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(CP3) Exam
Question 1. Which of the following best describes the primary function of cathodic protection? A) To increase the conductivity of the metal B) To prevent or reduce corrosion C) To increase the temperature of the metal D) To enhance metallurgical properties Answer: B Explanation: Cathodic protection works by making the protected metal the cathode of an electrochemical cell, thereby reducing or preventing its corrosion. Question 2. What is the main role of an anode in a cathodic protection system?
(CP3) Exam
A) To act as a current collector B) To supply electrons to the cathode C) To provide a physical barrier to corrosion D) To insulate the structure Answer: B Explanation: The anode sacrifices itself by corroding instead of the protected metal, thus supplying electrons to the cathode. Question 3. Which equation is used to calculate the cell potential in electrochemical cells? A) Faraday’s Law B) Ohm’s Law C) Nernst Equation
(CP3) Exam
Explanation: Pourbaix diagrams plot electrochemical stability, showing where a metal is immune, corroding, or passive. Question 5. Which of the following is NOT a type of corrosion? A) Uniform corrosion B) Pitting corrosion C) Galvanic corrosion D) Elastic corrosion Answer: D Explanation: Elastic corrosion is not a recognized corrosion type; the others are well-known corrosion mechanisms. Question 6. What does Ohm’s Law state?
(CP3) Exam
A) V = IR
B) V = I/R
C) V = R/I
D) V = I+R
Answer: A Explanation: Ohm’s Law states that voltage (V) is the product of current (I) and resistance (R). Question 7. What is the primary advantage of using magnesium as a sacrificial anode? A) High density B) High driving voltage C) Low cost
(CP3) Exam
Explanation: Zinc anodes are commonly used in seawater due to their suitable electrochemical properties. Question 9. What is the main purpose of a rectifier in an Impressed Current Cathodic Protection (ICCP) system? A) To measure voltage B) To supply direct current C) To increase AC voltage D) To decrease resistance Answer: B Explanation: Rectifiers convert AC to DC, which is required for ICCP systems.
(CP3) Exam
Question 10. Which of the following is an advantage of using mixed metal oxide (MMO) anodes? A) High consumption rate B) Low electrical conductivity C) Long service life D) Low output voltage Answer: C Explanation: MMO anodes are valued for their long service life and stability in ICCP systems. Question 11. What is the function of a reference electrode in a pipe-to- soil potential survey? A) To supply current
(CP3) Exam
Answer: D Explanation: The copper/copper sulfate electrode is standard for soil potential measurements. Question 13. What does a close-interval survey (CIS) detect along a pipeline? A) Pipe diameter variations B) Potential drops along the coating C) Changes in soil composition D) Pipe wall thickness Answer: B Explanation: CIS detects potential drops, indicating coating defects or inadequate protection.
(CP3) Exam
Question 14. Which current measurement device is best suited for large CP currents? A) Voltmeter B) Clamp ammeter C) Shunt resistor D) Galvanometer Answer: C Explanation: Shunt resistors allow accurate measurement of large currents by measuring voltage drop across a known resistance. Question 15. What is the typical purpose of using the Wenner four-pin method?
(CP3) Exam
D) Intergranular corrosion Answer: B Explanation: Coating holidays expose small metal areas, making them susceptible to pitting corrosion. Question 17. Why is current density important in CP system design? A) It determines the anode material B) It affects the voltage drop C) It ensures adequate protection D) It increases corrosion rate Answer: C Explanation: Adequate current density is necessary to achieve sufficient protection of the metal surface.
(CP3) Exam
Question 18. Which of the following is a characteristic of galvanic anode systems? A) Require an external power source B) Anode corrodes instead of the structure C) Use of high silicon cast iron anodes D) High output voltage Answer: B Explanation: In galvanic systems, the anode sacrifices itself, protecting the structure without external power. Question 19. Which parameter is most critical when selecting a cable for buried CP systems?
(CP3) Exam
D) No monitoring required Answer: B Explanation: ICCP systems depend on an external DC power source, making power reliability essential. Question 21. Which factor has the greatest impact on the resistance of a groundbed? A) Anode material B) Soil resistivity C) Cable length D) Anode weight Answer: B
(CP3) Exam
Explanation: Soil resistivity is the primary determinant of groundbed resistance. Question 22. What is the typical use of a deep well groundbed? A) For shallow pipeline protection B) When surface space is limited C) To protect internal tank surfaces D) For temporary installations Answer: B Explanation: Deep well groundbeds are used when surface area is restricted, providing a low-resistance ground path. Question 23. In a CP circuit, where is the protective current measured?
(CP3) Exam
D) To avoid current measurement Answer: B Explanation: Distributed anode beds help maintain uniform potential and minimize voltage drop along long pipelines. Question 25. What is measured during an ON/OFF potential survey? A) The potential with current applied and interrupted B) The pipe diameter C) Soil resistivity only D) The coating thickness Answer: A
(CP3) Exam
Explanation: ON/OFF surveys measure structure potential with CP current on and immediately after it is interrupted, isolating true polarization. Question 26. What does a negative pipe-to-soil potential indicate? A) The pipe is anodic B) The pipe is cathodic C) The pipe is unprotected D) The pipe is grounded Answer: B Explanation: A negative pipe-to-soil potential means the pipe is acting as a cathode, which is the goal of CP.
