250+ TOP MCQs on Corrosion and its Classification and Answers

Corrosion Engineering Multiple Choice Questions on “Corrosion and its Classification – 1”.

1. What is Corrosion?
a) Destruction or deterioration of a material
b) Conversion of metal atoms to metallic ions
c) Conversion of metal ions to metal atoms
d) Destruction of materials involving in the conversion of metal atoms into metal ions
Answer: d
Clarification: Corrosion is a destructive or deterioration of a material because of reaction with its environment. It occurs due to the higher stability of metal ions than the metal atoms.

2. Corrosion of metals is considered as the reverse of extractive metallurgy.
a) True
b) False
Answer: a
Clarification: Extractive metallurgy is a process of conversion of metal ions from the compounded state to metal atoms in the elemental state, whereas the corrosion occurs by the conversion of metal atoms into metal ions.

3. The chemical formula of rust is ______
a) Fe₁O
b) Fe₂O₃
c) Fe₃O₄
d) Fe(OH)₂
Answer: b
Clarification: Corrosion of Iron is generally known as rusting. The chemical reaction can be represented as 4Fe + 3O₂ ==> 2Fe₂O₃.

4. Which of the following materials will undergo Corrosion?
a) Metals only
b) Metals and Non-metals
c) Metals, Non-metals, Ceramics and Plastics
d) Metals, Non-metals, Ceramics, Plastics and Rubbers
Answer: d
Clarification: Corrosion is defined as the destruction or deterioration of a material because of reaction with its environment. Every material in the universe will undergo corrosion but it varies in time and form. Any Physical, Chemical or Mechanical deviation of the original material is known as Corrosion.

5. Corrosion of material by furnace gases is classified as _____
a) wet corrosion
b) dry corrosion
c) galvanic corrosion
d) crevice corrosion
Answer: b
Clarification: Dry corrosion occurs in the absence of moisture usually by vapors and gases whereas the wet corrosion, galvanic corrosion and crevice corrosion occurs in aqueous state or in the presence of moisture.

6. Which of the following is an example of wet corrosion?
a) Corrosion of metal in the water
b) Corrosion of iron in the presence of anhydrous calcium chloride
c) Corrosion of titanium in dry chlorine
d) Corrosion due to furnace gases
Answer: a
Clarification: Wet corrosion occurs when the liquid is present. This usually involves aqueous solutions or electrolytes as corrosive mediums. Corrosion of iron in the presence anhydrous calcium chloride, by furnace gases and by dry chlorine are classified under dry corrosion.

7. Corrosion maintenance is vital in _____ industries.
a) paper
b) petroleum
c) plastic toy
d) both petroleum and paper
Answer: d
Clarification: The operating conditions in both the petroleum and paper industry are mainly in aqueous state with various chemicals in it. Hence these are likely prone to various electrochemical reactions which causes corrosion. Maintenance works include periodic inspection and replacements of partially corroded parts. It minimizes costly catastrophic failures, unscheduled down time, resulting in increased production and revenue.

8. Which of the following subjects are important in understanding and controlling corrosion?
a) Thermodynamics
b) Electrochemistry
c) Both Thermodynamics and Electrochemistry
d) Material Characterization
Answer: c
Clarification: Thermodynamic studies and calculations indicate the spontaneous direction of the reaction. The thermodynamic stability of corrosion product is relatively higher than reactant. Whereas the electrochemistry deals with electrode kinetics of the reaction.

9. Deterioration of paint and rubber by sunlight or chemicals is not a corrosion.
a) True
b) False
Answer: b
Clarification: Any deviation in the physical, chemical and mechanical properties of a material is considered as corrosion. Here we can notice physical change so it is a corrosion.

10. Which of the following is an incorrect statement?
a) Corrosion is an irreversible process
b) Corrosion is a non-spontaneous process
c) Corrosion is a degradation process
d) Corrosion is a spontaneous process
Answer: b
Clarification: Corrosion is a spontaneous process which results in degradation of materials and it is irreversible in nature. Spontaneous reaction is a reaction which results in the formation of stable products from unstable without need of any external energy.

11. Which of the following is considered as high corrosive resistant material?
a) Mild steel
b) Cast iron
c) Zinc
d) Stainless steel
Answer: d
Clarification: Corrosion resistant material is the material which has less corrosion rate in a particular atmosphere without much degradation. Stainless steel (an alloy of iron, chromium, nickel) is considered as corrosion resistant material. This is because it forms chromic oxide layer over its surface to avoid physical contact with the outside environment.

12. Corrosion involves _______ reactions.
a) oxidation
b) reduction
c) displacement
d) both oxidation and reduction
Answer: d
Clarification: Corrosion is an electrochemical reaction. It occurs by therelease and gain of electrons from various species which are termed as oxidation and reduction respectively. It can be observed with change in the oxidation state of the species.

13. Which of the following are necessary in the process of corrosion?
a) Anode
b) Cathode
c) Electrolyte
d) Anode, Cathode and Electrolyte
Answer: d
Clarification: Corrosion occurs by the creation of electrochemical cell which includes a cathode, an anode and an electrolyte. A high reduction potential will act as cathode and other will acts as anode preferentially and electrolyte is needed to transfer ions between these two electrodes.

14. What is the reason for corrosion?
a) Stability of a metal ion
b) Stability of a metal atom
c) Passivation
d) Use of coatings
Answer: a
Clarification: Negative or less Gibbs free energy of the metal ions is the reason for corrosion whereas passivation and use of coatings decreases the extent of corrosion.

15. What are the advantages of corrosion?
a) Protection of metals by surficial oxide layer
b) Zn-carbon electrochemical reactions in the battery
c) Decrease in the strength of material
d) Protection of metals by the surficial oxide layer and Zn-carbon electrochemical reactions in the battery
Answer: d
Clarification: Initially passivating metals undergoes corrosion in order to form oxide layer. These thick, dense oxide layer acts as a strong barrier and protects the inner metal against corrosion. The Zn-carbon batteries works on the principle of galvanic corrosion. It involves conversion of chemical energy into electrical energy by these electrochemical reactions.