Tribological behavior of PTFE sliding against steel in sea water

In this paper the tribological behaviors of PTFE against GCr15 steel in air, distilled water, sea water and 3.5 wt.% NaCl solution were comparatively investigated. The influence of sea water composition on the tribological behavior of PTFE was also studied. Results show that the friction process in sea water was relatively stable, the friction coefficient and the wear rate of PTFE were slightly lower and a little larger than those in distilled water, respectively, but both were much lower than those in air and NaCl solution. In aqueous environment, medium affected the tribological behavior of PTFE mainly by corrosion to the counterface, the wear rate of PTFE depended on the corrosion extent of the counterface, and this wear model can be called indirect corrosive wear. In salt solution, green rusts were formed on the counterface and had some lubricating effect. In addition, the results show Mg2+ and Ca2+ were the key factors for the relatively low friction coefficient and wear rate of PTFE in sea water, because the corrosion of counterface was reduced and the lubricating effect of green rusts was enhanced as a result of the deposition of Mg(OH)2 and CaCO3 on the counterface.