Interesting thread with lots of doom and gloom predictions.
I have cleaned hundreds of aluminum insert bezels in an ultrasonic tank, and I can only recall one ever being affected in a negative way, and it was from a very cheap brand of watch. It was slightly less shiny and more of a matte finish when it came out, and I replaced the bezel. These are modern bezels though - vintage I would not do this with.
The thing is, not all ultrasonic machines are the same power, not all cleaning solutions are of the same strength, etc. So asking "is it safe" without knowing all those details is like having someone drill a hole in your tooth with no freezing...
I've never had a lume pip disintegrate on a modern watch - most are in a contained capsule in modern watches, or are made of a material that is something different than the regular lume mixture used to lume dials and hands, and is not affected by water (they would be pretty useless on a dive watch if they were damaged that easily).
Of course a prolonged time in an ultrasonic tank is not recommended. A few minutes is usually all that's needed, and I've had no issues doing that with aluminum bezels on modern watches. I use diluted Mr. Clean in my tank, so not anything overly aggressive as a cleaner. But of course the decision to do this or not is a personal one...
Cheers, Al
