The Effects Of Corrosion On Particle Emissions From A Grey Cast-Iron Brake Disc

Reducing exhaust emissions has been a major focus of research for a number of years since internal combustion engines (ICE) contribute to a large number of harmful particles into the environment. As a way of reducing emissions and helping to tackle climate change, many countries are announcing that they will ban the sale of new ICE vehicles soon. Electrical vehicles (EVs) represent a popular alternative vehicle propulsion system. However, although they produce zero exhausted emissions, there is still a concern of the non-exhausted emission, such as brake dust, which can still cause harm to human health and the environment. Despite EVs primarily using regenerative braking, they still require friction brakes to supplement as and when required. Moreover, EV’s will likely continue to use the traditional grey cast iron brake rotor, which is heavy and prone to corrosion which may exacerbate the brake wear emissions. This study concentrates on emissions from a conventional grey cast iron friction brake before and after exposure to a corrosive environment. The brake duty cycle chosen for this study is drag braking, as this produces near steady-state conditions at the friction interface. The test program consists of constant speed testing at three different brake hydraulic pressures, low, medium, and high, each for a duration of 90 minutes. Tests are conducted on uncorroded and corroded discs within an enclosed chamber on the Leeds brake dynamometer and airborne emissions are sampled using a Dekati electrical low-pressure cascade impactor (ELPI+). The corrosion cycle consists of exposing the brake rotor to a corrosive environment for 96 hours in a salt spray chamber. The corroded brake disc then undergoes the same test conditions as the uncorroded disc and wear emissions are compared. The post-test analysis consists of different microscopy techniques to investigate the topography and composition of the brake surfaces and wear particles. Gravimetric wear measurement methods are also incorporated into the post-test protocol to validate the Dekati real-time particle count data.