Steel Corten rust (Cor-Ten) is a weather-resistant steel that can more appropriately be described as atmospheric corrosion-resistant steel. It is a copper chromium alloy steel – this alloy exhibits a greater level of resistance to atmospheric corrosion than other unalloyed steels.
As for corten steels, the rusting process occurs in the same way but instead results in a more stable rust layer known as a patina, which adheres to the base metal and is less porous. When exposed to the weather, this naturally-developed patina regenerates continuously and creates a protective barrier that hinders the entry of oxygen, moisture, and pollutants.
Does this make corten steel rustproof? Not at all. Corten steel is left to rust in order to form a protective patina coating. While this results in a much lower corrosion rate compared to other steels, it does NOT make corten steel corrosion-proof.
Corten steel is corrosion-resistant, but it is not completely rust-proof. Environmental and climatic factors play a key role in determining how long the steel will last and how quickly the rust will develop.
- After six months of exposure to the atmosphere, Corten steel will corrode or patina. Weathering steel types require cycles of wet and dry weather to develop.
- Corten steel can last from a few decades to over 100 years due to rust, which provides corrosion resistance.
- Corten can be prevented from rusting by using saltwater or vinegar and peroxide combined with salt solutions.
It has become increasingly popular for architectural facades and outdoor sculptures. The material’s look is so attractive that entire buildings have been designed with it, and it has a legion of residential fans, including myself, around the world. The material appears unfinished and rustic at first glance, but that is one of the reasons why it is so appealing.
Despite its attractive appearance, weathering steel is not perfect for all applications. Before construction, carefully consider its use and placement. If used incorrectly, cor-ten can be difficult and even harmful to surrounding areas. You should avoid using this material where rust bleeding or runoff is likely to stain nearby paint, stucco, stone, or concrete. Unless otherwise indicated, rust bleeding or runoff can stain nearby paint, stucco, stone, or concrete. This material may also fail to form a protective patina in humid climates, allowing the steel to corrode.
Corten Steel Rust Runoff: How to Prevent It
Weathering steel products and structures often have concrete, stone, or brick surfaces below and around them, which are difficult to clean, so rust run-off and staining should be avoided. Runoff is caused by weathering, but it can be managed so drainage does not flow over vulnerable areas.
Gravel borders can be installed around weathered steel structures to catch run-off and prevent it from running over permanent surfaces such as concrete or stone, preventing staining.
Pre-patinating weathering steel with acidic spray prior to installation will initiate the patina process and minimize further rusting.
Rust can be prevented by galvanizing
By applying zinc to steel or iron, galvanizing prevents corrosion or rust.
Hot-dip galvanizing involves immersing iron or steel in molten zinc to form a protective coating.
Unlike hot-dip galvanizing, which can be done on-site, cold galvanizing compounds are zinc-rich corrosion-preventative coatings.
The 95% metallic zinc content of these cans qualifies them as an equivalent to hot-dip galvanizing in Underwriters Laboratories’ Component Program. As a result, you get the same level of protection that is provided by hot-dip galvanizing in the convenience of a can; shipped directly to you for application on-site. In the same way, as hot-dip galvanized products (DOD-P-21035A, formally MIL-P21035A), cold-galvanized products are subject to similar Federal Specifications.