I have a small pool service and a customer does not want to buy a new filter and just wants me to replace the grids. She wants to paint the filter when I am done. Is it safe to paint an old Stainless Steel Purex 60 SqFt Filter that looks ugly and has rust stains all over it?

What kind of paint (Oil base, Latex, or ?)

I think I heard somewhere that it is not ok to paint over something with pressure in it because it could cause it to explode. I don't remember were I heard this or for what product the discussion was about but I thought I should ask before cleaning up the old filter and letting her paint it to make it look better.

Thank you,
Happy Easter,
Moondoggy