AN ELECTROCHEMICAL IMPEDANCE STUDY OF THE BEHAVIOR OF SOME PRETREATMENTS APPLIED TO RUSTED STEEL SURFACES

The electrochemical impedance technique was applied to study the corro sive and electrochemical activity at the metal/rust interface in conne ction with the application of protective treatments to rusted steel. T he pretreatments assayed were tannic or gallic acid solutions of diffe rent concentrations. The impedance diagrams of the treated samples wit h these solutions were only slightly modified with reference to those obtained with untreated rusted steel. The shape of the low-frequency a rcs or tails in the Nyquist diagrams seems to be markedly influenced b y diffusion processes in the rust layer and/or by the porous nature of the rusted steel electrode.