Corrosion of 12Cr1MoV Super-heater in a Biomass Fired Boiler

The 12Cr1MoV secondary super-heater of a biomass vibration grate boiler suffered serious surface corrosion after service for only 200 h. Tubes were analyzed by optical microscopy, EDX and XRD. Grain boundary attack was found, and Cl- was rich at reaction front. The corrosion was ascribed mainly to Cl- in the biomass. The existence of alkali metal may promote the corrosion process because it tends to form low melting point salts. Some measures were proposed to reduce the corrosion rate.