Corrosion Resistance of Mild Steel Coated with Orgainc Material Containing Pyrazol Moiety

Fadoua El Hajjaji,Abdelfatah Hasan,Mustapha Taleb,Farid Abrigach,Manuel Algarra,María Martínez De Yuso,Shehdeh Jodeh,Othman Hamed,Enrique Rodríguez-Castellón

doi:10.3390/coatings8100330

Abstract

Pyridine (P1) and benzoic acid (P2) derivatives with pyrazole moieties were synthesized and evaluated as corrosion inhibitors for mild steel in acidic medium. The evaluation was performed by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and weight loss measurement. The surface morphologies of the control and steel samples coated with the pyrazole derivatives P1 and P2 were examined by the scanning electron microscopy (SEM), UV-Vis, and X-ray photoelectron spectrocopy (XPS) spectroscopies. Results revealed minor changes on steel surfaces before and after immersion in a 1 M HCl solution. Both derivatives, P1 and P2, showed good inhibition efficiency that is dependent on inhibitor concentration. Both P1 and P2 act as mixed-type inhibitors. The benzoic acid derivative (P2) showed a higher efficiency than P1, which could be attributed to the carboxyl group that is located at the para position to the amino group. This induces a direct electronic resonance between the two groups, the amino and the carboxyl. As a result of this, a higher electron density on the carboxyl group and a stronger bonding to the metal surface occurred. Results also show that, the bonding of both pyrazoles on mild steel surface obey Langmuir adsorption isotherm. Quantum chemical calculations were performed to theoretically define the relationship between the molecular structures and inhibition efficiencies of P1 and P2.

Highlights

Pickling process of steel includes using a strong acid such as hydrochloric acid or a mixture of hydrochloric acid and nitric acid
Sheets of mild steel with dimensions of S = 10 mm × 40 mm × 0.6 mm were scraped with a series of emery paper SIC (220, 400, 800, 1000 and 1200), washed with doubly distilled water acetone
The loss in the weight (w), The inhibition efficiency (IE) and surface coverage (θ) of coated samples were calculated according to Equations (1)–(3) [28]: wa − wb IE(%) = 1 − i × 100

Summary

Introduction

Pickling process of steel includes using a strong acid such as hydrochloric acid or a mixture of hydrochloric acid and nitric acid. Residual acid on steel surface after the pickling process causes the steel to corrode. Most of inhibitors used for this purpose are organic based materials contain coordination sites for Coatings 2018, 8, 330; doi:10.3390/coatings8100330 www.mdpi.com/journal/coatings. Coatings 2018, 8, 330 inhibitors used for this purpose are organic based materials contain coordination sites for metal coordination. The coordination sites include multiple bonds and heteroatoms such as sulfur, metal coordination. Bonds and heteroatoms such asoxygen sulfur, and nitrogen. These inhibitors prevent corrosion by blocking the active corrosion sites mainly by oxygen and nitrogen. These inhibitors prevent corrosion by blocking the active corrosion sites mainly complexing to the metal surface and forming by complexing to the metal surface and forminga aprotective protectivelayer layer[6,7,8]

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Conclusion