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

Abstract

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.

Keywords: Carbon steel; Corrosion; DFT calculations; HCl medium; Hydrazide derivative; Inhibitor; SE and AF microscope.

Scheme 1

Synthesis of DICA compound in one step from DIH compound

Fig. 1

a ¹HNMR of DICA synthesized Compound in DMSO-d₆, b ¹³CNMR of DICA synthesized Compound recorded in DMSO-d₆

Fig. 2

Langmuir adsorption isotherm for the compound DICA on LCS in 0.5 mol L^-1 HCl at different temperatures

Fig. 3

Arrhenius plots (left) (log k vs. 1/T) and transition-state plots (right) (log k/T vs. 1/T) for the corrosion of LCS in 0.5 mol L⁻¹ HCl without and with different concentrations of the DICA compound

Fig. 4

Open Circuit Potential versus Time curves of LCS in 0.5 mol L⁻¹ HCl without and with different concentrations of the DICA compound at 298 K

Fig. 5

Plots of potentiodynamic polarization measurements for dissolution of CS without and with different concentrations of compound DICA, at 25 °C

Fig. 6

Plot of Nyquist Impedance spectroscopy measurements for dissolution of CS without and with different concentrations of compound DICA, at 25 °C

Fig. 7

The Bode plots Left and Right for the corrosion of LCS in 0.5 mol L^-1 HCl without and with different concentrations of the DICA compound at 25 °C

Fig. 8

Equivalent circuit model used to fit experimental EIS data

Fig. 9

SEM image of pure LCS after polishing at 10 and 600 μm

Fig. 10

SEM image of LCS after immersing in 0.5 mol L^-1 HCl (10 & 600 μm)

Fig. 11

SEM image of LCS after immersing in 0.5 mol L^-1 HCl + 300 ppm of DICA (10 & 600 μm) exhibiting a smoother morphology and reduced corrosion damage

Fig. 12

AFM of pure LCS after polishing, indicating smoother surface and effective corrosion inhibition film formation

Fig. 13

AFM of LCS after immersing in 0.5 mol L^-1 HCl

Fig. 14

AFM of LCS after immersing in 0.5 mol L^-1 HCl + 300 ppm of DICA

Fig. 15

Geometrical structure, Active lone pair, interaction potential, electrostatic and charge density distribution of HOMO and LUMO levels of the inhibitor compound DICA

Fig. 15

Geometrical structure, Active lone pair, interaction potential, electrostatic and charge density distribution of HOMO and LUMO levels of the inhibitor compound DICA

Fig. 16

Side view and Top view for the adsorption of the DICA inhibitor on LCS

Fig. 17

Interaction Mechanism of DICA Compound with the LCS surface