What is the caustic embrittlement ? How to prevent it ?

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What is caustic embrittlement? How to prevent it ?

 It is inter crystalline fracture. It is cause by high concentration of caustic soda and the material under stress. The stress corrosion cracks follow the grain or crystal boundaries of the material and failure.
 Sodium sulphate or sodium nitrate is used for the prevention of caustic embrittlement.
 It can be found in highly stress area in boiler. Such as tube and tube plate connection, riveted head, seam and boiler mountings.