Electrochemical investigation of corrosion and wear interactions under fretting conditions

Two alloys commonly used for the steam generator components are under investigation to assess the effect of sliding regime on the fretting-corrosion damage in 3.5 wt% NaCl solution. Inconel-600 was forced to fret against stainless steel SS431S29 under variable applied load at constant displacement. A Modular Universal Surface Tester was employed to provide fretting motion and to control the applied normal load. The overall damage involved mechanical and corrosive wear and interactive effects between those two were generally observed. In situ electrochemical measurements were conducted during fretting including open circuit potential and potentiostatic current measurements. Fretting motion was found to cause the contact area to be more active and more prone to corrosion. Electrochemical analysis revealed the relationship between fretting sliding regime and corrosion behaviour of tested materials. The extent of surface damage as a function of different loads is discussed.

► Relationship between electrochemical response and fretting-corrosion action established.
► Rapid drop of open circuit potential related to passive film rupture under fretting conditions.
► Passive film damage related to normal load and displacement amplitude applied.
► Sliding transition from gross slip to stick-slip prevented excessive passive film breakdown.
► Chemical and mechanical components distinguished in overall surface damage process.