Galvanized surfaces are painted all the time. few key steps to follow -# 1 wash the surfaces with clean fresh water and a salt removing solution - then rinse again # 2 use a very fine abrassive # 70 - # 100 grit and low pressure 80 psi and very gentle & qucily blast clean all surfaces to be painted. you only want to change the color to a dull gray, DO NOT ATTEMPT TO REMOVE THE ZINC. A grit like Black Beauty 30/60 can be used but pressure should be further reduced to approx 50-60 psi # 3 prime with polyamide or similar primer # 4 top coat with aliphatic polyurethane.
I did paint mine a few years ago with rustolium white total cost was about $15. I also got rid of the rollers and put bunks on much easier to load. The paint has held up great and easy to touch up.