Dry and wet lab analysis on benzofused heterocyclic compounds as effective corrosion inhibitors for mild steel in acidic medium

•PQO and POO are efficient corrosion inhibitors for mild steel in 1 M H2SO4.•Polarization studies revealed mixed mode corrosion inhibition by the inhibitors.•Morphology studies indicated protective adsorption of inhibitors on mild steel.•Maximum inhibition efficiency of 95% is observed for PQO.•Quantum chemical results are in good agreement with experimental results.

The influence of two benzofused heterocyclic compounds, namely 2-phenylquinazolin-4(3H)-one(PQO) and 2-phenyl-4H-benzo[d]oxazin-4-one(POO) in controlling mild steel corrosion in 1 M H2SO4 solution was investigated using gravimetric and electrochemical methods. The experimental results revealed that both the inhibitors inhibit corrosion and their inhibition efficiency follows the order PQO > POO. A mixed mode of inhibition from polarization and a charge transfer mechanism from impedance study in the absence and presence of inhibitors were found. The passive film formed on the mild steel surface was characterized using SEM-EDX. Quantum chemical parameters derived using DFT performed at B3LYP/6-31G(d, p) level were used to correlate the molecular structure.

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