250+ TOP MCQs on Environments – Biological Corrosion and Answers

Corrosion Engineering Multiple Choice Questions on “Environments – Biological Corrosion”.

1. Biological corrosion is a deterioration of a metal by the corrosion process that occurs directly or indirectly due to the activity of living organisms.
a) True
b) False
Answer: a
Clarification: Biological corrosion is a deterioration of a metal by the corrosion process that occurs directly or indirectly due to the activity of living organisms. This includes micro and microorganism.

2. Which of the following environments in which the biological activity may influence corrosion?
a) Soil
b) Fresh and seawater
c) Petroleum products
d) Soil, freshwater, seawater and petroleum products
Answer: d
Clarification: Biological activity will influence the corrosion of materials in a variety of environments including soil, freshwater, seawater, and petroleum products. These living organisms are sustained by chemical reactions.

3. Which of the following is/are the processes that affect the corrosion behavior of metals by biological activity?
a) By influencing anodic and cathodic reactions
b) By influencing protective surface films
c) By producing deposits, by influencing anodic, cathodic reactions and protective surface films
d) By creating non-corrosive conditions
Answer: c
Clarification: The process that affects the corrosion behavior of metals by biological activity are:
i. By directly influencing anodic and cathodic reactions
ii. By influencing protective surface films
iii. By creating a corrosive environment
iv. By producing deposits.

4. Which of the following component is taken into account to classify aerobic and anaerobic organisms?
a) Nitrogen
b) Oxygen
c) Argon
d) Phosphorus
Answer: b
Clarification: Percentage or relative amount of oxygen in the environment is taken into account to classify the microorganisms into aerobic and aerobic bacteria. The anaerobic attack is pre-dominate in underground corrosion due to the non-availability of oxygen.

5. Which of the following organisms are regarded as microorganisms?
a) Bacteria
b) Fungi
c) Protozoa
d) Bacteria, fungi, protozoa, and nematodes
Answer: d
Clarification: Bacteria, fungi, protozoa, and nematodes are one of the microorganisms usually present in the soil. Biological activity that directly or indirectly affects the corrosion of metals is known as biological corrosion.

6. Which of the following anaerobic bacteria that influence the corrosion behavior of buried steel structures?
a) Sulfur-reducing bacteria
b) Sulfur-oxidizing bacteria
c) Thiobacillus thiooxidans
d) Sulfur-reducing and sulfur-oxidizing bacteria
Answer: a
Clarification: Sulfur-reducing anaerobic bacteria influences the corrosion behavior of buried steel structures. SO₄^-2+4H₂==>S^-2+4H₂O is the general chemical reaction of sulfur-reducing anaerobic bacteria.

7. Thiobacillusthiooxidans are the type of aerobic bacteria that are capable of oxidizing sulfur-bearing compounds to sulfuric acid.
a) False
b) True
Answer: b
Clarification: Thiobacillusthiooxidans are the type of aerobic bacteria that are capable of oxidizing elemental sulfur and sulfur-bearing compounds to sulfuric acid. 2S+3O₂+2H₂O==>2H₂SO₄ is the general chemical reaction of sulfur-oxidizing bacteria.

8. Which of the following coatings is/are used for the prevention of microbiological corrosion in buried steel?
a) Asphalt
b) Enamel
c) Plastic tape
d) Asphalt, enamel and plastic tape
Answer: d
Clarification: Microbiological corrosion influences the corrosion of buried steel structures in soil. This can be prevented by coatings such as asphalt, enamel, and plastic tape.

9. Which of the following is/are the preventions of microbiological corrosion in soil?
a) Use of substitute materials
b) Use of inhibitors
c) Applying coatings, use of inhibitors, cathodic protection and substitute materials
d) Cathodic protection
Answer: c
Clarification: Preventions to microbiological corrosion in soil:
i. Use of substitute materials such as asbestos and plastic
ii. Use of coatings such as asphalts and enamel
iii. Use of inhibitors and germicides
iv. Cathodic protection can be applied.

10. Which of the following acids are produced by microorganisms such as fungus and mold?
a) Oxalic acid
b) Lactic acid
c) Acetic acid
d) Oxalic acid, lactic acid, acetic acid, and citric acid
Answer: d
Clarification: Macroorganisms such as fungus and mold are also capable of influencing corrosion of metals in many environments. They assimilate organic matter and can produce considerable amounts of acids such as oxalic acid, lactic acid, acetic acid, and citric acid.

11. Which of the following materials is/are usually attacked by fungus?
a) leathers
b) Rubbers
c) Leathers, rubbers and bare and coated metals
d) Bare and coated metals
Answer: c
Clarification: Materials that are usually attacked by fungus are leathers, rubbers, and bare and coated metals. Though the attack of fungus on materials may not affect many mechanical properties it deteriorates the appearance of materials.

12. Which of the following is/are the preventions for the growth of mold on metal surfaces?
a) Periodic cleaning and storing in the high humid atmosphere
b) Periodic cleaning, reducing relative humidity during storage and applying toxic organic agents
c) Reducing relative humidity during storage and applying toxic organic agents
d) Periodic cleaning and reducing relative humidity during storage
Answer: b
Clarification: Preventions for the growth of mold on metal surfaces are:
i. Periodic cleaning of metal surfaces
ii. Reducing relative humidity during storage
iii. Applying toxic organic agents.

13. Which of the following is/are the aqueous organisms that influence the corrosion of metals in the water?
a) Barnacles, mussels, and algae
b) Fungus and mold
c) Sulfur-reducing and sulfur-oxidizing bacteria
d) Thiobacillus thiooxidans
Answer: a
Clarification: Aqueous organisms such as barnacles, mussels, and algae influence the corrosion of metals in water. This includes an increase in the requirement of power for a severely fouled ship and limits heat transfers in heat exchangers.