Comprehensive and Detailed Explanation From Exact Extract:
Concentration Cell Corrosion is defined in API RP 571 as a form of electrochemical corrosion driven by differences in concentration of corrosive species, most commonly oxygen, under deposits or within crevices.
This type of corrosion typically occurs:
Beneath deposits, scale, or fouling
In stagnant zones or crevices
Where oxygen concentration differs between adjacent areas
The area with lower oxygen concentration becomes anodic and corrodes preferentially, while the oxygen-rich area becomes cathodic.
Why the other options are incorrect:
Option B describes galvanic corrosion, not concentration cell corrosion.
Option C refers to high-temperature sulfidation, unrelated to concentration gradients.
Option D describes mechanical damage mechanisms, not electrochemical corrosion.
API RP 571 clearly categorizes concentration cell corrosion as being associated with deposits or crevice conditions, making Option A the correct description.
Referenced Documents (Study Basis):
API RP 571 - Section on Concentration Cell and Crevice Corrosion
API Corrosion Fundamentals Study Guide