Novel isoxazolium cationic Schiff base compounds as corrosion inhibitors for carbon steel in hydrochloric acid

The corrosion of carbon steel in 0.5 M HCl at 25 °C was investigated in the presence of two synthesized quaternary isoxazolium Schiff base series using gravimetric, polarization and electrochemical impedance measurements. The measurements showed a gradual increase in the inhibitors efficiencies by increasing the dose and hydrophobic chain length. The calculated activation energies proposed that the inhibitor molecules are adsorbed physically onto the metal surface. Surface activity-inhibition tendency relation showed the gradual increase of the inhibition efficiency by increasing the hydrophobic chain length.

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► Isoxazolium inhibitors show good corrosion inhibition for carbon steel in acidic medium.
► The corrosion rates decrease by increasing the inhibitors concentration and the chain length.
► Inhibition mechanism suggested as physisorption supported by adsorption free energy values.
► Inhibition efficiency increases by increasing the alkyl chains length attached to the molecules.