1. Which type of corrosion occurs when two dissimilar metals are in electrical
contact in an electrolyte?
A. Uniform corrosion
B. Galvanic corrosion
C. Crevice corrosion
D. Stress corrosion
Answer: B
Explanation: Galvanic corrosion occurs due to a potential difference between
dissimilar metals in contact within an electrolyte.
2. The most important factor controlling corrosion rate in soils is:
A. pH
B. Oxygen availability
C. Soil resistivity
D. Moisture content
Answer: C
Explanation: Soil resistivity is the key indicator of corrosivity. Low resistivity
generally means higher corrosion risk.
3. The minimum protection potential for steel in soil under cathodic protection
(per NACE SP0169) is:
A. –0.85 V vs Cu/CuSO₄
B. –0.95 V vs Cu/CuSO₄
C. –0.50 V vs Ag/AgCl
D. –1.20 V vs Cu/CuSO₄
Answer: A
Explanation: –0.85 V vs Cu/CuSO₄ is the industry criterion for steel in soil or
water under CP.
4. A coating that exhibits “holidays” is:
A. Too thick
,B. Containing pores or voids
C. Perfectly applied
D. Cathodic disbonded
Answer: B
Explanation: Holidays are small discontinuities in a coating film that expose
bare metal.
5. The main purpose of sacrificial anodes in CP systems is to:
A. Increase coating adhesion
B. Serve as a current source
C. Reduce pH
D. Strengthen pipeline walls
Answer: B
Explanation: Sacrificial anodes (like zinc, magnesium, aluminum) corrode
preferentially, supplying current to protect the structure.
6. Which corrosion form is most associated with stagnant solutions in shielded
areas?
A. Uniform
B. Galvanic
C. Crevice
D. Cavitation
Answer: C
Explanation: Crevice corrosion occurs where electrolyte becomes stagnant,
such as under gaskets or deposits.
7. The Langelier Saturation Index (LSI) is primarily used to:
A. Predict stress corrosion cracking
B. Estimate water scaling/corrosivity
C. Determine coating adhesion strength
D. Measure chloride content
Answer: B
Explanation: LSI indicates if water tends to be scale-forming or corrosive to
steel.
,8. What type of CP uses an external DC power source?
A. Sacrificial anode CP
B. Impressed current CP
C. Passive protection
D. Barrier protection
Answer: B
Explanation: Impressed Current CP (ICCP) applies DC current from a rectifier
to force polarization of the structure.
9. Which factor most affects the selection of coating type for buried pipelines?
A. Operator preference
B. Pipe diameter
C. Soil resistivity and environment
D. Paint color
Answer: C
Explanation: The corrosiveness of soil and environment dictates whether to use
FBE, polyethylene, coal tar, etc.
10. The Pourbaix diagram is a plot of:
A. Stress vs strain
B. pH vs potential
C. Temperature vs corrosion rate
D. Coating adhesion vs thickness
Answer: B
Explanation: Pourbaix diagrams show metal stability, passivation, or corrosion
regions as a function of potential and pH.
11. The main role of coating in corrosion control is to:
A. Eliminate galvanic corrosion completely
B. Provide a physical barrier to environment
C. Supply cathodic protection current
D. Increase electrical conductivity
Answer: B
12. Which of the following is a form of high-temperature corrosion?
A. Hydrogen embrittlement
, B. Oxidation
C. Crevice corrosion
D. Galvanic attack
Answer: B
13. Stray current corrosion is most likely in:
A. Isolated above-ground storage tanks
B. Areas near DC-powered transit systems
C. Marine splash zones
D. Dry desert pipelines
Answer: B
14. A rectifier used in ICCP typically converts:
A. AC → DC
B. DC → AC
C. High voltage DC → low voltage AC
D. DC → pulsed current
Answer: A
15. Which metal is typically used for sacrificial anodes in seawater?
A. Magnesium
B. Copper
C. Aluminum alloy
D. Lead
Answer: C
16. Which NACE standard covers field measurement of soil resistivity?
A. SP0169
B. TM0497
C. TM0101
D. TM0215
Answer: B
contact in an electrolyte?
