3-mercaptopropyltrimethoxysilane (MPS) has been used as a copper corrosion inhibitor in 0.100 mol L-1 KCl solution. The inhibition was studied as a function of the MPS pretreatment concentration in ethanol. The MPS concentration used was between 1.0 x 10(-8) mol L-1 and 1.0 x 10(-1) mol L-1. A freshly-cleaned Cu electrode was inserted in an ethanolic solution of MPS for 30 min for pretreatment, and was then exposed to a 0.100 mol L-1 KCl aqueous solution for 1 h. From the polarization resistance, the inhibition efficiency improved with increase in MPS concentration during the pretreatment. The MPS adsorption on Cu followed a Langmuir adsorption behaviour. However, at MPS concentrations larger than 1.0 x 10(-4) mol L-1 the inhibition decreased. Moreover, the inhibition efficiency decreased with increase in the exposure time of the MPS modified Cu electrode in the KCl aqueous solution. Polarization studies suggest that MPS is an anodic as well as a cathodic inhibitor, in the presence of dissolved oxygen. X-ray photoelectron spectroscopy (XPS) analysis of the Cu samples showed that the organic compound modifies the Cu surface and scanning electron microscopy (SEM) studies indicated that MPS protects the Cu surface when exposed for 350 h to laboratory environment. Polarized grazing angle Fourier transform-infrared (FTIR) microscopy analysis determined the presence of a polymer on the Cu surface.