If you have a balcony with cast iron panels and you are thinking of giving it a much needed makeover then you should be thinking of stripping off the old 10 or so layers of paint that have been applied to the panels over the years by the previous owners. We are talking of 90 yrs and over here.
There are a few options that you can use, it all depends on how much time and effort you want to put into it.
Use Paint Stripper, (preferably a water washable one to neutralise the stripper before undercoating). A wire brush, wire wool coarse grade, rubber gloves, safty glasses, paint scraper, sand paper and a dust mask for the sanding because of the lead based paints on the panels. Once cleaned paint with primer 2 coats then 2 top coats of oil based paint. Please note that it is important to undercoat thoroughly because the cast iron will bleed rust stains through the top coat if not undercoated liberally.
But the best way would be to remove the panels and “Shot Blast” them.