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What is the standard -850 mV criterion for cathodic protection of buried steel as specified in NACE SP0169, and what reference electrode is it measured against?

-850 mV measured to a saturated Ag/AgCl reference electrode

-850 mV (polarized or with IR drop considered) measured to a saturated copper/copper sulfate (CSE) reference electrode

-850 mV measured to a standard hydrogen electrode (SHE)

-850 mV measured to a zinc reference electrode

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2026 Statistics

Key Facts: AMPP CP1 Tester Exam

100

Exam Questions (81 scored + 19 unscored)

AMPP CP1 Exam Preparation Guide (Nov 2025)

3 hours

Exam Time (effective Nov 21, 2025)

AMPP CP1 EPG

$275

CBT Exam Fee (exam-only / retake)

AMPP 2024 Exam Fees

-850 mV CSE

Polarized CP Criterion

NACE SP0169

100 mV

Polarization Shift Criterion

NACE SP0169

3 years

Certification Validity

AMPP renewal policy

The AMPP CP1 Cathodic Protection Tester exam (effective Nov 21, 2025) contains 100 multiple-choice questions (81 scored + 19 unscored), a 3-hour time limit, and costs $275 via CBT at Pearson VUE. It is the entry-level CP credential from AMPP (formerly NACE), designed for field personnel who observe and measure CP systems under supervision. The body of knowledge covers corrosion fundamentals (30-40%), equipment and equipment management (5-15%), installation and field measurement (40-50%), industry practices (1-10%), and safety. CP1 certification is valid for 3 years and is the prerequisite background for the CP2 Cathodic Protection Technician credential.

Sample AMPP CP1 Tester Practice Questions

Try these sample questions to test your AMPP CP1 Tester exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1What is the standard -850 mV criterion for cathodic protection of buried steel as specified in NACE SP0169, and what reference electrode is it measured against?

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

Explanation: 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 because it is rugged, inexpensive, and reproducible.

2A CP tester measures a pipe-to-soil potential of -900 mV vs CSE with the rectifier ON. After instant-off, the potential reads -780 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 120 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

Explanation: The difference between the 'on' (-900 mV) and the instant-off (-780 mV) is 120 mV of IR drop in the measurement circuit. The polarized (instant-off) potential of -780 mV is less negative than -850 mV, so the -850 mV polarized criterion is NOT met. The -850 mV criterion in NACE SP0169 is based on the polarized potential with IR drop removed.

3Which of the following is the PRIMARY purpose of the instant-off (interrupt) technique when measuring pipe-to-soil potential?

A.To reduce meter battery consumption

B.To eliminate the IR drop component from the measurement so the polarized potential can be read

C.To measure AC voltage separately from DC

D.To verify rectifier efficiency

Explanation: The instant-off technique interrupts the CP current source momentarily so the voltage drop (IR drop) through the electrolyte and other resistive elements disappears almost immediately, while the polarization of the metal decays much more slowly. Reading the potential in that brief 'off' instant yields a value very close to the true polarized structure-to-electrolyte potential, which is what the -850 mV polarized criterion requires.

4A CP tester reads a pipe-to-soil potential of -0.780 V using a silver/silver chloride (Ag/AgCl, saturated KCl) reference electrode. Approximately what is the equivalent potential in mV vs CSE?

A.-661 mV

B.-780 mV

C.-899 mV

D.-960 mV

Explanation: A saturated Ag/AgCl reference has a potential of about +0.199 V vs SHE, while a copper/copper sulfate electrode (CSE) is about +0.318 V vs SHE. The difference is approximately 0.119 V (≈120 mV). Readings taken vs Ag/AgCl must be made more negative by ~120 mV to convert to CSE: -780 mV - 119 mV ≈ -899 mV vs CSE.

5What is the MOST common electrolyte used in a portable copper/copper sulfate reference electrode?

A.Distilled water

B.A saturated copper sulfate (CuSO4) solution with excess solid crystals

C.Sodium chloride solution

D.Potassium chloride gel

Explanation: A portable CSE uses a saturated copper sulfate solution with excess solid CuSO4 crystals, which keeps the solution saturated as temperature and usage change. The copper rod in contact with this saturated solution provides a stable, reproducible potential of about +0.318 V vs SHE, making it the standard reference for soil CP measurements.

6Which reference electrode is MOST appropriate for cathodic protection measurements on an offshore platform submerged in seawater?

A.Copper/copper sulfate (CSE)

B.Silver/silver chloride (Ag/AgCl) in seawater

C.Zinc (Zn) in fresh water

D.Calomel

Explanation: Silver/silver chloride electrodes using the seawater itself as the electrolyte (no filling solution) are the standard for marine and offshore CP because they are chemically stable in chloride-rich water and avoid the contamination problems a copper sulfate cell would have in saline conditions. The -800 mV criterion in seawater is commonly expressed versus Ag/AgCl seawater reference.

