Title: Polarisation resistance behaviour of corrosion inhibition of low carbon steel in H₃PO₄ acid

Authors: Aprael S. Yaro, Anees A. Khadom

Addresses: Department of Chemical Engineering, College of Engineering, University of Baghdad, Aljaderia, 10071, Baghdad Governorate, Iraq. ' Department of Mechanical Engineering, College of Engineering, University of Daiyla, Baquba, 32001, Daiyla Governorate, Iraq

Abstract: The non-linear region of polarisation curve near the corrosion potential can be discussed depending on data of over potential as a function of current densities. These data can be analysed by suggesting a mathematical model taking into account the effect of mass transfer on activation process. This model was used to evaluate the values of polarisation resistance R_p in presence and absence of potassium iodide (KI) as a corrosion inhibitor of low carbon steel in 2.5 M phosphoric acid at different temperatures. The values of polarisation resistance obtained by mathematical model compared with these obtained by Tafel parameters. The suggested ß-model was very useful in evaluating the values of R_p. The maximum value of polarisation resistance was 5049.13 Ωcm² at 30°C in presence of 0.05 M KI, while the minimum value was 1.885 Ωcm² at 60°C in absence of KI. These results indicate that the polarisation resistance values increased with the increase of KI concentration, and decreased with the increase of temperature.

Keywords: current density; Stern and Geary equation; polarisation resistance; potassium iodide; over potential; surface science; corrosion inhibition; low carbon steel; mathematical modelling; mass transfer.

DOI: 10.1504/IJSURFSE.2010.035145

International Journal of Surface Science and Engineering, 2010 Vol.4 No.4/5/6, pp.429 - 438

Published online: 09 Sep 2010 *

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