Synthesis, characterization, anticorrosion properties, and theoretical study of two α-aminophosphonate derivatives

Abstract

Two α-aminophosphonates derivatives, namely Diethyl ((phenylamino)(pyridine-2-yl) methyl) phosphonate (o-DPAPMP) and Diethyl ((phenylamino)(pyridine-3-yl) methyl) phosphonate (m-DPAPMP), have been synthesised using the Kabachnik Fields reaction, and their structures have been confirmed through melting point, UV-visible absorption, FT-IR, and NMR (¹H, ¹³C, ³¹P) spectroscopy techniques. Their potential as anticorrosion agents for XC48 carbon steel in a 0.5 M H₂SO₄ solution are evaluated using various techniques, including weight loss measurements, Tafel polarization, electrochemical impedance spectroscopy, atomic force microscope, contact angle measurements, density functional theory (DFT), and molecular dynamics (MD). The results revealed that o-DPAPMP and m-DPAPMP exhibited inhibition efficiencies of 94.56% and 93.66%, respectively. The inhibition mechanism involved the adsorption of the inhibitors onto the metal surface via the Langmuir adsorption isotherm, with the energy-free standard values revealing both physical and chemical. AFM analyses demonstrated that both inhibitors prevented the normal functioning of carbon steel, with o-DPAPMP showing stronger inhibitory efficiency than m-DPAPMP. Contact angle measurements confirmed the surface’s hydrophobic nature. Theoretical analyses using DFT and MD showed a strong correlation with experimental results.