Increasing acid dew point corrosion resistance by thin coating layer on steel

摘要

Acid dew point corrosion is a common phenomenon for industrial equipments such as duct, stack, gas gas heater (GGH) in plants using fossil fuels. During the burning process, sulfur in fossil fuel is oxidized to produce sulfuric dioxide (SO_2) and further oxidized to sulfuric trioxide (SO_3). Under the dew point temperature, water drops form on the surface of equipments along with sulfuric trioxide to develop sulfuric acid (H_2O+SO_3aH_2SO_4). Special steel products that are strong against acid dew point corrosion are on the market as cold rolled (CR) or hot rolled (HR) steel. Although these products have stronger corrosion resistance than normal steel, life span is still short and further increase of corrosion resistance is required. In this research, we applied thin coating layer to steel and studied how corrosion resistance is changed. Different types of coating were applied and tested. Localized corrosion that could occur by surface coating was monitored and possible solution was proposed. Coating layer was observed by various analytical tools including FT-IR SEM, EPMA, GDS etc.