Adsorption properties and inhibition of mild steel corrosion in 1 M HCl solution by some bipyrazolic derivatives: Experimental and theoretical investigations

The corrosion inhibition of mild steel in 1 M HCl by 1,1-bis(3-ethoxycarbonyl-5-methylpyrazolyl)-methane (P1) and 1,4-bis(3-ethoxycarbonyl-5-methylpyrazolyl)-butane (P2) has been studied at 308 K using electrochemical and weight loss measurements. Polarization curves reveal that the used compounds are mixed type inhibitors. Results show that inhibition efficiency increases when the inhibitor concentration increases. The comparative study of inhibitive performance of the two bipyrazolic derivatives revealed that P2 is more effective than P1. The adsorption of P2 on steel surface obeyed Langmuir's adsorption isotherm. The kinetic and thermodynamic parameters for mild steel corrosion and inhibitor adsorption, respectively, were determined and discussed. Obvious correlation was found between corrosion inhibition efficiency and quantum chemical parameters, using the Density Functional Theory method (DFT). The obtained theoretical results have been compared with the experimental results.