Category: Corrosion Engineering Objective Questions

Corrosion Engineering Multiple Choice Questions on “Eight Forms – Crevice Corrosion”.

1. Which of the following is/are the reasons for the cause of crevice corrosion?
a) The stagnant solution in the holes and gasket surfaces
b) The stagnant solution in the lap joints and surface deposits
c) Dissimilar metal contact
d) The stagnant solution in the holes, gasket surfaces, lap joints, and surface deposits
Answer: d
Clarification: Crevice corrosion is a type of corrosion in which dissolution of metal is due to the presence of stagnant solution in the small gaps (crevice) such as holes, gasket surfaces, lap joints, and surface deposits, etc.

2. Which of the following type of corrosion is localized in nature?
a) Crevice corrosion
b) Galvanic corrosion
c) Uniform corrosion
d) Inter-granular corrosion
Answer: a
Clarification: Crevice corrosion is localized corrosion because it occurs only at discrete sites on the metal surface. This occurs due to the presence of a stagnant solution in crevices (small spaces). This crevice corrodes rapidly by cathodically protecting adjacent surfaces.

3. Which of the following is the other name of crevice corrosion?
a) Filiform corrosion
b) Deposit or gasket corrosion
c) Two-metal corrosion
d) Surface corrosion
Answer: b
Clarification: Crevice corrosion occurs due to the presence of a stagnant solution in the crevices. These crevices are formed due to the corrosion deposits or gaps at the metal-gasket interface. Thus, it is also called as deposit or gasket corrosion.

4. Which of the following metal is more susceptible to crevice corrosion?
a) Titanium
b) Hastelloy C
c) Stainless steel-430
d) Titanium and stainless steel
Answer: c
Clarification: Stainless steel-430 is highly prone to crevice corrosion. The reasons are as follows:
1. Large critical current density
2. Wide active-passive transitions
3. Limited passive region

5. Which of the following combination results in crevice corrosion?
a) Metal and absorbent gaskets
b) Continuous weld metals
c) Metal and non-absorbent gaskets
d) Single metal piece
Answer: a
Clarification: Metal and absorbent gasket combination results in the crevice corrosion. Absorbent gaskets absorb water vapor from surrounding and make them stagnant at the metal–gasket interface. This results in crevice corrosion.

6. Which of the following characteristics of the crevice is a must to act as a corrosion site?
a) It should be wide enough to permit liquid entry
b) It should be narrow enough to maintain a stagnant zone
c) It should be wide enough to avoid a stagnant zone
d) It should be wide enough to permit liquid entry and narrow enough to maintain a stagnant zone
Answer: d
Clarification: Crevice is a small volume region formed between the interface of metal and gaskets. It acts as a corrosion site if is wide enough to permit liquid entry and narrow enough to maintain a stagnant zone.

7. What is the primary condition regarding the velocity of an electrolyte to form crevice corrosion?
a) The velocity of the electrolyte should be greater than 10cm/s
b) The velocity of the electrolyte should be less than 10cm/s
c) The velocity of the electrolyte should be equal to 10cm/s
d) The stagnant electrolytic solution should be present
Answer: d
Clarification: Crevice corrosion occurs due to the presence of stagnant electrolytic solution in the crevices. It acts at the corrosion sites and it results in the formation of localized corrosion. An increase in the velocity of the electrolyte decreases the extent of crevice corrosion.

8. The difference in metal ion or oxygen concentration between the crevice and its surroundings is the main reason for crevice corrosion.
a) True
b) False
Answer: a
Clarification: Crevice corrosion is mainly occurred due to the difference in metal ion or oxygen concentration between the crevice and its surroundings. This is due to the unavailability of oxygen in the crevice, this results in the dissolution of metal in a crevice by protecting adjacent surface cathodically.

