On Intensification of Iron Passivation by Benzotriazole in Aqueous Solutions

摘要

The passivation of iron and mild steel by benzotriazole (BTA) and its equimolar composition with sodium phenyl undecanoate (SFU) in a borate buffer solution with pH 7.36 is studied. BTA is shown to be an inefficient passivator compared to SFU. However, the passivating effect of BTA can be increased by means of the preliminary formation of its adsorption layer at a cathodic potential E = -0.65 V and its combined use with SFU. The adsorption of the inhibitors studied can be described formally by the Frumkin isotherm. An analysis of the attraction interactions between the adsorbing particles of the inhibitors enabled us to suppose that, at the adsorption of the mixture on the iron free of oxides (E= -0.65 V), a layer adjacent to the electrode surface consists mainly of SFU anions, while the outer layer is formed by BTA. The adsorption of BTA on the iron electrode surface, where the SFU monolayer was preliminarily adsorbed, is much stronger compared to that on the reduced surface of the same electrode. Based on this observation, a two-stage treatment of the surface of a mild steel with SFU followed by BTA passivating solutions is proposed. Corrosion tests under severe conditions of everyday abundant moisture condensation on the steel surface confirmed the high efficiency of the method.