Synthesis, characterization, theoretical calculations (DFT and MC), and experimental of different substituted pyridine derivatives as corrosion mitigation for X-65 steel corrosion in 1M HCl

Abstract Newly synthesized ρ-substituted pyridine derivatives (PYR-Cl, PYR-H, and PYR-OCH3) were characterized by FT-IR, MS, and 1HNMR. Quantum calculations indicate the insight compounds have active adsorption centers that suppress X-65 steel dissolution via DFT descriptors and MC simulation calculations. Electrochemical (potentiodynamic polarization and impedance) techniques were employed to investigate the inhibition performance of the studied substituted pyridine derivatives. The tendency of the studied pyridine derivatives to shield X-65 steel surface away from the HCl aggressiveness action depends on electron-donating and withdrawing effect of ρ-substitution groups (-Cl, -OCH3), according to Hammett constant (σ), and their addition concentrations. Tafel data indicated that the inhibition efficiency touches the peak (95.75%) at 1 × 10−3 M PYR-OCH3 at 25°C. The ρ-substituted pyridine derivatives adsorbed chemically and physically over X-65 steel surface (ΔGads ≈-38 kJmol−1) and followed the Langmuir adsorption isotherm model. Surface morphology (SEM and EDX) displayed the smooth X-65 steel surface due to the adsorbed-protective layer's formation. Both theoretical and experimental studies confirm the inhibition efficacy order of the tested pyridine derivatives, PYR-Cl