https://doi.org/10.15255/KUI.2003.003
Published: Kem. Ind. 53 (2) (2004) 55–61
Paper reference number: KUI-03/2003
Paper type: Original scientific paper
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Corrosion Inhibition of Mild Steel in 1 mol dm–3 HCl by Oxalic N-Phenylhydrazide N-Phenylthiosemicarbazide

Y. Harek and L. Larabi

Abstract

Oxalic N-phenylhydrazide N-phenylthiosemicarbazide (OPHPT), synthesized in our laboratory, was tested as inhibitor for the corrosion of mild steel in molar HCl by mass loss, potentiodynamic and polarization resistance measurements. It was found that OPHPT is a good inhibitor for the corrosion of mild steel in 1 mol dm–3 HCl and its inhibition efficiency (η) increases with its concentration and attains approximately 93 % at 5 × 10–4 mol dm–3. Polarization curves indicate that OPHPT acts as a mixed type inhibitor. The inhibitor was adsorbed on the mild steel surface according to the Langmuir adsorption isotherm model. Results show that the rate of corrosion of mild steel increased with increasing temperature over the range 25 – 55 °C, both, in the presence of inhibitor and in its absence. It was also found that, on the one hand, the inhibiting effect grows with the increase of the temperature of the corrosion medium and, in the other hand, the presence of inhibitor in the solution induces an increase of the activation energy of the corrosion process. The synergistic action of iodide ions on the inhibition of mild steel in 1 mol dm–3 HCl by OPHPT was also investigated. The corresponding results suggest that the presence of iodide ions in the solution stabilized the adsorption of OPHPT molecules on the metal surface and, therefore, improved the inhibition efficiency of OPHPT.

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Keywords

thiosemicarbazide, mild steel, inhibition corrosion, hydrochloric acid