Definition
A small, localized area of corrosion damage on a metal surface, typically appearing as a tiny cavity or hole where the protective oxide layer has broken down and the underlying metal has been eaten away.
Plain English
A small dent or hole in metal caused by corrosion. The metal looks fine on the surface, but a tiny patch has been chewed out, leaving a little crater.
Context Anchor
Seen during preflight inspections and maintenance inspections of metal parts, propeller blades, engine parts, and electrical contact surfaces.
Derivation
From the everyday word pit meaning a small hole or hollow. The term carries directly into metallurgy because that is exactly what corrosion damage looks like under magnification — small hollows scattered across the metal surface.
Why Pilots Care
Pits are early warning signs of corrosion. A surface that is pitting today can develop into structural weakness if left untreated. Pilots and mechanics watch for them on aluminum skin, control surfaces, and engine components during preflight and scheduled inspections.
Intuition Check
Do not picture a large hole in the ground. In aircraft maintenance, a pit is a small hollow or cavity in the surface of a part.
Example Sentence 1
The mechanic found several pits along the lower wing skin and recommended treatment before the next flight.
Example Sentence 2
Several pits along the spar required blending before the aircraft could return to service.