Abstract

The inhibition action of (E)-7-chloro-3-(4-methoxystyryl)quinoxalin-2(1H)-one (Q1) and 7-chloro-2-(4-methoxyphenyl)thieno(3.2-b)quinoxaline (Q2) have been investigated for mild steel corrosion in 1 M HCl at different temperatures ranges (303–333 K) using potentiodynamic polarization curves. It was found that the studied compounds exhibit a very good performance as corrosion inhibitors for mild steel in 1 M HCl. Results show that the inhibition efficiency increases with decreasing temperature and increasing inhibitors concentration. Thermodynamic parameters such as adsorption heat (\( \Updelta H_{\text{ads}}^{*} \)), adsorption entropy (\( \Updelta S_{\text{ads}}^{*} \)) and adsorption free energy (\( \Updelta G_{\text{ads}}^{*} \)) were obtained from experimental data at temperatures ranging from 303 to 333 K. Other thermodynamic parameters such as Ea, \( \Updelta H_{\text{a}}^{*} \), \( \Updelta S_{\text{a}}^{*} \) and pre-exponential factor have been calculated and discussed. Adsorption follows the Langmuir isotherm with negative values of free enthalpy suggesting a spontaneous adsorption process.

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