Inhibitive properties of quaternary ammonium bromides of N-containing heterocycles on acid mild steel corrosion. Part II: EIS results

Four quaternary ammonium bromides of different heterocyclic compounds were investigated as corrosion inhibitors of mild steel in 1 N HCl using electrochemical impedance spectroscopy. The results were compared with data obtained by the polarisation resistance method. The influence of concentration and temperature (30–60 °C) was checked as well. Two structure models were found to describe the processes taking place at the interface mild steel/1 M HCl + inhibitor. The simpler one can be considered as a degeneration of the more complex one when the two time constants approach similar values. By fitting the structural models to the experimental results the parameter values were evaluated, as well as the time constants. A good correlation was established between the EIS and the polarisation resistance results.