Selenium conversion coating on AZ31 Mg alloy: A solution for improved corrosion rate and enhanced bio-adaptability

Abstract Among the various new generation medical implant materials, magnesium (Mg) and its alloys have drawn attention because of their biodegradability with non-toxicity and avoidance of revision surgery. The purpose of this work is to reduce the corrosion rate of AZ31 Mg alloy with selenium conversion coating and to enhance antibacterial activity and bio-adaptability. The corrosion rate has been greatly reduced and the localized corrosion behavior was analyzed to examine the possibility of pitting. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Raman IR spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results indicated that the coating consists of magnesium hydroxide, magnesium selenite and selenium. The topographical analysis with the scanning electron microscope and surface profilometer show that the surface consists of heterogenous agglomerated granules with increased surface roughness, which aided the apatite formation after immersion in Earle's solution for 7 days. The hydrogen evolution rate was reduced to ~0.021 ml cm−2 day−1 and selenium release from the coating was around 12 μg cm−2 day−1, which is lower than the daily requirement of humans. In addition, the coating shows better antibacterial and anti-biofilm formation activity.