Attenuated total reflectance (ATR) spectroscopy was used to perform in situ studies of the corrosion inhibition of cuprous oxide (Cu2O) by benzotriazole (BTA) in aqueous solution at concentrations from 1 to 20 mu M. Because two separate processes occur simultaneously, that of Cu2O corrosion and corrosion inhibition by BTA adsorption, the spectral information was subjected to deconvolution by a conjugate gradient minimization algorithm. Under these conditions, a solution phase concentration of 7-10 mu M BTA nearly completely inhibited the corrosion of Cu2O in deionized water. Using a Langmuir adsorption model, this represented only 25% of the maximally covered surface area. (C) 2007 Elsevier B.V. All rights reserved.