Modified chitosan as an effective inhibitor against the corrosion of C-steel in HCl solutions.

Abstract2-((1<italic>H</italic>-Benzo[d]imdazole-2yl) thio)1(4-chlorophenyl) ethan-1-one modified chitosan (BIMC) was applied as an effective inhibitor for the corrosion of C-steel in 1.0 M HCl solution. Various techniques such as gravimetry, H2 evolution, electrochemical potentiodynamic, <italic>PD</italic>, and impedance spectroscopy were included. The data indicated that the rate of metal dissolution is lowered with more additions of the BIMC compound and increased with temperature. <italic>EIS</italic> measurements proved that the presence of the BIMC compound in the acidic media reduces the values of the double layer capacitance, <italic>C</italic>dl, and raises the charge transfer resistance, <italic>R</italic>ct explaining the formation of the passive layer of the BIMC inhibitor through an adsorption process. <italic>PD</italic> measurements proved that the BIMC compound is conducted as a mixed-kind inhibitor. The protection efficacy, <italic>η</italic> %, increased with more additions of the BIMC and was reduced with temperature. The <italic>η</italic> % takes higher values to reach 93% at 5 mg/L, at 25 °C. The protection process is controlled by the adsorption of the BIMC molecules on the metallic surface obeying Langmuir’s pattern. The computed ΔGads° values were found to depend on the temperature and varied between −31.42 and −34.62 kJ/mol. Such a conclusion could be attributed to the mixed adsorption mechanism. The higher values of <italic>K</italic>ads could confirm the stability of the adsorption process. The lowering in the <italic>K</italic>ads values with <italic>T</italic> can be related to the desorption of some BIMC molecules from the electrode surface. Theoretical quantum computation confirmed the adsorption of the BIMC compound in concurrence with the data obtained by practical techniques. [ABSTRACT FROM AUTHOR]