE ON ELECTROPHORETIC DEPOSITION OF NANO-HYDROXYAPATITE COATING ON BIODEGRADABLE AZ31 MAGNESIUM ALLOY AND ITS CORROSION PROPERTIES

Abstract

Magnesium alloys have recently gained attention among researchers due to their excellent biodegradability. However, rapid corrosion of Mg AZ31 alloys may cause an implant to fail before the bone has been fully restored. This study aimed to enhance corrosion resistance of Mg AZ31 alloy. In this study, hydroxyapatite (HA) powder coatings were prepared by using electrophoretic deposition (EPD) technique on AZ31 alloy for orthopaedic application. In this research, the voltage applied by EPD was increased from 10V to 50V. Coating morphologies, coating structures and corrosion properties were studied. FESEM observation was conducted on the formation of cracks, agglomeration and particle distribution. Corrosion test was performed by using an immersion test. Meanwhile, potentiodynamic test was evaluated by using pH value measurement and Tafel extrapolation. The presence of HA had successfully increased the corrosion resistance of bare AZ31. Through the FESEM observation, applied voltage of 20V had the highest corrosion resistance and least defects found amongst samples. Moderate applied voltage of 20V revealed the least defects and uniform coating layer because of charged particles attraction and repulsion to form a self-arrangement and high packing deposited layer. Therefore, the corrosion properties were increased by acting as an effective barrier to the corrosive environment.