Correlation Between Adsorption/Desorption of Surfactant and Change in Friction of Stainless Steel in Aqueous Solutions Under Different Electrode Potentials

Adsorption of sodium dodecyl sulfate (SDS) surfactant on the surface of gold or graphite in aqueous solutions has received extensive attention in the past. However, few studies have been done on the adsorption/desorption of SDS surfactant at surfaces of engineering materials as well as on their influence on friction behavior. In this article, quartz crystal microbalance (QCM), electrochemical spectroscopy, atomic force microscopy (AFM), lateral force microscopy (LFM), and ball-on-disc friction test have been jointly used to investigate the effects of electrode potential on adsorption and desorption of SDS surfactant, surfactant aggregate morphology on stainless steel surfaces, nanoscale and macroscale tribological behavior in dilute SDS aqueous solutions. Experiment results have shown that DS- anions adsorb on the surface of the stainless steel electrode and form stripe-shaped aggregates at the open circuit potential (+0.03 V vs. SCE), which corresponds to a low friction coefficient. Under the negative potential of -0.4 V versus SCE, the adsorbed aggregates of DS- anions are removed from the stainless steel surface, resulting in a high friction coefficient. By adjusting the electrode potential of stainless steel, both of the surfactant adsorption and tribological property can be controlled in a significant range.