Which of the following is a form of corrosion that involves selective dissolution of elements in an alloy, leaving a porous structure?

• A. General corrosion
• B. Erosion-corrosion
• C. Dealloying
• D. Ferroelectric corrosion

Answer: (C)

Selective dissolution of elements in an alloy, leaving a porous, sponge-like structure, is called dealloying. This happens when the elements in an alloy have different electrochemical nobility; under corrosive conditions the more active element dissolves away while the more noble element remains, forming a network of ligaments and a porous framework. The result is a high-surface-area, interconnected porous structure, which is not what you’d see with uniform general corrosion that erodes material evenly, nor with erosion-corrosion that combines wear with chemical attack. Ferroelectric corrosion isn’t a recognized corrosion mode in this context.