RMGA Corrosion Control and Cathodic Protection 3

Question 1

What is a copper-copper sulfate electrode (CSE) primarily used for in cathodic protection field work?

Accepted Answer

As a portable reference electrode for measuring pipe-to-soil potentials in the field

Answer

As a sacrificial anode material installed alongside buried gas pipe

Answer

As the primary anode in impressed current cathodic protection systems

Answer

As a sensor for detecting natural gas leaks near pipeline test stations

Question 2

What is the primary distinction between galvanic (sacrificial anode) and impressed current cathodic protection systems?

Accepted Answer

Galvanic systems rely on the natural electrochemical potential difference between metals and require no external power, while impressed current systems use an external DC power source (rectifier)

Answer

Galvanic systems use AC current while impressed current systems use DC current

Answer

Galvanic systems protect only aboveground piping while impressed current protects only buried pipe

Answer

Galvanic systems protect only bare steel while impressed current protects only coated pipe

Question 3

Which soil condition is generally considered most corrosive to buried steel gas pipelines?

Accepted Answer

Wet clay soil with low electrical resistivity, high moisture content, and poor drainage

Answer

Dry sandy soil with high electrical resistivity above 10,000 ohm-cm

Answer

Well-drained rocky soil with good natural aeration

Answer

Frozen permafrost soil in arctic or sub-arctic environments

Question 4

What is the purpose of an electrical isolation fitting (isolating joint) in a gas distribution system?

Accepted Answer

To electrically separate pipeline sections to control cathodic protection current boundaries and prevent interference between different protection zones

Answer

To reduce gas pressure at meter sets and service connections

Answer

To measure gas flow rates through distribution mains and service lines

Answer

To allow thermal expansion of the pipeline without stressing mechanical connections

Question 5

What does a Pearson survey or DCVG (Direct Current Voltage Gradient) survey detect on buried pipelines?

Accepted Answer

Coating defects and areas where cathodic protection current is entering the pipe through coating holidays

Answer

Internal pipe wall thickness loss from erosion or internal corrosion

Answer

The exact depth of burial of the pipeline along its route

Answer

Unauthorized third-party excavations near the pipeline right-of-way

Question 6

Microbiologically influenced corrosion (MIC) in gas pipelines is most commonly associated with which microorganism?

Accepted Answer

Sulfate-reducing bacteria (SRB) that thrive in oxygen-free (anaerobic) environments

Answer

Aerobic bacteria that require oxygen to survive in the surrounding soil

Answer

Nitrogen-fixing bacteria commonly found in agricultural soils near pipelines

Answer

Photosynthetic algae that colonize exposed aboveground pipe sections

Question 7

What is the significance of the 'instant-off' potential reading in cathodic protection surveys?

Accepted Answer

It is the pipe-to-soil potential recorded the instant after interrupting protection current, eliminating IR drop error to reveal the true electrochemical protection level

Answer

It measures the anode potential immediately after installation to confirm it is active

Answer

It indicates the potential at which cathodic disbondment of the coating begins to occur on the pipe surface

Answer

It is the potential reading taken inside the pipeline by an inline inspection tool