The corrosion resistance of boiler steels in simulated combustion atmospheres with various CO2 content

In the present study the common ferritic and austenitic steels (2.25Cr1Mo, X10, X20, TP347H, AC66, Sanicro28, Esshete 1250) usually used in biomass and waste combustion processes were investigated. The multi-sample exposure tests were carried out at isothermal temperature of 535 C in various simulated combustion atmospheres (22%H2O+ 5%O2 +xCO2 + N2) with different CO2 content varying from 0 to 25 vol-% for the samples without deposit and with filter/cyclone ash deposition. Post experimental analyses have been made using SEM/EDS and XRD techniques. The presence of the deposit increases the corrosion rate of all studied materials, especially for the ferritic steels. The corrosion rate increases with increasing CO2 content in the atmosphere. That behaviour was observed on no-deposited and deposited samples. The obtained result shows that for the ferritic steel the corrosion resistance increases with increasing Cr content in steel but only for non-deposited samples. The ferritic steels with deposits behave different. There is only a small difference on the corrosion rate of X10 (8.5 m-% Cr) and X20 (12.7 m-% Cr), even in some cases X10 exhibits better corrosion resistance. This effect could be especially observed in the atmospheres with high CO2 content.