Super-hydrophobic stearic acid layer formed on anodized high purified magnesium for improving corrosion resistance of bioabsorbable implants

Abstract

Magnesium and its alloys are ideal candidates for bioabsorbable implants. However, they can dissolve too rapidly in the human body for most applications. In this research, high purified magnesium (HP-Mg) was coated with stearic acid (SA) to slow the corrosion rate of magnesium in simulated body fluid at 37 ± 1 °C. HP-Mg was anodized (AC and DC voltages) to form an oxide/hydroxide layer, and then it was immersed in a SA solution. The SA coated layer surface, anodized layer, and the thickness of the oxide/hydroxide layer were investigated with Scanning Electron Microscopy (SEM). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) were used to estimate the corrosion rate of HP-Mg specimens. The results confirm that the hydrophobic coating can decrease the corrosion rate of HP-Mg by more than 1000x. The protectiveness of coated layer for anodized specimens with AC voltage continue for 2 and 3 weeks. For the HP-Mg coated anodized with DC voltage, the coated layer could improve the corrosion resistance for only a few days. Keywords: Magnesium, Biomaterials, Hydrophobic layer, Stearic acid, Simulated body fluid, Electrochemical impedance spectroscopy