Effect of Carbon Content on the Electrochemical Impedance of As-Cast CoCrMo Alloys

摘要

In this work, the effect of carbon content on the resultant impedance diagrams and surface appearance of ASTM-F75 as-cast cobalt-based alloys was investigated. The electrochemical properties of the alloys in the passive and transpassive states were studied. Potentiodynamic polarization and electrochemical impedance spectroscopy tests were carried out. It was found that the properties of passive film on CoCrMo alloy changed with potential. The highest resistance to pitting corrosion of the passive film was observed for the low C content alloy which was attributed to a greater chemical and microstructural homogeneity (e.g. a uniform distribution of fine carbides and fine grained structure) in the as-cast condition. The results of the investigation led to the conclusion that the use of low C content ASTM-F75 as-cast alloys in the manufacture of orthopedic implants may result in a lower release rate of corrosion products which should improve the in vivo performance of the implants.