ok I pickled the railings what is it you ask you use copper etching solution and etch the railings this helps the paint adhere and makes it less likely to pop off. heres how David Merriman explained it to me
copper alloys are poor substrates for paint adhesion. Pickling is the
process of introducing microscopic pits by acid/alkyd attack. Once pickled, you rub off the excess oxidized metal (do not sand or polish) and lay down the primer. The primer will stick very, very well. Don't do this and the primer-paint will eventually shrug off the work.
Brush on the Ferric Chloride and scrub it into the metal with the
brush till the metal darkens a bit. Then come back with fresh water spiked
with a little baking soda, and scrub to kill the acid. Rinse with fresh water, dry, and prime.