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Corrosion tests reveal H2S partial pressure increases corrosion rates in nickel-based alloy 718, suggesting critical implications for oilfield applications.
Purpose This study aims to investigate the corrosion behavior of oil-grade nickel-based alloy 718 in H2S/CO2 environments under high-temperature (150 °C) and high-pressure conditions. It focuses on the influences of H2S partial pressure on corrosion rates, product characteristics and passive film stability to guide its application in high-sulfur oilfields. Design/methodology/approach Corrosion immersion tests (720 h, 3 M NaCl, 150 °C) and electrochemical measurements were conducted at varying H2S partial pressures (0–3 MPa). The surface morphology, corrosion products and elemental composition were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS) and confocal microscopy to elucidate the corrosion mechanisms. Findings Increasing H2S partial pressure was found to accelerate both uniform and pitting corrosion rates, thicken corrosion product layers (rich in FeS/NiS) and reduce corrosion resistance. XPS analysis revealed an elevated Fe/S content and reduced Ni/Cr ratio in the products, indicating H2S-induced sulfide formation, which compromises the alloy’s passivation capabilities. Originality/value This study provides critical insights into the corrosion mechanism of alloy 718 in high-temperature and high-pressure environments over prolonged periods, aiding material selection in high-sulfur oilfield environments.
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Chen et al. (2025) studied this question.
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