Definition
A chemical process that forms a thin, stable, non-reactive film on the surface of a metal to protect it from corrosion. In aviation, passivation is commonly applied to stainless steel and other corrosion-resistant alloys by treating the surface with an acid solution (typically nitric or citric acid) that removes free iron and other contaminants and promotes the formation of a uniform protective oxide layer.
Plain English
A surface treatment that makes a metal part more resistant to corrosion by giving it a thin protective skin.
Context Anchor
Seen in aircraft maintenance, corrosion control, and repair records for metal parts.
Derivation
From the Latin 'passivus', meaning 'capable of suffering' or 'inactive'. The metal surface is made chemically 'passive' — meaning it no longer readily reacts with its environment.
Why Pilots Care
Corrosion is a major airworthiness issue. Passivated parts last longer and stay reliable in harsh conditions like salt air, fuel exposure, and humidity. Knowing a part has been passivated tells a pilot or mechanic it has been treated to resist the kind of slow damage that can compromise structural integrity.
Analogy
It is like helping a metal form a very thin protective skin so the outside air and moisture do not attack it as easily.
Intuition Check
Passivation does not mean the part has been painted or covered with a thick coating. It means the metal surface itself has been made less chemically reactive.
Example Sentence 1
After fabrication, the stainless steel fittings were sent out for passivation before being installed on the aircraft.
Example Sentence 2
Maintenance procedures require passivation of aluminum skin panels exposed during structural repairs.