Corrosion Engineering MCQs on “Eight Forms – Cavitation and Fretting Corrosion”.
1. Which of the following type of corrosion is caused by the formation and collapse of vapor bubbles in a liquid near the metal surface?
a) Filiform corrosion
b) Fretting corrosion
c) Cavitation damage
d) Crevice corrosion
Answer: c
Clarification: Cavitation damage is the special form of erosion-corrosion that occurs by the formation and collapse of vapor bubbles in a liquid near a metal surface.
2. Which of the following equipment encounters cavitation damage in the service?
a) Hydraulic turbines
b) Ship propellers
c) Pump impellers
d) Hydraulic turbines, ship propellers, and pump impellers
Answer: d
Clarification: Cavitation damage occurs in hydraulic turbines, ship propellers, pump impellers, and other surfaces where high-velocity liquid flow and pressure changes are encountered.
3. Which of the following condition is/are correct regarding the boiling point of a liquid with an increase in pressure?
a) Decreases up to triple point
b) Increases up to triple point
c) Increases up to the critical point
d) Decreases up to the critical point
Answer: a
Clarification: As the pressure of a liquid decreases, its boiling point decreases up to its triple point. As the pressure increases its increases up to a critical point.
Example: At higher altitudes boiling point of liquids reaches low as atmospheric pressure decreased.
4. Which of the following will result due to cavitation damage of a metal?
a) Mechanical action
b) Chemical dissolution
c) Both mechanical action and chemical dissolution
d) Neither mechanical action nor chemical dissolution
Answer: c
Clarification: Cavitation damage is the special form of erosion-corrosion that occurs by the formation and collapse of vapor bubbles in a liquid near a metal surface. It results in the mechanical and chemical dissolution of metal.
5. Cavitation damaged can be reduced by changing the design to minimize hydrodynamic pressure differences in process streamflow.
a) False
b) True
Answer: b
Clarification: Cavitation damaged can indeed be reduced by changing the design to minimize hydrodynamic pressure differences in process streamflow. It reduces the impingement area and force of the stream.
6. Which of the following type of corrosion is depicted in the given figure?
a) Fretting corrosion
b) Crevice corrosion
c) Cavitation damage
d) Pitting corrosion
Answer: c
Clarification: Cavitation damage is depicted in the given figure. It occurs by the formation and collapse of vapor bubbles in a liquid near a metal surface. And it results in mechanical action and chemical dissolution of metal.
7. Which of the following type of corrosion that occurs at contact areas between materials under load subjected to vibration or relative motion?
a) Fretting corrosion
b) Crevice corrosion
c) Cavitation damage
d) Pitting corrosion
Answer: a
Clarification: Fretting corrosion is the special type of erosion-corrosion that occurs at the contact areas between materials under load subjected to vibration or relative motion.
8. Which of the following is/are the other names of fretting corrosion?
a) Friction oxidation
b) Wear oxidation
c) False brinelling
d) Friction oxidation, wear oxidation and false brinelling