How to Remove Rusty or Seized Screws

In this guide, we're going to discuss how to resolve the issue of seized, stuck, damaged, or rusted screws. We'll also provide some handy tips to help you avoid the problem in the future.

After all, even a single seized screw could lead to further complications and consequences as major as immobilising a production line. When it comes to seized screws, prevention is always an important course of action.

During maintenance or troubleshooting, you may be confronted with stuck or rusty screws and bolts. Indeed, mechanical structures and industrial machinery can be affected by many adverse factors, such as thermal shocks, bad weather conditions, or chemical and fluid splashes.

Factors such as these can weaken the surface treatments of the materials and thus accelerate the process of corrosion. The bolts ensuring the assembly of the various mechanical elements are often the first to be impacted.

Seizing is another issue that can be the cause of screws and nuts jamming. It's common in mechanical applications when two or more metal components are subjected to friction.

Seizure is a concept well-known to mechanics and maintenance teams. It's linked to friction leading to the transfer of particles between two surfaces. In the case of a screw-nut assembly, the friction between the threads causes minuscule particles of material such as protective coatings to become detached. The accumulation of these particles can impede and - in severe cases - block the assembly and cause the screw or bolt to experience seizing.

Luckily, it's easy to predict the potential for seizing to occur. It is more likely to happen in fastenings made from materials that are sensitive to friction, such as aluminium, titanium, and stainless steel.

As corrosion occurs, the volume of the affected parts increases due to the additional layer of rust covering the assembly. This causes additional pressure to the threads and locks the assembly in place, making removal or adjustment much more challenging.

So, how can you avoid seizing and what are the best ways to remove stuck screws?

Lubrication is essential when servicing and maintaining machinery and mechanical structures. It can help to improve performance and prolong the lifespan of moving parts. However, the maintenance of static assemblies is also crucial as it can help to avoid the risk of assemblies becoming seized. Failure to address or rectify these issues can be detrimental and could cause disruption to production lines or machinery if left unchecked.

Lubrication

Lubrication before assembly is essential. The purpose of the lubricant is to protect the surfaces of the threads against corrosion, but also to limit the mechanical stress on the threads as this is a cause of seizing.

The choice of lubricant is also important. You must take into account both the nature of the materials and the conditions to which the assembly will be subjected, such as temperature, humidity, and the presence of any chemicals.

A dry lubricant such as Molybdenum Disulphide lubricant should be a suitable solution for general-purpose assembly lubrication. It's designed to avoid the formation of deposits of dust or impurities between the threads, helping to reduce friction and prevent seizing. Another popular option is WD-40.

Observation

Before the assembly is addressed, observation is key. It will alert you to any potential difficulties in loosening the fastener and noticing any significant issues will make it easier to tackle the problem successfully.

You should look out for:

• Evidence of corrosion
• Traces of possible lubrication

The presence of rust - even minor traces - will be instrumental in determining the state of corrosion. On the flip side, the presence of lubricant typically means it will be possible to loosen the screw with standard tools such as a flat or adjustable spanner. The absence of lubrication, however, could indicate a possible seizing.

Use the Right Tools

If the screw head shows signs of corrosion, it is better to opt for ring spanners, hex sockets, or bi-hex sockets. These tools are supported on the six sides of the head to allow force to be better distributed. However, if the screw head is damaged or too blunt, locking pliers will provide the necessary gripping force to continue the removal process.

In some cases, a grinder can be used as a last resort to extract a screw and nut connection. This won't always be possible though, as there needs to be enough space for the grinder to access the problem assembly. Equipped with a thin disk for precision, an angle grinder could also be used to rework a stripped screw head to restore a new slot for extra grip. Creating a groove could also make it possible to insert a flat-head screwdriver.

Thermal Shock

As mentioned above, thermal shock is a method used to weaken rust. As the fastening heats and cools, the materials expand and contract, weakening the bonds created during the process of corrosion or seizing.

However, thermal shock with heat is more frequently used to free stuck bolts. The application of heat is typically carried out with a blow torch or heat gun. One method involves heating the bolt or screw head, before immediately shocking it with cold water to achieve a sudden difference in temperature.

Safety is paramount, so if you do use heat, make sure to remove any plastic or rubber components that could be damaged by high temperatures before you start. Similarly, ensure you have removed or cleaned away any potentially flammable lubricant or penetrating oil before applying heat.

Mechanical Shock

Impact wrenches or impact drivers may be able to overcome the seized or rusted screw. The shocks caused can break the bonds and may loosen stubborn screws. This technique is often used in the automotive industry for loosening wheel studs. The same result could also be achieved using a hammer to hit the screws with force.

Despite regular maintenance and the application of lubricant to prevent seizing or corrosion of assemblies, fastenings may still occasionally encounter these issues. The key is to be patient and avoid using excessive force, which could cause further damage.

The use of penetrating oil is recommended initially and will be sufficient in the majority of cases. However, if penetrant is not enough, many alternative methods are also available. These include thermal or mechanical shocks, but also the use of specific tools such as sockets, pliers, screw extractors, or even angle grinders.