Corten Steel

Weathering steel that forms its own protective patina — planters, screens, facades and signage.

How Corten Weathers

Corten is steel alloyed with copper, chromium, nickel and phosphorus. It rusts like any steel, but the rust it forms is dense and tightly bonded rather than flaky, and that layer then slows further corrosion instead of accelerating it. Left alone, it protects itself.

It needs wet and dry cycles to do this. Rain, then drying, repeatedly. Corten kept permanently wet — in standing water, buried in soil, sandwiched against a surface that stays damp — never stabilises and will keep corroding straight through. Corten kept permanently dry indoors never develops the patina at all and just looks like slightly odd steel.

Vancouver, as it happens, is close to ideal for it. Wet winters and dry summers give exactly the cycling the alloy wants.

Runoff and Staining

This is the part nobody mentions until it has already happened.

For roughly the first year, rain running off Corten carries iron oxide with it and stains whatever it lands on. Concrete, pavers, stucco, cedar decking, light-coloured stone — all of it will take an orange-brown mark, and on porous surfaces the mark is effectively permanent.

It is entirely manageable if it is designed for. We detail drip edges to throw water clear, set planters on gravel or a sacrificial layer rather than straight onto finished concrete, and keep the base of screens off pale hard landscaping. Where the surface below is precious, we will say so before anything is fabricated.

After the patina stabilises, runoff drops off sharply. It never quite reaches zero.

Planters and Screens

Planters are the most common Corten job we build, and the one with the most ways to get it wrong.

A planter must drain freely and the steel must not sit in wet soil indefinitely. We build with a drainage gap and a raised base, and for anything permanent we recommend an internal liner so the growing medium never touches the plate directly. Wall thickness matters too — soil pushes outward with real force, and a planter that looks fine empty will bow visibly once it is full and watered.

Screens and privacy panels are the easier win. Laser or plasma-cut patterns in Corten plate throw good shadows, need no finishing, and are one of the few exterior features that genuinely improve with age. The main design constraints are wind loading and how the panel is fixed, both of which we work out at the drawing stage.

Facades and Cladding

On facades and cladding, Corten becomes an assembly problem more than a metal problem.

The panels themselves are straightforward. What matters is everything behind them: a ventilated cavity so both faces can dry, fixings and a substructure in stainless or an equally durable material, and isolation from any dissimilar metal that would set up a galvanic cell. Corten fixed with plain steel fasteners will fail at the fasteners first.

Any facade work of scale goes through the architect and the building envelope consultant, and we build to their details. What we bring is the fabrication, the panel layout and honest advice on what the material will actually do in year three.

What to Expect Year One

Corten does not arrive rusted. New plate is grey-blue mill finish, and clients are routinely alarmed by it.

A rough timeline in this climate, with the usual caveat that exposure and orientation change everything:

• Weeks one to four — patchy orange appears, unevenly, often blotchy. This stage looks worse than the finished result.
• Months two to six — colour evens out and deepens toward a red-brown. Runoff staining is at its heaviest here.
• Months six to eighteen — the patina tightens and darkens. Runoff reduces sharply.
• Beyond two years — a stable deep brown that keeps shifting slowly for the life of the piece.

We can accelerate the first stage in the shop with a chemical treatment if a client cannot live with the grey-and-blotchy phase. It brings the colour forward; it does not skip the weathering.

Free in-house consultation

We come to you, measure the site, and talk through options and budget before you commit to anything. No charge, no obligation.

Call (778) 805-5333 or email sales@trussmetal.com