,AMPP CP1 Exam | Cathodic Protection Specialist (2026)
Q&A
1. Which of the following best describes the primary goal of a cathodic protection (CP)
system in corrosion control?
A) To increase the corrosion rate of the protected structure for uniform metal loss
B) To convert the protected metallic structure into a cathode, thereby reducing its corrosion
C) To increase the electrical resistance of the soil around the structure
D) To create an electrical connection between two dissimilar metals
Correct Answer: To convert the protected metallic structure into a cathode, thereby
reducing its corrosion
Rationale: Cathodic protection reduces corrosion by making the entire structure a cathode,
preventing anodic metal dissolution. The protected metal becomes the cathode of a
corrosion cell, which stops the oxidation reaction that causes metal loss. The other options
describe incorrect mechanisms.
2. In an electrochemical corrosion cell, oxidation occurs at which electrode?
A) The cathode
B) The anode
C) The reference electrode
D) The electrolyte
Correct Answer: The anode
Rationale: Oxidation (loss of electrons) occurs at the anode, which is the site of metal
dissolution and corrosion. Reduction (gain of electrons) occurs at the cathode. Reference
electrodes measure potential but do not participate in the corrosion reaction.
,3. What is the standard -850 mV criterion for cathodic protection of buried steel as specified
in NACE SP0169, and against which reference electrode is it measured?
A) -850 mV measured to a saturated Ag/AgCl reference electrode
B) -850 mV (polarized or with IR drop considered) measured to a saturated copper/copper
sulfate (CSE) reference electrode
C) -850 mV measured to a standard hydrogen electrode (SHE)
D) -850 mV measured to a zinc reference electrode
Correct Answer: -850 mV (polarized or with IR drop considered) measured to a saturated
copper/copper sulfate (CSE) reference electrode
Rationale: NACE SP0169 specifies a -850 mV criterion for protected buried carbon steel
measured with a saturated copper/copper sulfate reference electrode (CSE), with voltage
drops other than those across the structure-to-electrolyte boundary considered. The CSE
(+0.318 V vs SHE) is the standard field reference for soil applications.
4. According to Ohm's Law, if the voltage in a circuit is 12 V and the resistance is 4 Ω, what is
the current?
A) 48 A
B) 3 A
C) 0.33 A
D) 16 A
Correct Answer: 3 A
Rationale: Ohm's Law states that V = I × R. Therefore, I = V / R = 12 V / 4 Ω = 3 A. The other
options result from incorrect application of the formula.
5. A CP tester measures a pipe-to-soil potential of -920 mV vs CSE with the rectifier ON. After
instant-off, the potential reads -810 mV vs CSE. Which of the following statements is MOST
accurate?
, A) The structure meets the -850 mV polarized criterion
B) The IR drop is 110 mV and the instant-off potential does not meet the -850 mV polarized
criterion
C) The structure is overprotected
D) The CSE reference is contaminated
Correct Answer: The IR drop is 110 mV and the instant-off potential does not meet the -850
mV polarized criterion
Rationale: The difference between the 'on' (-920 mV) and the instant-off (-810 mV) is 110
mV of IR drop in the measurement circuit. The polarized (instant-off) potential of -810 mV is
less negative than -850 mV, so the structure does not meet the criterion.
6. What is the primary function of a shunt in a CP circuit?
A) To measure current flow by providing a known low-resistance path
B) To convert AC to DC power
C) To isolate the structure from stray currents
D) To increase the voltage output of a rectifier
Correct Answer: To measure current flow by providing a known low-resistance path
Rationale: A shunt is a precision resistor of known low resistance placed in series with a
circuit. By measuring the voltage drop across the shunt and applying Ohm's Law, the current
can be calculated. This is commonly used to measure rectifier or bond currents.
7. A technician measures a pipeline potential of -820 mV vs Cu/CuSO₄. The soil is dry with
high resistivity. What is the most appropriate conclusion?
