The Effects of Corrosion on Particle Emissions from a Grey Cast Iron Brake Disc

Abstract

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 entering 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 exhaust emissions, there is still concern regarding non-exhaust emission, such as brake dust, which can potentially cause harm to human health and the environment. Despite EVs primarily using regenerative braking, they still require friction brakes as a backup as and when required. Moreover, most EVs continue to use the traditional grey cast iron (GCI) brake rotor, which is heavy and prone to corrosion, potentially exacerbating brake wear emissions. This study concentrates on emissions from a conventional grey cast iron friction brake before and after exposure to a corrosive environment. It was found that the effect of corrosion increases both the number and mass of particle emissions by over 50% and inhibits braking performance by reducing the coefficient of friction. The surface of the brake disc was also found to be affected by corrosion as many crevices and pits were formed.

Corrosion Stiction in Automotive Braking Systems

“…As a result, the components of the braking systems might undergo corrosion during service. In particular, the brake discs are particularly exposed to corrosion due to the intrinsic low corrosion resistance of the gray cast iron in aggressive environments [ 50 , 51 ]. As discussed above, corrosion affecting the braking system of BEV, HEV, and PHEV vehicles is a critical aspect not only regarding the braking performance but also the emission of particulate matter.…”

State of the art on challenges for friction material manufacturers – raw materials, regulations, environmental, and NVH aspects

“…But the reduced usage of brake pads can cause moisture to build-up on surface of brake pads instigating corrosion. Ghouri 82 carried out corroded and uncorroded test to see the effects of corrosion on particle emissions from GCI brake rotor. It was observed that the braking performance is affected by corrosion as it reduced the contact area between friction couple.…”

Light-Duty Vehicle Brake Emission Factors

“…However, poor corrosion resistance and excessive wear result in high brake particle emissions. For example, a study found that the effect of corrosion inhibited braking performance by reducing the coefficient of friction and significantly increased both the number and mass of particle emissions by at least a factor of 2 and up to 30 times compared with the uncorroded disc under the same test conditions [13]. Various treatments (e.g., cryogenic, heat) can improve the tribological properties and reduce the wear [14].…”