9. Which of the following chemical reaction that usually occurs in the crevice?
a) M⁺+H₂O=MOH
b) M⁺+Cl^–=MCl_(s)
c) M⁺Cl^–+H₂O=MOH_(aq)+H⁺Cl^–
d) 4OH^–=O₂+2H₂O+4e^–
Answer: c
Clarification: As the metallic ion concentration increases in the crevice, the migration of chloride ions takes place to neutralize that. After that, metal chlorides undergo hydrolysis and results in the formation of insoluble metal hydroxide and free acid.

10. Which of the following ions that accelerate the dissolution rate of metals or alloys in a crevice?
a) H⁺, OH^–
b) H⁺, Cl^–
c) OH^–, Cl^–
d) OH^–, Cl^– and H^–
Answer: b
Clarification: H⁺ and Cl^– ions accelerate the dissolution rate of metals and alloys in the crevice. These are produced by hydrolysis of metal chlorides. It accelerates corrosion because hydrogen ion decreases pH value (more acidic) and chloride ion attacks the metallic surface in the crevice.

11. Which of the following metal is highly resistant to crevice corrosion?
a) Stainless steel
b) Copper
c) Aluminum
d) Hastelloy C-276
Answer: d
Clarification: Hastelloy C-276 is the best crevice corrosion-resistant metal. The composition of Hastelloy C-276 is 15.5%Cr, 54.7%Ni, 15.5%Mo, 3.8%W, and 0.5%Mn. Whereas the other metals depend on oxide film for their corrosion resistance.

12. As the metal dissolution within the crevice increases, the rate of oxygen reduction on adjacent surfaces increases.
a) True
b) False
Answer: a
Clarification: Metallic dissolution in the crevice cathodically protects the external surface. Electrons transfer from M==>M⁺ⁿ+ne (in crevice) to compensate O₂+H₂O+4e==>4OH (adjacent surface).

13. What is the incubation period associated with a crevice attack?
a) 1 month – 10 months
b) 1 hour – 10 hours
c) 1 day – 10 days
d) 6 months – 1 year
Answer: d
Clarification: The incubation period is the time required to initiate the crevice corrosion on metal. It usually in the range of 6 months to 1 year. It depends on many factors such as the material used, corrosive medium, temperature, etc.

14. Metals or alloys that depend on oxide films for corrosive resistance are highly susceptible to crevice corrosion.
a) True
b) False
Answer: a
Clarification: Metals or alloys that depend on oxide films for corrosive resistance are highly susceptible to crevice corrosion. These passive films are destroyed by high concentrations of hydrogen and chloride ions, and the metallic dissolution increases rapidly.

15. Which of the following type of corrosion is depicted in the given figure?

a) Galvanic corrosion
b) Uniform corrosion
c) Crevice corrosion
d) Pitting corrosion
Answer: c
Clarification: Crevice corrosion is localized corrosion that occurs due to the formation of crevices (small volume gaps) on various metal or gasket junction. A crevice will act as a corrosion site when it is wide enough to permit liquid entry and narrow enough to maintain a stagnant zone.

Corrosion Engineering Multiple Choice Questions on “Materials – Thermoplastics”.

1. Which of the following is/are the classification of plastics based on the thermal behavior?
a) Thermoplastics
b) Thermosetting
c) Neither thermoplastics nor thermosetting
d) Thermoplastics and thermosetting
Answer: d
Clarification: Plastics can be categorized based on various parameters such as monomer units, temperature behavior, and structure. Thermoplastics and Thermosetters are the two types of plastics based on thermal behavior.

2. What is meant by thermoplastic?
a) It softens on heating and returns to original hardness on cooling
b) It hardens on heating and returns to original hardness on cooling
c) It hardens on heating and retains hardness on cooling
d) It softens on heating and retains hardness on cooling
Answer: a
Clarification: Thermoplastics is one of the type of plastics which softens on heating and returns to original hardness on cooling. Fluorocarbons, polyether, and nickel are examples of thermoplastics.

3. Which of the following thermoplastic is corrosion-resistant to all environments up to 550°F?
a) Polyvinyl chloride
b) Polystyrene
c) Teflon
d) Polyethylene
Answer: c
Clarification: Teflon is one of the fluorocarbons which is regarded as noble metals of plastics. It is corrosion-resistant to practically all environments up to 550°F. The monomer of Teflon is denoted as CF₂=CF₂.

