The pressure on the automotive industry to become more sustainable, to minimize its own ecological footprint and, despite all this, to put a high-quality and durable product on the road is once again increasing sharply in the context of the structural shift toward e-mobility. In the chassis area, requirements are growing with regard to increasing the service life of individual components while at the same time saving weight. In addition, the use of new materials such as high-strength steels and new construction methods is creating new challenges, especially for long-term corrosion protection. Some classic coating processes can now only partially meet these requirements.
Today's standard coating for such components is cathodic electrodeposition. This coating process is very effective as a barrier layer against corrosion, but shows weaknesses if the surface of the coating has been damaged - for example by stone chipping - and corrosive medium can penetrate to the substrate surface. Today, the automotive industry is increasingly looking for ways to increase the protective effect of pure paint layers. Electrocoat layers, for example, are combined with other coatings; this is known as multi-layer systems. However, the application of various different layers causes additional work with significant costs, and these systems also quickly achieve total coating thicknesses in the range of more than 100 µm. An interesting alternative is the use of zinc flake technology, which achieves increased corrosion protection with significantly thinner layers than comparable systems. A decisive factor, especially with high-strength steels, is that electroless plating makes hydrogen embrittlement impossible. Furthermore, the coating of cavities is possible without any problems, and by using additional topcoats, the corrosion protection can be drastically increased once again - without the need for chromium-containing or other heavy metals.
In order to qualify the Geomet zinc flake coating from NOF Metal Coatings on a control arm, intensive test series were carried out on coated components - including various mechanical tests and corrosion tests as well as a dynamic driving test. Initial field tests of the wishbones coated with zinc flake confirmed the positive results from the OEM approval tests. For the future, NOF Metall Coatings expects to expand the current platform to other models of the Stellantis Group and thus further increase the current wishbone volume. Furthermore, several test series with other OEMs and TIER 1s with Geomet-coated components have been successfully completed. In general, it can be said that there is great potential for the use of zinc flake technology in the chassis area and that new application possibilities are opening up, not least as a result of electromobility.
Read more about the series application of zinc flake coating at a major French car manufacturer in the March issue of the magazine for surface technology or as a premium subscriber right here online!