Threadlockers are anaerobic adhesives specifically designed to seal and lock threaded components in a mechanical assembly. Most threadlockers take at least 10 minutes to gain handling strength and approximately 24 hours to harden into a thermoset plastic and provide full strength (this process is called curing). However, the time may differ depending on the type and strength of the thread locker. Read on to know more about the cure time of different thread lockers and how you can reduce it.
How Does the Liquid Threadlocker Dry?
An important point that needs to be remembered is liquid threadlockers can dry in the absence of air. So, you will notice that any excess adhesive on the outside of the mechanical parts will remain liquid as it is exposed to air.
The drying or curing speed of threadlockers depends on various factors like:
- Base metals
- Gaps or clearance between components
- Surface cleanliness
- Part size
- Part shape
- The level of humidity.
Read on to see how the top 3 factors affect the drying speed.
How do the above factors affect drying?
I went through the technical data sheets of LOCTITE threadlockers to understand the impact of these factors on cure time, so that I will be explaining it for LOCTITE here.
- Base metal - Those metals that have more free ions allow threadlockers to cure faster - said, those metals that corrode faster are also the ones that allow threadlockers to dry faster. You will get handling strength in 5 to 10 mins and full strength in 3 to 6 hours with these active metals.
These metals are known as “Active” metals, and some examples of these are Brass, Copper, Steel. While the opposite of these is called “Inactive” metals, and threadlockers take a longer time to dry on these. Some examples of inactive substrates are Zinc, Chromium, Stainless Steel. You will get handling strength in 20 to 30 mins and full strength in 24 hrs on these inactive metals.
- Gap or clearance between components: This is the second-factor post base metal to affect the drying time. As such, there’s isn’t much gap between the mating nut-bolts. But sometimes, the gaps can be larger, and the threads can be deeper.
Let’s take the example of a steel nut-bolt—Threadlockers dry fastest when the gap is less than 0.05 mm. Handling strength comes in 5 to 10 mins, and full-strength comes in 3 to 6 hours. For gaps between 0.05 mm and 0.25 mm, the handling time can be between 10 to 30 mins, and full-strength comes in 24 hrs.
- Temperature: The third important factor that affects curing or drying time is the temperature of the nut bolt. In regions with tropical climates, the summer temperatures are around 40oC, and this enables the fastest drying. So, a steel nut bolt at 40oC will allow the threadlocker to get handling strength in 5 mins to 10 mins and full strength in 30 mins to 3 hrs. At 22oC this takes slightly longer - 10 mins to 30 mins to gain handling strength and 3 to 6 hrs to gain handling strength. For regions with colder climates or during the colder season, the drying time slows down a lot - at 5oC it takes threadlockers 20 mins to 1 hr to get handling strength and 24 hours to get full strength.
How can I Make Threadlocker Dry Faster?
Here are some tips on how you can make a threadlocker dry faster:
- Clean the nut and bolt surface thoroughly before application of the threadlocker. Any grease, dust or dirt particles reduce the effective surface area and effective free ions, thereby slowing down curing.
- Only apply a thin layer of the threadlocker. Over-application of the adhesive will increase the curing time.
- Apply clamps to the bonding surfaces and press them together as tight as you can. This forces all the extra air out of the threadlocker’s centre, thereby making it dry faster.4. Install a fan or dehumidifier in the same place as the bonding items to remove moisture. The presence of dampness in the air increases the time needed to dry the threadlocker. So, eliminate as much humidity from the air as feasible. Also, it is better to carry out the process inside where there is much lesser humidity.
- Set up a space heater near the items if the air temperature is less than 22oC . Make sure to maintain a distance of at least 2 feet between the heater and the application area, as the heater poses a fire hazard. Now, regulate the heater to increase the air temperature to a minimum of 25oC for faster curing.
- In the case of inactive base metals, use primers or activators. These help to fasten the reaction of bond formation. You can read more about primers and activators here
While, on average, threadlockers get handling strength in 10 mins and full strength in 24 hours, there are various factors that affect the curing or drying time. The above methods that can tackle the impact of temperature, metal substrate and gap will help expedite the drying process.