4. Which of the following is the chemical name of nylon (6, 6)?
a) Polyethylene terephthalate
b) Hexamethylene adipamide
c) Polytetrafluoroethylene
d) Polyvinyl fluoride
Answer: b
Clarification: The chemical name of nylon (6.6) is hexamethylene adipamide. It is derived from the monomers of nylon that are hexamethylenediamine and adipic acid.

5. Which of the following thermoplastics is used for making eye lenses?
a) Polytetrafluoroethylene
b) Polyethylene terephthalate
c) Polymethyl methacrylate
d) Polyvinyl chloride
Answer: c
Clarification: Polymethyl methacrylate is the polymer of many methyl methacrylate monomeric units. It is used for making eye lenses as it is transparent to light. It is usually denoted as PMMA.

6. Which of the following is/are the monomers of nylon (6,6)?
a) Hexamethylenediamine
b) Adipic acid
c) Both Hexamethylenediamine and adipic acid
d) Neither Hexamethylenediamine nor adipic acid
Answer: c
Clarification: Hexamethylenediamine and adipic acid are the two monomers of nylon (6,6). The chemical formula of hexamethylenediamine and adipic acid is NH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-NH₂ and HOOC-CH₂-CH₂-CH₂-COOH respectively.

7. Which of the following is/are the examples of thermoplastics?
a) Polypropylene
b) Polystyrene
c) Polyvinyl chloride
d) Polypropylene, polystyrene and polyvinyl chloride
Answer: d
Clarification: Thermoplastics are the type of plastics that soften on heating and return to their original hardness when cooled. Polypropylene, polystyrene, polyethylene, fluorocarbons, and polyvinyl chloride are examples of thermoplastics.

8. Which of the following thermoplastic monomer is depicted in the given figure?

a) Polystyrene
b) Teflon
c) Polyvinyl chloride
d) Polyurethane
Answer: a
Clarification: Styrene is depicted in the given figure and it is the monomer of polystyrene. It is an amorphous, colorless, rigid, and hard plastics. The monomer of polyvinyl chloride and Teflon is CH₂=CH-Cl and CF₂=CF₂ respectively.

9. Which of the following is the monomer of Polyvinyl chloride (PVC)?
a) CF₂=CF₂
b) CH₂=CH-Cl
c) COOH-CH₂-CH₂-CH₂–CH₂COOH
d) C₆H₅-CH=CH₂
Answer: b
Clarification: Vinyl chloride (CH₂=CH-Cl) is the monomeric unit of polyvinyl chloride. It is used for piping and cable insulation extensively. CF₂=CF₂, COOH-CH₂-CH₂-CH₂–CH₂COOH and C₆H₅-CH=CH₂ are the monomers of Teflon, nylon, and polystyrene respectively.

10. Degradation of plastics is due to swelling, loss of mechanical properties, softening, hardening, and spalling.
a) True
b) False
Answer: a
Clarification: Corrosion of plastics is not the same as that of metals. Corrosion of metals results in the dissolution of metal ions whereas corrosion or degradation of plastics is due to swelling, loss of mechanical properties, softening, hardening, and spalling.

Basic Corrosion Engineering Questions and Answers on “Environments – Sea Water and Fresh Water”.

1. Which of the following is/are true regarding seawater?
a) It contains 3.4% salt
b) It has a pH around 8
c) It is a good electrolyte with high electrical conductivity
d) Seawater is a good electrolyte with high electrical conductivity with 3.4% salt and pH around 8
Answer: d
Clarification: Seawater is a good electrolyte with high electrical conductivity with 3.4% salt and pH around 8. It can cause galvanic and crevice corrosion to various metals.

