CP4 – Cathodic Protection Specialist
Certification Exam
1. The primary objective of cathodic protection is to:
A. Increase soil resistivity
B. Reduce corrosion rate to an acceptable level
C. Strengthen pipeline wall thickness
D. Remove oxygen from the electrolyte
Answer: B
Explanation: CP reduces metal corrosion by shifting potential
to a more negative, protective value.
2. The -850 mV (Cu/CuSO₄) criterion for steel in soil applies
primarily to:
A. Atmospheric corrosion
B. Internal pipeline corrosion
C. External buried structures
D. Aboveground tanks
Answer: C
Explanation: The -850 mV ON potential criterion is widely
used for buried steel CP effectiveness.
3. A sacrificial anode system uses which principle?
A. Water cooling
B. Galvanic coupling
,C. Electrochemical coating
D. Ion exchange
Answer: B
Explanation: A more active metal (anode) corrodes
preferentially to protect the structure.
4. Which anode material is most common in seawater
impressed current systems?
A. Magnesium
B. Zinc
C. Graphite
D. MMO/Ti (Mixed Metal Oxide on Titanium)
Answer: D
Explanation: MMO/Ti anodes provide long life and high
efficiency in seawater.
5. The polarization of a protected structure is defined as:
A. Total circuit resistance
B. Shift from native potential due to CP
C. Change in pipe thickness
D. Amount of coating damage
Answer: B
Explanation: Polarization is the change in structure potential
achieved by cathodic protection.
,6. Which measurement distinguishes IR-free CP potential?
A. ON potential
B. Soil resistivity
C. Instant OFF potential
D. Anode open-circuit potential
Answer: C
Explanation: Instant OFF removes IR drop from current flow,
giving a more accurate structure potential.
7. Soil resistivity is most commonly measured using:
A. Wenner 4-pin method
B. Potential survey
C. ER probe
D. DCVG
Answer: A
Explanation: Wenner method is the standard technique for
soil resistivity profiling.
8. The primary function of a rectifier in an impressed current
system is to:
A. Convert AC to DC
B. Increase soil pH
C. Pump electrolyte
D. Provide cathodic discharge
, Answer: A
Explanation: Rectifiers convert AC to DC to drive current to
the structure.
9. A coating holiday is best described as:
A. A surface roughness zone
B. A defect in coating exposing bare metal
C. An area of overprotection
D. A type of anode
Answer: B
Explanation: Holidays expose bare steel, increasing CP
current demand.
10. CP interference can occur when:
A. Structures are deeply buried
B. CP current affects nearby metallic structures
C. Soil resistivity is high
D. Coating is high quality
Answer: B
Explanation: Stray currents may leave adjacent structures,
causing accelerated corrosion.
11. The primary corrosion cell in soil involves:
A. Two metals in direct contact
B. Oxygen gradient in soil
Certification Exam
1. The primary objective of cathodic protection is to:
A. Increase soil resistivity
B. Reduce corrosion rate to an acceptable level
C. Strengthen pipeline wall thickness
D. Remove oxygen from the electrolyte
Answer: B
Explanation: CP reduces metal corrosion by shifting potential
to a more negative, protective value.
2. The -850 mV (Cu/CuSO₄) criterion for steel in soil applies
primarily to:
A. Atmospheric corrosion
B. Internal pipeline corrosion
C. External buried structures
D. Aboveground tanks
Answer: C
Explanation: The -850 mV ON potential criterion is widely
used for buried steel CP effectiveness.
3. A sacrificial anode system uses which principle?
A. Water cooling
B. Galvanic coupling
,C. Electrochemical coating
D. Ion exchange
Answer: B
Explanation: A more active metal (anode) corrodes
preferentially to protect the structure.
4. Which anode material is most common in seawater
impressed current systems?
A. Magnesium
B. Zinc
C. Graphite
D. MMO/Ti (Mixed Metal Oxide on Titanium)
Answer: D
Explanation: MMO/Ti anodes provide long life and high
efficiency in seawater.
5. The polarization of a protected structure is defined as:
A. Total circuit resistance
B. Shift from native potential due to CP
C. Change in pipe thickness
D. Amount of coating damage
Answer: B
Explanation: Polarization is the change in structure potential
achieved by cathodic protection.
,6. Which measurement distinguishes IR-free CP potential?
A. ON potential
B. Soil resistivity
C. Instant OFF potential
D. Anode open-circuit potential
Answer: C
Explanation: Instant OFF removes IR drop from current flow,
giving a more accurate structure potential.
7. Soil resistivity is most commonly measured using:
A. Wenner 4-pin method
B. Potential survey
C. ER probe
D. DCVG
Answer: A
Explanation: Wenner method is the standard technique for
soil resistivity profiling.
8. The primary function of a rectifier in an impressed current
system is to:
A. Convert AC to DC
B. Increase soil pH
C. Pump electrolyte
D. Provide cathodic discharge
, Answer: A
Explanation: Rectifiers convert AC to DC to drive current to
the structure.
9. A coating holiday is best described as:
A. A surface roughness zone
B. A defect in coating exposing bare metal
C. An area of overprotection
D. A type of anode
Answer: B
Explanation: Holidays expose bare steel, increasing CP
current demand.
10. CP interference can occur when:
A. Structures are deeply buried
B. CP current affects nearby metallic structures
C. Soil resistivity is high
D. Coating is high quality
Answer: B
Explanation: Stray currents may leave adjacent structures,
causing accelerated corrosion.
11. The primary corrosion cell in soil involves:
A. Two metals in direct contact
B. Oxygen gradient in soil
