Years ago I restored an old slicing machine. Made somewhere around 1919, by the "American Slicing Machine Co." - long since out of business. My dilemma was that the machine was painted glossy black, no doubt lead paint with more lead in it than a car battery. So if I tried to make it period-authentic, I'd have a problem finding lead based enamel. Could use acrylic, but I figured it wouldn't hold up to normal use.
Cast components were pretty rough:
So, I chose to powder-coat all the castings, which were iron and zinc. The place which did the work was having a real problem with out-gassing when the castings were heated in the powder coating process. Cast iron tends to soak up grease and oil, probably from contact with the food. So they had to do the project twice, but it turned out beautifully the second time. And powder coating is exceptionally rugged as well. I use it occasionally, and it can cut a piece of beef so thin you can see thru it and the finish is tough as nails. The guide shafts were made of chrome plated steel, chrome all worn off, so I replaced them with stainless steel. There were also some Inconel parts which I kept original.
Powder coating may have a place in coin op refurbishing, but I'm not sure where.