2. Which of the following is/are the factors that affect corrosion in seawater?
a) Temperature and velocity
b) Oxygen content and biological organisms
c) Temperature, velocity, oxygen content and biological organisms
d) Temperature, velocity and oxygen content
Answer: c
Clarification: The factors that affect the corrosion of materials in seawater are:
i. Temperature
ii. Velocity
iii. Oxygen content
iv. Biological organisms.

3. Which of the following region of the seacoast environment have high corrosion based on the given figure?

a) Quiet seawater
b) Splash region
c) High tide area
d) Mud line
Answer: b
Clarification: Greatest corrosion occurs in the splash region due to alternate wetting and drying and also aeration. We know oxygen and moisture are the primary requirements for corrosion of metals.

4. Which of the following regions of the seacoast environment shows the effect of the pitting of metals and alloys?
a) Quiet seawater
b) High tide region
c) Low tide region
d) Splash region
Answer: a
Clarification: Pitting is extremely localized corrosion which results in holes or cavities. Quiet seawater in the region of the seacoast environment that shows the effect of the pitting of metals and alloys. An increase in the velocity of a corrosive solution decreases the pitting tendency of a metal.

5. Corrosion by seawater at greater depth is usually decreased because of the lower temperature.
a) False
b) True
Answer: b
Clarification: Corrosion by seawater at greater depth is usually decreased because of the lower temperature. It decreases by 40°F for one-mile depth.

6. Which of the following impurities contaminates the brackish water due to tidal action in rivers and bays near the ocean?
a) Chlorides
b) Bromides
c) Hydrides
d) Metal oxides
Answer: a
Clarification: Chloride ions are the impurities that contaminate the brackish water due to the tidal action in rivers and bays near the ocean. The source of these chloride ions is sodium chloride in seawater.

7. Which of the following metals have high resistance to crevices in quiet seawater?
a) Hastelloy C
b) Titanium
c) Hastelloy C and Titanium
d) Nickel-copper alloy
Answer: c
Clarification: Hastelloy C and titanium have high resistance to crevices in quiet seawater. Due to this, these metals are used for various corrosive seawater applications. Whereas nickel-copper alloy shows less resistance.

8. Which of the following alloy has high cavitation resistance that usually used for ship propellers and pumps impellers in seawater?
a) Titanium
b) Stellite
c) 17-7 Stainless steel
d) Nickel aluminum bronze
Answer: b
Clarification: Stellite is a cobalt-chromium alloy with high cavitation resistance that usually used for ship propellers and pump impellers in seawater. Composition of Stellite is 27–32% chromium, 4–6% tungsten, 0.9–1.4% carbon, with additions of nickel, iron, silicon, manganese, and molybdenum and cobalt as balance.

9. Which of the following factors that affect the corrosivity in freshwater?
a) Oxygen content
b) Hardness
c) Chloride content
d) Oxygen content, hardness and chloride content
Answer: d
Clarification: Factors that affect the corrosivity in freshwater are:
i. Oxygen content
ii. Hardness
iii. Chloride and sulfur content.

10. Which of the following type of water is more corrosive?
a) Hard water
b) Hard and soft water
c) Soft water
d) High-purity water
Answer: c
Clarification: In hard water, carbonates often deposit on the metal surface and protect it from corrosion. Whereas in soft water protective deposits do not form. Hence, soft water is more corrosive than hard water and high-purity water.

11. Which of the following metals are widely used for handing freshwater?
a) Cast iron
b) Stainless steel
c) Galvanized steel
d) Cast iron, stainless steel, and galvanized steel
Answer: d
Clarification: Cast iron, stainless steel, steel, and galvanized steel are widely used for handling freshwater. Metals such as copper, brass, aluminum, monel, and cupronickels are also used with the factors of temperature, contamination, and longer life.

12. Which of the following corrosion defects that affect the reliability of tubing?
a) Selective weld metal attack
b) Improper pickling and heat treatment
c) Residual stresses, selective weld metal attack, improper pickling, and heat treatment
d) Selective weld metal attack and residual stresses
Answer: c
Clarification: Corrosion defects that affect the reliability of tubing are:
i. Inadequate alloying
ii. Selective weld metal attack
iii. Improper pickling
iv. Residual stresses
v. Improper heat treatment.

