Which of the following can be used in underground or immersion situations?

• A. Electrochemical etching
• B. Sacrificial metals
• C. Cathodic protection
• D. Anodic stripping

Answer: (C)

Cathodic protection is used for buried or submerged structures by driving the metal surface to a protective, more negative potential so that corrosion reactions are suppressed. This is done either with sacrificial anodes that corrode in place, or with an impressed current from an external power source, all arranged to keep the structure as the cathode. In underground or immersion environments, such a low-impedance, continuous flow of electrons ensures the entire surface remains protected even in moist soil or seawater where corrosion is active. Sacrificial metals are part of one CP approach (galvanic protection), but the overarching method is cathodic protection. Electrochemical etching is just a material-analysis process, not a protection method, and anodic stripping is an electrochemical technique used for sample prep or analysis, not for protection.