Experimental and computational studies on the inhibition performances of benzimidazole and its derivatives for the corrosion of copper in nitric acid

The inhibitive performance of seven synthesized 2-(2-benzimidazolyl)-4 (phenylazo) phenol (BPP_1–7) derivatives was investigated experimentally on the corrosion of copper in 2.0 MHNO3 acid using mass loss, thermometric and DC potentiodynamic polarization techniques. Quantum chemical calculations was investigated to correlate the electronic structure parameters of the investigated benzimidazole derivatives with their inhibition efficiencies (IE%) values. Global reactivity parameters such as EHOMO, ELUMO, the energy gap between ELUMO and EHOMO (ΔE), chemical hardness, softness, electronegativity, proton affinity, electrophilicity and nucleophilicity have been calculated and discussed. Molecular dynamics simulation was applied on the compounds, to optimize the equilibrium configurations of the molecules on the copper surface. The areas containing N atoms are most possible sites for bonding Cu (111) surface by donating electrons. Binding constant (Kb), active sites (1/y), lateral interaction (f), equilibrium constant (Kads) and standard free energy of adsorption (ΔG˚) values obtained from either kinetic model and/or Frumkin adsorption isotherm were compared and discussed. Thermodynamic functions and activation parameters such as: Ea, ΔH*, ΔS* and ΔG* at temperatures 303, 313, 323 and 333 K were determined and explained. IE% values of the examined compounds on Cu (111) surface followed the order arrangement: BPP_1 BPP_2 BPP_3 BPP_4 BPP_5 BPP_6 BPP_7. The theoretical data obtained as compatible with experimental results showed that the studied benzimidazole derivatives (BPP_1–7) are effective inhibitors for the corrosion of copper in nitric acid solution