Efficiency of corrosion inhibitors in mitigating corrosion of steel under elevated temperature and chloride concentration

The performance of five corrosion inhibitors, with varying composition, in decreasing the rate of corrosion of mild steel immersed in the simulated concrete pore solution with three levels of chloride contamination (1000, 1500 and 2000 mg/L) and three exposure temperatures (25, 40 and 55 °C) was studied utilizing potentiodynamic polarization (PDP) technique. The morphology of the steel surfaces exposed to the aforesaid conditions was characterized using a scanning electron microscope. Uniform corrosion was noted in the specimens exposed to a temperature of up to 40 °C. However, pitting corrosion was indicated in the specimens exposed to 55 °C. An increase in the temperature or chloride concentration increased the rate of corrosion. The effect of temperature on the corrosion rate was more pronounced, particularly when it was increased from 40 to 55 °C, than the chloride concentration. Further, the use of inhibitors changed the pitting corrosion to uniform corrosion. All the investigated inhibitors were effective in minimizing in decreasing the corrosion current density, both at high temperature and high chloride concentration. However, among the five inhibitors investigated, the performance of calcium nitrite-based and amino carboxylate type inhibitors was better than that of modified amino alcohol-based inhibitors.