Experimental, quantum chemical and Monte Carlo simulations studies on the corrosion inhibition of mild steel in 1 M HCl by two benzothiazine derivatives

Two benzothiazine derivatives namely, methyl 3-hydroxy-2-(p-tolyl)-3,4-dihydro- 2h-benzo[b][1,4]thiazine-3-carboxylate (mbt), ethyl 3-hydroxy-2-(p-tolyl)-3,4- dihydro-2h-benzo[b][1,4]thiazine-3-carboxylate (ebt) were examined as a corrosion inhibitors for mild steel in 1.0 m hcl using electrochemical impedance spectroscopy (eis) and potentiometric polarization (pdp). the results show that both compounds are good inhibitors and their inhibition efficiencies reached 97% at 10^-3 m. the percentage inhibition efficiency (η %) increased with the increase of inhibitor concentration due to the adsorption of the inhibitory molecules on the metal surface. the tafel polarization study revealed that both inhibitors act as a mixed type inhibitor. furthermore, it has been established that the adsorption follows the langmuir adsorption isotherm. quantum chemical parameters were calculated using the density functional theory (dft) method and monte carlo simulations. the correlation between theoretical and experimental results was discussed.