Hot-dip galvanizing vs powder coating
Finishes. Published Oct 7, 2026 by ManuFx.
Both protect steel from rust, in different ways. How each works, where each lasts and when to use the two together.
TL;DR
- Galvanizing: a zinc layer that keeps protecting steel where it is scratched.
- Powder coating: a smooth, coloured film that seals steel from air and water.
- For long life outdoors, galvanize. For colour and finish, powder coat. For both, do both.
Hot-dip galvanizing
The steel is dipped in molten zinc at about 450 °C. The zinc bonds to the steel in layers and covers every surface the bath reaches, inside hollow sections too.
Zinc corrodes before steel does. Where the coating is scratched, the zinc around the scratch still protects the bare steel.
Powder coating
Dry powder is sprayed onto the part with an electrostatic charge, then baked so it melts into a smooth, continuous film in almost any colour.
It protects as a barrier: the steel is safe while the film is whole, but rust can start where a deep scratch reaches the metal.
Zinc protects steel even where the coating is broken.
Which to use
It depends on where the part will stand and whether it will be seen.
- Outdoor structures: galvanizing, for long life with little upkeep.
- Indoor and visible parts: powder coating, for colour and finish.
- Both: powder coating over galvanizing, called a duplex system.
What to specify
Name the coating standard on the drawing: ISO 1461, ASTM A123 or IS 4759 for hot-dip galvanizing.
Say which surfaces must stay uncoated, such as threads and mating faces.