Molecular weight distribution and corrosion inhibitor activity of 4-vinylpyridine oligomer synthesized using low concentration hydrogen peroxide as the initiator

Abstract

Low molecular weight 4-vinylpyridine oligomer or O(4-VP) has been synthesized using 0.25 M hydrogen peroxide as the initiator. The resulting O(4-VP) was characterized by Fourier transform infrared (FTIR) spectroscopy for identification of functional groups, and mass spectroscopy (MS) for determination of molecular weights. O(4-VP) was tested as a corrosion inhibitor of mild steel in a corrosive solution saturated with carbon dioxide using wheel test and electrochemical methods, i.e., electrochemical impedance spectroscopy (EIS) and Tafel plots. Mild steel surface analysis was performed by scanning electron microscopy (SEM). The product of the synthesis is a viscous orange compound. The mass spectrum showed that O(4-VP) had a mass (m/z) of 100–900, which is in accordance with the chain length of 1–9 monomer units, where the chain length of 4 (tetramer) is the most abundant fraction. The FTIR results show no significant difference between the monomer and O(4-VP). The wheel test as a screening test showed that O(4-VP) exhibited corrosion inhibitor activity. This activity was confirmed by the results of EIS and Tafel analyses, which also demonstrated that protection increased with increasing concentration of O(4-VP) and temperature. At temperature 70°C and a concentration of 150 mg L –1 , the protection by O(4-VP) reached 81.9% (based on EIS) and 87.8% (based on Tafel plots). Protection of mild steel was also confirmed by the surface morphology of the sample obtained by SEM characterization.