Electrophoretic Deposition of Nanohydroxyapatite on Homogenized Magnesium Based Alloy for Biomedical Applications

Magnesium (Mg) alloys are promising biodegradable implant materials. If successful, they do not require second surgical operation for their removal. However, the focus of this study is to address the limitation of fast degradation rate (DR) which hinders the clinical application of Mg alloys. The bio-corrosion rate of any intermetallic alloy is related to its beta (β) phase volume fraction. Thus, homogenization heat treatment (HHT) was carried out to reduce the β phase. The influence of β phase and the hydroxyapatite powders (HAp) was employed to slow down the initial DR of Mg AZ91 alloy. Samples were cut from Mg grade AZ91 alloy ingot in 10mm x 10mm x 3mm dimension. The samples were prepared and divided into two; the first part was classified as as-received sample (sample a) while the second one was processed for HHT. HHT was carried out at 410°C/10h, cooled inside the furnace and named as homogenized sample (sample b). The HAp was synthesized using a simple wet chemical precipitation technique (SWCPT) and deposited on sample b via electrophoretic deposition (EPD) at different voltages with different deposition times. The HAp, uncoated and coated samples were characterized. Potentiodynamic polarization (PP) and immersion tests were carried out in stimulated body fluid (SBF) to estimate the DR and in vitro bioactivity of Mg AZ91 respectively. The results revealed a significant drop in DR from sample a (1.421 mm per year) to coated sample h (3.73 x 10-4 mm per year). Keywords: Magnesium alloy, biodegradable implants, beta phase, homogenization heat treatment, hydroxyapatite, electrophoretic deposition.