Crevice effect in systems under tribocorrosion conditions: Mechanisms competition

摘要

Crevice corrosion has been invoked as one of the main degradation mechanisms for hip joint implants deterioration. However, its influence and real effect on deterioration have not been clarified yet. Clearance between femoral ball and trunnion can generate a suitable gap for crevice phenomena, Preliminary OCP results (open circuit potential) in a groove/cylinder configuration (Ti6Al4V/Quartz and CoCr/Quartz couples) shown changes in the potential, after 10 days in a static test. Taking into account real hip joint prostheses conditions, these results could be considered as negligible. However, once passive potential was applied, there was a current indicating the material dissolution. Fretting corrosion is considered an actuating degradation mechanism in artificial hip joints as well. Therefore, a wear model based on the third body approach for describing the degradation of titanium alloys under fretting corrosion was developed based on mass flows. In this paper, material dissolution by crevice corrosion mechanisms and volume wear from fretting corrosion approach are analyzed in order to understand and quantify the influence of every mechanism in prostheses deterioration.