There are several types of corrosion on the flue gas side of the heated surfaces

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People usually clean the dust from the boilers after shutting them down, and it’s common to find severe dust accumulation on the tube walls. After cleaning, corrosion of those tube walls becomes quite severe. So, what are the common types of corrosion caused by flue gas? 1. Sulfur corrosion of water wall tubes. If slag formation occurs on the water wall, under a reducing atmosphere and at certain temperatures, severe corrosion of the outer surface of the water wall tubes can occur. The areas most affected by this corrosion are those with high heat loads and high tube wall temperatures, such as near the burners and in the furnace of liquid slag discharge systems. There are two types of corrosion caused by slag formation on the water wall of coal-fired boilers: sulfate corrosion and sulfide corrosion. These two types of corrosion often occur simultaneously, with sulfate corrosion being the more common one. This issue deserves even more attention in boilers that burn high-sulfur coal. 2. High-temperature sulfur corrosion of superheater tubes. High-temperature sulfur corrosion in superheaters is caused by liquid high-temperature viscous ash, primarily resulting from the accumulation of complex sulfates on the tube walls. The liquid complex sulfates formed at high temperatures (550–710°C) are corrosive to the metal of the tube walls, with the corrosion being particularly severe at 650–700°C. 3. Low-temperature sulfur corrosion of air preheaters. The main causes of low-temperature sulfur corrosion in air preheaters are the same as those of low-temperature ash adhesion; ash accumulation leads to both ash blockage and corrosion problems, which should be addressed through unified measures.