A effect of sodium dodecylsulfate on the corrosion of copper in sulphuric acid media

Abstract

The effect of sodium dodecylsulfate (SDS) on copper corrosion in a solution of 0.5 M H 2SO 4 + x M SDS was studied using electrochemical polarisation measurements. The critical micelle concentration (CMC) of SDS in 0.5 M H 2SO 4 is 8 × 10 −4 M, and the experimental concentrations of SDS were in the range below and above the CMC. It was found that SDS is a good anodic inhibitor at lower anodic overpotentials, i.e. very close to the rest potential. Adsorption of the inhibitor obeys the Langmuir isotherm. Plots of log [ θ/(1− θ)] versus log c inh yielded straight lines with a slope change at the CMC. Accordingly, the CMC could be determined from these electrochemical measurements. The values of Δ G ads calculated from the Langmuir plots are negative, suggesting that the inhibitive action of SDS in 0.5 M H 2SO 4 results from the electrostatic adsorption of C 12H 25SO 4 − ions onto the positively charged copper surface.