Corrosion properties of nanocrystalline Co-Cr coatings

Nanocrystalline and conventional Co-Cr (ASTM F75) coatings were prepared by plasma spraying for possible orthopedic implant applications. Scanning ele ctron microscopy and transmission electron microscopy were used to study th e macrostructure and microstructure of the resultant sprayed coatings. The corrosion resistance was characterized by an in vitro potentiodynamic anodi c polarization technique in a pseudophysiological solution. The nanocrystal line coating has higher porosity, lower corrosion current density, and less localized damage than that of the conventional one, demonstrating better a pplication potential for orthopedic implants. A change in the atomic compos itional difference between the grain interior and the grain boundary, the p resence of residual strain in the grain interiors, and a change in the repa ssivation kinetics are discussed as possible explanations for the enhanced corrosion behavior observed. (C) 2001 Biomedical Engineering Society.