The effect of sodium dodecylsulfate (SDS) on copper corrosion in a solution of 0.5M H 2 SO 4 + xM SDS was studied using electrochemical polarisation measurements. The critical micelle concentration (CMC) of SDS in 0.5M H 2 SO 4 is 8 x 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 logc i n h yielded straight lines with a slope change at the CMC. Accordingly, the CMC could be determined from these electrochemical measurements. The values of ΔG a d s calculated from the Langmuir plots are negative, suggesting that the inhibitive action of SDS in 0.5M H 2 SO 4 results from the electrostatic adsorption of C 1 2 H 2 5 SO 4 - ions onto the positively charged copper surface.