The Downsides of Weathering Steel: What You Should Know

PSA: Weathering steel can corrode, and you might want to rethink using it.  

Did you know weathering steel can corrode in certain environments? But wait — “it’s supposed to have natural corrosion resistance!” True … but only sometimes. While weathering steel has a protective patina, if it’s in the wrong conditions, it can corrode faster than you’d expect, leading to costly repairs, structural issues, and maintenance headaches. Before you commit to using it, here’s what you need to know.  

Weathering Steel 101

Weathering steel, AKA Cor-ten steel, is a low-alloy steel designed to form a protective rust-like patina (we love a good patina finish!) when exposed to the elements.

Cor-ten fence along a bridge.

What’s the catch about Cor-ten?

Weathering steel may seem like the way to go. But (and it’s a big “but”) there are four cons you should consider before choosing it for your project. 

1. Environment Vulnerability

You’d think weathering steel would thrive in any weather, but that’s not the case. The ideal environment for weathering steel features wet and dry cycles, which help the patina develop and stabilize. Too much humidity? Nope. Poolside? See ya! Salty air? Hard pass. These conditions can challenge its corrosion resistance; here’s why: 

• High-chlorine environments (like near pools or industrial areas) can compromise the protective patina, accelerating the corrosion process and leading to failing steel structures well before the end of their intended lifespans.   

• Coastal or high-humidity regions (think Florida) with salty breezes and areas prone to frequent water retention are particularly problematic and can lead to unchecked corrosion.1

2. Potential Staining

While the rusting patina may look aesthetically appealing, it has a downside: “bleeding.” During the patina’s formation, rust particles can wash onto nearby surfaces, leaving stains that might discolor adjacent areas. This can be a dealbreaker for projects where appearances matter (and they almost always do).1 

Cor-ten bleeding on concrete.   

Photo from Unsplash.

3. Limited Availability

Weathering steel isn’t always as accessible as traditional steel. It isn’t exactly hanging out at every corner hardware store. So, depending on your location, you might face longer lead times or higher material costs, which could delay your project or stretch your budget.1 

4. Design Limitations

Smart design plays a critical role in the longevity of weathering steel structures. By addressing design challenges up front, you can significantly extend the lifespan of weathering steel and reduce corrosion risks. Here are some key things to consider: 

• Avoid crevices, cavities, or features that trap moisture. 

• Ensure areas, where corrosion products (known as pack-out) might accumulate, are minimized. 

• Incorporate adequate drainage to keep water from lingering on surfaces.1 

Weathering steel can be chosen at times; however, it’s not a one-size-fits-all solution. Understanding the limitations and planning for environmental and design factors will ensure it performs as desired. 

What’s an Alternative When You Need an Alternative?

Hot-dip galvanized steel — which can be coated with Natina’s rustic color — is perfect for any area, including those “aggressive” environments. It has none of the cons listed above for weathering steel and even more pros. 

Natina-treated transmission poles in a forested area.

1. Strong Against the Elements

Weathering steel corrodes over time, meaning you may need extra-thick sections to make up for the mass loss (cha-ching). Hot-dip galvanized steel? No mass loss, no extra steel, no extra cost.2

2. Easy to Inspect & Maintain

Unfortunately, that rust that’s so beloved on weathering steel makes it really hard to tell if the structure is failing. So, inspections are expensive and extensive. Hot-dip galvanized steel, on the other hand, resists corrosion inside and out. With Natina’s patina on top, you get a natural look that doesn’t require continual application of color.2     

Natina-treated transmission poles in Canada.

3. Patina Perfection with Natina

OK, we don’t want to brag, but our patina on hot-dip galvanized steel is ready onsite, compared to weathering steels. That weathering steel look takes 3-5 years to fully develop!2 Ours? Within 4-8 weeks. It has all the beauty of weathering steel’s patina without the need for extended amounts of time and weather exposure for it to develop.  

4. Electric Company-Approved

The “pack-out” (the buildup of rusty corrosion from weathering steel) can cause arcing of electricity from pole to power pole. Thankfully, hot-dip galvanized steel is used for the exact opposite reason: no incidents when used for generation, transmission, and distribution.2 And when those power poles are somewhere like bordering a national forest, the last thing you want is a shiny steel pole sticking out. Natina’s color solution helps make these necessary electric structures visually fit into their surroundings.  

If your project would be better with hot-dip galvanized steel but you still want the visual mitigation and beauty of the patina, contact us today for expert guidance on planning your next construction project! 

Sources 

1 DIS-TRAN Steel 

2 Galvanize It