CHARACTERIZATION AND PROPERTY OF THE NICOTINIC ACID/CALCIUM PHOSPHATE COMPOSITE COATINGS ON MG ALLOY

摘要

Magnesium and its alloys exhibit great potential as biodegradable implant materials. However, their poor corrosion resistance may result in the premature failure during actual applications. Protective coatings can effectively improve the corrosion resistance and prolong the service life of Mg alloys as biodegradable implants. It is necessary that the protective coatings are with good bioactivity. In this paper, the biodegradable behaviour of Mg-3Zn alloy in stimulated body fluid (SBF) was investigated, and then the nicotinic acid/calcium phosphate composite coatings were prepared to improve its corrosion resistance. The Mg alloy was first immersed into the nicotinic acid solution for 10 min to obtain a thin bottom layer, and then was electrodeposited with calcium phosphate coating. The surface morphology was observed with SEM. The chemical composition was analyzed by XPS and XRD. The corrosion resistance was evaluated by polarisation curves. The results indicate that Mg-3Zn alloy shows good bioactivity in view of the deposition of hydroxylapatite particles on its surface in SBF. Nicotinic acid pretreatment can obtain a thin protective film as well as increasing the surface roughness for achieving a good adhesion with the subsequent calcium phosphate coating. Electrodeposition with the agitation of ultrasonic can reduce the grain size of the calcium phosphate coating to nanometer scale. The polarisation curves demonstrate that the nicotinic acid/calcium phosphate composite coatings can greatly improve the corrosion resistance of Mg alloys.