What is precote®?precote® is a pre-applied two-component adhesive for thread locking and sealing. Based on the patented omniTECHNIK microencapsulation process droplets of our proven two-component acrylate system are enveloped inside a thin polymer wall. precote® is produced by integrating the individual microencapsulated components within a lacquer-like, reactive binder system. precote® applied in liquid form dries to create a dry non-tacky coating that is permanently attached to the threaded part.
How is precote® working?Pressure and/or shear stress rupture the microcapsules in the precote® coating when the pre-coated threaded parts are assembled. The liquid components are released and the mixture cures in conjunction with the binder system. After curing precote® adhesives offer a combination of maximum locking effect and reliable sealing. The different requirements concerning strength, friction value and temperature stability can be fulfilled by our microencapsulated modified acrylates in combination with precote® binders.
Advantages of precote®precote® combines the advantages of chemical thread locking with the omniTECHNIK microencapsulation technology. precote® is the advanced solution for all application areas where high security standards, easy handling and efficiency in mass production are required.
Advantages of precote® coated threaded parts:
- captive coating
- safe to operate
- constant assembly values
- no additional mechanical sealing and locking devices necessary
- coated parts can stored for several years before use
- automatic pre coating through qualified and certified coating partners
Sealing function of precote® coated threaded partsprecote® coatings are homogeneous circumferential coatings. The polymerization of the adhesive closes the threads resulting in a reliable sealing. For sealing functions a coating length of minimum 4 thread leads is necessary. If polymerized precote® can withstand very high pressure. This sealing property also prevents corrosion in the threaded connection.
Optimal conditions for the use of precote®Thread - mating thread
- The tolerance must be 6g/6H, even after galvanic treatments. At lower tolerances the coating can't get into the gap and is scraped off.
- The thread lead-in should be manufactured according to DIN 76 and have a countersink of minimum 1.05 x nominal diameter.
- The surfaces of the mating parts should be tested positive with the precote® coating. Lubricants and other influences can affect the function.
- The material combination of the mating parts has to be compatible, e.g. coefficient of linear thermal expansion.
- The position and the length of the precote® coating have to be adjusted to the application.
- The filling ratio has to be optimized to the thread geometry. A filling ratio of 60-80% is sufficient for most applications. A higher filling ratio doesn't increase the strength but leads to scraping of the product.
- Avoid contaminations of the coating, e.g. oil.
- Top coats should be applied after precote® coating.
- To achieve secure sealing a minimum of 4 pitches have to be coated and be assembled overlapping.
- Please note the information "Packing recommendations for precote® coatings".
- Threads with precote® coating should be assembled in one motion without axial feed force.
- The assembly speed should be controlled at pre-assembly and slow at the final tightening.
- The curing times are to be observed.
Further useful information
- precote® is a two-component adhesive that doesn't need exclusion of air or metal ions for curing.
- precote® coatings can also be used with plastic screws. However, the breakaway torque will be lower than with steel screws.
- The service temperatures of all precote® coatings are tested. The data in the technical information states the continuous operation temperature range.
- All precote® coating materials are tested positive after assembly for their chemical resistance according to automotive specifications. The standard test media are petrol, diesel, anti-freeze, brake fluid, motor oil and transmission oil, both mineral and synthetic.
- Thread coatings for locking and sealing are designed for single use only. Reuse is not reliable and the locking or sealing function is not defined.
There are the following options if reassembly is necessary:
- Use a new, unused precote® coated screw after thoroughly cleaning the mating thread from adhesive residues.
- Clean the thread and the mating thread and reassemble with an anaerobic adhesive. Parts damaged by initial assembly and use must not be reused.
- The friction coefficient is the key value to get constant preload in serial applications. precote® coatings are available with different friction coefficients. The data can be found in the product overview or the product information.
- Transport locks are temporarily effective clamp coatings. The torque has to be defined to find the suitable product for the application.