7The 100 mV polarization decay criterion in NACE SP0169 is used to demonstrate adequate cathodic protection. How is it measured?

A.The 'on' potential is 100 mV more negative than the native potential

B.The structure is depolarized and the polarized potential decays by at least 100 mV from the instant-off toward the native potential

C.The native potential is 100 mV more negative than -850 mV

D.Hourly potential readings differ by less than 100 mV

Explanation: The 100 mV polarization shift criterion is demonstrated by recording the instant-off (polarized) potential, then allowing the structure to depolarize (current off) and recording the final depolarized potential. A shift of at least 100 mV in the positive direction (less negative) confirms at least 100 mV of polarization was provided by CP. This is useful where the -850 mV criterion is impractical, such as dissimilar metals or elevated temperatures.

8Which of the following is the PRIMARY safety hazard when interrupting a rectifier feeding a pipeline with coating faults near a high-voltage AC transmission line?

A.Radio frequency interference

B.Induced AC voltage on the pipeline becoming a shock hazard

C.Rectifier overheating

D.CSE contamination

Explanation: Parallel co-location with HVAC transmission lines induces AC voltage on the pipeline (capacitive, inductive, and conductive coupling). With the rectifier on, the CP bond can sometimes drain induced AC through the grounding system; interrupting may leave the AC voltage higher and present a shock hazard at test stations. NACE SP0177 provides AC safety thresholds (personnel safety typically at 15 V AC and below).

9What is the primary function of a shunt in a CP test station or rectifier?

A.Provide a reference electrode connection

B.Allow current measurement by reading the voltage drop across a known resistance

C.Protect against lightning

D.Isolate the structure from the anode bed

Explanation: A shunt is a precision low-value resistor whose voltage drop is proportional to the current flowing through it (V=IR). A CP tester uses a voltmeter to read the millivolt drop across the shunt and then applies the shunt rating (for example, 10 A / 50 mV means 0.2 A/mV) to determine the current. This avoids breaking the circuit to insert an ammeter.

10Ohm's Law states the relationship between which three quantities?

A.Power, time, and energy

B.Voltage, current, and resistance

C.Voltage, frequency, and capacitance

D.Current, inductance, and reactance

Explanation: Ohm's Law: V = I × R, where V is voltage (volts), I is current (amps), and R is resistance (ohms). It is the single most important electrical relationship used by CP testers — for shunt calculations, rectifier output calculations, and IR-drop estimates.

About the AMPP CP1 Tester Exam

The AMPP CP1 Cathodic Protection Tester certification is the entry-level credential in AMPP's Cathodic Protection program. It validates the ability to observe, record, and measure the effectiveness of galvanic and impressed-current CP systems on underground and submerged metallic structures. Certification requires the CP1 Practical (hands-on) Exam delivered during the CP1 Course plus the CP1 Theory Exam (NACE-CP1-001, computer-based at Pearson VUE), successful completion of Ethics for the Corrosion Professional, and an approved application. AMPP recommends at least 6 months of CP-related work experience before attempting certification.

Assessment

100 multiple-choice questions (81 scored + 19 unscored pretest items); closed-book with a limited reference PDF (effective Nov 21, 2025)

Time Limit

3 hours (includes 4 min NDA + 6 min tutorial)

Passing Score

Pass/fail cut score set by AMPP subject matter experts (criterion-referenced)

Exam Fee

$275 (CBT exam-only / retake); exam fee is included in the CP1 Course fee for candidates attending the course (AMPP (Association for Materials Protection and Performance))

AMPP CP1 Tester Exam Content Outline

40-50%

Installation and Field Measurement

Pipe-to-soil potential measurement, instant-off technique, IR-drop mitigation, CIPS, DCVG, soil resistivity (Wenner 4-pin, ASTM G57), coupon use, and test-station commissioning

30-40%

Fundamentals of Corrosion

Electrochemical cells, Ohm's law, Kirchhoff's laws, Faraday's law, CP theory (galvanic vs impressed current), native and polarized potentials, shielding, and stray current basics

5-15%

Equipment and Equipment Management

High-input-impedance voltmeters, clamp-on ammeters, shunts, reference electrodes (CSE, Ag/AgCl, Zn), interrupters, pipe locators, and meter calibration

1-10%

Industry Practices and Requirements

NACE SP0169, SP0177, SP0286, TM0497, TM0102, -850 mV polarized criterion, 100 mV polarization shift, and field documentation

1-10%

Safety

Electrical safety at rectifiers (NFPA 70E, LOTO), induced AC hazards near HVAC lines, confined-space and gas-atmosphere hazards at test boxes, and stop-work authority

