250+ TOP MCQs on Materials – Metals and Alloys and Answers

Corrosion Engineering Multiple Choice Questions on “Materials – Metals and Alloys – 1”.

1. Which of the following properties of metal is often required to consider by corrosion engineer?
a) Physical properties
b) Mechanical properties
c) Chemical properties
d) Physical, mechanical and chemical properties

Answer: d
Clarification: Properties of a metal that is often required to consider by corrosion engineers are:

 

• Physical properties such as density, modulus of elasticity
• Mechanical properties such as strength, hardness
• Chemical properties such as corrosion resistance, reactivity.

 

2. Which of the following is not a mechanical property of a metal?
a) Impact strength
b) Creep strength
c) Modulus of elasticity
d) Stress-rupture

Answer: c
Clarification: At a certain point, modulus of elasticity is considered as the physical property of a metal. Because it is an inherent property that cannot be changed by heat treatment or cold working.

3. Which of the following is/are the types of cast irons?
a) Gray cast iron
b) Malleable cast iron
c) Nodular cast iron
d) Gray cast iron, malleable cast iron, and nodular cast iron

Answer: d
Clarification: Cast iron is a generic term that applies to the high carbon-iron alloys containing silicon. Types of cast irons are gray cast iron, white cast iron, malleable cast iron, and nodular cast iron.

4. What is the composition of high-silicon cast iron named Durichlor that has the highest corrosion resistance among cast irons?
a) 14% silicon, 0.95% carbon and 3% molybdenum
b) 10% silicon, 1% carbon and 3% molybdenum
c) 14% silicon and 0.95% carbon
d) 10% silicon and 1% carbon

Answer: a
Clarification: The composition of Durichlor is 14% silicon, 0.95% carbon, and 3% molybdenum. It is a high-silicon cast iron that has the highest corrosion resistance among cast irons.

5. The excellent corrosion resistance of high-silicon irons is due to the formation of a passive SiO₂ surface layer.
a) True
b) False

Answer: a
Clarification: High-silicon cast iron is the type of alloy cast Irons that are formed with high silicon content (up to 14%). The excellent corrosion resistance of these alloys is due to the formation of a passive SiO₂ layer.

6. Which of the following metal is/are regarded as pure iron commercially?
a) Ingot iron
b) Armco iron
c) Wrought iron
d) Ingot and Armco iron

Answer: d
Clarification: Ingot and Armco iron are regarded as pure irons commercially. These are relatively weak and not used where strength is a major requirement. Whereas wrought iron is a mechanical mixture of slag and low-carbon steel.

7. Which of the following are the parameters of the iron-carbon diagram on the x and y-axis respectively?
a) Carbon percentage and Iron percentage
b) Carbon percentage and temperature
c) Temperature and carbon percentage
d) Iron percentage and temperature

Answer: b
Clarification: The iron-carbon phase diagram is an equilibrium phase diagram formed with carbon percentage and temperature parameters on the x and y-axis respectively. It consists of various phases such as alpha iron, austenite phase, delta iron, and its combinations.

8. Which of the following is/are the classification types of stainless steel?
a) Martensitic stainless steels
b) Ferritic stainless steels
c) Austenitic stainless steels
d) Martensitic, ferritic and austenitic stainless steels

Answer: d
Clarification: Stainless steel is a generic term that applies to iron-carbon-chromium and nickel alloy system. Types of stainless steels are Martensitic stainless steels, ferritic stainless steels, austenitic stainless steels, and precipitation-hardened steels.

9. Which of the following statements are correct regarding the austenite phase in an iron-carbon phase diagram?
a) It is non-magnetic in nature
b) The maximum percentage of carbon is 2.1%
c) It has a face-centered cubic structure
d) The austenitic phase has a face-centered cubic structure with a 2.1% maximum percent carbon and non-magnetic in nature.

Answer: d
Clarification: Austenite is one of the phases in the iron-carbon phase diagram. It has a face-centered cubic structure with 2.1% maximum percent carbon and it is non-magnetic in nature.

10. Which of the following properties of aluminum contributing to its widespread applications?
a) High corrosive resistance
b) Good strength-weight ratio
c) Nontoxic corrosion products
d) High corrosive resistance, good strength-weight ratio, and nontoxic corrosion products

Answer: d
Clarification: The properties of aluminum that contribute to its widespread applications are high corrosion resistance, good strength-weight ratio, nontoxic corrosion products, appearance, and electrical and thermal conductivity.

11. Which of the following metal is utilized in trucks, automobile engines, aircraft, and missiles?
a) Stainless steel
b) Carbon steels
c) Magnesium
d) Cast irons

Answer: c
Clarification: Magnesium is one of the lightest commercial metal with specific gravity 1.74. It is utilized in trucks, automobile engines, aircraft, and missiles. Whereas metals such as stainless steel, carbon steels, and cast irons are regarded as heavy metals.

12. Which of the following corrosion products of lead serve as protective films?
a) Lead sulfates
b) Lead oxides
c) Lead phosphates
d) Sulfates, oxides, and phosphates of lead

Answer: d
Example: Lead and its alloys are usually used piping, radiation shield, and storage batteries. It is resistant to corrosion in sulfuric acid, chromic acid, and phosphoric acid. Sulfates, oxides, and phosphates of lead are the corrosion products of lead that act as protective films.

13. Which of the following alloying element of stainless steel that attributes a large increase in stress-corrosion resistance?
a) Nickel
b) Chromium
c) Carbon
d) Nickel and chromium

Answer: a
Clarification: Stainless steel is a generic term that attributes to the alloy system of iron-carbon-chromium and nickel. Addition of nickel as alloying element up to 10% attributes in a rapid and large increase in stress-corrosion resistance of stainless steel.

14. Which of the following metal/alloy has the highest stress-corrosion resistance?
a) Aluminum
b) Inconel
c) Stainless steel
d) Titanium

Answer: b
Clarification: Typical composition of an Inconel is chromium 20-23%, iron 5%, molybdenum 8-10% and nickel around 60-65%. Inconel has the highest stress-corrosion resistance whereas aluminum, stainless steel, and titanium are prone to stress corrosion cracking.