TITLE:
7-(2-Ethyltiophenyl) Theophylline as Copper Corrosion Inhibitor in 1M HNO3
AUTHORS:
Ouédraogo Augustin, Akpa Sagne Jacques, Diki N’guessan Yao Silvère, Diomande Gbe Gondo Didier, Coulibaly Nagnonta Hippolyte, Trokourey Albert
KEYWORDS:
Corrosion, 7-(2-Ethyltiophenyl) Theophylline, Mass Loss, SEM, DFT
JOURNAL NAME:
Journal of Materials Science and Chemical Engineering,
Vol.6 No.8,
August
31,
2018
ABSTRACT: 7-(2-ethyltiophenyl) theophylline was used as copper corrosion inhibitor in 1M HNO3 solution. The study was performed using mass loss, scanning electron microscopy (SEM) and Density Functional Theory (DFT) methods. The results show that the inhibition efficiency increases up to 91.29% with increase of the inhibitor concentration (from 0.05 to 5 mM) but decreases with raising temperature of the solution. Copper dissolution was found to be temperature and 7-(2-ethyltiophenyl) theophylline concentration dependent. The thermodynamic functions related to the adsorption of the molecule on the copper surface and that of the metal dissolution were determined. The results point out a spontaneous adsorption and an endothermic dissolution processes. Adsorption models including Langmuir, El-Awady and Flory-Huggins isotherms were examined. The results also suggest spontaneous and predominant physical adsorption of 7-(2-ethyltiophenyl) theophylline on the metal surface which obeys Langmuir isotherm model. Further investigation on the morphology using scanning electron microscopy (SEM) has confirmed the existence of a protective film of inhibitor molecules on copper surface. Furthermore, the global and local reactivity parameters of the studied molecule were analyzed. Experimental and theoretical results were found to be in good agreement.