Investigation of 1-butyl-3-methyl-1H-benzimidazolium iodide as inhibitor for mild steel in sulfuric acid solution

•BMBIMI is an effective mixed-type inhibitor for mild steel in H2SO4 solution.•The inhibition efficiency increases with the increment of inhibitor concentration.•BMBIMI takes the flat mode adsorbed on the metal surface by benzimidazole ring.•The adsorption is an exothermic process and obeys Langmuir adsorption isotherm.

A newly benzimidazole derivative, 1-butyl-3-methyl-1H-benzimidazolium iodide (BMBIMI), has been tested as inhibitor for mild steel in 0.5 M H2SO4 solution via various approaches including weight loss, electrochemical measurements, scanning electron microscope (SEM), atomic force microscope (AFM) and theoretical calculations. The obtained results reveal that BMBIMI is an effective mixed-type corrosion inhibitor for mild steel, and the adsorption of BMBIMI on the mild steel surface is found to obey the Langmuir adsorption isotherm, thus the thermodynamic and kinetic parameters governing the adsorption process are calculated and discussed. Moreover, theoretical calculations give further insight into the mechanism of inhibition of BMBIMI.