Anti‐Corrosive Behavior of Nitro‐Engineered 1,3,4‐Thiadiazoles for Mild Steel C‐1030: A Comprehensive Potentiodynamic Study

The corrosion inhibition behavior of two nitro‐substituted 1,3,4‐thiadiazoles derivatives namely, 2‐NPTMP and 4‐NPTMP, toward mild steel C‐1030 in 1 M HCl was evaluated by weight‐loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and surface analysis. Gravimetric measurements showed maximum inhibition efficiencies of approximately 82%–83% at 80 ppm (303 K) with a slight decline at higher temperatures, suggesting adsorption‐controlled inhibition. EIS studies revealed a significant increase in charge‐transfer resistance with inhibition efficiencies of 84.4% and 90.2%, respectively, while PDP confirmed the mixed‐type with reduced corrosion current density and minimal shift in corrosion potential. The Δ G ° ads values between −33.8 and −36.9 kJ mol −1 confirmed the Langmuir adsorption isotherm, which, in turn, involves both chemisorption and physisorption. The formation of a compact, protective inhibitor film on the steel surface was supported by SEM and EDX analyses. The superior performance of 4‐NPTMP was attributed to the molecular planarity and electron delocalization, enhancing the anti‐corrosive property.