Alumina-coated Brake Discs with Intention for Reduced Non-exhaust Emission and Increased Ride Comfort of Electrical Vehicles

Regenerative brake, disc coatings or pad formulations with new tribology aim to avoid generating brake wear particulates on one hand. On the other hand, vacuum and filter systems aim to collect the particulate matter for disposal. This paper will briefly describe the non-exhaust emission (NEE) and corrosion issues of brake systems of electrical vehicles (EV). The methods reported for NEE reduction will then be concisely reviewed. A new cost-effective coating technology, called PEA (plasma electrolytic aluminating), will be particularly presented in this talk for fighting NEE where alumina-coatings are prepared on commercial cast iron brake discs. Brake dynamometer test results show the coatings can increase friction levels and reduce wear for both brake discs and pads. The coatings can greatly increase corrosion/rust resistance. A car test also shows that the coated discs can reduce the braking distance and make wheel rims much cleaner. The better driving comfort and modulation should result from more consistent friction forces and less stick-slip problems during each brake event, which is a very important performance factor for advanced driver assistance systems (ADAS) and autonomous driving systems of EV. It is expected that the coated discs may last as long as the lifespan of passenger cars. Therefore, the sapphire coatings would benefit the brake system in terms of better sustainability and environmental friendliness.