A) The pipeline is fully protected and no action is needed
B) The measurement likely contains significant IR drop error and the true potential may be
less negative
Q&A
1. Which of the following best describes the primary goal of a cathodic protection (CP)
system in corrosion control?
A) To increase the corrosion rate of the protected structure for uniform metal loss
B) To convert the protected metallic structure into a cathode, thereby reducing its corrosion
C) To increase the electrical resistance of the soil around the structure
D) To create an electrical connection between two dissimilar metals
Correct Answer: To convert the protected metallic structure into a cathode, thereby
reducing its corrosion
Rationale: Cathodic protection reduces corrosion by making the entire structure a cathode,
preventing anodic metal dissolution. The protected metal becomes the cathode of a
corrosion cell, which stops the oxidation reaction that causes metal loss. The other options
describe incorrect mechanisms.
2. In an electrochemical corrosion cell, oxidation occurs at which electrode?
A) The cathode
B) The anode
C) The reference electrode
D) The electrolyte
Correct Answer: The anode
Rationale: Oxidation (loss of electrons) occurs at the anode, which is the site of metal
dissolution and corrosion. Reduction (gain of electrons) occurs at the cathode. Reference
electrodes measure potential but do not participate in the corrosion reaction.
,3. What is the standard -850 mV criterion for cathodic protection of buried steel as specified
in NACE SP0169, and against which reference electrode is it measured?
A) -850 mV measured to a saturated Ag/AgCl reference electrode
B) -850 mV (polarized or with IR drop considered) measured to a saturated copper/copper
sulfate (CSE) reference electrode
C) -850 mV measured to a standard hydrogen electrode (SHE)
D) -850 mV measured to a zinc reference electrode
Correct Answer: -850 mV (polarized or with IR drop considered) measured to a saturated
copper/copper sulfate (CSE) reference electrode
Rationale: NACE SP0169 specifies a -850 mV criterion for protected buried carbon steel
measured with a saturated copper/copper sulfate reference electrode (CSE), with voltage
drops other than those across the structure-to-electrolyte boundary considered. The CSE
(+0.318 V vs SHE) is the standard field reference for soil applications.
4. According to Ohm's Law, if the voltage in a circuit is 12 V and the resistance is 4 Ω, what is
the current?
A) 48 A
B) 3 A
C) 0.33 A
D) 16 A
Correct Answer: 3 A
Rationale: Ohm's Law states that V = I × R. Therefore, I = V / R = 12 V / 4 Ω = 3 A. The other
options result from incorrect application of the formula.
5. A CP tester measures a pipe-to-soil potential of -920 mV vs CSE with the rectifier ON. After
instant-off, the potential reads -810 mV vs CSE. Which of the following statements is MOST
accurate?
, A) The structure meets the -850 mV polarized criterion
B) The IR drop is 110 mV and the instant-off potential does not meet the -850 mV polarized
criterion
C) The structure is overprotected
D) The CSE reference is contaminated
Correct Answer: The IR drop is 110 mV and the instant-off potential does not meet the -850
mV polarized criterion
Rationale: The difference between the 'on' (-920 mV) and the instant-off (-810 mV) is 110
mV of IR drop in the measurement circuit. The polarized (instant-off) potential of -810 mV is
less negative than -850 mV, so the structure does not meet the criterion.
6. What is the primary function of a shunt in a CP circuit?
A) To measure current flow by providing a known low-resistance path
B) To convert AC to DC power
C) To isolate the structure from stray currents
D) To increase the voltage output of a rectifier
Correct Answer: To measure current flow by providing a known low-resistance path
Rationale: A shunt is a precision resistor of known low resistance placed in series with a
circuit. By measuring the voltage drop across the shunt and applying Ohm's Law, the current
can be calculated. This is commonly used to measure rectifier or bond currents.
7. A technician measures a pipeline potential of -820 mV vs Cu/CuSO₄. The soil is dry with
high resistivity. What is the most appropriate conclusion?
A) The pipeline is fully protected and no action is needed
B) The measurement likely contains significant IR drop error and the true potential may be
less negative
