Development of appropriate thickness ceramic coatings on 316 L stainless steel for biomedical applications

In this study, ceramics such as alumina, magnesia-stabilized zirconia (MSZ) and yttria-stabilized zirconia (YSZ) of different thicknesses have been deposited over 316 L stainless steel substrate by the air plasma spray (APS) technique. The coated specimens were characterized by scanning electron microscopy (SEM), metallography and X-ray diffraction (XRD) techniques. The coatings of different thicknesses were evaluated for corrosion resistance by various electrochemical techniques in deaerated Hank's solution of pH 7.4 at 37 degreesC, which simulates body fluid conditions. The results revealed that among four different thicknesses of alumina, the 150-mum-thick alumina coating provides good protection and increases the breakdown potential. While all thicknesses of MSZ coating provides very good protection, breakdown potential increases considerably for the 150-mum-thick coating. The breakdown potential increases marginally for the 50-mum-thick YSZ coating. Among the three types of coatings, the MSZ coating has been identified as a suitable coating material and its optimum thickness is 150 mum as it increases the breakdown to a maximum value. Therefore, the present results show that the plasma-sprayed MSZ ceramic coating of 150 mum helps in improving the corrosion resistance of 316 L stainless steel considerably. (C) 2002 Elsevier Science B.V. All rights reserved.