What paint to use to fill engraved letters on aluminium plate?
For best results you need a etching type paint for aluminum or a Zink oxide primer then any paint. Aluminum oxidizes with air so it needs a primer or a paint designed for aluminum that actually etches so it bonds with the metal. Annodizing is used to protect the surface it is a plating type of solution in a bath so it is a bit different (and the surface is usually harder than aluminum.