Effect of soft cations on carbon steel corrosion in chloride media

Abstract

Abstract The effect of soft cations (Na+, K+, NH4 +) on the corrosion behavior of carbon steel in chloride (Cl−) media was investigated using various electrochemical and nonelectrochemical techniques. Data revealed that the corrosion rate is higher in the case of ammonium chloride solution following the order NH4 +>K+>Na+. The polarization and electrochemical impedance spectroscopy (EIS) measurements indicated a significant influence of cations on both the corrosion rate and the mechanistic reaction pathway of carbon steel dissolution in Cl− media. The EIS measurement showed two time constants in all the cases. Electrical equivalent circuit was employed to model the EIS data. The surface morphology and the corrosion products were also analyzed. It was found that the hydration energy of cations and the initial pH of the solution play a critical role in describing the effect of cations present in Cl− media on carbon steel corrosion.