19 Mar How to Prevent Rust Run-Off
Weathering steel is well-known for the rusty, orange-brown “patina” that it develops overtime. While this aesthetically-appealing patina serves as a protective, corrosion-resistant barrier, it can produce rust run-off as it develops.
The Weathering Process
Just like standard steel, weathering steel is silver in its original state. When exposed to moisture, air, and other elements, standard steels have the tendency to rust. This rust layer becomes porous and detaches from the metal surface.
With weathering steels, the rusting process happens in the same way, but the steel produces a patina. This naturally-developed protective patina regenerates continuously to stop further access of oxygen, moisture and pollutants.
In the early years of its development, the patina can cause rust run-off, which can stain the areas surrounding the steel structure or product. The risk is highest during the early months because the corrosion rate is at its highest. As the corrosion rate slows, the risk of staining will decrease. But, the good news is that this potential problem can be avoided.
How to Prevent Rust Run-Off
Areas below and around weathering steel products and structures are often concrete, stone or brick, which are all fairly difficult surfaces to clean, so it’s important to consider how you can prevent rust run-off and stains. Because the run-off is a part of the weathering process, it cannot be prevented. However, the run-off can be managed so that the drainage does not flow over vulnerable surfaces.
One way to prevent staining from initial run-off is to install a gravel border around the weathering steel structure to catch the run-off and keep it from running over more permanent surfaces, such as concrete or stone. The gravel border can be easily replaced as needed.
Another way to prevent staining is to “pre-patina” the weathering steel with an acidic spray. This spray will initiate the patina process prior to installation and minimize further rust run-off.
For structural building purposes, consider including drip details on the bottom flanges of girders to ensure that bearing shelves have generous falls to internal substructure drainage systems. These drip details will cause the water to drip off of the steel rather than run along its surface and onto the surfaces surrounding it.
We also recommend sealing vulnerable substructures with washable coatings to facilitate cleaning if the rust run-off causes staining.
Contact Central Steel Service
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 and making your buying experience easy.