The in vitro and in vivo corrosion characteristics of two alloys, cast Co-Cr-Mo (ASTM F75) and wrought Ni-Cr-Mo, were evaluated using electro-chemical corrosion analysis. Two in vitro electrolytic solutions were utilized, an isotonic saline solution consisting of 0.9 w/o NaCl in distilled water and an isotonic saline solution with 10 v/o sterile calf serum. The in vivo environment was created by implanting cylindrically shaped specimens of each alloy into the back muscles of New Zealand white rabbits. Cyclic anodic and cathodic polarization curves were generated for the three test conditions and subsequently were compared. Anodic curves conducted using the isotonic saline and isotonic saline plus serum electrolyte solutions were very similar to the anodic curves generated for the implanted alloy specimens for both alloys. The corrosion rates predicted from the in vitro and in vivo cathodic polarization curves were not statistically different for the three test conditions. Overall, the corrosion data generated using the in vitro environmental conditions adequately predicted the in vivo corrosion behavior of the cast Co-Cr-Mo and wrought Ni-Cr-Mo alloys.

Porous metallic surfaces are currently being applied to both orthopedic and dental implant devices. The increased surface areas provided by these systems have caused many in the health sciences to be concerned over an accelerated release of corrosion products into the adjacent and systemic tissues. The objective of this study was to evaluate the corrosion characteristics of six available porous alloy systems by utilizing electrochemical corrosion analyses. The surface area provided by the selected porous structures increased 1.2 to 7.2 times over that of the solid forms of the alloys. The corrosion rate for the porous alloys was in a range of 1.2 to 5.2 times greater than that for the solid alloys. In general, the increase in corrosion rate at the corrosion potential was not of the same magnitude as the increase in surface area. At potentials greater than the corrosion potential, the corrosion rates for the porous alloys were normally greater than the rates experienced by the solid alloys. In conclusion, the porous alloy systems investigated demonstrated increased corrosion magnitudes. Since the long-term effects of the released metallic constituents have not been evaluated at this time, surface treatments aimed at reducing the corrosion rates should continue to be evaluated.

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