Powder coating versus galvanising: which finish for which job

These two get treated as alternatives when they are really answers to different questions. Choosing badly is expensive, because the correction is usually stripping everything back and starting again.

Powder coating

An electrostatically applied powder, oven cured so it bonds to the steel. It is tough, comes in any RAL colour, and looks far better than brush paint. What it does not do is protect steel it is not covering: a scratch through to bare metal will rust from that point.

Hot-dip galvanising

The steel is dipped in molten zinc, which bonds metallurgically and protects sacrificially — meaning even a scratch stays protected, because the zinc around it corrodes first. The finish is a mottled grey you do not get to choose.

Where each belongs

• Gates, burglar bars, railings at a house: powder coat. It is seen, it needs to match, and it is not in a harsh environment.
• Structural steel, walkways, anything in a wash bay or near chemicals: galvanise.
• Outdoor steel that must be a specific colour and last: galvanise, then powder coat over it. This is the belt-and-braces option and it is worth the extra on anything you do not want to revisit.

One practical warning

Galvanising happens in a bath, so the item has to fit in it, and it needs vent holes in closed sections or it cannot be dipped safely. Both of those affect the design, which means the decision belongs at the drawing stage, not after fabrication.