NACE CP2 2025”2026 ACTUAL EXAM REVIEW 150
QUESTIONS AND CORRECT ANSWERS WITH RATIONALES
COVERING THE MOST TESTED QUESTIONS GUARANTEE
A+ GRADE
1. Cathodic protection is primarily used to prevent which type of corrosion?
☐ A. Atmospheric corrosion
☐ B. Fretting corrosion
☐ C. High-temperature corrosion
☑ D. Electrochemical corrosion
Rationale: CP only works on corrosion that involves an electrochemical reaction (metal +
electrolyte).
2. A structure is polarized when:
☑ A. Its potential is shifted negatively from its native potential
☐ B. It is isolated from the soil
☐ C. The coating is fully intact
☐ D. Its potential rises positively
Rationale: CP polarizes a structure more negative relative to its free-corrosion potential.
3. What is the minimum number of reference electrodes required to perform a
close-interval survey?
☑ A. One
☐ B. Two
☐ C. Three
☐ D. Four
Rationale: CIS uses a single portable reference electrode taking sequential readings.
4. Which reference electrode is most commonly used in soil environments?
,☑ A. Copper/Copper Sulfate (Cu/CuSO₄)
☐ B. Silver/Silver Chloride
☐ C. Zinc
☐ D. Platinum
Rationale: Cu/CuSO₄ is standard for soil CP measurement.
5. The −850 mV criterion applies to which reference electrode?
☑ A. Cu/CuSO₄
☐ B. Ag/AgCl seawater
☐ C. Zn seawater
☐ D. MnO₂ soil electrode
Rationale: The NACE −850 mV criterion is defined using Cu/CuSO₄.
6. “Instant off” potential is recorded to remove which error?
☑ A. IR drop error
☐ B. Temperature error
☐ C. Electrode contamination
☐ D. Voltage drift
Rationale: Instant off readings temporarily remove IR drop for true polarization.
7. An anode that dissolves during operation is a:
☐ A. Impressed current anode
☑ B. Sacrificial anode
☐ C. Noble anode
☐ D. Permanent inert anode
Rationale: Galvanic anodes corrode as they provide current.
8. Which metal is NOT used for sacrificial anodes?
☐ A. Zinc
☑ B. Copper
☐ C. Aluminum
,☐ D. Magnesium
Rationale: Copper is too noble and cannot act as a sacrificial anode.
9. Magnesium anodes are best suited for:
☑ A. High-resistivity soils
☐ B. Marine environments
☐ C. Concrete tanks
☐ D. Buried pipelines in wet clay
Rationale: Mg has high driving voltage ideal for high-resistivity environments.
10. A rectifier converts:
☑ A. AC to DC
☐ B. DC to AC
☐ C. DC to pulse waves
☐ D. AC to variable frequency
Rationale: CP requires DC; rectifier supplies it.
11. The output of a rectifier is controlled by:
☐ A. Soil resistivity
☐ B. Pipe diameter
☑ C. Tap settings or electronic controls
☐ D. Anode mass
Rationale: Rectifier settings determine how much voltage/current is applied.
12. Interference current from foreign pipelines typically causes:
☑ A. Accelerated corrosion at discharge areas
☐ B. No effect
☐ C. Reduced coating defects
☐ D. Increased polarization
Rationale: Where stray current leaves a structure, corrosion increases.
, 13. Soil resistivity is measured using the:
☑ A. Wenner four-pin method
☐ B. Kelvin bridge
☐ C. Two-pin continuity test
☐ D. Clamp-on ammeter
Rationale: Wenner 4-pin is standard for soil resistivity.
14. Continuity testing verifies:
☑ A. Electrical connection between segments
☐ B. Coating thickness
☐ C. pH levels
☐ D. Pipe diameter
Rationale: Continuity ensures CP current can reach all parts.
15. Anode bed spacing affects:
☐ A. Pipe diameter
☐ B. Coating color
☑ C. Current distribution
☐ D. Pipe material
Rationale: Spacing determines how evenly current flows.
16. Groundbed resistance decreases when:
☑ A. Anodes are placed deeper
☐ B. Soil is drier
☐ C. Resistivity is higher
☐ D. Cable size is reduced
Rationale: Deep groundbeds reach lower resistivity layers.
