Corrosion Engineering Multiple Choice Questions on “Environments – Alkalies”.
1. What is meant by caustic embrittlement?
a) Decrease in compressive strength due to caustic accumulation
b) The phenomenon of metal to become brittle due to caustic accumulation at the rivets
c) Entrapment of caustic content between atoms to cause brittleness
d) The phenomenon of metal to become more tensile due to caustic accumulation
Answer: b
Clarification: Caustic embrittlement is the phenomenon of metal to become brittle due to caustic accumulation at the rivets. The cold working of rivets is the main reason for caustic embrittlement.
2. Which of the following statements is/are correct regarding caustic embrittlement?
a) Mild carbon steels are susceptible to caustic embrittlement
b) It occurs in concentrated hydroxide environment
c) It occurs around the rivets
d) Mild carbon steels are susceptible to caustic embrittlement in concentrated hydroxide environment around the rivets
Answer: d
Clarification:
i. Mild carbon steels are susceptible to caustic embrittlement
ii. It occurs in concentrated hydroxide environment
iii. It occurs around the rivets due to cold working.
3. Which of the following is/are the preventions of caustic embrittlement?
a) Optimize stress concentration
b) Avoid caustic environment
c) Use of nickel-based alloys, avoid caustic environment and optimize stress concentration
d) Use mild carbon steels
Answer: c
Clarification: Preventions of caustic embrittlement are:
i. Optimize stress concentration
ii. Avoid caustic environment
iii. Use of nickel-based alloys.
4. Which of the following common alkalies that results in stress-corrosion cracking of steel?
a) Caustic soda
b) Caustic soda and caustic potash
c) Caustic potash
d) Sodium carbonate
Answer: b
Clarification: Caustic soda and caustic potash are the common alkalies that result in stress-corrosion cracking of steel. It usually occurs in high concentrations only.
5. Which of the following metal is suitable under all conditions of concentration and temperature in caustic soda?
a) Nickel
b) Aluminum
c) Titanium
d) Carbon steel
Answer: a
Clarification: Nickel is suitable under all conditions of concentrations and temperatures in the caustic environment. The corrosion resistance of material directly proportional to the nickel content of an alloy.
6. Aluminum is a very poor resistant material for handling caustic environments and rapidly attacked even by dilute solutions.
a) False
b) True
Answer: b
Clarification: Aluminum is a very poor resistant material for handling caustic environments and rapidly attacked even by dilute solutions. But it is adopted in an ammoniacal environment such as refrigeration systems and storage tanks.
7. Which of the following metal results in stress corrosion cracking in an ammoniacal solution?
a) Aluminum and its alloys
b) Nickel and its alloys
c) Copper and its alloys
d) Stainless steels
Answer: c
Clarification: Copper and its alloys result in stress corrosion cracking in ammoniacal solutions. The decomposition of organic materials containing nitrogen has caused stress corrosion cracking.
8. Oxygen is the primary cause of cracking in ammoniacal solution rather than nitrogen.
a) True
b) False
Answer: a
Clarification: Oxygen is the primary cause of cracking, with as little as 0.01 ppm required in the ammoniacal solution. A slip step or film rupture is a mechanical method of this cracking.
9. Which of the following can be used to inhibit stress corrosion cracking in ammoniacal solutions?
a) Addition of 0.2% water
b) Addition of 0.025% hydrazine in refrigeration
c) Addition of oxidizing agents
d) Either addition of 0.2% water or addition of 0.025% hydrazine in refrigeration
Answer: d
Clarification: Oxygen and oxidizing agents are the primary cause of stress corrosion cracking in ammoniacal solutions. It can be inhibited by the addition of 0.25% of water or the addition of 0.025% hydrazine in refrigeration.
10. Which of the following is/are used for ammoniacal solution applications?
a) Cast iron and steel
b) 430 and 304 type stainless steels
c) Cast iron, steel, 430 and 304 type stainless steels
d) Copper and cast irons
Answer: c
Clarification: Ammonia and ammoniacal solutions generally do not present a difficult corrosion problem. We usually use cast iron, steel, and 430, 304 type stainless steels for low and high temperatures respectively.