Atotech’s high-performance coating systems for OEM fastener standards | FASTENER EURASIA MAGAZINE
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Atotech’s high-performance coating systems for demanding OEM fastener standards

By Dennis Gündel
Global Product Manager, Zinc Flake Coatings

Superior zinc flake coatings – versatile solutions to meet demanding OEM requirements

For decades, many industries have relied on the multifunctional properties of zinc flake coatings. The automotive industry has especially contributed to the continuous advancement of this technology. Ever increasing requirements for corrosion protection (NSST and CCT resistance) have pushed manufacturers to continually develop products that raise the bar for durability and quality.

As an innovator, the automotive industry is constantly setting trends, not only in terms of new technologies, but also in terms of optimized manufacturing processes. Fully automated assembly lines create ever greater challenges for fastener suppliers, from downsizing fasteners for reduced weight demands to developing solutions for faster assembly, so automotive manufacturers can increase productivity, optimize costs and increase process reliability.

As a result, the fastener portfolio has been streamlined which, in turn, has had a direct impact on the coatings used. Today’s selective coatings must be both universal in application and reliable. On the one hand, coatings must be suitable for a variety of materials, ensuring that fasteners exhibit the same assembly properties regardless of whether they are affixed to steel, aluminum or e-coated parts. On the other hand, they must meet specific requirements for coefficient of friction, heat loosening and corrosion protection.

The answer to sophisticated coefficient of friction requirements

A prime example of the highly complex requirements that fasteners must meet today is the latest Daimler specification MBN 10544. Daimler’s test defines new coefficient of friction requirements in which individual values are evaluated and multiple factors must be taken into account and tested. This includes the need for higher tightening speeds that comply with the latest assembly technologies, multiple-mounting specifications for bolts and new washer materials including steel, e-coat and aluminum for testing against the fastener surfaces. The standard CoF window must be within a range of μtot 0.08 and 0.14 and Daimlerhas specified another set of CoF ranges that must be met for multiple mountings against different washer materials.

The sophisticated demands of the MBN 10544 specification require a single coating system that can be used for a wide range of Daimler fasteners. Atotech is able to supply such a coating system utilizing: Zintek® 200 + Zintek® Top LV. Atotech’s silver base coat Zintek® 200 provides superior cathodic corrosion protection. The highly demanding CoF requirements are handled by the sophisticated, thin layer, water-based top coat Zintek® Top LV that provides a clear finish. Thanks to its reactive properties, Zintek® Top LV also contributes additional corrosion protection, while its integrated lubricant ensures that MBN 10544’s complex CoF requirements can be easily met.

The outstanding performance from the combination of Zintek® 200 and Zintek® Top LV also meets Volkswagen’s TL 245 specification and fulfils requirements for multiple mounting and heat loosening (VW 01131). In addition, the system meets BMW’s corrosion protection and CoF behavior requirements (BMW GS 90100). This zinc flake and top coat coat combination also performed exceptionally in corrosion testing even with thermal pre-conditioning for 96 hours at a temperature of 180 °C, which is a typical requirement by members of the German Car Association (VDA).

The new black standard

The automotive industry always has high expectations when it comes to aesthetics. One of the biggest challenges for black finishes is to maintain color uniformity and long-term stability. Automotive specifications, like Volkswagen’s TL 180, outline high-performance standards for black, zinc flake finishes and apply to various kinds of fasteners, including metric parts. It features some of the most complex corrosion protection and color stability requirements made even more challenging due to Volkswagen’s desired coefficient of friction properties and heat-loosening requirements.

In response, Atotech developed, and got approved, simplified coating sequences that further improve performance standards. This includes the state-of-the-art zinc flake coating combinations of the Zintek® 300 HP black base coat together with the either of the Techseal® Black SL VA or Techseal® Black S T top coats. These advanced zinc flake finishes help reduce the number of chemicals compared to legacy systems. The high-performance black base coat Zintek® 300 HP exhibits outstanding corrosion protection properties, such as increased delay of white corrosion with top-notch drying and flow characteristics. With its semi-bright, deep black appearance, the organic top coat Techseal® Black SL VA provides outstanding coverage and excellent chemical resistance. Techseal® Black SL VA meets the challenging requirements for multiple mounting on e-coat and aluminum with low deviation while simultaneously providing limited heat-loosening properties. For parts that require a lubricant-free finish in line with the TL 180 specification, Atotech offers Techseal® Black S T, an approved finish that provides excellent chemical resistance and features an attractive matt black appearance. The ductile coating can be used for clips, clamps and other fasteners. Both of the approved top coats show minimal signs of abrasion.

The combination of Zintek® 300 HP and Techseal® Black SL VA or Techseal® Black S T are currently the leading zinc flake processes for VW TL 180. Not only have they been well received by manufacturers, they have also been praised as the best approved systems with the highest performance standards and ease of handling.

The perfect coating for all kinds of fasteners

Atotech pays special attention to the needs and requirements of the automotive industry. The company continuously works with OEMs and the whole supply chain around the globe to establish new coating and quality standards. Atotech offers a variety of coating systems and solutions that meet or exceed the demanding requirements of the automotive industry worldwide, regardless of the requirements for corrosion resistance, assembly characteristics, improved durability and appearance of fasteners.

 

About Atotech
Atotech is a global leader in surface-finishing solutions. Through a comprehensive systems-and-solutions approach, the company delivers chemistry, equipment, and service to support diverse industries such as consumer electronics, especially mobile devices and computing; global automotive; communication infrastructure; and many other industrial end-markets. Atotech’s relentless R&D efforts and global TechCenter presence allows it to deliver pioneering and sustainable products combined with unparalleled on-site customer support – making Atotech a critical partner to over 8,000 customers worldwide.
Atotech, headquartered in Berlin, Germany, is a team of 4,000 experts in over 40 countries generating annual revenues of $1.2 billion (2019). Atotech has manufacturing operations across Europe, the Americas, and Asia.