13. Corrosion decreases with an increase in the purity of water.
a) True
b) False
Answer: a
Clarification: Corrosion decreases with increasing purity of the water because of less solid and gases and increasing electrical resistance. Resistance is a measure of water purity.

14. Which of the following types of corrosion has been seen in stainless steels in high purity water containing oxygen?
a) Cracking of solution-quenched stainless steel only
b) Intergranular attack and cracking of solution-quenched steel
c) Intergranular attack only
d) Neither intergranular corrosion nor cracking of solution-quenched steel
Answer: b
Clarification: Intergranular corrosion and cracking of solution-quenched stainless steel and alloys have been observed in high-purity water containing oxygen.

15. Which of the following metals/alloys are used for handling high-purity water in nuclear applications?
a) Zirconium and its alloys
b) Stainless steels
c) Inconel and Incoloy
d) Zirconium and its alloys, stainless steels, Inconel and Incoloy
Answer: d
Clarification: Zirconium and its alloys, stainless steels, Inconel and Incoloy are the metals/alloys that are used for handling high-purity water in nuclear applications.

Corrosion Engineering Multiple Choice Questions on “Eight Forms – Filiform Corrosion”.

1. Which of the following characteristics of active-passive metal will acquire optimize crevice corrosion resistance?
a) A narrow active-passive transition
b) A small critical current density
c) An extended passive region
d) A narrow active-passive transition, a small critical current density, and an extended passive region
Answer: d
Clarification: The optimum crevice corrosion resistance of active-passive transition metal is acquired by having the following characteristics: i. A narrow active-passive transition
ii. A small critical current density
iii. An extended passive region

2. Which of the following corrosion testing describe the test for crevice corrosion?
a) Occluded cell corrosion
b) Galvanic effect
c) Atmospheric exposure testing
d) Kesternich chamber testing
Answer: a
Clarification: Occluded cell corrosion is a corrosion testing that describes crevice corrosion. In this test, a narrow gap is maintained between two metal in a stagnant corrosive solution. An occluded cell is also known as crevice corrosion.

3. The incubation period is the amount of time required to initiate crevice corrosion on a corrosive site.
a) True
b) False
Answer: a
Clarification: The incubation period is the time required to initiate the crevice corrosion on a corrosive site. It depends on many factors such as
i. Type of crevice formed
ii. Nature of material used
iii. Temperature
iv. The difference in the concentration of oxygen in the crevice and its surroundings

4. The crevice corrosion index is an index is to assist the selection of materials for construction.
a) True
b) False
Answer: a
Clarification: Crevice corrosion index (CCI) is developed by Streicher. CCI is an index used to assist the selection of materials for construction. It minimizes the chances of crevice formation by proper material selection.

5. Which of the following are the methods and procedures to minimize crevice corrosion?
a) Use of welded joints instead of riveted joints
b) Avoid sharp edges and stagnant areas
c) Removal of deposits frequently
d) Use of welded joints instead of riveted joints, avoid sharp edges and stagnant areas and removal of deposits frequently
Answer: d
Clarification: Combating or minimizing crevice corrosion can be done as follows:
l. Use of welded joints instead of riveted or bolted joints
ll. Avoid sharp edges and stagnant areas
lll. Regular inspection
lV. Removal of deposits frequently
V. Use of non-absorbent gaskets

6. Which of the following is a non-absorbent gasket?
a) Polyethylene
b) Isoprene
c) Teflon
d) Polyethylene and isoprene
Answer: c
Clarification: Teflon (CF₂=CF₂) is a non-absorbent gasket. It is used in the industrial application to minimize the crevice corrosion. Whereas polyethylene and isoprene (rubber) is absorbent to fluids such as water and acids.

