Corrosion Behavior of Carbon Steel in Concentrated LiBr-LiNO3-KCl Solution at Elevated Temperature

摘要

Corrosion of carbon steel has been investigated for200 h in concentrated aqueous solution of mixed LiBr-LiNO3-KCl-LiOH salts at elevated temperatures as functions oftemperature and concentration of LiNO3 and Li2MoO4O. Thestructure and composition of the surface films were analyzed byXRD, SEM and XPS. At 463 K, addition of LiNO3 (>0.0125mol/kg) decreased the total amount of iron corroded (WT), amountof iron ions in the oxide (WF) and amount of Fe2+ ions dissolvedinto the eater (WD) drastically, however pits were observed. AtLiNO3=3.01 mol/kg, WT and WF increased as temperature rises,whereas WD decreased as temperature rises. Pit was observed atLiNO3=3.01 mol/kg between 363 K and 463 K. below 403 K, pitdepth was less than 15μm, while above 433 K the pit depth wasmore than 80μm. These corrosion behavior did not depend on theaddition of Li2MoO4. Outermost parts of oxide films formed atLiNO3=3.01 mol/kg, were composed of γ-Fe2O3 and thedecrease in the LiNO3 concentration changed the compositionfrom γ-Fe2O3 to Fe2O3. The role of surface film in the corrosionbehavior was discussed in terms of its ion-selectivity and OH- ionstabilizing ability.