Improving the Corrosion Resistance of Magnesium Alloy by Magnesium Phosphate/Glass Composite Coatings Using Sol-Gel Method

Coating of Mg alloys with Mg-phosphate is usually performed by complex and costly methods. This work was mainly aimed at using Mg-phosphate ceramic for Mg metal implants by simple and cost-effective spin coating combined with a sol-gel approach. Where, Mg-phosphate ceramic particles were dispersed with different percentages (0, 10, and 30 wt. %) in the glass sol (85 SiO2 - 10 CaO - 5 P2O5 system) as a coating solution. The coated substrates were characterized by TGA, XRD, FTIR, contact angle, and SEM/EDX analyses, and the in vitro bioactivity test was performed in revised simulated body fluid (rSBF). The results showed the coating thickness was 8.8 +/- 0.8, 5.4 +/- 0.6, and 5 +/- 0.7 mu m for MP0, MP10, and MP30, respectively. Moreover, the coatings increased the hydrophilicity of the metal surface. All coatings enhanced the formation of an apatite-bone like layer on the Mg metal surface, and they were viable with oral epithelial cells at a concentration <= 125 mu g/ml. Moreover, MP0 and MP10 coatings significantly enhanced the corrosion resistance of the metal, while; MP30 coating did not show a significant effect on it. Thus, the percentage of Mg-phosphate in the coating was valuable for corrosion resistance when it was <= 10 wt. %. As a result, the composite coatings showed promising coatings for Mg metal substrate to enhance its corrosion resistance at low percentages of Mg-phosphate ceramic.