I used this on a stainless gun. I have heard that Ultrasonics can remove bluing and plating, but I have never seen this first hand.
The ultrasonic action itself won't remove bluing, or destroy plastics, but the liquid you use may. I don't think the action will remove plating, but I do not know for sure.
I have reports that it will separate the poly coat that CZ uses on many of its handguns (e.g. my CZ 75 P01 slide).