FAA Aviation Mechanic Airframe (AMA)Airframe StructuresEasy
A technician is preparing bare aluminum sheet stock prior to painting and applies a chemical bath that produces a thin, gold-to-yellowish iridescent conversion coating on the surface, improving corrosion resistance and paint adhesion without requiring an electrical current. Which process is being performed?
- ACadmium plating
- BAlodine (chromate conversion coating)
- CAnodizing
- DZinc chromate priming
Show answer & explanationAnswer & explanation
Correct answer: B. Alodine (chromate conversion coating)
Alodine, also called chromate conversion coating, is a chemical dip or wipe process that forms a thin protective oxide/chromate film directly on bare aluminum without electric current, giving the characteristic gold tint. Anodizing requires electrolytic current and produces a thicker oxide layer.
Why the other options are wrong
- A. Cadmium plating is an electroplated metallic coating, not a chemical conversion coating.
- C. Anodizing is an electrochemical process requiring an electric current, not a simple chemical dip.
- D. Zinc chromate is a paint primer applied after surface treatment, not the conversion coating itself.
Alodine / Chromate Conversion Coating
A non-electrolytic chemical treatment applied to bare aluminum that forms a thin protective, corrosion-resistant film and improves paint adhesion.
- Produces gold/yellow iridescent finish
- No electric current required
- Applied before priming and painting
Memory trick: Alodine = A liquid dip, no electricity needed.