Electrochemical Study on Friction and Wear of Some Commercial Materials in Liquid Environments

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Friction and wear characteristics of materials under unidirectional-sliding and fretting conditions was investigated in air, in pure water, and in saline to elucidate the friction and wear mechanism in corrosive environments. In air, the analysis of three-dimensional topographies on severe and mild worn-surfaces made possible to study the condition for the transition from severe to mild wear. In liquid environments the effects of contact load, pre-corrosion time, weight-concentration of solution, dissolved-oxygen content(DO), and cathodic protection on the transition of wear mode was investigated. The effect of dissolved oxygen on the friction and wear during fretting was also studied.1. The increase in the area of flat surfaces due to the wear of asperities resulted in the rapid decrease in the mean contact pressure of real contact area. This process caused the transition from severe to mild wear.2. The contact load for the transition from severe to mild wear in liquid environments wa … More s very higher than the contact load in dry air.3. In pure water, severe wear occurred when pre-corrosion time was shorter, the transition from severe to mild wear observed at a certain pre-corrosion time, and mild wear appeared at longer time than the time.4. In 0.5 wt% saline, mild wear occurred in the range of DO 0.05-18mg/l, and the wear rate was reduced with the decrease in DO. In 0.01 wt% saline the wear mode changed from mild to severe wear at DO lower than 2mg/l.5. In saline mild wear predominated irrespective of DO due to the incomplete corrosion protection between applied potentials E=-0.50--0.80 V(vs. Ag/AgCl). At E -0.90 V severe wear appeared with the seizure of contact surfaces.6. During the fretting of pure iron in pure water and in saline, friction was higher at less DO content and decreased with the increase in the DO content. On the other hand, fretting wear presented the reverse tendency as the friction.7. During the fretting of pure copper in saline, the relationship between DO and friction was the same as observed in the fretting of iron. The variation of wear with DO content was very complicated for the temperature of saline. Less