Materials Science:In vitro Crevice Corrosion Behavior of Implant Materials
AbstractThe crevice corrosion susceptibility of cold-worked Type 316LVM stainless steel, cast Co-Cr-Mo, wrought Co-Cr-W-Ni, non-nitrided and nitrided Ti-6Al-4V ELI, and c.p. Ti, Grades 1 and 4, was studied in vitro by means of a crevice cell. Occlusion was created by interfacing a disc specimen and a Teflon bar. Specimens were mechanically prepared through 2-4 μm Al 2 O 3 and passivated in 30% HNO 3 , followed by steam sterilization. Tests were performed in a deaerated Ringer's solution, maintained at pH = 7 and 37°C. Anodic polarization was conducted potentiostatically at pre-selected levels, and resultant currents were monitored: stainless steel, 50 and 100 mV (S.C.E.), 450 min; non-stainless materials, 600 mV, 1000 min. Results for the stainless steel demonstrated that a HNO 3 passivation treatment reduced its crevice corrosion susceptibility. For the non-stainless steel materials, no crevice corrosion susceptibility was observed, although a dulling and discoloration of c.p. Ti was evident. Recognizing that 600 mV is in excess of the O 2 reduction potential in vivo, it was concluded that, in the absence of fretting, implants of these non-stainless steel materials would not experience significant corrosion loss under crevice conditions.