How to Pass the AMPP CP1 Tester Exam

What You Need to Know

Passing score: Pass/fail cut score set by AMPP subject matter experts (criterion-referenced)
Assessment: 100 multiple-choice questions (81 scored + 19 unscored pretest items); closed-book with a limited reference PDF (effective Nov 21, 2025)
Time limit: 3 hours (includes 4 min NDA + 6 min tutorial)
Exam fee: $275 (CBT exam-only / retake); exam fee is included in the CP1 Course fee for candidates attending the course

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

AMPP CP1 Tester Study Tips from Top Performers

1Memorize the standard reference electrode potentials vs SHE: Cu/CuSO4 = +0.318 V, Ag/AgCl (sat KCl) = +0.199 V, Zn ≈ -1.10 V, and practice converting readings between references

2Master NACE SP0169 criteria: -850 mV polarized vs CSE (with voltage drop considered) and the 100 mV polarization shift criterion

3Understand IR drop and why the instant-off technique is needed to obtain a valid polarized potential

4Know Ohm's law and how to read a shunt (e.g., 10 A / 50 mV ratio), including common rectifier troubleshooting patterns (open vs short circuit)

5Practice Wenner 4-pin soil resistivity calculations: ρ = 2πaR; know that low-resistivity soils (<1,000 ohm-cm) are most corrosive

6Study the difference between galvanic anodes (Mg, Zn, Al-Zn-In) and impressed-current anodes (MMO, graphite, HSCI) and when each is used

7Review CIPS and DCVG basics: their purposes, typical survey intervals (1-3 m), and what they reveal about coating condition

8Know safety hazards at rectifiers (LOTO / NFPA 70E), AC induction near HVAC lines (SP0177 15 V threshold), and gas atmospheres in test boxes

Frequently Asked Questions

What is the AMPP CP1 Cathodic Protection Tester certification?

AMPP CP1 Cathodic Protection Tester is the entry-level credential in AMPP's Cathodic Protection certification program (formerly NACE CP1). It validates foundational ability to observe, record, and measure the effectiveness of galvanic and impressed-current CP systems on buried pipelines, tanks, and other underground or submerged metallic structures. CP1 is the gateway to the higher-level CP2 Technician, CP3 Technologist, and CP4 Specialist credentials.

How many questions are on the CP1 Theory exam and how long is it?

Effective November 21, 2025, the CP1 Theory Exam (NACE-CP1-001) contains 100 multiple-choice questions — 81 scored plus 19 unscored pretest items — with a 3-hour time limit (including 4 minutes for the non-disclosure agreement and 6 minutes for the system tutorial). It is delivered as a closed-book computer-based test at Pearson VUE test centers, with a limited reference PDF available inside the test interface for select equations and conversions.

What does CP1 cost and how is it scheduled?

The CP1 Theory Exam costs $275 (CBT) when purchased as an exam-only or a retake per the June 2024 AMPP fee schedule. For candidates attending the CP1 Course, the exam fee is included in the course fee. Scheduling is done through Pearson VUE after AMPP application approval.

What are the prerequisites and work experience requirements for CP1?

There are no required prerequisites to attend the CP1 Course. AMPP strongly recommends 6 months of CP-related work experience, a high school diploma or GED, and basic math skills. For CP1 certification, candidates must pass the CP1 Practical (hands-on) Exam delivered during the course, pass the CP1 Theory Exam at Pearson VUE, complete the Ethics for the Corrosion Professional eCourse (or equivalent), and submit an approved CP1 application.

What topics are covered on the CP1 Theory exam?

The CP1 body of knowledge covers five domains: Fundamentals of Corrosion (30-40%) including electrochemistry, Ohm's law, Faraday's law, and CP theory; Equipment and Equipment Management (5-15%) including voltmeters, ammeters, shunts, reference electrodes, and interrupters; Installation and Field Measurement (40-50%) including pipe-to-soil potential, soil resistivity, CIPS, DCVG, and coupons; Industry Practices and Requirements (1-10%); and Safety (electrical, AC induction, gas atmospheres).

How does CP1 differ from CP2, CP3, and CP4?

CP1 Tester observes, records, and measures CP system effectiveness (entry-level field personnel). CP2 Technician is intermediate — testing, troubleshooting, and supervising installation of CP systems. CP3 Technologist interprets field data and performs design calculations. CP4 Specialist is the highest level, covering advanced CP design, attenuation calculations, interference mitigation, and complex applications including offshore, reinforced concrete, and internal tank CP.

How long is CP1 certification valid and how is it renewed?

CP1 certification is valid for 3 years. Renewal requires an approved recertification application, at least 1.5 years of CP work experience during the most recent 3-year period, the required Professional Development Hours (PDHs), and payment of a non-refundable processing fee. Candidates track their PDHs via the AMPP My Certification Portal.