Investigating the Corrosion Inhibition Mechanisms of Alkanolammonium Salts: A Case Study with Ethylethanolammonium 4-Nitrobenzoate on Carbon Steel in Saline Solution

This study explores the potential corrosion inhibition mechanisms of alkanolammonium salts, exemplified by ethylethanolammonium 4-nitrobenzoate (EEA4NB), for carbon steel, utilizing experimental and theoretical methods. The interactions between metal and inhibitor, focusing on adsorption behavior in saline solutions, will be thoroughly investigated. Analysis of potentiodynamic polarization curves and electrochemical impedance spectroscopy reveals that the inhibition efficiency (IE) increases with the rising concentration of EEA4NB, reaching 96% at 5 × 10−3 M. Negative adsorption free energy and a high adsorption equilibrium constant suggest the spontaneous formation of a protective inhibitor layer on the metal surface, effectively blocking reaction sites and reducing the corrosion rate, according to the Langmuir isotherms model. As confirmed by scanning electron microscopy, physical and chemical interactions contribute to the adsorption mechanisms. Quantum chemical calculations explore the relationship between EEA4NB molecular configuration and inhibition efficiencies. The study emphasizes the potential efficacy of alkanolammonium salts, exemplified by EEA4NB, as effective corrosion inhibitors for carbon steel in aggressive environments.