Moving beyond washers

Threaded fasteners sit at the heart of almost every mechanical assembly. Yet despite their critical role, the methods used to secure them have changed surprisingly little in many sectors.

Mechanical locking devices such as castellated nuts, lock wires, nylon-insert nuts and serrated washers have long been relied upon to prevent loosening. However, as industrial demands increase and equipment operates under greater vibration, temperature fluctuation and dynamic load, these traditional solutions are showing their limitations.

Threadlocking technology offers a fundamentally different approach. Rather than relying on friction alone or additional mechanical components, anaerobic threadlockers chemically secure and seal the fastener in place. They remain liquid in the presence of air but cure into a solid thermoset polymer when confined between metal surfaces, filling the gaps between threads and eliminating lateral play. The result is a fastener that maintains clamp load, resists vibration and prevents corrosion and leakage.

For many maintenance teams, threadlockers are still perceived as a corrective measure, something applied only after bolts have started to loosen. In reality, the technology was designed to prevent failure from occurring in the first place. Since their introduction in the 1950s, anaerobic threadlockers have become standard across automotive, aerospace, heavy equipment and electronics industries, securing billions of threaded fasteners every year.

The shortcomings of traditional locking methods are often hidden in ongoing maintenance routines. Washers can embed into mating surfaces, lose preload over time and fail to compensate for vibration-induced micro-movement. They also add complexity to assembly and increase torque requirements. Adhesive threadlocking simplifies the process by securing, sealing and protecting in a single step.

A recent large-scale solar installation highlights the impact of making the shift from washers to threadlocking. The operator was experiencing severe reliability challenges across its site. Solar panels were mounted using M6 bolts with washers, but exposure to outdoor conditions and vibration led to bolts loosening over time. This resulted in annual re-tightening of 296,000 bolts, repeated washer replacement and, in some cases, complete fastener failure causing panels to detach.

The solution was to introduce a structured threadlocking process using LOCTITE 243. After cleaning the bolts, the threadlocker was applied using controlled dispensing to provide consistent coverage. By replacing washers with adhesive threadlocking, the operator eliminated bolt loosening issues entirely. Annual re-tightening was no longer required and unscheduled downtime was significantly reduced.

This case illustrates a broader point. Threadlocking should not be viewed as a reactive repair tool but as a preventative engineering control. By maintaining clamp load and eliminating micro-movement from the outset, threadlockers protect assemblies from wear, vibration damage and environmental ingress.

Selecting the right product depends on application requirements. Strength grades range from low for easy disassembly to high for permanent assemblies. Cure speed, viscosity and temperature resistance must also be considered, with most grades capable of handling temperatures up to 180degC and specialty formulations up to 230degC. Proper application is straightforward. A few drops applied to the bolt threads prior to assembly provide full coverage once engaged, with wicking grades available for post-assembly locking.

Modern formulations continue to evolve, offering primerless adhesion on passive metals, improved oil tolerance, higher temperature stability and safer handling profiles with reduced hazard labelling. Automated dispensing systems further enhance precision and repeatability in high-volume production environments.

With billions of fasteners assembled with anaerobic threadlockers worldwide every year, the technology is already proven at scale. The question is no longer whether threadlockers work, but whether relying on washers alone is still fit for purpose in modern engineering environments.

By shifting the mindset from reactive tightening to proactive prevention, manufacturers and maintenance teams can improve reliability, reduce inspection cycles and lower the total cost of ownership across their assets. Threadlocking is not a last resort. It is a design decision that secures performance from the start.