Corrosion Behavior of Solution- Annealed CoCrMo Medical Implant Alloys

Corrosion behavior of solution annealed high-carbon and low-carbon CoCrMo wrought alloy, commonly used in medical joint implants, was investigated. The surface passivation properties remained similar with and without the various solution anneal conditions, while the rate of corrosion was lower for solution annealed high-carbon CoCrMo. Corrosion was found to target phase boundaries and certain grain boundaries in the high-carbon alloy. This preferential corrosion may be due to chromium depletion at the boundaries, higher grain boundary energy as a function of the misorientation angle between the neighboring grains, or both. These findings suggest that solution annealing the high-carbon CoCrMo alloys may lower the implant’s rate of corrosion in vivo due to the more corrosion-resistant microstructure.