Corrosion and hydrogen permeation inhibition of St3–steel in H2S/CO2 media by AKB-1 organic inhibitor

• G.R. Gurbanov¹, N.R. Akhundova², A. Kulbey³ and Z.Y. Xin⁴

¹ Department of Oil and Gas Transportation and Storage, Azerbaijan State Oil and Industry University, Azadlig Avenue 20, AZ1010, Baku, Azerbaijan
² Department of Oil and Gas Engineering, Azerbaijan State Oil and Industry University, Azadlig Avenue 20, AZ1010, Baku, Azerbaijan
³ Department of Pipeline Transport and Hydraulics, Euphrosyne Polotskaya State University of Polotsk, 29 Blokhin Street, 211440, Novopolotsk, Vitebsk Region, Republic of Belarus
⁴ Xuxin Trading Co., Ltd., Guanzhang Road 18, Dongguan, Guangdong Province, 523000, China

Abstract: The corrosion inhibition and hydrogen permeation behavior of St3 carbon steel were investigated in aggressive environments containing H₂S (400 ppm), CO₂ (1 atm), and mixed H₂S/CO₂ media in a 3 wt.% NaCl solution using the AKB-1 organic inhibitor at concentrations of 5–15 ppm. Gravimetric measurements, electrochemical polarization, electrochemical impedance spectroscopy (EIS), and hydrogen permeation techniques were employed to evaluate the protective performance of the inhibitor. The results showed that AKB-1 significantly reduced the corrosion rate of St3 steel in all investigated media, and its protective efficiency increased with inhibitor concentration. The highest inhibition efficiency reached 98.0% in H2S medium, 94.8% in CO2 medium, and 96.8% in mixed H₂S/CO₂ medium at an inhibitor concentration of 15 ppm. Hydrogen permeation studies demonstrated that AKB-1 effectively retarded hydrogen transport through the steel membrane, with the hydrogen diffusion retardation coefficient reaching γH=15.4 in H₂S medium. Electrochemical results indicated that the inhibitor predominantly suppressed the anodic dissolution process and increased charge transfer resistance. Adsorption analysis showed that surface coverage exceeded θ=0.9 at 15 ppm and followed the Frumkin adsorption isotherm. The calculated adsorption free energy (ΔG_ads=−21 to −24 kJ/mol) suggests that the inhibitor acts mainly through physical adsorption mechanisms. The obtained results demonstrate that AKB-1 is an effective corrosion inhibitor for steel operating in H₂S/CO₂–containing environments.

Keywords: St3 steel, AKB-1 organic inhibitor, H2S/CO2 corrosion, hydrogen diffusion, electrochemical impedance spectroscopy (EIS), adsorption isotherm, corrosion protection, hydrogen embrittlement

Int. J. Corros. Scale Inhib., 2026, 15, no. 3, 431-453
doi: 10.17675/2305-6894-2026-3-19

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