Effect of carbon content on the resistance to localized corrosion of as-cast cobalt-based alloys in an aqueous chloride solution.

The effect of carbon content on the resistance to localized corrosion of ASTM-F75, as-cast cobalt-based alloys, was studied using potentiostatic polarization tests in Ringer's solution. Critical pitting potentials were estimated from the potentiostatic polarization curves and were found to increase with decreasing carbon content. The highest resistance to pitting corrosion observed at low C contents was attributed to a greater chemical and microstructural homogeneity 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.