16 Nov FAQ: Can Weathering Steel be Purchased Pre-Rusted?
The unpolished, rustic texture and orange-brown color of weathering steel is sought after for a range of applications. As a trusted weathering steel supplier, we are often asked if weathering steel, also referred to as corten steel, can be purchased “pre-rusted.”
The probably more correct answer is no, and yes! Weathering steel is produced and supplied from producing mills “as rolled,” which means just raw steel — not further treated or pre-weathered and left to develop a patina naturally. For more impatient consumers, treatments can be applied to accelerate the patina process. If you are working on a smaller scale project, you can expedite the process as described below. If you are working on a larger scale project, there are some companies that professionally pre-weather and seal or just pre-weather weathering steel. We would be happy to refer you when the time comes.
The Patina Process
When exposed to moisture, air and other outdoor elements, most low-alloy steels have the tendency to rust and corrode over time. Weathering steel, on the other hand, produces a stable rust layer, called a “patina,” which services as a protective, corrosion-resistant barrier. The patina regenerates continuously as it is exposed to weather and prevents further access of oxygen, moisture and pollutants.
How quickly the patina forms depends on the environment of the weathering steel. For instance, we’ve found that the patina forms faster when the steel is exposed to more cycles of wet and dry weather. In more consistent (mostly dry or mostly wet) weather environments, it may take longer for the patina to form. We’ve also found that cold-rolled materials tend to form a patina quicker than hot-rolled materials.
The beauty of weathering steel’s naturally-produced, protective patina is that it constantly evolves, becoming deeper in color and texture overtime to perfectly blend with the surrounding landscape. While you cannot purchase pre-rusted weathering steel, there are ways to expedite the patina process.
How to Expedite the Patina Process of Weathering Steel
Because we have had several customers inquire about ways to expedite the patina process or “pre-patina” weathering steel before installation, we tested two pre-patina treatment options using three ¼-inch hot-rolled weathering steel squares.
We treated one square with just water, the second with a hydrogen peroxide, vinegar and salt water mixture, and the third with muriatic acid. If you need to pre-patina weathering steel to minimize run-off staining or for other reasons, the hydrogen peroxide, vinegar and salt water mixture is the better option as it weathers more naturally. The muriatic acid should be used with caution because it may cause flaking and odd coloring. With either option, consider applying a clear coat sealant once the pre-patina finish is obtained.
Contact Central Steel Service for High Strength Weathering Steels
Do you have more questions about weathering steel? Contact one of our experienced sales associates. As a trusted supplier of weathering steel, we are committed to providing customers with an exceptional level of service to make your buying experience easy.