The effect of sodium dodecylsulfate (SDS) on the copper corrosion in 0.5 mol dm(-3) H2SO4 solution has been studied by electrochemical and in situ Raman spectroscopic measurements. It has been shown that SDS is a corrosion inhibitor for copper on the entire range of potentials studied and presents a synergistic effect on the inhibitive action of benzotriazole (BTAH). It has been also observed that SDS inhibits the H+/H-2 reaction on the copper electrode below or above the cmc. The surfactant film, at - 750 mV (SCE) obeys a Langmuir adsorption isotherm considering 1.2 surface sites for each adsorbed SDS molecule, when [SDS] < cmc. The equilibrium adsorption constant, K = 1.7 x 10(3) mol dm(-3) , suggests the presence of a chemical adsorption. The spectroscopic results have shown that the SDS adsorbs on the copper surface with both moieties, the hydrophobic and hydrophilic, interacting with the copper surface. The in situ spectroelectrochemical results have also shown that SDS co-adsorbs on the copper surface in the presence of BTAH and that the structure of the co-adsorbed SDS molecules is different from that observed in the absence of BTAH.