7. Which of the following is also known as under film corrosion?
a) Crevice corrosion
b) Filiform corrosion
c) Galvanic corrosion
d) Pitting corrosion
Answer: b
Clarification: Filiform corrosion is a special type of crevice corrosion. It is also known as under film corrosion as it occurred under protective coatings or films. It usually seen on food and beverage cans.

8. Which of the following is/are the effects of filiform corrosion?
a) Weakens the metal
b) Decreases tensile strength
c) Affects surface appearance
d) Weakens the metal, decreases tensile strength and affects the surface appearance
Answer: c
Clarification: This filiform corrosion affects only surface appearance on metal-coated food and beverage cans that are exposed to the high humid atmosphere. It doesn’t weaken the metal as well as decreases the tensile strength.

9. Which of the following industry has major concern on filiform corrosion?
a) Petroleum industry
b) Canning industry
c) Automobile industry
d) Petroleum and automobile industry
Answer: b
Clarification: The Canning industry has a major concern on filiform corrosion. As canning is a preservation method by sealing the container’s airtightly and applying epoxy coating on the metal surface. Whereas the petroleum and automobile industry face uniform and galvanic corrosion as a major concern.

10. Which of the following ion/ions that result in the blue-green color of the active head in a corrosion filament?
a) Ferrous ions
b) Ferric oxide ions
c) Hydrated ferric oxide ions
d) Ferric oxide and hydrated ferric oxide ions
Answer: a
Clarification: A under film corrosion filament consists of an active head and inactive tail. The active head contains ferrous ions, that have a characteristic color of blue-green. Whereas inactive tail contains ferric oxide and hydrated ferric oxide ions, that has a characteristic color of red-brown.

11. Which of the following type of corrosion filament interaction is depicted in the given figure?

a) Reflection of corrosion filament
b) Splitting of corrosion filament
c) Joining of corrosion filament
d) Death trap of corrosion filament
Answer: d
Clarification: Since the growing filaments can’t cross inactive tails, they frequently get trapped and dies as the available space is decreased. This is known as the death trap.

12. Which of the following is the most environmental factor of filiform corrosion?
a) Relative humidity of the atmosphere
b) Temperature
c) pH of the environment
d) Temperature and pH of the environment
Answer: a
Clarification: Relative humidity of the surroundings is the most environmental factor of filiform corrosion. It occurs primarily between 65% to 90% relative humidity. If the relative humidity is less than 65%, the metal is unaffected.

13. What are the preventions of filiform corrosion?
a) Use of coatings with low water permeability
b) To store in low-humidity environment
c) To store in high-humidity environment
d) Use of coatings with low water permeability and to store in a low-humidity environment
Answer: d
Clarification: Filiform corrosion is a special type of crevice corrosion, occurs under metal coatings in a relatively high-humidity environment
Preventions to filiform corrosion:
i. Use of coatings with low water permeability
ii. To store in a low-humidity environment
iii. Use of brittle films or coatings

14. Which of the following type of corrosion is depicted in the given figure?

a) Crevice corrosion
b) Galvanic corrosion
c) Filiform corrosion
d) Uniform corrosion
Answer: c
Clarification: Here, the figure depicts the corrosion of steel under film or coating. This corrosion is called filiform corrosion and it is caused due to the relative humidity of the atmosphere.

Corrosion Engineering Multiple Choice Questions on “Materials – Thermosetters”.

1. What is meant by thermosetting plastic?
a) It softens on heating and returns to original hardness on cooling
b) It hardens on heating and retains hardness on cooling
c) It hardens on heating and returns to original hardness on cooling
d) It softens on heating and retains hardness on cooling
Answer: b
Clarification: Plastics are readily divided into two types based on their thermal behavior. One is thermoplastic and another one is thermosetting. Thermosetting polymers are the polymers that harden on heating and retains hardness on cooling.

2. Which of the following is/are the example of thermosetting polymers?
a) Epoxies
b) Polyesters
c) Phenolics
d) Epoxies, polyesters, and phenolics
Answer: d
Clarification: Thermosetting polymers is one of the classifications of polymers based on the thermal behavior of polymers. Epoxies, polyesters, and phenolics are examples of thermosetting polymers.

