What is caustic embrittlement explain?

Caustic embrittlement is a phenomenon that occurs in boilers where caustic substances accumulate in boiler materials. It also can be described as the cracking of riveted mild steel boiler plates. Caustic embrittlement is also known as stress corrosion cracking.

What is caustic embrittlement and what is the major source of this type of damage in boiler generating tubes?

Caustic embrittlement, a specific form of stress corrosion, results in the intercrystalline cracking of steel. Intercrystalline cracking results only when all of the following are present: specific conditions of stress, a mechanism for concentration such as leakage, and free NaOH in the boiler water.

What is caustic cracking?

Caustic cracking is a form of stress corrosion cracking most frequently encountered in carbon steels or iron-chromium-nickel alloys that are exposed to concentrated hydroxide solutions at temperatures of 482°F (250°C). Caustic cracking is also known as caustic embrittlement.

Is Hard Water responsible for caustic embrittlement?

NaOH is sodium hydroxide, which is also commonly known as caustic soda, soda lime or lye. So, by using hard water, the Caustic embrittlement in boilers take place mainly due to the formation of NaOH.

What are the contributing factor for caustic embrittlement?

Causes of Caustic Embrittlement (1) a susceptible material (carbon steel) (2) a specific chemical species (concentrated hydroxide) and. (3) tensile stress (around the riveted holes)

What is scale and sludge?

If the precipitation takes place in the form of loose and slimy precipitate, it is called sludge. On the other hand, if the precipitated matter forms a hard, adhering crust/coating on the inner walls of the boiler, it is called scale.

What causes caustic embrittlement in boiler?

The presence of sodium hydroxide makes the water alkaline. At anode , sodium hydroxide attacks the surrounding material and then dissolves the iron of the boiler as sodium ferrate forming rust. This causes embrittlement of boiler parts like rivets, bends and joints, which are under stress.

How do you prevent caustic embrittlement in a boiler?

Caustic embrittlement can be prevented through:

1. Control of stress level (residual or load) and hardness.
2. Avoid alkalis.
3. Use of materials known not to crack in the specified environment.
4. Control temperature and or potential.

How can caustic embrittlement be prevented?

Answer: Caustic embrittlement can be avoided : by using sodium phosphate as softening agent, instead of sodium carbonate ; by adding tannin or lignin to boiler water, since these blocks the hair-cracks, thereby preventing infiltration of caustic soda solution in these; by adding sodium sulphate to boiler water.

How can caustic embrittlement be avoided?

Which substance can cause caustic embrittlement?

Caustic Embrittlement is a form of corrosion caused by a high concentration of sodium hydroxide (Na(OH)). It is characterized by the formation of irregular intergranular cracks on the metal. particularly at places of high local bends such as bends and joints causes caustic embrittlement.

What causes hydrogen embrittlement?

Hydrogen Embrittlement occurs when metals become brittle as a result of the introduction and diffusion of hydrogen into the material. The degree of embrittlement is influenced both by the amount of hydrogen absorbed and the microstructure of the material.

What are caustic properties?

Chemical Properties. Sodium hydroxide, NaOH,also referred to as caustic soda or sodium hydrate (and formerly known as lye), is a white,massive, deliquescent crystalline solid that is soluble in water,alcohol, and glycerol . It melts at 318°C (606 OF) and is the most widely used and available alkaline chemical.

Is caustic corrosive?

corrosive | caustic |. is that corrosive is eating away; having the power of gradually wearing, hanging, or destroying the texture or substance of a body; as the corrosive action of an acid while caustic is capable of burning, corroding or destroying organic tissue.

What is caustic service?

Caustic Service is most often used to describe something that is suitable for service with Caustic Soda, Sodium Hydroxide, NaOH, Lye. This is caustic, as in very basic with plenty of -OH’s and has a pH of 12-14 for a very concentrated solution. Carbon steel or certain plastics are most often used.