Fretting corrosion is most likely to occur under which condition?

• A. When two surfaces fit tightly together but can move relative to one another
• B. When surfaces are in complete contact with no movement
• C. When surfaces are coated with oil
• D. When there is no load on the parts

Answer: (A)

Fretting corrosion happens when two surfaces are in contact and experience small, repeated sliding against each other under load. Those micro-motions rub the surface, disrupt the protective oxide film, and wash away lubricant, which accelerates wear and corrosion at the contact point. The scenario where two parts fit tightly together but can move relative to one another provides that exact combination of contact with relative motion under load, making fretting most likely. If there’s no movement, no load, or adequate lubrication, fretting is unlikely to develop.