Definition
A corrosion-protection method in which a more chemically active (less noble) metal is attached to, or coated onto, a structural metal so that the active metal corrodes preferentially, leaving the protected metal intact. The classic aviation example is zinc coating on steel hardware, or zinc-chromate primers and cladding layers used to protect aluminum alloys.
Plain English
A weaker metal is deliberately put in contact with the part you want to protect. That weaker metal corrodes first and gets eaten away, sparing the important part underneath.
Context Anchor
Seen in aircraft maintenance when discussing corrosion protection, protective coatings, plated hardware, and metal parts exposed to moisture.
Derivation
From Latin sacrificium, meaning to give something up. The protective metal is sacrificed -- it gets corroded away on purpose -- so that the structural part survives.
Why Pilots Care
Prevents hidden structural weakening that could lead to airframe failure or expensive repairs.
Analogy
It is like a cheap outer cover on a phone case taking the scratches so the phone itself does not. The cover is meant to take the damage first.
Intuition Check
Sacrificial corrosion does not mean unwanted corrosion is being ignored. It means a protective metal is corroding first by design, so the more important metal is protected.
Example Sentence 1
The zinc plating on the steel bolts provides sacrificial corrosion protection, so once the plating is worn through, the bolts should be replaced.
Example Sentence 2
Replacement of the sacrificial corrosion plates was scheduled every annual to maintain protection on the wing attach points.