Analysis of Corrosion Behavior and Surface Properties of Plasma-Sprayed HA/Ta Coating on CoCr Alloy

The cobalt-chromium (CoCr) alloys have been extensively used as implants, especially in total joint replacements and in odontology, due to their superior mechanical properties and wear resistance in vivo. However, the excessive release of the Co' and Cr' ions from CoCr implants can lead to adverse health issues, such as hypersensitivity and inflammatory reactions. The present study aimed to improve the corrosion resistance of a medical grade CoCr alloy (ASTM F-1537) plasma-sprayed with tantalum (Ta)-reinforced hydroxyapatite (HA) coating. The weight percent (wt.%) of Ta content in HA coating was varied at three levels, i.e., 10, 20, and 30%. In vitro corrosion behavior was investigated by electrochemical measurements in Ringer's solution along with surface properties analysis. The results revealed an increase in surface hardness value with an incremental increase in Ta content in the HA coating. The surface of HA as well as Ta-reinforced HA coatings possessed adequate roughness and demonstrated hydrophilic nature. With the Ta reinforcement in HA coating, the E-corr values shifted toward nobler potentials and I-corr values declined noticeably which indicated an increase in corrosion resistance of the surface. The results of the study indicate that the proposed Ta reinforcement in HA is potentially important for CoCr bio-implant applications.