Thread sealant for pipes (anaerobic pipe sealing)
Sealing pipes with anaerobic adhesive (called pipe sealing)
It is important that pipe constructions are tight enough to avoid corrosion of the parts or possible leakage. Therefore, it is recommended to use adhesive to seal or secure the constructions. With the right adhesive type (a pipe sealant) for the task, you can ensure that the pipes are completely sealed and do not slip apart.
General about anaerobic adhesives as pipe sealants
This one-component adhesive type is ideal for locking threads, hydraulic fittings, and equally for sealing pipe constructions. It is characterized by resistance to a wide range of chemicals and is easy to dose both manually and automatically. Curing begins in the absence of oxygen and in contact with metal ions. This ensures a long open time, allowing sufficient time for proper assembly. Anaerobic adhesives are available in many different viscosities. Finally, they have a heat resistance of about 150–200ºC, good impact strength, and resistance to vibrations.
Strengths
Very simply, anaerobic adhesives can be divided into three strength categories: low, medium, and high strength. The reality is more nuanced, but this is the common way to categorize strength. To illustrate the range, it is possible to have an anaerobic adhesive with a breaking torque of 6 Nm and one with a breaking torque of 60 Nm. Newton meters (Nm) measure the adhesive’s breaking torque, indicating when the adhesive "breaks" when trying to separate bonded parts either by hand or tool. For pipe sealing, medium or high strength is often optimal since pipes usually need to stay bonded for a long time and be relatively resistant.
Anaerobic adhesives come in many colors. This has no visual impact on the finished product since the adhesive cures without oxygen—meaning it is applied in places where it is not visible. However, the color often indicates strength. For example, blue anaerobic adhesive is often medium strength, while green and red adhesives often indicate high strength. Like any rule, there are exceptions, so caution is advised.
Approvals
Many pipe sealing adhesives come with various approvals for gas and drinking water, which can be very relevant for pipe joining and sealing. Look for approvals such as the German DVGW/KTW or the international health and safety organization NSF ANSI 61. Approval from the British WRAS is also a good indicator that the adhesive is safe for contact with drinking water.
Active and passive metals
Regardless of the metal, always clean the part of grease and dirt before applying adhesive. However, there are differences between metals to consider when bonding.
Active metals have certain chemical properties making them suitable for bonding. They are mostly found on the left side of the periodic table (e.g., lithium, potassium, and sodium), though exceptions like copper exist. Certain alloys, such as brass, are also active metals. Anaerobic adhesive adheres very well to these active metals, and curing time is significantly shorter than on passive metals. When bonding passive metals such as stainless steel or aluminum, curing time is long. Here, using an activator with metal ions can speed up the curing process.
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