A no-ionic gemini surfactant, namely bis(2-((2-palmitoamidoetil) amino) etil) 1H-imidazol-4,5dicarboxilate, was synthesized from the fatty acids contained in the palm oil and evaluated as corrosion inhibitor for UNS S41425 type supermartensitic stainless steel in presence of H 2 S. Used techniques involved potentiodynamic polarization curves, linear polarization resistance and electrochemical impedance measurements. Additionally, the obtained inhibitor was characterized by Infrared and 1H, 13C RMN spectroscopy. Results have shown that the corrosion rate of the steel was markedly decreased by the addition of the imidazole-type of inhibitor, reaching its maximum efficiency at certain inhibitor concentration, decreasing with a further increase in its concentration. This decrease in the corrosion rate was due to the physical adsorption of the inhibitor on to the steel surface following a Langmuir type of adsorption isotherm, affecting both anodic and cathodic reactions.

The effect of concentration of an organic imidazoline as inhibitor on internal stress corrosion cracking (SCC) behavior of an API X70 pipeline steel exposed to a brine solution was studied. The SCC process using simultaneously the slow strain rate stress test (SSRT) and electrochemical measurements was performed. Fracture surface analysis and secondary cracking were observed through a scanning electron microscopy (SEM). According to SEM fractography and SSRT results, the steel showed high SCC susceptibility with a brittle fracture and several secondary cracks without addition of inhibitor, whereas the addition of inhibitor to brine solution was effective to increase the SCC resistance of steel at concentrations of inhibitor of 50 and 100 ppm. A further addition of concentration of inhibitor had a negative effect on the mechanical properties of the steel. Electrochemical measurements results are in accordance with the SCC susceptibility, indicating that corrosion inhibitor film suppressed the anodic and cathodic reactions increasing the resistance to SCC until concentration of 100 ppm. Further addition of inhibitor aggravated the localized corrosion due to local desorption of inhibitor molecules. The Hilbert–Huang transform (HHT) analysis revealed the contribution of different corrosion process contained in the electrochemical current noise (ECN) signals at several inhibitor concentrations.

In the present investigation a novel non-ionic gemini surfactant, namely bis(2-((2-palmitoamidoetil) amino) etil) 1H-imidazol-4,5-dicarboxilate, was synthesized from the fatty acids contained in the palm oil and evaluated as corrosion inhibitor for UNS S41425 type supermartensitic stainless steel in a sour solution. The obtained results from electrochemical techniques showed that, the inhibition efficiency increased with increase of the inhibitor concentration. The maximum inhibition efficiency was reached 99% at 100 ppm. The potentiodynamic polarization measurements indicated that the gemini surfactant acts as anodic type inhibitor. The adsorption of the inhibitor on the UNS S41425 surface in the sour solution was found to obey Langmuir’s adsorption isotherm.

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Purpose This paper aims to use an imidazole-based n-ionic Gemini surfactant derived from palm oil to inhibit the sulfide stress corrosion cracking of a supermartensitic stainless steel. Design/methodology/approach The slow strain rate testing technique, hydrogen permeation tests and potentiodynamic polarization curves have been used. Findings Addition of the inhibitor below the critical micelle concentration (CMC) decreased the corrosion current density (icorr), but not enough to avoid embrittlement due to the entry of hydrogen into the steel. Instead, the addition of the inhibitor close to the CMC decreased the icorr, suppressed the entry of hydrogen and inhibited the sulfide stress cracking of steel. Finally, the addition of inhibitor above the CMC led to a slight increase of icorr and promoted localized corrosion, however, the sulfide stress cracking of steel was inhibited. Originality/value A green sulfide stress corrosion cracking inhibitor of a supermartensitic stainless steel has been obtained.