Synthesis, characterization and inhibition effect of new antipyrinyl derivatives on mild steel corrosion in acidic solution

Newly antipyrinyl derivatives 4 and 5 were synthesized from the reaction of enaminonitrile 3 with 1-nitroso-2-naphthol and salicyaldehyde, respectively, and used to protect mild steel dissolution in 1.0 M HCl solutions using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy measurements. It was shown that these inhibitors act as good corrosion inhibitors for mild steel protection. The inhibition efficiencies were attributed to the simple blocking effect by adsorption of inhibitor molecules on the mild steel surface. The results showed that inhibitors acts as a mixed-type inhibitor. Relationship between molecular structure and their inhibition efficiency was elucidated by quantum chemical calculations.