Severe corrosion in heating systems is caused by \"underscale corrosion\"

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The last edit to this post was made by Wang Wei2 on 2024-1-29 at 10:04. Severe corrosion in heating systems is always caused by \"under-scale corrosion\". Example: A cement pole factory built three new steam curing kilns; within less than half a year, the steam supply systems suffered severe corrosion and damage, resulting in their need to be scrapped. Analysis: The problem lies in the water; the boiler feed water is from deep wells, and a compound silicate treatment agent at a concentration of 1/1000 by weight is added. The solid solutes, total hardness, chloride ions, and suspended solids in the water do not meet the standards for boiler feedwater. During operation, foaming often occurs inside the furnace, with a large number of liquid droplets being carried out of the boiler, which deteriorates the quality of the steam. After the steam is ejected from the return pipes in the economizer, its volume expands sharply and its temperature drops significantly; when it comes into contact with the surface of the heating system, which is at a higher temperature, the water vapor evaporates and salts deposit on that surface. It causes \"underscale corrosion\" on the system’s surface in a humid and hot environment. The so-called \"underscale corrosion\" generally refers to the formation of a layer of solid deposits and corrosion products on the metal surface, creating a locally intensified corrosion environment. The “scale” here forms on the outer surface of the metal, and the reason for this is naturally due to the special working conditions in this area. The high solid content in the steam leads to scaling on the external surfaces of the system, thereby exacerbating corrosion. This is likely just one of the consequences of poor quality boiler feed water; as for its impact on the boiler itself, it is probably also negative.