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

The effect of sodium dodecylsulfate (SDS) on copper corrosion in a solution of 0.5 M H2SO4 + x M SDS was studied using electrochemical polarisation measurements. The critical micelle concentration (CMC) of SDS in 0.5 M H2SO4 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 cinh yielded straight lines with a slope change at the CMC. Accordingly, the CMC could be determined from these electrochemical measurements. The values of ΔGads calculated from the Langmuir plots are negative, suggesting that the inhibitive action of SDS in 0.5 M H2SO4 results from the electrostatic adsorption of C12H25SO4− ions onto the positively charged copper surface.