Study of the Inhibition Efficiency for Some Novel Surfactants on the Carbon Steel (Type H-11) Pipelines in 0.5M HCl Solution by Potentiodynamic Technique

In this article, three deferent surfactants as corrosion inhibitor were prepared in two steps. In the first step, maleic anhydride was amidated with dodecylamine to produce 2-ene-4-dodecanamide butanoic acid. In the second step, the resulting product was further esterified with different molecular weights of polyethylene glycol (m.wt. = 200, 400, and 600), namely, polyoxy ethylenyl-xene-4-dodecanamide butanoic acid, where x = 2, 4, or 6 according to molecular weights of polyethylene glycol used). The chemical structures of these inhibitors were confirmed by FTIR and H-1 NMR. The corrosion inhibition effect of the synthesized inhibitors has been investigated on the carbon steel (type H-11) pipelines in 0.5 M HCl solution by the potentiodynamic polarization method. From the obtained results, it was found that the maximum inhibition efficiency (90.44%) was exhibited by polyoxy ethylenyl-6-ene-4-dodecanamide butanoic acid, while the minimum inhibition efficiency (79.84%) was obtained by polyoxy ethylenyl-2-ene-4-dodecanamide butanoic acid at 200 ppm and 35 degrees C. Also, the values of activation energy and thermodynamic parameters were calculated and discussed. Adsorption of the synthesized inhibitors was found to follow the Langmuir's adsorption isotherm. Mixed physical and chemical adsorption mechanism is proposed.