The inhibition of Cu corrosion by 1-propanethiol (1-PT) and propyltrimethoxysilane (PTS) molecules, in 0.100 mol L-1 KCl solution, was investigated and compared to 3-mercaptopropyltrimethoxysilane (MPS). Corrosion inhibition was studied as a function of the 1-PT and PTS concentration in ethanol, between 1.0 x 10(-7) mol L-1 and 1.0 x 10(-2) mol L-1. Inhibition efficiency was calculated from Tafel plots in 0.100 mol L-1 KCl solution. It improved with an increase in 1-PT or PTS concentration. The maximum efficiency was obtained at a 1-PT or PTS concentration of 1.0 x 10(-3) mol L-1 or 1.0 x 10(-5) mol L-1, respectively. Adsorption of 1-PT and PTS on copper followed a Langmuir behaviour. Potentiostatic polarization measurements indicated that 1-PT and PTS are mixed anodic/cathodic inhibitors, in the presence of dissolved oxygen. When the inhibitor exposure time of the pretreated Cu surface in 0.100 mol L-1 KCl solution was varied, a loss on the corrosion inhibition efficiency was observed for the three (MPS, PTS and 1-PT) compounds. However, the 1-PT compound maintained excellent protection in the first 12 h of exposure to a 0.100 mol L-1 KCl solution; afterwards, there was a significant loss in the inhibition efficiency. Surface analysis studies with Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) showed that the inhibitors modified the Cu surface.