Abstract
Two novel aryloxy alcohol derivatives, one containing a terminal C≡C bond (RH-1) and an allyl ether containing a C=C bond (RH-2), were synthesized and evaluated as corrosion inhibitors for St-3 carbon steel in a hydrogen sulphide (H₂S)-containing medium. Their molecular structures were characterized by Fourier-transform infrared (FTIR) spectroscopy and nuclear magnetic resonance - ¹H NMR and ¹³C NMR. Corrosion inhibition performance was investigated using gravimetric measurements, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, surface characterization and density functional theory (DFT) calculations. Gravimetric experiments were conducted over the temperature range of 25 to 50 °C using inhibitor concentrations of 10 to 30 ppm. Both compounds effectively reduced the corrosion rate, with inhibition efficiency increasing with inhibitor concentration. At 25 °C and 30 ppm, EIS showed maximum inhibition efficiencies of 97.0 % for RH-1 and 94.0 % for RH-2. EIS measurements showed a substantial increase in charge-transfer resistance and a decrease in double-layer capacitance, consistent with progressive inhibitor adsorption and formation of a protective interfacial layer. Surface analyses further supported the formation of protective inhibitor-containing films on the steel surface. DFT calculations indicated greater electron-donating ability and a stronger adsorption tendency for RH-1, consistent with its superior experimental inhibition performance. The higher efficiency of RH-1 was associated with its propargyl (C≡C) functionality, which promotes stronger interaction with the steel surface than the allyl (C=C) functionality of RH-2. The combined experimental and theoretical results demonstrate that these aryloxy alcohol derivatives provide effective corrosion inhibition of carbon steel in H₂S-containing environments.