Introduction:
Corten steel, often praised for its rustic and edgy aesthetic appeal, has gained popularity in architectural design due to its naturally weathering and interesting appearance. However, despite its alluring design possibilities, Corten steel is not a material to be relied upon for architectural projects, especially when considering the development of a “protective surface layer” made of ferro-oxyhydroxide. In this post, we will delve into the reasons why we do not recommend Corten steel for architectural applications, focusing on its composition, stability, protective properties, lifespan, and the issue of contamination.
Composition:
Corten steel is known for the layer of ferro-oxyhydroxide it develops over time. Ferro-oxyhydroxide, a compound formed from iron’s reaction with oxygen and water, shares similarities with standard rust (iron oxide). However, they have distinct differences, particularly regarding their suitability as protective layers for architectural applications.
Stability:
Ferro-oxyhydroxide is more stable than standard rust. Rust is a form of iron oxide that is formed when iron reacts with oxygen and water, primarily in the form of iron(III) oxide (Fe2O3). Ferro-oxyhydroxide, on the other hand, is a different compound that contains iron and oxygen but is typically in the form of iron(II) oxyhydroxides, such as FeOOH or Fe(OH)2.
Iron(III) oxide, which is the primary component of rust, is relatively stable under standard atmospheric conditions, but it is not as stable as iron(II) oxyhydroxides. Iron(II) oxyhydroxides are more stable in reducing environments where iron is in its +2 oxidation state. They are also often found as minerals, such as goethite (α-FeOOH) and lepidocrocite (γ-FeOOH), and are less prone to oxidation and corrosion compared to standard rust.
So, in terms of stability, ferro-oxyhydroxides are generally more stable than standard rust in certain environmental conditions. However, the relative stability of these compounds can depend on specific circumstances and the presence of other factors, such as pH, oxygen levels, and other chemicals in the environment.
Protective Properties:
While ferro-oxyhydroxide initially provides some protection due to its rapid formation on iron surfaces, its instability makes it unsuitable for long-term architectural applications.
Standard rust can offer limited protection initially, but it, too, is not a durable, long-lasting solution and can lead to structural weaknesses over time.
Lifespan:
Corten steel’s lifespan is challenging to estimate precisely, as manufacturers are often reluctant to provide specifics. However, in moderate environmental conditions, a ferro-oxyhydroxide coating may last around 5 to 10 years, while harsh conditions can reduce its lifespan to 2 to 5 years.
Corten longevity is also tricky to fully assess because failure points can more readily occur on vulnerable areas even sooner than the lifespan claim. Where the material on the whole appears solvent, leaks and structural issues arise. Time and again we’ve seen this occur. But it’s not just us. The industry is filled with case studies. Here’s one of them:
https://www.bloomberg.com/news/articles/2015-04-24/a-look-back-at-the-omni-coliseum-and-how-it-helped-revitalize-downtown-atlanta
…“On the outside, its weathered steel facade, commonly referred to as Cor-Ten, was a stylish choice but ultimately a poor one. “We thought it fit the very industrial nature of that site,” Ventulett tells CityLab. Weathering steel is supposed to allow the material to develop a resistance to corrosion over time, functioning as a natural protective layer. But that’s not what happened in hot and humid Atlanta. The steel rusted through and water leaks plagued the building even though the roof pods were eventually covered with a rubberized material. “If I were doing it again I wouldn’t use Cor-Ten,” says the architect.”…
Superior Alternatives:
We build with permanence. Long life is our standard. Offering you only the options we’d use on our own projects is the moral thing to do.
We’d vastly prefer to steer you toward an artistic, specially patinated copper with rustic design attributes sealed with a clear coat which would ensure a much longer-lasting solution.
Also, extremely popular are our specialty painted galvalume and aluminum options. We fabricate from an array of beautiful rustic paint finishes: https://spenglerindustries.com/rustic-roof-with-permanence/ And these can be made to custom specifications as well depending on the size of your project. They also can be made in marine grade options appropriate for proximity to the ocean. https://spenglerindustries.com/rustic-horizontal-metal-panels-near-the-ocean/
https://spenglerindustries.com/colored-metal-for-coastal-applications/
Additionally, chromium oxide over stainless steel offers an array of solutions for all environments: https://spenglerindustries.com/the-difference-between-chromium-oxide-and-titanium-nitride-finishes/ And no, it’s not just shiny. They can make magic on finish options. This is a pricier alternative, but you can guarantee an extremely long finish regardless of environment.
There are options out there. If you are looking for something specific, please allow us to help you find appropriate alternatives to short-term hacks.
International Perspective:
Corten steel is forbidden for architectural applications in Germany, underlining its unreliability as a building material in regions with appropriate building standards.
Construction and Staining:
Corten steel is known for its unsightly rust runoff and staining, which can mar the aesthetic of a structure. It’s messy and difficult to manage even with the best design preplanning.
Contamination:
Working with ferro-oxyhydroxide can lead to tool and equipment contamination with rust or iron oxide, primarily due to the instability and loose structure of the material. The transformation of ferro-oxyhydroxide into more crystalline forms of iron oxide can result in the release of loose particles that settle on tools and equipment, especially during handling, cutting, or grinding of materials containing ferro-oxyhydroxide.
We have made a commitment to a clean facility where no contamination on any of our other materials can occur.
Conclusion:
While Corten steel may be visually appealing, its unstable ferro-oxyhydroxide layer, susceptibility to rust and corrosion, limited lifespan, and contamination risks make it an unreliable choice for architectural applications. When considering materials for your architectural projects, it’s advisable to opt for more durable and long-lasting alternatives that provide both aesthetic appeal and structural reliability.
If you’re seeking a similar look without all the baggage of rust, call today and we’ll help you discover the perfect, permanent options that offer a similar design aesthetic.
801-462-5264
Related articles:
https://spenglerindustries.com/rustic-finishes/
https://spenglerindustries.com/rustic-roof-with-permanence/
https://spenglerindustries.com/rustic-horizontal-metal-panels-near-the-ocean/