2,3-Diphenylbenzoquinoxaline: A new corrosion inhibitor for mild steel in sulphuric acid

2,3-diphenylbenzoquinoxaline (2,3DPQ) has been synthesized and its inhibiting action on the corrosion of mild steel in 0.5 M H2SO4 has been assessed by weight loss method at 30 °C. The results of the investigation show that this compound has excellent inhibiting properties for steel corrosion in sulphuric acid. Inhibition efficiency increases with increase in the concentration of the inhibitor. The adsorption of 2,3DPQ onto the mild steel surface followed the Langmuir adsorption model with the free energy of adsorption ΔGads0 of −11.4 kJ mol−1. Quantum chemical calculations were employed to give further insight into the mechanism of inhibition action of 2,3DPQ.