Effects of a Corrosion Inhibitor on the Corrosion of Steels under Thin Solution Layers

Abstract

The effects of 0.5 mmol L^－1 sodium molybdate and 0.5 mmol L^－1 aluminum lactate on the corrosion of steels under 10 mmol L^－1 NaCl solution layers were investigated. Electrochemical measurements were carried out using a siphon cell to form solution layers of 0.2 mm-1.0 mm thickness on the samples. From the potentiodynamic polarization measurements, the diffusion limiting current, j_lim and the anodic current, j_anode were measured and the changes by the effects of the corrosion inhibitor were evaluated. There was no change of j_lim, while j_anode decreased, indicating that used inhibitors reduced the anodic reaction rate. From the electrochemical impedance measurement results, impedance behavior under the solution layer was different from that in the bulk solution, and it was suggested that the protective layer structure changed with the quantity of solution.