Inhibitive properties, thermodynamic and quantum chemical studies of alloxazine on mild steel corrosion in H2SO4

Alloxazine (ALLOX) was tested as corrosion inhibitor for mild steel in 0.5 M H2SO4 solution using non-electrochemical technique (gravimetric and UV–Visible spectrophotometric measurements) at 303–333 K. ALLOX acts as inhibitor for mild steel in acidic medium. Inhibition efficiency increases with increase in concentration of ALLOX but decrease with rise in temperature. The adsorption of ALLOX was found to follow Temkin adsorption isotherm model. Both the activation and thermodynamic parameters governing the adsorption process were calculated and discussed. The adsorption follows a first-order kinetics. DFT study gave further insight into the mechanism of inhibition action of ALLOX.

Research highlights
► Alloxazine (ALLOX) is found to be a good inhibitor for the corrosion of mild steel in 0.5 M H2SO4.
► The adsorption of ALLOX on mild steel surface was found to accord with the Temkin adsorption isotherm and also follows the first-order reaction.
► The corrosion inhibition is satisfactorily discussed by both thermodynamic and kinetic parameters.
► The inhibitive mechanism is explained by UV–Visible spectroscopy and quantum chemical calculation results.