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Caustic embrittlement is the cracking of boiler metal caused by

  • A.concentrated sodium hydroxide at stressed points
  • B.dissolved oxygen attacking the metal surface
  • C.an excess of calcium sulphate in the water
  • D.carbon dioxide dissolved in the condensate

Answer: A

Free caustic concentrates in the crevices at riveted or stressed joints and attacks the iron along its grain boundaries, giving intercrystalline cracks with no loss of thickness. Adding tannin, lignin or phosphate prevents it.

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