Factors influencing the bio-tribo-corrosion and chemistry on cobalt alloys: A brief literature review

Cobalt-chromium-molybdenum (CoCrMo) alloys are commonly employed for load-bearing implants, such as hip and knee prostheses, owing to their mechanical properties and excellent passivity characteristics to reduce corrosion. The interaction between biological environment and the metallic surface under an articulating condition is extremely complex. The metal is exposed not only to the harsh biological environment as well as mechanical loading, leading to the conjoined action of mechanical (wear) and electrochemical (corrosion) degradations of the material; termed as tribo-corrosion. Tribo-chemical film formation can affect the surface response towards tribo-corrosive processes. The fundamental mechanisms of the tribo-corrosive degradation and surface chemistry are recognized to contribute to the orthopaedic implants’ longevity problem; an understanding of those mechanisms is therefore essential. This manuscript aimed to briefly review the current knowledge of the tribo-corrosion and tribo-chemistry phenomena from the pre-clinical studies’ point of view on the CoCrMo alloys used for hip bearing implants. This overview highlighted that the tribo- corrosion and tribo-chemical reactions during sliding are sensitive to the biological species interaction, as well as several unexplored factors in the environment. These findings contribute to the further knowledge and pre-clinical understanding of protein-metal interactions occurring in films formation and the system variables effect on the metallic load-bearing surfaces.