Abstract
Recently sodium dodecylsulfate (SDS) and some other surfactants have been shown to be promising inhibitors for the pitting corrosion of stainless steels and aluminum alloys in chloride media. In the present research, the effect of other compounds such as multivalent metal cations and other surfactants on the pitting inhibition of 304 stainless steel by SDS was investigated to determine its inhibition behavior in relevant mixed systems. It was shown that calcium ion increased the pitting inhibition efficiency of SDS. The efficiency increase was attributed to the increased SDS adsorption in the presence of calcium. Cationic surfactant dodecyltrimethyl ammonium chloride (DTAC) was also found to improve the pitting inhibition efficiency of SDS. It was proposed that DTAC complexes with SDS through electrostatic and hydrophobic interactions, leading to higher adsorption of the surfactants. Nonionic surfactant octylphenol ethylene oxide (Triton-X-100) was not able to enhance the pitting inhibition by SDS. At high concentrations, Triton-X-100 even reduced the inhibition efficiency of SDS. The decreased inhibition efficiency is possibly due to decreased SDS adsorption density and/or less protective adsorption layer with the addition of Triton-X-100.
