Due to the potential difference between the metal surface and the iron scale, local corrosion of the metal is caused, and this corrosion is generally pit corrosion, which mainly occurs below the water wall tube with deposits and where the heat load is high. For example, near the burner, on the fire side of the furnace tube, etc., it is very easy to cause metal perforation or over-temperature explosion. Although the high oxides of copper and iron can corrode steel, the corrosion effect is limited, but when oxygen is supplemented, the corrosion will continue and aggravate.
The hazard is very large. On the one hand, it will cause a large area of corrosion on the metal surface of the deactivated equipment in a short period of time. On the other hand, the iron content of the feed water increases when the unit starts and runs due to the formation of deposits on the metal surface and the rough state of the metal surface due to the deactivation of corrosion. It not only aggravates the formation of iron scale in the furnace tube, but also aggravates the corrosion of thermal equipment during operation.
