Shop notes · Finishing · 4 min
Powder coat or galvanise? Choosing a finish for outdoor steel
What each finish costs, how long it lasts outside, and why the answer for a stair on the coast is usually both.
“Painted black” on a drawing can mean four different finishes with four different lifespans. If the steel lives indoors, almost anything works. Outdoors, the choice decides whether it looks the same in fifteen years or needs a scaffold in five.
Powder coat on blasted steel
We grit blast to SA2½, apply a zinc-rich primer and a polyester topcoat, and cure it in the oven. It looks crisp, comes in any RAL colour, and on a typical inland site lasts 15 to 20 years before it needs attention. It is the right finish for handrail, gates and anything people touch.
Hot-dip galvanising
The steel is dipped in molten zinc, which coats every face, inside and out, including the inside of tube. It is the most durable single finish there is, but it is grey, it is not smooth, and it adds a fixed three-day turn to the lead time.
Both: the duplex system
Galvanise, then powder coat. The zinc protects the steel; the powder protects the zinc and gives you the colour. It costs more once and very little afterwards, which is why nearly every external stair and coastal balustrade we make goes out duplex.
A rough guide
| Where it lives | What we recommend |
|---|---|
| Indoors, dry | Powder coat or primer only |
| Outdoors, inland | Zinc-rich primer plus powder coat |
| Outdoors, coastal or industrial | Galvanised plus powder coat |
| Hidden structural | Blast and prime, or galvanise |
Not sure where yours sits? Tell us on the quote form where the steel will live, and we will name the system on the quote.
