Temperature performance of a thione quinoxaline compound as mild steel corrosion inhibitor in hydrochloric acid medium

Abstract

The inhibiting action of 3-methyl-1-prop-2-ynylquinoxaline-2(1H)-thione (Pr-N-Q=S) on mild steel in molar hydrochloric acid has been investigated in the temperature range from 35 to 80 °C using weight loss measurements. It was shown that the inhibition efficiency increased with Pr-N-Q=S concentration and remained constant and so higher close to 96 % at 10-3M though temperature rising. The apparent activation energies (Ea), enthalpies (ΔH*) and entropies of activation (ΔS*) values provided evidence of the inhibitory effect of Pr-N-Q=S. Langmuir isotherm model fitted well the adsorption of Pr-N-Q=S onto metallic surface in acidic media. Furthermore, spontaneity of the adsorption process, evaluated from the sign of free energy (ΔadsG°) values, showed a decrease upon temperature increase in the presence of Pr-N-Q=S.