Corrosion and Erosion | What is meant by Corrosion and Erosion?
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Corrosion and Erosion
Corrosion in boilers can almost always be traced to one or both of two problems. The most common cause is dissolved oxygen entering the system via the feed-water. The oxygen causes very localized corrosion to occur in the form of pitting. The pits are small but deep pinpoint holes which eventually can penetrate tube walls and cause their failure. Another common cause of corrosion in boiler systems is low pH within the boiler. This reduced pH may result from carbon dioxide infiltration or form contamination by other chemicals. Oxygen corrosion is normally controlled by driving the oxygen from the feed-water in a deaerating heater or by chemically removing it with an oxygen scavenger such as sodium sulfite.
Erosion is a term used when metal is attacked by the abrasive action of liquid, vapour or gas. Solid particles in flue gas which erode the boiler tubes is a well known factor. Tube surface deterioration by soot blowing action is also a common case of erosion. Tubes are externally eroded by soot blowing action when some gritty substance impinges on tube surface.