Assessment of in-vivo corrosion of Ti and CoCrMo joint implants by electrochemical measurements in human synovial liquids

Understanding the corrosion behavior of biomedical materials in the human body is an essential step for the development of improved materials and clinical procedures in arthroplasty. In this work, the corrosion behavior of Ti and CoCrMo alloys in human synovial fluids directly extracted from patients was investigated through an electrochemical experimental protocol, including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results show that the corrosion behavior of both materials largely depends on patients. The obtained corrosion rates of both materials correspond well to the metal ion release rate detected in patients with joint implants revealing the adequateness of the electrochemical experimental protocol for quantifying in-vivo corrosion of biomedical implants. Based on the results, no significant risk of galvanic corrosion of Ti/CoCrMo coupling is anticipated. The rates of wearaccelerated corrosion (one of the main degradation mechanisms of metallic artificial hip joints) were theoretically extracted from the present electrochemical measurements using an established tribocorrosion model. Those material loss rates are patient-dependent and can be up to two orders of magnitude higher than the static corrosion rates, indicating that the nature of the patient can critically affect the degradation rate of the joint implant.