What are the two main types of cathodic protection?

• A. Organic coatings and paints
• B. Sacrificial anodes and impressed current protection
• C. Thermal insulation and UV blockers
• D. Cladding and plating

Answer: (B)

Cathodic protection works by making the metal surface a cathode so it resists corrosion. The two practical ways to achieve this are sacrificial anodes and impressed current protection.

With sacrificial anodes, you attach a more electrochemically active metal—such as zinc, magnesium, or aluminum—to the structure. That active metal corrodes in place of the protected metal, delivering electrons to the structure and keeping its surface at a protective potential. This method is simple and effective for smaller, accessible areas, but you have to replace the anodes as they dissolve over time.

Impressed current protection uses an external power source to drive current from inert anodes into the electrolyte, pushing electrons into the protected metal to maintain a negative, protective potential. This allows precise control of the protective current and is suitable for large structures or difficult-to-inspect areas where sacrificial anodes wouldn’t be practical.

Other options listed are barrier approaches (organic coatings and paints) or unrelated processes (like insulation or finishing methods) rather than active CP methods.