Initiation and developmental stages of steel corrosion in wet H2S environments

• The initiation and development stages of steel corrosion in wet H2S environment were investigated.
• Preferential dissolution at the grain boundaries of steel allowed corrosion products to form and accumulate.
• The shapes and crystal types of corrosion products at various steel layers differed.
• With increasing duration time, the S2− peak with a binding energy of 161.2 eV gradually decreased.
• A model of the formation process of corrosion product films was proposed.

The initiation and various developmental stages of steel corrosion in H2S environments were investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Results revealed that grain boundaries corrode at the initiation stage and that corrosion products initially form on both sides of the grain boundary and then accumulate. Corrosion products grew at the interface between the steel and corrosion product layer at the developmental stage. XPS analyses showed the composition and valence states of the corrosion products, and a model of the formation process of corrosion product films was proposed.