17. A polarized potential of −1.80 V vs Cu/CuSO₄ may indicate:
QUESTIONS AND CORRECT ANSWERS WITH RATIONALES
COVERING THE MOST TESTED QUESTIONS GUARANTEE
A+ GRADE
1. Cathodic protection is primarily used to prevent which type of corrosion?
☐ A. Atmospheric corrosion
☐ B. Fretting corrosion
☐ C. High-temperature corrosion
☑ D. Electrochemical corrosion
Rationale: CP only works on corrosion that involves an electrochemical reaction (metal +
electrolyte).
2. A structure is polarized when:
☑ A. Its potential is shifted negatively from its native potential
☐ B. It is isolated from the soil
☐ C. The coating is fully intact
☐ D. Its potential rises positively
Rationale: CP polarizes a structure more negative relative to its free-corrosion potential.
3. What is the minimum number of reference electrodes required to perform a
close-interval survey?
☑ A. One
☐ B. Two
☐ C. Three
☐ D. Four
Rationale: CIS uses a single portable reference electrode taking sequential readings.
4. Which reference electrode is most commonly used in soil environments?
,☑ A. Copper/Copper Sulfate (Cu/CuSO₄)
☐ B. Silver/Silver Chloride
☐ C. Zinc
☐ D. Platinum
Rationale: Cu/CuSO₄ is standard for soil CP measurement.
5. The −850 mV criterion applies to which reference electrode?
☑ A. Cu/CuSO₄
☐ B. Ag/AgCl seawater
☐ C. Zn seawater
☐ D. MnO₂ soil electrode
Rationale: The NACE −850 mV criterion is defined using Cu/CuSO₄.
6. “Instant off” potential is recorded to remove which error?
☑ A. IR drop error
☐ B. Temperature error
☐ C. Electrode contamination
☐ D. Voltage drift
Rationale: Instant off readings temporarily remove IR drop for true polarization.
7. An anode that dissolves during operation is a:
☐ A. Impressed current anode
☑ B. Sacrificial anode
☐ C. Noble anode
☐ D. Permanent inert anode
Rationale: Galvanic anodes corrode as they provide current.
8. Which metal is NOT used for sacrificial anodes?
☐ A. Zinc
☑ B. Copper
☐ C. Aluminum
,☐ D. Magnesium
Rationale: Copper is too noble and cannot act as a sacrificial anode.
9. Magnesium anodes are best suited for:
☑ A. High-resistivity soils
☐ B. Marine environments
☐ C. Concrete tanks
☐ D. Buried pipelines in wet clay
Rationale: Mg has high driving voltage ideal for high-resistivity environments.
10. A rectifier converts:
☑ A. AC to DC
☐ B. DC to AC
☐ C. DC to pulse waves
☐ D. AC to variable frequency
Rationale: CP requires DC; rectifier supplies it.
11. The output of a rectifier is controlled by:
☐ A. Soil resistivity
☐ B. Pipe diameter
☑ C. Tap settings or electronic controls
☐ D. Anode mass
Rationale: Rectifier settings determine how much voltage/current is applied.
12. Interference current from foreign pipelines typically causes:
☑ A. Accelerated corrosion at discharge areas
☐ B. No effect
☐ C. Reduced coating defects
☐ D. Increased polarization
Rationale: Where stray current leaves a structure, corrosion increases.
, 13. Soil resistivity is measured using the:
☑ A. Wenner four-pin method
☐ B. Kelvin bridge
☐ C. Two-pin continuity test
☐ D. Clamp-on ammeter
Rationale: Wenner 4-pin is standard for soil resistivity.
14. Continuity testing verifies:
☑ A. Electrical connection between segments
☐ B. Coating thickness
☐ C. pH levels
☐ D. Pipe diameter
Rationale: Continuity ensures CP current can reach all parts.
15. Anode bed spacing affects:
☐ A. Pipe diameter
☐ B. Coating color
☑ C. Current distribution
☐ D. Pipe material
Rationale: Spacing determines how evenly current flows.
16. Groundbed resistance decreases when:
☑ A. Anodes are placed deeper
☐ B. Soil is drier
☐ C. Resistivity is higher
☐ D. Cable size is reduced
Rationale: Deep groundbeds reach lower resistivity layers.
17. A polarized potential of −1.80 V vs Cu/CuSO₄ may indicate:
