PHMSA Corrosion Control of Pipeline
Systems Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. Which of the following is the primary cause of external corrosion on
pipelines?
A) High operating pressure
B) Soil moisture and chemistry
C) Pipeline vibration
D) Cathodic protection systems
B) Soil moisture and chemistry
Rationale: External corrosion is primarily influenced by soil environment
factors such as moisture, pH, resistivity, and presence of electrolytes.
2. What is the main purpose of cathodic protection (CP) on pipelines?
A) Increase pipeline pressure
B) Prevent external corrosion
C) Control internal flow velocity
D) Detect leaks
B) Prevent external corrosion
Rationale: CP works by making the pipeline the cathode of an
electrochemical cell, preventing metal loss from corrosion.
3. What type of current is commonly used in impressed current cathodic
protection (ICCP) systems?
, A) Alternating current (AC)
B) Direct current (DC)
C) Pulsed current
D) None
B) Direct current (DC)
Rationale: ICCP systems use DC to drive electrons to the pipeline to
suppress corrosion.
4. Which coating type provides the primary defense against external
pipeline corrosion?
A) Asphalt coating
B) Fusion-bonded epoxy (FBE)
C) Galvanic coating
D) Paint only
B) Fusion-bonded epoxy (FBE)
Rationale: Coatings like FBE provide a barrier against moisture and
corrosive elements, reducing external corrosion risk.
5. A pipeline operating in soil with low resistivity is at risk of:
A) Internal corrosion
B) External corrosion
C) Mechanical failure
D) Flow turbulence
B) External corrosion
Rationale: Low soil resistivity increases the rate of electrochemical
reactions, accelerating external corrosion.
6. The purpose of a reference electrode in CP testing is to:
A) Measure pipeline diameter
B) Measure pipe-to-soil potential
C) Apply protective coatings
D) Detect cracks
, B) Measure pipe-to-soil potential
Rationale: Reference electrodes measure the electrochemical potential,
ensuring CP is adequate.
7. Which of the following metals is commonly used for sacrificial anodes
in pipelines?
A) Copper
B) Magnesium
C) Stainless steel
D) Aluminum
B) Magnesium
Rationale: Magnesium has a more negative potential than steel, allowing
it to corrode preferentially and protect the pipeline.
8. A “holiday” in pipeline coating refers to:
A) A seasonal maintenance shutdown
B) A defect in coating exposing steel
C) A cathodic protection test point
D) A leak detection sensor
B) A defect in coating exposing steel
Rationale: Holidays are coating flaws where steel is exposed, creating a
localized corrosion risk.
9. Which parameter indicates sufficient CP protection on a bare steel
pipe in soil?
A) -0.85 V CSE or more negative
B) 0 V
C) +0.85 V CSE
D) Any positive voltage
A) -0.85 V CSE or more negative
Rationale: -0.85 volts vs. copper/copper sulfate electrode (CSE) is the
standard threshold indicating adequate cathodic protection.
Systems Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. Which of the following is the primary cause of external corrosion on
pipelines?
A) High operating pressure
B) Soil moisture and chemistry
C) Pipeline vibration
D) Cathodic protection systems
B) Soil moisture and chemistry
Rationale: External corrosion is primarily influenced by soil environment
factors such as moisture, pH, resistivity, and presence of electrolytes.
2. What is the main purpose of cathodic protection (CP) on pipelines?
A) Increase pipeline pressure
B) Prevent external corrosion
C) Control internal flow velocity
D) Detect leaks
B) Prevent external corrosion
Rationale: CP works by making the pipeline the cathode of an
electrochemical cell, preventing metal loss from corrosion.
3. What type of current is commonly used in impressed current cathodic
protection (ICCP) systems?
, A) Alternating current (AC)
B) Direct current (DC)
C) Pulsed current
D) None
B) Direct current (DC)
Rationale: ICCP systems use DC to drive electrons to the pipeline to
suppress corrosion.
4. Which coating type provides the primary defense against external
pipeline corrosion?
A) Asphalt coating
B) Fusion-bonded epoxy (FBE)
C) Galvanic coating
D) Paint only
B) Fusion-bonded epoxy (FBE)
Rationale: Coatings like FBE provide a barrier against moisture and
corrosive elements, reducing external corrosion risk.
5. A pipeline operating in soil with low resistivity is at risk of:
A) Internal corrosion
B) External corrosion
C) Mechanical failure
D) Flow turbulence
B) External corrosion
Rationale: Low soil resistivity increases the rate of electrochemical
reactions, accelerating external corrosion.
6. The purpose of a reference electrode in CP testing is to:
A) Measure pipeline diameter
B) Measure pipe-to-soil potential
C) Apply protective coatings
D) Detect cracks
, B) Measure pipe-to-soil potential
Rationale: Reference electrodes measure the electrochemical potential,
ensuring CP is adequate.
7. Which of the following metals is commonly used for sacrificial anodes
in pipelines?
A) Copper
B) Magnesium
C) Stainless steel
D) Aluminum
B) Magnesium
Rationale: Magnesium has a more negative potential than steel, allowing
it to corrode preferentially and protect the pipeline.
8. A “holiday” in pipeline coating refers to:
A) A seasonal maintenance shutdown
B) A defect in coating exposing steel
C) A cathodic protection test point
D) A leak detection sensor
B) A defect in coating exposing steel
Rationale: Holidays are coating flaws where steel is exposed, creating a
localized corrosion risk.
9. Which parameter indicates sufficient CP protection on a bare steel
pipe in soil?
A) -0.85 V CSE or more negative
B) 0 V
C) +0.85 V CSE
D) Any positive voltage
A) -0.85 V CSE or more negative
Rationale: -0.85 volts vs. copper/copper sulfate electrode (CSE) is the
standard threshold indicating adequate cathodic protection.
