Which protection method has been used effectively to control pitting on body exposed surfaces?

• A. Electroplating
• B. Thermal treatment
• C. Anodic Protection
• D. Cathodic Protection

Answer: (D)

Pitting is a localized corrosion process where tiny areas on a metal surface become anodic and dissolve while the surrounding metal stays relatively intact. To prevent pits, you need to shift the entire surface to a more negative, or cathodic, potential so the driving force for metal loss at those anodic sites is greatly reduced. Cathodic protection accomplishes this by making the exposed surface the cathode, either through attaching sacrificial anodes that corrode instead of the protected metal or by applying an external current that drives the surface to a negative potential. With the surface held in this cathodic state, the conditions that promote pit initiation and growth are suppressed, so pits are minimized or prevented on exposed surfaces. This approach is especially effective for steel and other metals in marine or soil environments where pitting is a common concern. Other methods may coat or alter the material, but they don’t reliably inhibit localized pit formation across exposed areas in the same way cathodic protection does.