Caffeine as a corrosion inhibitor of mild steel
in hydrochloric acid
H. Elmsellem1, A. Aouniti1, M.H. Youssoufi2, H. Bendaha2, T. Ben hadda2,
1Laboratoire de Chimie Appliquée et environnement (LCAE-URAC18), Faculté des Sciences,
Université Mohammed Premier, Oujda, Morocco
2Laboratoire de la chimie des matériaux (LCM), Faculté des Sciences, Université Mohammed
Premier, Oujda, Morocco.
3Laboratoire de chimie physique, Centre Régionale des Métiers de l'Education et de Formation ''CRMEF'',
Région de l'Orientale, M-60000 Oujda, Morocco.
4Department of Chemistry, Science College, Al-Najah National University, P.O. Box 7, Nablus, Palestine;
* Corresponding author. E-mail: firstname.lastname@example.org
Received: 18 March 2013; revised version accepted: 10 October 2013
Corrosion inhibition of mild steel in 1 M HCl was investigated in the absence and presence of different concentrations of Caffeine. Weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy techniques were employed. Impedance measurements showed that the double-layer capacitance decreased and charge-transfer resistance increased with increase in the inhibitor concentration and hence increasing in inhibition efficiency. Potentiodynamic polarization study showed that the inhibitor act as cathodic-type inhibitor. The inhibitor was adsorbed on the steel surface according to the Langmuir adsorption isotherm model and quantum calculation parameters (dipole moment, EHOMO, ELUMO and ?E). It was concluded that the high corrosion inhibition efficiency of Caffeine was associated with its strong adsorption as a barrier film on the mild steel surface. E (%) values obtained from various methods used are in good agreement.
Keywords: Mild steel; Caffeine; Inhibition; Corrosion; HCl; DFT.