From a single source 08 September 2023

In December of last year, SurTec International GmbH acquired omniTECHNIK Mikroverkapselungs GmbH – one of the top suppliers in the market for precoating materials in the field of fasteners and threaded parts, through its precote® brand.

The precote® product program serves a wide variety of applications in the field of thread precoating worldwide, including automotive, eMobility, mechanical engineering, aerospace, household appliances and other industries. The precote® portfolio offers a variety of technologies to secure screws against unwanted loosening, as well as seal and reproducibly set desired mounting parameters. 

With the acquisition by SurTec, and the integration into the Freudenberg Group, it is now possible for precote® to exploit the market potential for innovative coating technologies even further. A prime example is the production of fasteners for components in eMobility. Not only are these fasteners optimally pretreated with SurTec solutions prior to treatment with precote®; they can be used in a variety of applications, such as in battery housings – where the surfaces are also excellently protected from corrosion by SurTec technologies. 

This means that SurTec can now offer the entire process of surface treatment of components for battery housings from a single source. According to the company motto ‘Innovating Together’, the joint research and development of future solutions is also significantly easier; meaning that collaborations with sister companies, such as Freudenberg Sealing Technologies, can complete the partnership.

From phosphating to microencapsulation

Starting with the wire, each of the process steps in screw manufacturing is critical to ensure the highest quality of the final product. SurTec is able to ensure the finished product meets the very highest requirements as it has a broad portfolio of products for every process step, guaranteeing all requirements are optimally met.

The majority of fasteners are manufactured via cold forming. In this process, a metal wire is first phosphated, then the wire is pressed into a screw over four to six stages. 

Phosphating plays an important role in the cold forming of the fasteners, as it ensures the required forming behaviour of the metal parts. The phosphating forms a protective layer on the surface of the parts, which reduces friction and wear during the forming process. After cold forming, however, the parts must be freed of the phosphate layer to avoid brittleness and to allow further coating of the screw. The selection of the appropriate phosphating process, and subsequent dephosphating, are critical to the quality and properties of the fasteners. 

Before the fasteners can be coated with precote®, they must be protected from corrosion. This is done by means of galvanic coating of the screws or bolts, for example with zinc nickel. Depending on the area of application, different solutions, including the corresponding after treatment, are available. For example, SurTec 717 or SurTec 759 processes are excellently suited for bulk goods. Corrosion protection plays an important role not only in fasteners, but in the overall battery housing for eMobility.

Finally, there is the thread locking application, with the type of special precote® thread locking dependent on the respective area of application of the fastener. For example, flange head screws are used in battery housings in eMobility, which are treated with SurTec and precote® products. 

Coatings such as precote® 85 and precote® 15 ensure a perfect combination. The microencapsulated precote® 85 offers reliable thread locking under dynamic loads, as well as a seal in the thread. Therefore combining two of the most important 

properties in the screw connection. The set low friction number also allows for constant assembly conditions and reproducibly high utilisation of the screw. 

precote® 15, applied thinly under the flange head, provides an additional seal of the connection under the head. The non-reactive material is stable yet soft enough to be pressed into the surface roughness of the joining partners during assembly and to fill them safely for a high sealing effect. Thus, a stable screw connection is made possible, which has almost no loss of clamp load even under the influence of temperature and dynamics. 

In general, precote® coatings have a high chemical resistance and are stable and safe up to a temperature range of more than 150°C. They are therefore suitable for a wide range of applications. 

Ideal solutions for eMobility

With the addition of precote® coatings for fasteners, SurTec’s offer for eMobility is ideally complemented, with both SurTec and precote® technologies ensuring screws are optimally prepared for use in battery housings, for example. 

Also, within eMobility, the aluminium light metal is very interesting for the construction of battery housings. The battery of electric vehicles can weigh several hundred kilograms, so the use of aluminium can significantly reduce the weight of vehicles. The material also has excellent thermal conductivity, has high stability and excellent impact resistance. These properties make it the ideal housing material. However, since the electric car batteries are located in the underbody of the vehicle, due to their design, they are permanently exposed to various environmental influences. On the one hand, it must be absolutely ensured that no moisture enters the housing. In addition, excellent protection against corrosion is of paramount importance here. While aluminium already has good native corrosion protection, it is shown that it is not sufficient under corrosive conditions and under continuous loading.

Choosing the right surface coating therefore enables state of the art, lightweight battery housings with reliable and long life. With its SurTec 650 chromium (III) containing passivation, surface treatment specialist SurTec offers a suitable solution that has already been proven in the surface treatment of bare aluminium surfaces. In combination with a seal, passivation prevents moisture from entering the battery compartment.

The technology provides low electrical contact resistance and electromagnetic compatibility. Passivation is therefore a suitable solution for surface treatment, including housings for batteries or for electronic control units (ECU). Due to the superior corrosion protection, additional e-coatings of the battery housing are considered unnecessary. The SurTec 650 passivation layer’s special surface properties are appreciated not only in the automotive environment, but also in the aerospace and 5G industries.

Innovating together

SurTec, like many other companies in the Freudenberg Group, has been a preferred partner for many years in numerous industrial areas from the design phase to prototyping and final high volume production. When developing new solutions, the company benefits from a lively exchange of experience from its sister companies, such as Freudenberg Sealing Technologies, and is thus able to deliver entire technology packages to users.

The functional coatings division at SurTec is constantly expanding. At present, the focus is on matched systems from a single source, such as zinc-nickel coatings from SurTec and precote® thread locking for fasteners. 

Will Lowry Content Director t: +44 (0) 1727 743 888

Will joined Fastener + Fixing Magazine in 2007 and over the last 12 years has experienced every facet of the fastener sector – interviewing key figures within the industry and visiting leading companies and exhibitions around the globe. Will manages the content strategy across all platforms and is the guardian for the high editorial standards that the brand is renowned.