Influence of Mechanical and Chemical Factors on Transition Between Severe and Mild Wear in Saline Solution

Pin-on-disk wear tests of carbon steels in saline solution were carried out at high loads to study the effects of mechanical and chemical factors on the transition between severe and mild wear. The factors were load, presliding time, concentration of saline solution, dissolved oxygen content, and applied potential for cathodic protection. Severe wear and seizure appear at low concentration levels of saline solution and the transition takes place at a certain concentration level of saline solution. The concentration level for the transition is higher under argon-saturated condition than under air-saturated condition. Mild wear is predominant over the whole range of dissolved oxygen content from 0.5 to 18 ppm in 0.5 wt percent saline solution and the wear rate decreases with decreasing dissolved oxygen content. The mild wear occurs in the range from 2 to 18 ppm in 0.01 wt percent saline solution, whereas the wear mode moves to severe wear below 2 ppm. Mild wear predominates under incomplete cathodic protection between −0.50 and −0.80 V (versus Ag/AgCl in 0.5 wt percent saline solution. The applied potential for the transition from initial to steady wear is more negative under higher dissolved oxygen content condition. Complete severe wear occurs below −0.90 V (versus Ag/AgCl) with a risk of seizure.