Corrosion inhibition of X70 steel by tetrabutylammonium iodide in 1 M HCl at different temperatures

• H. Ahmed¹, F. Mahmoud² and Z. Abdelhalim³

¹ Laboratoire physico-chimie des Matériaux (LPCM), Université Amar Telidji BP 37G 03000 Laghouat, Algeria
² Laboratoire de Mécanique (LM), Université Amar Telidji BP 37G 03000 Laghouat, Algeria
³ Plateaux Techniques D'analyses Physico-Chimiques (PTAPC) CRAPC 03000 Laghouat, Algeria

Abstract: The corrosion inhibition of X70 steel in 1 M HCl by tetrabutylammonium iodide (I-TBA) was investigated by means of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The polarization and EIS tests indicate that the dissolution of X70 steel increased as the temperature increased. The EIS results indicate that the protection efficiency (%IE) rises with an increase in the concentration of I-TBA and reaches an optimal value of 72% at 0.8 mM at 35°C. Potentiodynamic polarization studies clearly revealed that I-TBA acted essentially as a mixed-type inhibitor. Thermodynamic parameters were obtained from potentiodynamic polarization curves at different temperatures (25–55°C), which suggested that the adsorption of (I-TBA) on the metal surface obeyed the Langmuir adsorption isotherm model. The values of ΔG_ads (from –28.31 to –31.44 kJ/mol) imply that the adsorption of I-TBA on X70 steel surface in 1 M HCl at the examined temperatures involves both physisorption and chemisorption. The value of enthalpy change is positive, which indicates that the adsorption process is endothermic. SEM analysis suggests that I-TBA forms a protective layer on the X70 steel surface. Finally, the theoretical study by DFT calculations and Monte Carlo simulation showed the inhibitory properties of the TBA molecule and the way of its arrangement on the metal surface; these results are somewhat compatible with the experimental results.

Keywords: corrosion inhibition, X70 steel, tetrabutylammonium, adsorption

Int. J. Corros. Scale Inhib., 2023, 12, no. 2, 489-510
doi: 10.17675/2305-6894-2023-12-2-7

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