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 Hankʹs solution of pH 7.4 at 37 °C, which simulates body fluid conditions. The results revealed that among four different thicknesses of alumina, the 150-μm-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-μm-thick coating. The breakdown potential increases marginally for the 50-μm-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 μm as it increases the breakdown to a maximum value. Therefore, the present results show that the plasma-sprayed MSZ ceramic coating of 150 μm helps in improving the corrosion resistance of 316 L stainless steel considerably.