Corrosion Behavior of Candidate Materials Used for Critical Parts of Urea Hydrolysis Equipment in Gas Denitrification

Corrosion behavior of candidate alloys such as 316L stainless steel, 316Lmod stainless steel, HR3C stainless steel, Inconel718 alloy and TC4 alloy used for critical parts of urea hydrolysis equipment in gas denitrification was studied in simulated urea hydrolysis environment. The results show that different degree of dissolve corrosion was happened for 316L and 316Lmod stainless steel at the initial stage. In the following corrosion stage, corrosion product deposition increased and a large surface of corrosion products exfoliation were observed on 316L stainless steel which was mainly pitting corrosion, while uniform corrosion and deposition of corrosion products dominated the corrosion process for 316Lmod stainless steel. TC4 alloy, Inconel718 alloy and HR3C stainless steel showed a better corrosion resistance compared with 316L and 316Lmod stainless steel. There was a dense titanium oxide layer with 3 μm in thickness formed on surface of TC4 alloy and mixed oxides consisting of Cr₂O₃ and Fe₂O₃ formed by hydrothermal synthesis reaction were the main corrosion products. A small amount of dissolve corrosion was observed on Inconel718 alloy at the initial stage and in later stage deposition of corrosion products dominated the corrosion process. Intergranular corrosion was clearly observed in HR3C stainless steel at the initial stage and deposition of corrosion products dominated the following corrosion process of HR3C stainless steel.