Adsorption and corrosion inhibition mechanism of Schiff base-conjugated oligoelectrolyte on mild steel in acidic media: electrochemical and surface characterization studies

Abstract

The potential of conjugated oligoelectrolyte (COE) derivatives to mitigate corrosion in mild steel remains unexplored. This paper presents a detailed description of the preparation and characterization of a Schiff base-conjugated oligoelectrolyte (BTC-SBCOE), followed by its investigation as a corrosion inhibitor. The Schiff base (SB) synthesized from benzene-1,3,5-tricarbaldehyde with 4-aminophenol is functionalised with an ionic polar pendant at the terminal oxyl position to afford BTC-SBCOE and is characterized by FTIR, ¹H-NMR, and ¹³C-NMR measurements, as well as mass spectrometry. In acidic media, quaternary ammonium bromide groups improve the stability and effectiveness of BTC-SBCOE by creating a steric-electrostatic barrier. The gravimetric technique, electrochemical impedance spectroscopy, and potentiodynamic polarization are utilized to assess the anticorrosion effectiveness of BTC-SBCOE towards the dissolution of mild steel in 2 M HCl (7.2%) at different concentrations and in the temperature range of 25–80 °C. The gravimetric investigations suggest an inhibition efficiency of 90.38% at 5 mM. Surface examination employing scanning electron microscopy and atomic force microscopy validated the formation of a protective layer on the surface. The thermodynamic analysis results indicate that the binding of BTC-SBCOE is governed by physical and chemical adsorption on the mild steel surface, which prevents corrosion. The overall finding indicates that BTC-SBCOE is a long-lasting and efficient corrosion inhibitor for mild steel in acidic media.