Adsorption and Inhibitive Effects of 2-Thiobenzylbenzimidazole (TBBI) at Aluminium Alloy AA3003/ 1M Hydrochloric Acid Interface

The interfacial behavior of 2-Thiobenzylbenzimidazole (TBBI) between aluminium alloy AA 3003 and 1M hydrochloric acid solution was investigated by mass loss technique. Mass loss is concentration and temperature dependent. The influence of temperature has been studied in the absence and in presence of TBBI in the hydrochloric solution in the range 35-55ºC. Adsorption isotherms models including Langmuir, Temkin, Freundlich and El-Awady were tested. It was found that the inhibitor adsorbs on the metal according to the modified Langmuir adsorption isotherm. Some thermodynamic adsorption parameters ( , ) as well as activation parameters including apparent activation energy (Ea), change in activation enthalpy ( ) and change in activation entropy ( ) have been calculated and analyzed. Furthermore the Dubinin-Raduskevitch model has been used to distinguish between chemisorption and physisorption. The properties most relevant to the potential action as a corrosion inhibitor of TBBI have been calculated: highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELUMO), energy gap (ΔE), dipole moment (µ) and charges on the adsorption centers (S, N) and C atoms in benzimidazole and benzyl rings. These calculations were performed using the Gaussian suite of programs level by DFT/B3LYP/6-31G (d,p). The theoretical results are consistent with the experimental data.