How to Reapply Bolt Lubricant

Structural bolting components, whether uncoated or galvanized, are lubricated for installation purposes. Sometimes it is necessary to reapply bolt lubricant. Though the types of structural bolt lubricant vary, both have a chance of coming off prior to installation. This is typically caused by exposure to the elements from improper jobsite storage. Reapplication of the lubricant is typically required prior to installation. Here, we’ll go over how and when to reapply lubricant on structural bolting assemblies.

Reapplying Bolt Lubricant on Uncoated Assemblies

While there are no specific ASTM requirements that uncoated bolting assemblies be lubricated, their lubricant comes from the left over water-soluble oil from production. This oil ensures ease of installation. The lubricant can wash away when exposed to condensation, or it can evaporate when their containers are left open.  If this happens, the assemblies can be difficult to install, and the bolt’s ductility is lessened due to the stress of tightening the non-lubricated bolt.

If the bolting assemblies have lost their lubrication, you may reapply an oil-based structural bolt lubricant, like stick wax or liquid wax, prior to installation. To reapply bolt lubricant, put it on the nut’s threads and inside face. It’s important that the lubricant is on the inside face of the nut, because much of the torque used to tighten the bolt is to get past the friction between the nut and washer or steel. Once the bolt lubricant is reapplied, you may be required to retest the bolting assemblies or recalibrate your wrenches prior to installation. Refer to the RCSC for more details.

Reapplying Bolt Lubricant on Galvanized Assemblies

In contrast to uncoated bolting assemblies, galvanized nuts are lubricated with a dry, wax-based bolt lubricant. Because it isn’t oily, you may not be able to feel this lubricant. The ASTM requires that the lubricant be dyed to ensure that the nuts have been lubricated (Note: the color is not specified and varies from manufacturer to manufacturer).

Similar to the uncoated bolting assemblies, if the nuts have lost their lubrication, reapply a wax-based lubricant on the nut’s threads and inner face. There is no need to lubricate the bolt or washer. Once the lubricant has been reapplied, you must retest the assembly. Refer to the RCSC for more details on testing.


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