The corrosion-protective performance of plasma-polymerized (PP) films on metal substrates has been investigated by cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and surface potential measurements. A PP film from cyclohexane was deposited on Fe, Ni, and Cu substrates usings a radiofrequency generator. A PP film-coated metal substrate was employed as the working electrode in aerated NaCl aqueous solution and the cyclic voltammogram was measured repeatedly ten times upon application of a triangular potential between -1 and 1 V vs, the initial corrosion potential of the sample. The cyclic voltammogram depended strongly on the metal substrate: with Fe and Ni, only an anodic current was observed; with Cu, an anodic and subsequently a cathodic current appeared. For all the metals, the anodic current level in the voltammograms at the same potential sweep number decreased with increasing film deposition time. The anodic current level for Fe and Cu increased with increasing potential sweep number, but that for Ni exhibited a maximum, followed by a decrease. The anodic current level for the metal substrates decreased in the order Fe > Ni > Cu. The cathodic current for Cu decreased with an increase in the deposition time and increased with an increase in the potential sweep number. The dependence of the cyclic voltammogram on the metal substrate is discussed in terms of the PP film thickness and the positive charge on the film surface, as well as the standard reduction potential of the metal. The corrosion potential for PP film-coated metal substrates also changed with the deposition time; this change is suggested to be related to the increase in the positive charge on the surfaces.