How to free seized nuts and bolts with penetrating oil

Heating with a torch may not be the best method for freeing stuck parts; consider penetrating oil instead

By Liza Klein January 19, 2022
Courtesy: Kano Laboratories

One of the many things Benjamin Franklin is known for is his quote from 1789: “Nothing is certain, except death and taxes.” If he was alive today, he would likely modify his quote to include: “Another certainty: metal rusts.” Rust is the kryptonite that affects all exposed metal; there is no escaping it. Many things can cause metal parts to seize up, including chemicals, corrosion, paint, environmental factors and over-tightening; but rust is the biggest culprit. When critical components in an assembly rust, disassembly can become difficult. A nut or bolt needs to be loosened, a frozen key must be removed, a seized clamp has to be opened or a set screw just won’t budge.

There are many different methods for freeing stuck parts including drilling, grinding or cutting the part. In these examples, there are risks. For example, the part to be loosened may be damaged or destroyed beyond repair, requiring replacement (if, that is, a replacement part can be found in time or at all). Drilling, grinding and cutting also present potential physical hazards to personnel and the surrounding equipment.

Appy heat

A common technique used when attempting to salvage a part is to apply heat. The heat source may come in the form of a propane torch, acetylene torch, heat gun, induction heat or a heated element (see Figure 1). So how does it work?

Figure 1: A common technique used when attempting to free a stuck part is to apply heat. The process involves many risks and requires great skill.

Figure 1: A common technique used when attempting to free a stuck part is to apply heat. The process involves many risks and requires great skill. Courtesy: Kano Laboratories

“Scientifically, heat expands metals, and two different sizes or types of metals such as a nut and a bolt will expand at different rates. This can help break the bonds of rust,” said Sevan Demirdogen, CEO of Kano Laboratories, producer of Kroil Penetrants. “As metal cools, it contracts at different rates, and continues to separate seized parts. However, using heat to remove frozen or seized components can be tricky and risky. As such, heat should only be applied in special circumstances by highly experienced workers, using proper equipment in a controlled environment.”

While using heat can be effective, there are many risks, and executing this process requires great skill. Without the proper technique, many challenges can result, including:

  • Fire/burn risk. When working with heat or an open flame, workers run the risk of burning themselves, someone else or adjacent materials. Working near flammable materials and/or chemicals is even more dangerous.
  • Accessibility. Not everything you want to take apart is at ground level or on a work bench. Many times, equipment is either high above ground, underground or in tight spaces. In these instances, heat-generating equipment or open flames may be nearly impossible to apply properly and safely.
  • Mobility. It’s not easy to carry heat generating equipment along with all the tools required for a given job; this can be especially cumbersome when multiple locations are involved.
  • Dangerous gasses. Using an open flame in an unventilated, confined space can create a dangerous atmosphere due to toxic gasses, carbon monoxide and/or oxygen depletion.
  • Damaged or destroyed metal. If one overheats metal to a molten glow, they can damage or destroy the nut, bolt and any other adjacent parts. In cases involving hardened steel, applying heat can actually break down the hardening properties.

A different solution, penetrating oil

When it comes to freeing rusted and corroded items, nothing rivals powerful penetrants. Penetrating oil has been used for decades to effectively loosen stuck metal parts, without the inherent risks of using heat. In contrast to the challenges noted above, penetrants provide alternative solutions.

Penetrants are safer and more effective than the heat option, as they allow direct application to affected areas using application straws. Using a penetrant instead of heat also keeps more delicate materials like gaskets, valve seats, o-rings and insulation from being damaged.

Canned penetrants can be transported nearly anywhere, allowing workers to do their jobs effectively without having to wait for heat generating equipment to arrive.

Penetrating oil also saves time, as they work quickly to loosen stuck parts. Even if extra breakdown time is needed, workers can move on to other things rather than wait around. Heating, on the other hand, requires full attention throughout the process. Penetrating oil also provides lubrication and corrosion protection that heat doesn’t.

“Penetrating oils have been used and trusted by maintenance, repair and operations (MRO) pros, service technicians and experienced DIYers for decades,” Demirdogen said. “The best penetrating oils quickly loosen rusted nuts and bolts, free frozen shafts, pulleys and more. With Kroil, no space is too tight to penetrate, thanks to its ability to seep into the smallest opening or crevice.”

“Having a good penetrant is crucial when specialty parts, nuts and bolts are involved,” said Barry Lefavour of Big Jim’s Auto Body. “If we can’t get bolts off, we may end up breaking them, which creates many more problems. The penetrating oil gets in there and loosens things up, so we can crack them free. It saves a lot of time, because if we break something and we don’t have it in stock, we may have to place a special order. In such cases, the car sits longer, tying up the shop.”

Sometimes a part is so seized that heat may need to be considered as a possible option. So, can heat be used in conjunction with a penetrant? Yes, said Demirdogen, but with some important warnings.

Penetrants are flammable and should never be used around an open flame. Similarly, do not apply heat immediately after an item has been sprayed with a penetrant or any other chemical.

Never apply penetrants to a freshly heated part for several reasons. First, there is a fire and burn risk. Second, extreme heat can cause the chemicals in penetrants to evaporate quickly, preventing them from working to their fullest potential.

Do not use penetrating oils and heat at the same time, but in alternating steps. Be sure to remove any oil from the surface of the part and all surrounding areas before applying heat or open flame. On tough jobs, carefully pre-heat the part, let it cool and then apply the penetrant. As Demirdogen said, “If a worst-case scenario demands the use of heat, then carefully heat it, cool it, Kroil it and wrench it free.”

Whenever rust or corrosion slows you down, reach for a premium penetrating oil instead of a torch. You’ll be able to complete tough jobs safely and more efficiently than the heat alternative.


Liza Klein
Author Bio: Liza Klein is vice president of marketing at Kano Laboratories in Nashville, Tenn., a leading producer of Kroil-branded penetrating oils and lubricants for the industrial maintenance, repair and operations.