Not recommended where pitting may occur?

• A. Cathodic protection
• B. Anodic protection
• C. Mechanical polishing
• D. Coatings with epoxy

Answer: (B)

Pitting is a localized form of corrosion that starts at tiny defects or flaws and continues where the protective films on the metal surface can’t reform quickly. Anodic protection works by forcing the metal to become more positive to create a protective oxide film on the surface. However, inside a pit the chemistry becomes highly acidic and the protective oxide film cannot form or remains broken down. In those conditions, applying an anodic potential can drive dissolution at the pit rather than stop it, making pitting worse. That’s why anodic protection is not recommended when pits may occur.

Cathodic protection, by contrast, lowers the metal potential and generally helps suppress dissolution and pitting, while mechanical polishing and epoxy coatings reduce initiation sites or block access to the surface (though coatings must remain intact to be effective).