Final answer:
Concentration cell corrosion is prevented by avoiding differences in concentration of corrosive agents during repairs, such as uneven oxygen levels that lead to the formation of galvanic cells on damaged protective coatings.
Step-by-step explanation:
Concentration cell corrosion can be controlled and prevented by avoiding the creation of differences in concentration of the corrosive agents (such as oxygen) during repair work. When surfaces such as iron or steel are coated with protective paint, scratches or damages to this protective layer can expose the underlying metal to environmental factors like O₂ and moisture, which can lead to the formation of a galvanic cell. This galvanic cell can have half-cells of identical composition except that one half-cell becomes the anode with a lower concentration of O₂, and the other becomes the cathode with a higher concentration of O₂. This difference promotes the corrosion process, with the iron being oxidized to Fe²⁺ (aq) at the anode and the oxygen being reduced at the cathode. To prevent such corrosion, factors such as pH, presence of CO₂, and air exposure should be carefully controlled during repairs to maintain uniform environmental conditions across the metal surface, thus preventing differential aeration which is a common cause of concentration cell corrosion.