Long-term corrosion investigation of AISI 316L, Co-28Cr-6Mo, and Ti-6Al-4V alloys in simulated body solutions

The long-term weight loss, ion release and surface composition of AISI 316L, the Co-28Cr-6Mo and Ti-6Al-4V alloys were investigated in phosphate buffered solutions (PBS) with various bovine serum albumin (BSA) concentrations. All the samples lost weight up to 14 weeks and then started to gain weight. This can be explained by precipitation of dissolved ions on the surface after 14 weeks of immersion. The quantities of the dissolved ions were measured in immersed solution for 8, 14 and 22 weeks by induced coupled plasma-optical emission spectrometer (ICP-OES). The amounts of Fe released from 316L, and Co and Mo released from the Co-28Cr-6Mo alloy decreased after 14 weeks of immersion in PBS and BSA solutions. This observation coincides with the weight change of the samples. The oxide layer composition and concentration of the specimens exposed to solutions for 22 weeks were identified by X-ray photoelectron spectroscopy (XPS) analysis. The XPS results revealed that chromium is the main component of the 316L and Co-28Cr-6Mo alloy. The high Cr concentration of the 316L and Co-Cr-Mo oxide layer corresponds with the slow dissolution rate of Cr compared to other alloying elements of the 316L and Co-28Cr-6Mo alloy.

► Weight loss of AISI 316L, Co-28Cr-6Mo, and Ti-6Al-4V alloys in PBS solutions at various BSA concentrations was investigated by static immersion experiments for 8, 14, and 22 weeks. ► Immersed solutions were analyzed by ICP-OES test to detect the amount of ion released from the selected bio-materials. ► Surface concentrations of the specimens were measured by XPS analysis. ► Samples gained weight after 14 weeks of immersion ► Weight gain of the samples can be related to precipitation of Fe on 316L, and Co on Co-28Cr-6Mo.