A. Uniform corrosion
B. Galvanic corrosion
C. Crevice corrosion
D. Stress corrosion
Answer: B
Explanation: Galvanic corrosion occurs due to a potential difference between
dissimilar metals in contact within an electrolyte.
2. The most important factor controlling corrosion rate in soils is:
A. pH
B. Oxygen availability
C. Soil resistivity
D. Moisture content
Answer: C
Explanation: Soil resistivity is the key indicator of corrosivity. Low resistivity
generally means higher corrosion risk.
3. The minimum protection potential for steel in soil under cathodic protection
(per NACE SP0169) is:
A. –0.85 V vs Cu/CuSO₄
B. –0.95 V vs Cu/CuSO₄
C. –0.50 V vs Ag/AgCl
D. –1.20 V vs Cu/CuSO₄
Answer: A
Explanation: –0.85 V vs Cu/CuSO₄ is the industry criterion for steel in soil or
water under CP.
4. A coating that exhibits “holidays” is:
A. Too thick
,B. Containing pores or voids
C. Perfectly applied
D. Cathodic disbonded
Answer: B
Explanation: Holidays are small discontinuities in a coating film that expose
bare metal.
5. The main purpose of sacrificial anodes in CP systems is to:
A. Increase coating adhesion
B. Serve as a current source
C. Reduce pH
D. Strengthen pipeline walls
Answer: B
Explanation: Sacrificial anodes (like zinc, magnesium, aluminum) corrode
preferentially, supplying current to protect the structure.
6. Which corrosion form is most associated with stagnant solutions in shielded
areas?
A. Uniform
B. Galvanic
C. Crevice
D. Cavitation
Answer: C
Explanation: Crevice corrosion occurs where electrolyte becomes stagnant,
such as under gaskets or deposits.
7. The Langelier Saturation Index (LSI) is primarily used to:
A. Predict stress corrosion cracking
B. Estimate water scaling/corrosivity
C. Determine coating adhesion strength
D. Measure chloride content
Answer: B
Explanation: LSI indicates if water tends to be scale-forming or corrosive to
steel.
,8. What type of CP uses an external DC power source?
A. Sacrificial anode CP
B. Impressed current CP
C. Passive protection
D. Barrier protection
Answer: B
Explanation: Impressed Current CP (ICCP) applies DC current from a rectifier
to force polarization of the structure.
9. Which factor most affects the selection of coating type for buried pipelines?
A. Operator preference
B. Pipe diameter
C. Soil resistivity and environment
D. Paint color
Answer: C
Explanation: The corrosiveness of soil and environment dictates whether to use
FBE, polyethylene, coal tar, etc.
10. The Pourbaix diagram is a plot of:
A. Stress vs strain
B. pH vs potential
C. Temperature vs corrosion rate
D. Coating adhesion vs thickness
Answer: B
Explanation: Pourbaix diagrams show metal stability, passivation, or corrosion
regions as a function of potential and pH.
11. The main role of coating in corrosion control is to:
A. Eliminate galvanic corrosion completely
B. Provide a physical barrier to environment
C. Supply cathodic protection current
D. Increase electrical conductivity
Answer: B
12. Which of the following is a form of high-temperature corrosion?
A. Hydrogen embrittlement
, B. Oxidation
C. Crevice corrosion
D. Galvanic attack
Answer: B
13. Stray current corrosion is most likely in:
A. Isolated above-ground storage tanks
B. Areas near DC-powered transit systems
C. Marine splash zones
D. Dry desert pipelines
Answer: B
14. A rectifier used in ICCP typically converts:
A. AC → DC
B. DC → AC
C. High voltage DC → low voltage AC
D. DC → pulsed current
Answer: A
15. Which metal is typically used for sacrificial anodes in seawater?
A. Magnesium
B. Copper
C. Aluminum alloy
D. Lead
Answer: C
16. Which NACE standard covers field measurement of soil resistivity?
A. SP0169
B. TM0497
C. TM0101
D. TM0215
Answer: B
