I tried doing our shelves - they weren't plastic coated, but chrome, and the chrome had pitted and flaked and come off completely in places. What a job! I tried painting them with a spray, which looked like a dogs dinner, and ended up stripping them with Nitromors and then caustic soda, to get off the paint that I'd tried. Someone then recommended that Coca Cola would remove the plating, which it did, and then I sanded them with increasinly fine grades of emery paper. I then painted them by hand with a metallic silver finish, several coats, and now they look really good - but unfortunately the ends which fit into the slots in the plastic sides of the fridge now leave rusty marks. Next job is to sand those ends again, repaint them, and then probably use something like clear nail polish (too girly, OK........ anyone any better suggestions..........?!) to seal just the very ends to stop them rusting!
Mind you, to buy replacement shelves would have cost a small fortune - but getting them back to what I considered clean and 'food-friendly' was not easy!