Effects of the Concentration of Sodium Lauryl Sulfate Solution and NaCl Additive on the Potential-Controlled Friction

Abstract

1--10mM sodium lauryl sulfate (SLS) aqueous solution and its mixture with 10-1000mM NaCl additive have been used in friction test of ZrO(2)/Stainless steel pairs to investigate the effects of the concentrations of surfactant and supporting electrolyte on potential-controlled friction. The experiments were conducted on a home-made 3 ball/disc type tribotester equipped with an electrochemical cell. Three potential control modes, namely open circuit, positive potential and negative potential, were carried out in this study. Experiment results have shown that friction coefficient can be changed by an external potential as low as 0.2V DC when the surfactant concentration is low. The ascending time and the descending time of the friction coefficient with response to the change of the control potential have indicated that the concentration of NaCl additive higher than 100mM is not good for achieving a fast and substantial potential-controlled friction effect, and the concentration of NaCl additive should be controlled less than 10mM. Analysis of the experiment results revealed that the friction change is not induced as a result of the electrolysis of water, but by adsorption and desorption of surfactant on metal surfaces due to the change in surface potential.