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Mr. John Smith

Job title



The automotive industry continually strives to increase efficiency and reduce emissions through a variety of methods. Such approaches typically involve attaining technological advancements in engine performance, enhancing aerodynamic efficiency, or reducing vehicle weight [1]. Despite numerous effects, one area that appears to be largely overlooked is the effect of the brake system on environmental emission. A key by-product of the braking mechanism is the emission of particles from the brakes into the environment. These particles not only cause pollution but also pose possible risks to human health [2]. No current legislation exists in terms of limiting the quantity or type of brake emissions produced, despite there being stringent legislation in place with regards to exhaust emission [3]. It is speculated that friction brakes will become one of the dominant sources of particulate emissions because of the rising number of electric vehicles on the road each year [4]. Electric vehicles still require friction brakes to supplement regenerative braking and it is likely that these will continue to use the traditional grey cast iron brake rotor, which is both heavy and exhibits poor corrosion resistance, and is therefore likely to contribute significantly to brake wear emissions. In order to understand the inter-relation between brake rotor corrosion and particulate emission, this study concentrates on quantifying such emissions from a conventional grey cast iron friction brake both before and after exposure to a corrosive environment. The ‘drag braking’ duty cycle was chosen for this study, as this produces near steady-state conditions at the friction interface. Test were at a constant speed of 150 rpm at three different brake hydraulic pressures, 5 10 and 15 bars. As for the brake pad material, OEM-recommended brake pad materials are used. The duration of each test was 90 minutes, and each test was repeated three times. Tests were conducted within an enclosed chamber on the Leeds brake dynamometer and airborne emissions were sampled using a Dekati electrical low-pressure cascade impactor (ELPI+). After the three repeated test cycles have been completed, the brake wear particles captured by the ELPI+ were examined as described below. The corrosion test consisted of exposing the brake rotor to a corrosive environment in a salt spray chamber. The salt spray conditions were based on the ASTM B117-11 standard, under 96 hours of exposure. The corroded brake disc then underwent the drag brake duty cycles which as before were repeated three times for each pressure condition. Similarly, to the non-corroded tests, the brake wear particles were collected from the ELPI+ and later examined. The post-test analysis consisted of using different microscopy techniques to investigate the topography and composition of the brake wear particles. Gravimetric wear measurement methods were incorporated into the post-test protocol. Advanced characterisation techniques such as energy-dispersive X-ray spectroscopy (EDX) and secondary electron microscope (SEM) were used to characterise the surfaces of the brake pads and to characterise and identify the elements of the brake wear particles collected from the ELPI+ before and after the corrosion cycles. References [1] “Vehicle Efficiency | EESI.” [Online]. Available: [Accessed: 15-Jan-2020]. [2] “‘London throat’: Toxic brake dust could cause condition, scientists say - BBC News,” [Online]. Available: [Accessed: 25-Jan-2020]. [3] “Pollution warning over car tyre and brake dust - BBC News.” [Online]. Available: [Accessed: 03-Dec-2019]. [4] P. Monks et al., “AIR QUALITY EXPERT GROUP. Non-Exhaust Emissions from Road Traffic,” p. 51014, 2013.

University of Leeds: Mr. Ishmaeel Ghouri, Prof. David Barton

The effects of corrosion on particle emissions from a grey cast iron brake disc

EB2022-FBR-013 • Oral • EuroBrake 2022 • Environmental impact of brake wear particulate emissions


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