Do Rusted High-strength Bolts Require A Larger Torque Wrench To Remove?

Generally speaking, rusted high-strength bolts usually require greater torque to remove. The following is a detailed analysis:

Rust causes increased friction

Generally speaking, rusted high-strength bolts usually require greater torque to remove. The following is a detailed analysis:

Rust causes increased friction

When high-strength bolts rust, rust will fill the tiny gaps between the bolt and the nut and between the bolt and the connected parts. When trying to remove the bolt, the presence of rust greatly increases the friction between the thread pairs and between the bolt head and the surface of the connected parts. According to the torque calculation formula T=K×F×dT=K×F×d (where TT is torque, KK is torque coefficient, FF is preload, and dd is bolt nominal diameter), when removing the bolt, in order to overcome the increased friction, a larger torque is required to turn the bolt.

Physical hindrance of rust

Rust may cause the fit between the bolt and nut to become tighter, and may even cause the thread to deform to a certain extent. This physical hindrance will further increase the difficulty of disassembly, making it impossible to loosen the bolt with the torque applied under normal circumstances. The torque must be increased to break the restraint caused by the rust and allow the bolt to start turning.

Possible special cases

However, in some extreme cases, if the rust is very severe, the rust has severely damaged the material structure of the bolt, and the bolt has become fragile and brittle. Excessive torque may cause the bolt to break instead of normal disassembly. At this time, it is not possible to simply rely on increasing the torque for disassembly. Other methods may be needed, such as using rust removers, heating, etc. to treat the rust first and reduce the torque required for disassembly.

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