White rust is a common problem in the structural steel industry. It is typically caused by improper jobsite storage and a lack of air circulation. Aside from it harming the physical appearance of the bolt, white rust can break down the layer of protective coating on the bolt.
Many structural bolts are galvanized for their protection and durability. This galvanized coating is made of zinc, which is one of the best ways to prevent corrosion on steel. White rust is made up of zinc hydroxide, which is formed when zinc reacts with water and air. Zinc hydroxide is unstable and consumes the protective zinc coating. This typically happens when fasteners are “nested” together (packed flat one on top of another) and water gets in between the fasteners. It looks like white powder covering the surface of the coating (see image below). Fortunately, there are a few simple ways to prevent white rust from forming on your structural bolting components.
Jobsite Storage
Proper jobsite storage is something we often stress, because it is the number one way to prevent issues with fasteners. There is always a greater chance for white rust formations when fasteners are improperly stored outdoors and exposed to the elements. It’s important to make sure your fasteners are receiving proper care from the moment they enter your jobsite. When the fasteners are delivered, make sure they are stored properly at the time you receive them. For more information on proper jobsite storage, check out our blog post.
Air Circulation
As we mentioned, when fasteners are “nested” together, white rust is more likely to form due to a lack of air flow and moisture getting trapped in between the fasteners. Fasteners are sent in bins that ensure proper air circulation. It’s important to keep the fasteners stored in a way that maintains air flow and allows any moisture to evaporate.
Bottom Line
White rust typically occurs when fasteners are stored improperly and exposed to moisture. Be sure your products are not “nested” and have proper air circulation to prevent white rust from forming. Though there are ways to treat white rust (depending on severity), prevention will save you time, money, and frustration. As always, proper jobsite storage is vital to the protection of your fasteners.