The problem with powder coating is that it is thick, and difficult to apply evenly. It would probably stick to chrome, but there are other issues.
You may get a sufficiently thin coat in one area but another may be twice as thick, which fills in the engravings. Look at the serial number of the M3. These engravings are not as deep as the Leica script engravings.
I powder coated many cameras that had been stripped to brass, but often it required stripping it off again (with messy, smelly, toxic chemicals) and re-applying due to these problems.
When it worked it looked great and is very durable. I used a semi matte powder which masked finger prints and wasn't overly 'bling.'
Powder coating the levers and dials was tedious. It won't work on most, such as on Leica M shutter speed dials. Had to make fixtures so they were all connected together...
It also requires batch processing. You'd want to powder coat a lot of parts at the same time. Wouldn't make much sense to do one camera.
And even a little bit of excess in the wrong location meant that parts wouldn't fit together, which meant a lot of tedious labor removing the excess, often from hard-to-reach locations...