Influence of molybdate ion and pH on the fretting corrosion of a CoCrMo - Titanium alloy couple

The addition of molybdate ion decreased the release of cobalt by 32% and increased the after-to-before ratio of the polarization resistance by 8 × at pH 4.5, but had not effect on these parameters at pH 7.6. Film deposits in the wear scar were more pronounced in the presence of molybdate ion. The addition of molybdate ion to the medium had a significant protective effect for the CoCrMo only at pH 4.5, possibly because the lower pH allowed for more molybdate-induced protein film formation.