Duragal steel posts often seem like a strong, long-lasting choice for building projects. They’re pre-galvanised and marketed as corrosion resistant — which sounds reassuring. But here’s the truth: Duragal is not designed for direct in-ground use, or anywhere near the coast. Once exposed to damp soil or salt air, the protective coating breaks down quickly, and rust follows faster than most homeowners expect.
The thin zinc coating on Duragal works fine in dry, above-ground conditions. Underground or in coastal air, however, it doesn’t last. Once moisture gets through, corrosion attacks the bare steel. Over time, this can compromise structural integrity.
Red flags to look for:
- Flaking or bubbling on the steel surface near ground level.
- Orange-brown staining that creeps upward from the base.
- Soft, weakened patches where the coating has failed.
- In coastal areas, noticeable rust appearing within just a few years.
What you can do about it:
- Inspect regularly — especially around the soil line or in damp/coastal conditions.
- Rust-treat, paint, and wrap with Denso Tape — if the posts are still structurally sound, apply a rust converter, protective paint, and wrap the in-ground section with Denso Tape to slow corrosion.
- Replace deteriorated posts — swap out with hot-dip galvanised steel or H5-rated treated timber designed for soil and coastal use.
- Use stirrups or post shoes — cutting posts above ground and re-supporting them on proper concrete footings eliminates direct soil contact.
- Seek professional advice — a Licensed Builder or steel fabricator can advise whether posts should be repaired, reinforced, or replaced
Duragal posts might look durable on day one, but in the ground or near the coast, rust is almost inevitable. Left unchecked, that corrosion can compromise both safety and structure.
The bottom line: if you’re building, renovating, or maintaining a property, choose materials suited to the environment. And if you already have Duragal posts installed, now is the time to check them — before hidden rust turns into an expensive problem.
