This set of Engineering Chemistry Assessment Questions and Answers focuses on “Protective Measures Against Corrosion”.
1. Which of the following method is adopted for preventing corrosion by acids?
a) Deaeration
b) Removal by using ion-exchange resin
c) Neutralisation with lime
d) Dehumidification
View Answer
Explanation: Neutralisation with lime is done for preventing corrosion by acids. Lime is a calcium-containing inorganic material in which carbonates, oxides and hydroxides predominate.
2. Which of the following method is adopted for preventing corrosion by salts?
a) Deaeration
b) Removal by using ion-exchange resin
c) Neutralisation with lime
d) Dehumidification
View Answer
Explanation: To prevent corrosion by salts, they are removed by using ion-exchange resins. Through this Na+ and Cl– gets separated.
3. Which of the following method is adopted for preventing corrosion by moisture?
a) Deaeration
b) Removal by using ion-exchange resin
c) Neutralisation with lime
d) Dehumidification
View Answer
Explanation: To prevent corrosion by moisture, moisture from the air is removed by dehumidification using silica gel.
4. The organic or inorganic substances which when added to the environment are able to reduce the rate of corrosion are called ___________
a) Inhibitors
b) Stimulants
c) Insulators
d) Stipulator
View Answer
Explanation: The organic or inorganic substances which when added to the environment are able to reduce the rate of corrosion are called inhibitors. They are also called corrosion inhibitors. A substance that prevents or decreases the rate of a chemical reaction is called a reaction inhibitor.
5. Which of the following readily sublime and form a protective layer on the metal surface?
a) Anodic inhibitor
b) Cathodic inhibitor
c) Volatile inhibitors
d) Non-volatile inhibitors
View Answer
Explanation: Volatile or vapour-phase inhibitors readily sublime and form a protective layer on the metal surface.
6. Which of the following is not an anodic inhibitor?
a) Alkalis
b) Molybdates
c) Phosphates
d) Dicyclohexyl ammonium nitrile
View Answer
Explanation: Alkalis, molybdates, phosphates and chromates are examples of anodic inhibitors.
7. The process by which Ta, Nb and Ti combine with carbon to form respective carbides and prevent corrosion is known as ___________
a) Passivation
b) Neutralisation
c) Inhibition
d) Stimulation
View Answer
Explanation: The process by which Ta, Nb and Ti combine with carbon to form respective carbides and prevent corrosion is known as neutralisation. The pH of the neutralized solution depends on the acid strength of the reactants.
8. The process which lowers the content of sulphur and phosphorus in steels is known as ___________
a) Refining
b) Passivation
c) Inhibition
d) Stimulation
View Answer
Explanation: The process which lowers the content of sulphur and phosphorus in steels is known as refining. It removes the impurities or unwanted elements from the steels.
9. Annealing is a heat treatment given to metals to ___________
a) Prevent dezincification
b) Remove the residual stresses
c) Lower the sulphur content
d) Form a protective layer
View Answer
Explanation: Annealing is a heat treatment given to metals to remove the residual stresses. It involves heating a material to above its re-crystallization temperature, maintaining a suitable temperature, and then cooling.
10. Anodised oxide coatings are used for the protection of Al, Zn, Mg and their alloys from corrosion.
a) True
b) False
View Answer
Explanation: Anodised oxide coatings are used for the protection of Al, Zn, Mg and their alloys from corrosion. They help in preventing corrosion by eliminating contact from the environment and air.
11. Which of the following statement is incorrect about the anodic coating?
a) Protects the metal from corrosion sacrificially
b) Base metal is not corroded
c) Example- coating of tin on iron
d) No negative consequence
View Answer
Explanation: Example- coating of zinc on iron. All the other options are correct.
12. Organic coating is inert organic barrier whose protective value depends upon its impermeability to gases, salts and water.
a) True
b) False
View Answer
Explanation: Organic coating is inert organic barrier whose protective value depends upon its impermeability to gases, salts and water. If the gases or salts are permeable to the organic coating, it will be useless. So the organic coating should be selected accordingly.
13. Electrochemical protection is ___________
a) Anodic protection
b) Sacrificial Anodic protection
c) Impressed current cathodic protection
d) Cathodic protection
View Answer
Explanation: Electrochemical protection is cathodic protection(CP). It is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell.
14. Magnesium is used in high resistivity electrolytes due to its ___________
a) Neutral potential
b) Most positive potential
c) Most negative potential
d) Zero potential
View Answer
Explanation: Magnesium is used in high resistivity electrolytes due to its most negative potential. Magnesium has the highest negative potential according to the electrochemical series.
15. Which of the following metal is not used as a sacrificial anode?
a) Zinc
b) Copper
c) Magnesium
d) Aluminium
View Answer
Explanation: Zinc, aluminium, magnesium are used as a sacrificial anode. Copper is not used as a sacrificial anode.
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