Benzimidazole-modified chitosan (CS-BISP) was utilized as an effective mitigator controlling the destruction of Al, and the generation of H2 in dilute HCl solutions. The techniques of gasometry, mass loss, potentiometry, galvanostatic polarization, GP, and electrochemical impedance spectroscopy, EIS, were involved. The rate of the produced H2 is found to depend on the concentration of the CS-BISP and the temperature. EIS data indicated that the existence of CS-BISP in the HCl solution increases the charge transfer resistance, Rct, and reduces the doublelayer capacitance, Cdl, confirming the presence of an insulating film on the metal surface via an adsorption mechanism. GP data explained that the CS-BISP behaves as an effective inhibitor of a mixed kind. The protection efficiency was raised with increasing the CS-BISP concentration and is lowered by temperature. The protection efficiency reaches 94.2% at 300 mg L􀀀 1, at 25 ◦C. The free energy of adsorption, ΔGoads, varied between – 26.13 and 􀀀 26.88 kJ/mol depending on the solution temperature which emphasizes the presence of physical and chemical adsorption mechanisms. The negative sign of ΔGoads proved a spontaneous adsorption process with the stability of the adsorbed film. The reduction in the Kads value with temperature signifies the desorption of a few of the CS-BISP polymeric molecules from the surface of the Al electrode. The CS-BISP molecule was theoretically examined utilizing density functional theory and Monte Carlo simulations. The theoretical parameters coincide with the experimental results.