As replied by other guest, it is true that almost company has its own standard
for painting requirements. (But they are almost similar, painting is painting, nothing
unique)
Most cases, hand rail, gratings and other structural items that are galvanized does not need painting.
Yellow is frequently used for hand rail and safety guard for safety notice.
Gray is also frequestly used for all other structural components.
According with my experience painting heaters for refinery.
if is not galvanized You have to sandblast at least sspc 6. or sspc 2 and then paint with zinc rich primer (Carbozinc F 11 or Carbozinc 859, TH= 75 μ) After that you can paint with some epoxy (Carboguard 890) RAL 1023 (safety yellow). OR CARBOTHANE 134 HG RAL 1023
If the part is galvanized the preparation is SSPC 1 and you can paint with some epoxy like CARBOGUARD 888 (TH= 75 μ) and then paint with CARBOTHANE 134 HG RAL 1023. (TH= 75 μ TO 125μ)