3. Which of the following is/are the raw materials of Bakelite?
a) Phenol
b) Formaldehyde
c) Both phenol and formaldehyde
d) Neither phenol nor formaldehyde
Answer: c
Clarification: Bakelite is one of the most widely used thermosetting plastics for various domestic and industrial applications. Phenol or carbolic acid and formaldehyde are the raw materials of Bakelite.

4. Which of the following polyester is used in the space mirror satellite?
a) Mylar
b) Dacron
c) Vibrin
d) Dypol
Answer: a
Clarification: Thermosetting polymers such as Mylar, Dacron, Vibrin, and Dypol are categorize under polyester. The satellite was made of thin, reflective Mylar film.

5. Silicones are used for molding compounds, laminating resins, and insulation for electric motors and electronic equipment.
a) True
b) False
Answer: a
Clarification: Silicones are used for the molding compounds, laminating resins, and insulating for electric motors and electronic equipment because of its outstanding heat resistance. It can be demonstrated by Si–O–Si bond with alkyl groups on either side of the silicon atom.

6. What is the chemical name of the compound that is depicted in the given figure?

a) Formaldehyde
b) Bakelite
c) Urea
d) Vinyl chloride
Answer: c
Clarification: The compound that is depicted in the given figure is urea. It is one of the monomers of bauxite and beetle. It combines with formaldehyde to form plastics that used for the applications of kitchen dishware and utensils.

7. What is the abbreviation of FRP regarding reinforced plastics?
a) Filtrate-reinforced plastic
b) Fiber-reinforced plastic
c) Filter-reinforced plastic
d) Fume-reinforced polymer
Answer: b
Clarification: FRP can be abbreviated as Fiber-reinforced plastic regarding reinforced plastics. Carbon fibers, alumina fibers, an aramid fiber can be reinforced into plastics for better strength and corrosion resistance.

8. Which of the following thermosetting plastics that comes under phenolics?
a) Bakelite
b) Durez
c) Resinox
d) Bakelite, Durez, and Resinox
Answer: d
Clarification: Phenolics materials such as Bakelite, Durez, and Resinox are made up of phenol and formaldehyde. It uses for various applications such as electrical sockets, telephones, valves, and coatings.

9. Which of the following category that materials such as Epon, Durcon, and Araldite belong to?
a) Epoxies
b) Silicones
c) Phenolics
d) Polyesters
Answer: a
Clarification: Epon, Durcon, and Araldite belong to epoxies. These materials are the best combination of corrosion resistance and mechanical properties. It is mainly used as protective coatings, linings, and adhesives.

10. Which of the following is not a thermosetting plastic?
a) Dacron
b) Bakelite
c) Polystyrene
d) Polyester
Answer: c
Clarification: Thermosetting plastic is a plastic that hardens on heating and retains hardness on cooling. Dacron, Bakelite, and Polyester are examples of thermosetting plastics whereas Polystyrene is the example of thermoplastics.

Corrosion Engineering Multiple Choice Questions on “Environments – Soil and Aerospace”.

1. The corrosivity of soils varies over a wide range because of the variety of composition.
a) True
b) False
Answer: a
Clarification: The corrosivity of a particular solution depends on its composition. So, the corrosivity of soils varies over a wide range because of the variety of composition.

2. Which of the factors that affect the corrosiveness of soils?
a) Moisture
b) Acidity
c) Oxygen
d) Moisture, oxygen, acidity and stray currents
Answer: d
Clarification: The factors that affect the corrosiveness of soils are moisture, oxygen, acidity, alkalinity, the permeability of air and water, stray currents, and biological organisms.

3. Which of the following is a good measure of corrosivity?
a) Thermal conduction
b) Electrical resistance
c) Thermal resistance
d) Mechanical properties
Answer: b
Clarification: Electrical resistance is a good measure of corrosivity of a corrosive solution. Higher electrical resistance lowers the corrosivity of a solution. Dry soils are generally not very corrosive due to high electrical resistance.

