Benzotriazole derivative as an effective corrosion inhibitor for low carbon steel in 1 M HCl and 1 M HCl + 3.5 wt% NaCl solutions

5–methyl–1H–benzotriazole (MHB) has been investigated as an inhibitor for the corrosion of low carbon steel in 1 M HCl and 1 M HCl + 3.5 wt% NaCl solutions. Results from electrochemical measurements (open circuit potential (E_ocp), electrochemical impedance spectroscopy (EIS), linear polarization (LPR) and potentiodynamic polarization (PDP)) confirm that MHB effectively impeded the low carbon steel corrosion in both solutions with up to 80% at 298 K. At 298 K, MHB functioned as a mixed–type inhibitor. At 333 K, MHB protection efficiency decreased and its inhibition mechanism became more cathodic. Combining MHB with 5 mM KI significantly improve its performance at 298 K and 333 K, whereby 85% efficiency is recorded at 333 K. The combined effect also minimized surface degradation of the steel during the corrosion. The calculated synergism parameter shows that the enhanced inhibition performance of MHB + KI in 1 M HCl solution is synergistic in nature. FTIR analysis provides proof of MHB adsorption and interaction with Fe, as reasons for the inhibition. The performance of MHB is more effective in 1 M HCl than in 1 M HCl + 3.5 wt% NaCl solution.