Synthesis and characterizations of 4,6-dihydroxyisophthalohydrazide derivative for mitigation corrosion inhibition of low carbon steel in acidic medium

In the oil and gas industry, carbon steel is widely used but suffers from severe corrosion in acidic environments, particularly in the presence of CO₂ and H₂S. This study presents the synthesis and evaluation of a novel eco-friendly compound, 2,2'-(4,6-dihydroxyisophthaloyl) bis(N-phenylhydrazine-1-carbothioamide) (DICA), as an effective corrosion inhibitor for low-carbon steel in 0.5 M HCl solution. Structural characterization was confirmed through NMR, elemental analysis, and mass spectrometry. The corrosion inhibition performance was investigated using weight loss (WL), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). DICA demonstrated outstanding inhibition efficiency, reaching 91.41% at 300 ppm concentration and 298 K, indicating a strong concentration-dependent protective effect. Surface morphology analysis by SEM and AFM revealed a significant reduction in steel surface roughness and corrosion damage due to DICA adsorption. Complementary density functional theory (DFT) calculations and Monte Carlo simulations corroborated the mixed-mode adsorption mechanism involving both chemisorption and physisorption. These findings confirm the potential of DICA as a high-performance, environmentally benign inhibitor for protecting carbon steel in aggressive acidic media.