Definition
A form of corrosion that appears as a general roughening, etching, or pitting of the visible surface of a metal part, often accompanied by a powdery deposit of corrosion products. It typically results from direct exposure of the metal to moisture, salts, or other corrosive agents, and is the most easily detected form of corrosion because it is on the outside of the part where it can be seen.
Plain English
Damage on the outer face of a metal part caused by reaction with air, water, or chemicals. It looks dull, rough, pitted, or covered in a chalky deposit, and it sits on the surface where you can see it.
Context Anchor
Seen during aircraft inspection, cleaning, and maintenance, especially on exposed metal skins, fasteners, fittings, and other parts that can collect moisture or dirt.
Derivation
Corrosion comes from the Latin corrodere, meaning to gnaw away. Surface corrosion is corrosion that gnaws at the outer face of the metal — the part you can actually see and touch.
Why Pilots Care
If left untreated, surface corrosion can progress inward, weaken the structure, and eventually require expensive repairs or grounding.
Intuition Check
Do not assume surface corrosion is only cosmetic because it is on the surface. In aircraft maintenance, visible surface corrosion can be the first sign of material damage that needs attention.
Example Sentence 1
During the inspection, the technician found surface corrosion on the underside of the wing near the drain holes and treated it before returning the aircraft to service.
Example Sentence 2
Applying a protective coating after cleaning stopped the surface corrosion from spreading further.