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Feb 7, 2020

REACh compliant coatings to meet cyclic corrosion testing

Cyclic corrosion testing

More automotive companies are in the process of specifying cyclic corrosion testing to assess long term fastener coating performance. Typically, these tests comprise of 24-hour cycles of salt fog, elevated temperatures and high humidity. These tests can extend for more than 40 cycles. They are regarded as an aggressive accelerated test regime and require high performance coatings to be able to withstand the testing procedures. Coupled with this, any coating must also be REACh and end of life vehicle (EoLV) compliant. 

Zinc-nickel

Zinc-nickel alloy finishes are a preferred coating to meet these test regimes and environmental directives. Compared to alternatives, such as organic-based coatings and zinc only, these finishes offer more control over the thickness of coatings and virtually eliminate zinc corrosion products.

These factors allow coating engineers to specify high performance protective finishes even on fasteners with fine dimensional tolerances and recessed heads. Zinc-nickel is also proven to reduce the damaging effects of hydrogen embrittlement – a frequent problem with coatings for exterior fasteners. It also provides an excellent basis for a black coating with extremely good aesthetics.

ZinKlad 1000

Predicting this requirement for higher coating performance, ESI Automotive launched the range of ZinKlad 1000 finishes. These silver or black range of finishes combine a homogenous metallic zinc-nickel (12 – 17% nickel) deposit of 8 microns minimum thickness. This hard-metallic coating is further protected against the formation of white corrosion products by the application of TriPass ELV trivalent chromium passivates. Finally, a dry film Torque ‘N’ Tension lubricant is applied to both further increase corrosion resistance and modify the surface properties to ensure uniform torque and clamping characteristics.

To meet ever increasing demand for high performance zinc-nickel coatings, in 2019 MacDermid Alpha Automotive confirmed the increased capacity for ZinKlad 1000. In Europe several new plating lines have been approved for this system. This increased availability will give further unrivaled support for automotive manufacturers in the region.

In summary today’s fastener design and corrosion engineers are faced with the challenge of specifying coatings which meet aggressive cyclic corrosion test criteria, be environmentally compliant and meet their friction requirements. ZinKlad 1000 zinc-nickel system is hexavalent chromium-free and meet these industry demands for the highest performance coatings. 

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