Environmentally Benign Water-Soluble Sodium L-2-(1-Imidazolyl) Alkanoic Acids as New Corrosion Inhibitors for Mild Steel in Artificial Seawater

Three novel natural amino acid-derived sodium L-2-(1-imidazolyl)alkanoic acids (IZSs), namely, sodium 2-(1H-imidazol-1-yl)-4-methylpentanoate(IZS-L), sodium 2-(1H-imidazol-1-yl)-3-phenylpropanoate (IZS-P), andsodium 2-(1H-imidazol-1-yl)-4-(methylthio)butanoate (IZS-M), wereinvestigated as corrosion inhibitors. The IZSs were synthesized followingthe green chemistry principles, and their structure was characterizedusing FTIR and NMR techniques. The corrosion study results revealthat a moderate concentration of IZSs (having low solution conductivity)showed potential corrosion inhibition for mild steel in artificialseawater. At longer immersion, IZS-P forms a uniform protective filmand exhibits the potential inhibition efficiency of 82.46% at 8.4mmol L-1. Tafel polarization results reveal thatIZS-P and IZS-M act as mixed types with an anodic predominantly corrosioninhibitor. The electrochemical impedance spectroscopy results signifythat IZSs inhibit mild steel corrosion through the formation of aninhibitor film on the metal surface, which was further confirmed bythe FTIR, SEM, EDX, and XPS studies. DFT result shows that in IZS-P,the benzylic group (-CH2-Ph) has greaterelectron distribution compared to isobutyl (-CH2CH(CH3)(2)) in IZS-L and methythioethyl group(-CH2CH2SCH3) which supportedthe corrosion inhibition performance at longer immersion [IZS-P (82.46%)> IZS-M (67.19%) > IZS-L (24.77%)].

Automated summary

Three types of natural amino acid-derived sodium L-2-(1-imidazolyl)alkanoic acids (IZSs) were synthesized and tested as corrosion inhibitors for mild steel in artificial seawater. The IZSs showed potential corrosion inhibition, with IZS-P exhibiting the highest inhibition efficiency of 82.46%. Tafel polarization and electrochemical impedance spectroscopy results confirmed the mixed corrosion inhibition behavior of IZS-P and IZS-M, which formed a protective film on the metal surface.