Nature of Current Increase for a CoCrMo Alloy: 'transpassive' Dissolution vs. Water Oxidation

摘要

The 渢ranspassivebehavior of a CoCrMo alloy has been investigated to clarify the nature of thecurrent increase at high anodic potential (0.5-0.7 VAg/AgCl). The total amount of released metal ions wasdetermined after the potentiostatic measurements. According to the calculation through Faradayslaw,the metal dissolution only contributes to part of the total current recorded. Electrochemical AFMmapping did not show pronounced topography changes at 0.65 VAg/AgCl, while light optical microscopyobservation revealed fast evolution of oxygen bubbles. Evidently water oxidation is another importantprocess largely contributing to the current increase at the high potential.