Corrosion Mechanism of Q235 Steel Coated with Conductive Concrete in Saline-Alkaline Soil Environment

The corrosion mechanism of Q235 steel coated with conductive concrete composite in water-saturated saline-alkaline soil environment were studied by polarization curve and electrochemical impedance spectroscopy (EIS). The synergistic corrosion inhibition mechanism of Na₂MoO₄ and Na₃PO₄ compound corrosion inhibitor was discussed. The results show that after the conductive concrete accelerated corrosion for 45 d in the saline-alkaline soil environment, a large number of holes and a small number of cracks appearred on the sample surface. The corrosion process underwent three stages:concrete degradation, formation and rupture of passivation film, and corrosion stabilization. When the surface of Q235 steel formed a film structure, its electrochemical impedance spectroscopy had three time constants. Among them, the Warburg impedance appeared on the samples with and without the addition of corrosion inhibitor after corrosion for 20 d and 45 d, respectively. And the corrosion reaction was jointly controlled by diffusion and charge transfer. Afte adding 3 g/L Na₂MoO₄ and 3 g/L Na₃PO₄ compound corrosion inhibitor, the surface of Q235 steel could form a dense adsorption film, which hindered the corrosion reaction, and its corrosion inhibition rate was 89.88%.