Caustic Embrittlement. - Interview Questions, Tutorials, Certification QuestionsWritten by V RSunday, 09 January 2011 06:19 -

Caustic embrittlement is a type of corrosion produced by the joint action of stess and causticalkalinity.The source of alkalinity in the boiler is due to - Presence of residual Na2CO3 in water.This undergo hydrolysis at high temperature andpressure in boilers to give NaOH. - Presence of NaHCO3 in boiler water. The sodium hydroxide containing water,when passed through small cracks in the stressedareas get concentrated and corrodes the area by forming sodium ferrate and getdisintegrated.Caustic cracking is generally intercrystalline,largely takes place in stressed areasand irregularly formed. The iron in contact with dilute sodium hydroxide near by the pores present in the bends andjoints becomes the anodic part and iron in contact with concentrated sodium hydroxide in thepores become the cathodic part.A number of minute electrochemical cells are formedsurrounding each pores.So intense corrosion takes place.

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