Corrosion Fundamentals Practice Questions

These questions test the corrosion fundamentals required to understand cathodic protection.

Study Focus

Focus on corrosion cells, anodic and cathodic areas, electrolytes, metallic paths, oxidation, reduction, coatings, and why CP reduces corrosion.

Practice Questions

  1. Which part of a corrosion cell experiences metal loss?

    1. The cathode
    2. The electrolyte
    3. The anode
    4. The reference electrode

    Answer: C. Metal loss occurs at the anode where oxidation occurs.

  2. What is the role of the electrolyte in a corrosion cell?

    1. It allows ionic current flow
    2. It prevents all electrical activity
    3. It acts as the metallic return path
    4. It converts DC power to AC power

    Answer: A. The electrolyte allows ionic current flow between anodic and cathodic areas.

  3. Oxidation is best described as:

    1. Gain of coating thickness
    2. Loss of electrons
    3. Removal of electrolyte
    4. Reduction in soil resistance only

    Answer: B. Oxidation is loss of electrons and occurs at the anode.

  4. Which statement about coatings and CP is correct?

    1. Coatings increase the exposed metal area
    2. Coatings eliminate the need for all inspection
    3. Coatings reduce exposed area, and CP protects exposed metal at defects
    4. Coatings make steel immune to corrosion forever

    Answer: C. Coatings reduce exposed metal area, while CP protects exposed metal where coating defects exist.

  5. What is the metallic path in a corrosion cell?

    1. The path that allows electron flow
    2. The reference electrode solution
    3. The soil pore water only
    4. The plastic coating

    Answer: A. The metallic path allows electrons to move between anodic and cathodic areas.

  6. Why can corrosion be localized?

    1. All soil is always identical
    2. Environmental and surface conditions can vary across the structure
    3. Steel cannot have anodic areas
    4. CP current cannot flow through soil

    Answer: B. Coating defects, oxygen differences, soil variation, moisture, dissimilar metals, and stray current can create localized corrosion cells.

  7. In cathodic protection, the protected structure is forced to behave more like:

    1. An anode
    2. A coating holiday
    3. A cathode
    4. An electrolyte

    Answer: C. CP reduces corrosion by forcing the structure in the cathodic direction.

  8. Which condition can support corrosion on buried steel?

    1. Contact with conductive moist soil
    2. Perfect electrical isolation from all electrolytes
    3. No electrolyte contact
    4. No anodic or cathodic areas

    Answer: A. Moist conductive soil can act as an electrolyte.

  9. Reduction reactions occur at the:

    1. Anode
    2. Coating holiday only
    3. Rectifier stack
    4. Cathode

    Answer: D. Reduction reactions occur at cathodic areas.

  10. Which statement is false?

    1. A corrosion cell requires an electrolyte
    2. Metal loss occurs at anodic areas
    3. Coatings can reduce CP current demand
    4. Corrosion requires a rectifier

    Answer: D. Corrosion does not require a rectifier. A rectifier is used in impressed current CP systems.

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