Low-Temperature Nitrocarburizing of Austenitic Stainless Steel for Combat Corrosion in H2S Environments

The time-dependent experiment was performed to investigate the corrosion behavior of low-temperature liquid nitrocarburized (LNC) 304 austenitic stainless steel in wet H 2 S environments. Characteristics of H 2 S corrosion products, as well as localized corrosion behavior, were investigated using X-ray diffraction (XRD), scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), and optical profilometry. The results revealed that the untreated steels, of which the H 2 S corrosion product layer on the untreated surface thickened but displayed a layered defect structure as the corrosion proceeded, had a higher weight loss than the LNC. Energy-dispersive spectroscopy (EDS) served to reveal the relationship between corrosion behavior and the content of sulfur, chromium, and other elements, and the valences of these elements were illustrated by XPS. The surface morphology after removing corrosion products showed that the presence of nitrocarburized S phase could prevent general corrosion and inhibit pit propagation.