Corrosion Behavior of High-Cr–Ni Materials in Biomass Incineration Atmospheres

In this paper, the corrosion test of high-Cr-Ni tubes was carried out in a biomass incinerator by replacing the original heated surface tube with a test tube. The investigated materials are high-Cr-Ni stainless steels (TP347H, SP2215, and Sanicro25) and alloy (HT700T). Long-term services (>4000 h) to investigate the corrosion rates and corrosion characteristics of the materials have been carried out. The appearance, element content, and composition of corrosion products after corrosion of the specimens were analyzed. Analysis indicates that the deposits are mainly composed of alkali metal salts, iron oxides, iron sulfates, and complex salts. Moreover, the corrosion morphology of the materials with different Cr-Ni contents varies greatly. TP347H has a high corrosion rate (0.11 mm/1000 h) with intergranular corrosion cracks and pitting on the windward side. However, the corrosion pattern of HT700T is comprehensive corrosion and the corrosion rate is low (0.015 mm/1000 h). Using corrosion rate as a criterion for corrosion resistance, HT700T has the highest corrosion resistance, while TP347H has the lowest. The corrosion behavior is also related to the corrosion resistance index (CI) value based on the content of critical elements. The order of material corrosion resistance predicted by the CI value is the same as reflected by the corrosion rate.