The inhibition of corrosion of mild steel
in hydrochloric acid solution
in the presence of phosphite crystal
L. Herrag1, A. Chetouani1, 2, B. Hammouti1*, A. Aouniti1, B. El Bali3, M. Lachkar4
1LCAE-URAC18, Faculté des Sciences, Université Mohammed Premier, Oujda, Morocco.
2Laboratoire de chimie physique, Centre Régional des Métiers de l'Education et de la Formation ''CRMEF''.
3 Laboratory of Mineral Solid and Analytical Chemistry, Faculty of Sciences,
4 Laboratoire d’Ingénierie des Matériaux Organométalliques et Moléculaires, Unité Associée au CNRST (URAC 19), Faculté des Sciences, Université Sidi Mohamed Ben Abdellah, B.P.1796 (Atlas), 30000 Fès, Morocco.
* Corresponding author. E-mail: firstname.lastname@example.org
Received: 15 January 2012; revised version accepted: 22 March 2012
The inhibition behaviour of a phosphite compound: Ph-Mn(H2PO3)3.H2O (abbr. Ph-Mn) on C38 steel in 1M HCl solutions are investigated at 308K by weight loss measurements, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) methods. The values of the inhibition efficiency calculated from these techniques are reasonably good agreement. EIS measurements show an increase of the transfer resistance with the inhibitor concentration. The inhibition efficiency increases when the inhibitor’s concentration rises, to reach 93 % for the value 10-3 M. Potentiodynamic polarization measurements clearly reveal that the investigated compound is of mixed type and acts essentially as cathodic inhibitor. The temperature effect on the corrosion behaviour of mild steel in 1M HCl with and without the inhibitors at 10-3 M are studied in the temperature range from 308 and 353 K, the associated activation energies has been determined. The adsorption of the inhibitor on the metal surface in the acid solution is found to obey Langmuir’s adsorption isotherm. The determination of activation and adsorption parameters indicated that the inhibition action in the presence of Ph-Mn is due to physical adsorption. Also an inhibition mechanism is proposed for the inhibitive effect of Ph-Mn.
Keywords: Corrosion; Mild steel; Corrosion inhibitors; Acid; Hybrid phosphite.