Contribution à la compréhension des phénomènes d’inhibition de la corrosion d’un acier au carbone par des dérivés hydrazides.

Abstract

Four sulfonohydrazide derivatives, which are either commercially available or newly synthesized, were investigated as corrosion inhibitors for XC38 carbon steel in 1 M HCl using electrochemical measurements (potentiodynamic polarization, linear polarization resistance, electrochemical impedance spectroscopy) and theoretical calculations by Density Functional Theory or DFT. Results obtained show that the synthesized derivatives are good corrosion inhibitors for carbon steel in molar HCl, unlike commercial products that stimulate the metal corrosion in this media. The inhibition efficiency of the synthesized hydrazides increases with their concentration and with the immersion time, but decreases with increasing temperature. Substituting a methyl group for a hydrogen atom improves the effectiveness. These inhibitors display a mixed-type. They adsorb onto the metal surface and block its active sites for steel dissolution and/or hydrogen evolution, which thereby hinders the overall metal corrosion in the aggressive environment. The thermodynamic study shows that their adsorption on the steel surface is spontaneous. This adsorption proceeds via physisorption (main mechanism) and chemisorption modes and obeys the Langmuir adsorption isotherm. Good correlations were obtained between the anti-corrosion performances of these donor-acceptor compounds and their molecular properties.