Synthesis and Characterization of an Azo Dye: 4-(phenyldiazenyl) phenyl 2-furoate. Electrochemical and XPS Study of its Adsorption and Inhibitive Properties on Corrosion of Carbon Steel in Saline Water

The azo derivative namely 4-(phenyldiazenyl) phenyl 2-furoate (PPF), was obtained by an esterification reaction between 4-(phenyldiazenyl) phenol and 2-furoyl chloride in pyridine. The dye was characterized using elemental analysis, nuclear magnetic resonance (H-1 and C-13) and mass spectrometry with electro-spray ionization (ESI) techniques. The inhibitive properties of PPF on the corrosion of carbon steel in saline water (SW) have been investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). Electrochemical measurements showed that PPF acts as corrosion inhibitor of carbon steel in SW, by suppressing simultaneously the cathodic and anodic processes via adsorption on the carbon steel surface. The results indicated that an increase in the inhibitor concentration leads to an increase in both the charge-transfer resistance (R-ct) and inhibition efficiency (IE) and to a decrease of the corrosion current density (i(corr)). Moreover, adsorption is spontaneous and is best described by Temkin isotherm. In the presence of PPF, XPS analysis confirmed the existence of a superficial layer providing a good corrosion protection of the electrodes. Parameterized Model number 3 (PM3) method was successfully used to predict the electron density distribution inside of PPF molecule.