Influence of Concentrations of LiOH and Li₂MoO₄ on Polarization Curve of Carbon Steel in Concentrated LiBr Solutions

Abstract

We have investigated influence of concentrations of LiOH and Li₂MoO₄ on corrosion behavior of SS400 carbon steel immersed in concentrated LiBr solutions at 393 and 438 K for a short period about 0.2 ks. The corrosion behavior was evaluated by measurement of polarization curve. As a result, the following were obtained: Addition of LiOH to 65 mass% LiBr solution induced suppression of cathodic current around the corrosion potential to shift the corrosion potential lower. Further, two-step active dissolution current was found around the corrosion potential and passive current in the higher potential region. On the other hand, addition of 0.03 mass% Li₂MoO₄ to 65 mass% LiBr + 0.2 mass% LiOH solution induced small suppression of cathodic current around corrosion potential, and more addition of 0.06 mass% made the cathodic current slightly increase. Two-step active dissolution and passivation phenomena were found in the anodic polarization curve like those in the solution without Li₂MoO₄. The anodic current density was almost independent of the concentration of Li₂MoO₄. Corrosion rates of the steel immersed in various solutions at 393 K for the short period were almost the same as 1.5 A・m^―2. In the solutions at 438 K, corrosion rate decreased with an increase in LiOH concentration and increased with an increase in Li₂MoO₄ concentration.