C4INOXit®
Long-term corrosion protection and fine dust reduction a challenge for the automotive industry and electric mobility
Electric vehicles use the electric motor for braking (recuperation), so that only 5% - 10% of the installed brake system for the friction brake (including the brake discs) are used in everyday life. 90% - 95% of the braking processes are realized by the electric motor. As a result, the brake discs remain in the vehicle much longer and problems with the corrosion of a grey cast iron brake disc inevitably arise.
Mechanical "freebraking" with the aim of "derusting" of the friction surface by the driver is generally no longer possible due to the built-in system control of electric vehicles, or "freebraking" installed by the automobile manufacturer and interval-based on the system side often leads to soiling of the brake pads and after a certain time affects the comfort behavior of the brake.
In the absence of an industrializable and cost-effective long-term corrosion protection for brake discs that ensures long-term corrosion resistance, brake discs in electric mobility today are replaced at fixed intervals in combination with system-side freebraking.
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The above applies to internal combustion engines in the sense that the brakes can be released manually, but the corrosion leads to problems with the service life of the brake discs, the comfort behaviour of the brake, the soiling of the rims and the rusted appearance of the brake disc, which is perceived as disturbing.
In addition, today's uncoated grey cast iron-based brake discs in combination with brake pads cause a significantly high proportion of particulate emissions in our city centres. According to expert estimates, half of the particulate matter caused by vehicles in our inner cities is caused by exhaust fumes, up to 20% by tire abrasion and up to 30% by the friction brake (combination brake disc/brake pad). The industry expects a European regulation of the particulate matter emission caused by the friction brake to be introduced in 2024/2025 in order to meet the socially increased environmental awareness. This regulation would have a significant impact on combustion engines, since electric vehicles, as previously stated, mainly use recuperation for braking. It was therefore necessary to develop a surface quality on the brake disc that would have a positive effect on wear without having a negative impact on comfort behavior or other parameters of the brake disc.
In order to realize long-term corrosion protection and fine dust reduction in parallel, attempts are being made to combine different coating processes (e.g. paint/CCD). On the other hand, it is possible to realize the fine dust reduction only on the friction surface and also to realize the long-term corrosion protection, but only on the friction surface of the brake disc (CCD or LMD). The disadvantage with regard to the desired long-term corrosion protection of all currently applied processes or the use of a combination of different processes is that they do not provide permanent protection of the entire brake disc body (especially not on the friction surface) (e.g. paint), or the entire brake disc body is protected permanently, but this is associated with high manufacturing costs, since two coating solutions are combined (e.g. paint/CCD), or only the friction surface of the brake disc is protected permanently (CCD or LMD) and this is associated with high manufacturing costs and corrosion of the uncoated surfaces (e.g. ventilation channel).
C4INOXit® eliminates all the disadvantages described above and, with just one coating layer, provides lasting long-term corrosion protection for the entire brake disc body, leads to a significant reduction in fine dust particulate matter and shows manufacturing costs that are known today from nitrieding-based coating processes (e.g. FNC).