Company on the A38 Tyburn Road, Birmingham, knew their stuff when I spoke to them. (I’ve plenty of powder coating experience through work). Alloy is a problem if your touching 280c+. 200c is fine. Oven baking is better, but some use a moving line through radiant heaters, & these are a problem because they speed up/slow down the line to suit the mass of the part your baking. Get the speed wrong & your in trouble. Not a problem on fence posts, but bike frames are another matter.
To get old paint off…a chemical strip then light “blast” as a key for powder. I say blast, as in reality all it does is dull the surface. Most decent mfrs will have done this before the original powder went on, so its still there when the powder comes off. What you don’t want is some oaf with a shotblaster used for cleaning up castings. The acid won’t hurt the alloy, it’s not James Bond type acid. 😕