4. Which of the following type of corrosion is/are dominant due to backfills such as stones, cinders, wood, and metal?
a) Crevice corrosion
b) Pitting corrosion
c) Crevice and pitting corrosion
d) Neither crevice nor pitting corrosion
Answer: c
Clarification: Crevice and pitting corrosion are the types of corrosion that dominate due to backfill such as stones, cinders, wood, and metal. Because these foreign particles result in the formation of crevices.

5. Which of the following is/are true regarding underground structures?
a) Ordinary carbon steels and cast irons are commonly used
b) Organic coatings can be used
c) Cathodic protection is applied to protect it from corrosion
d) Usually made of carbon steel and cast irons with or without organic coatings and supported by a cathodic protection system
Answer: d
Clarification: Underground structures are usually made up of ordinary carbon steels and cast irons with or without organic coatings. These structures are also supported by a cathodic protection system to minimize corrosion.

6. Which of the following type of corrosion is pre-dominate in underground corrosion?
a) Aerobic corrosion
b) Anaerobic corrosion
c) Aerobic and anaerobic corrosion
d) Neither aerobic nor anaerobic corrosion
Answer: c
Clarification: The anaerobic type of attack is pre-dominate in underground corrosion. It is due to the non-availability of oxygen as it decreases with an increase in depth.

7. Which of the following areas of aircrafts face severe corrosion problems?
a) Fuel tank due to oxidizers and fuel
b) High-temperature corrosion in blast nozzles
c) The outer structure of the plane due to vacuum
d) Fuel tank due to oxidizers and fuel, high-temperature corrosion in blast nozzles
Answer: d
Clarification: Fuel tank due to oxidizers and fuel and high-temperature corrosion in blast nozzles are the two areas that aerospace face severe corrosion problems. Whereas the hard vacuum of space does not cause corrosion.

8. Which of the following materials is/are used for blast nozzles in aerospace?
a) Aluminum oxide and cemented tungsten carbide
b) Aluminum oxide cemented tungsten carbide and boron carbide
c) Cemented tungsten carbide only
d) Aluminum oxide and boron carbide
Answer: b
Clarification: Aluminum oxide, cemented tungsten carbide, and boron carbide is the materials that are used for blast nozzles in aerospace. These materials are also known as refractory materials.

9. Which of the following is/are the prime considerations in space vehicles and aircraft?
a) High strength-weight ratios for materials and high ratios of payload to the vehicle’s weight
b) High strength-weight ratios for materials only
c) High ratios of payload to vehicles weight only
d) Neither high strength-weight ratios for materials nor high ratios of payload to the vehicle’s weight
Answer: a
Clarification: High strength-weight ratio for materials and high ratios of payload to vehicle weight are the two prime considerations in space vehicles and aircraft.

10. Rusting of high-strength steel due to resident water can cause stress-corrosion and hydrogen embrittlement.
a) False
b) True
Answer: b
Clarification: Rusting of high-strength steel due to resident water can cause stress-corrosion and hydrogen embrittlement. Hydrogen charging of steel during electroplating can cause a brittle fracture.

11. Which of the following is/are the primary materials regarding the construction of aircraft?
a) Aluminum
b) Magnesium and titanium
c) Aluminum, magnesium, titanium, and iron
d) Titanium and magnesium
Answer: c
Clarification: Aluminum, magnesium, titanium, and iron and their alloys are the primary materials regarding the construction of aircraft. These are selected based on a high strength-weight ratio for materials and high ratios of payload to vehicle weight.

12. Which of the following corrosion protective systems is/are included in aircraft industries?
a) Anodizing, cladding and conversion coatings
b) Anodizing and cathodic protection
c) Conversion coatings and anodizing
d) Cathodic protection only
Answer: a
Clarification: Anodizing, cladding, and conversion coatings are the corrosive protective systems used in aircraft industries. Whereas cathodic protection cannot be used in the aircraft industry due to non-conductive electrolytes.