Definition
A chemical conversion coating applied to aluminum and aluminum alloy surfaces that forms a thin, corrosion-resistant film and provides a good base for paint adhesion. It is typically applied by brush, spray, or immersion and leaves a characteristic gold or yellow-brown tint on the treated surface.
Plain English
A chemical treatment brushed or sprayed onto bare aluminum to protect it from corrosion and help paint stick to it. It leaves a yellowish tint on the metal.
Context Anchor
Seen in aircraft maintenance, especially during aluminum repair, surface preparation, corrosion control, and painting procedures.
Derivation
Alodine is a brand name (originally from Henkel) that has become the common shop term for this type of chromate conversion coating, similar to how 'Band-Aid' is used for adhesive bandages. Knowing it is a brand name helps explain why it is capitalized and why technical documents may also call it a 'chromate conversion coating.'
Why Pilots Care
Prevents hidden corrosion that can weaken airframe structure and lead to costly or dangerous failures.
Intuition Check
Alodine is not paint. It is a chemical treatment applied to bare aluminum before primer or paint, mainly to help protect the metal and prepare the surface.
Example Sentence 1
After sanding the corrosion off the wing skin, the technician applied Alodine to the bare aluminum before priming.
Example Sentence 2
The maintenance manual requires a uniform Alodine film on all bare aluminum surfaces exposed during inspection.