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Portugaliae Electrochimica Acta

Print version ISSN 0872-1904

Abstract

AL-SAWAAD, Hadi Z.; FAILI, Naem T.  and  ESSA, Ali. H.. Evaluation of Vicine as a Corrosion Inhibitor for Carbon Steel Alloy. Port. Electrochim. Acta [online]. 2019, vol.37, n.4, pp.205-216. ISSN 0872-1904.  http://dx.doi.org/10.4152/pea.201904205.

In the present study, vicine was extracted from sunflower seeds, and has been evaluated as a corrosion inhibitor for carbon steel alloy, at different concentrations and temperatures. Vicine showed maximum inhibiting efficiency of 97%, at 25 ºC. The inhibitor's efficiency was reduced when the temperature increased. Kinetic parameters (Ea, ?H*, ?G* and ?S*) were calculated. The corrosion reaction was suppressed by vicine, because the energy barrier of the corrosion reaction was increased, and it became non-spontaneous, by an endothermic process. Furthermore, ?Hads, ?Gads and ?Sads were also calculated, and showed that the inhibitor was physically adsorbed by a spontaneous and exothermic process. The corrosion was inhibited by simple blocking the reaction sites. The adsorption process obeyed the Langmuir adsorption isotherm. The theoretical and experimental studies depicted that the inhibitor worked by a mixture of physical-chemical adsorption modes.

Keywords : corrosion inhibitors; vicine; acidic corrosive media; hydrochloric acid; carbon steel alloy.

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