Question

Write short notes on Caustic Embrittlement.

Answer 1

Caustic embrittlement is the phenomenon in which the material of a boiler becomes brittledue to the accumulation of caustic substances.

A tube damaged by caustic embrittlement. White caustic deposits can be seen inside.

As water evaporates in the boiler, the concentration of sodium carbonate increases in the boiler. Sodium carbonate is used in softening of water by lime soda process, due to this some sodium carbonate maybe left behind in the water. As the concentration of sodium carbonate increases, it undergoes hydrolysis to form sodium hydroxide.

Na2CO3 + H2O → 2NaOH + CO2

Answer 2

Answer:

The phenomenon known as caustic embrittlement occurs when a boiler's material becomes brittle as a result of the buildup of caustic chemicals.

Explanation:

• The amount of sodium carbonate in the boiler rises as the water in the boiler evaporates.
• Because sodium carbonate is used in high pressure boilers to soften water via the lime soda process, some sodium carbonate may end up in the water.
• Sodium carbonate undergoes hydrolysis as its concentration rises, resulting in sodium hydroxide.
• The water becomes alkaline when sodium hydroxide is present.
• By means of capillary action, this alkaline water seeps into tiny fissures found in the boiler's inner walls.
• As the water inside the gaps evaporates, the hydroxide concentration keeps continuously rising.
• The cathode is the diluted area, while the anode is the concentrated area under high stress.
• At the anode, sodium hydroxide assaults the surrounding material before dissolving the boiler's iron and creating rust with sodium ferrate.

As a result, stressed boiler components like rivets, bends, and joints become brittle.

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