The corrosion inhibition of carbon steel in lithium bromide solution by hydroxide and molybdate at moderate temperatures

Abstract

The corrosion inhibition of carbon steel by OH − and MoO 4 2− was studied in LiBr solutions of 1–23 m (mol kg −1-H 2O) at 120 and 160°C. Both inhibitors were effective in reducing corrosion, but pitting was likely to occur in the LiBr solutions of low and intermediate concentrations. In the highly concentrated solutions only simultaneous use of OH − and MoO 4 2− was effective for passivation, otherwise heavy general corrosion was observed. Passive films were always composed of magnetite. The depth profiles of the films were analyzed by XPS, a.c. impedance and corrosion potential were monitored under some conditions. The results are discussed in terms of competitive actions between Br − and OH − in several processes such as adsorption, formation of complex ions, acceleration of breakdown and the formation of passive films.