Effect of sodium dodecylsulfate on copper corrosion in sulfuric acid mediain the absence and presence of benzotriazole

The effect of sodium dodecylsulfate (SDS) on the copper corrosion in 0.5 mo l dm(-3) H2SO4 solution has been studied by electrochemical and in situ Ram an spectroscopic measurements. It has been shown that SDS is a corrosion in hibitor for copper on the entire range of potentials studied and presents a synergistic effect on the inhibitive action of benzotriazole (BTAH). It ha s been also observed that SDS inhibits the H+/H-2 reaction on the copper el ectrode below or above the cmc. The surfactant film, at - 750 mV (SCE) obey s a Langmuir adsorption isotherm considering 1.2 surface sites for each ads orbed 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 s urface with both moieties, the hydrophobic and hydrophilic, interacting wit h 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. (C) 1999 Elsevier Science S.A. All rights reserved.