painting grey and ductile cast iron valves with pf4

[enas]

we manufacturing valves and accessories for water and swerage works, it's made of ductile or grey cast iron when we coating it with pf4, it doesn't get dry fast and makes no smooth surface and can be taken off the surface.
what we do wrong???
what is the best solvent to it

thanks
enas

 

[robsalv]

? what's pf4?