While the topic of copper in brake friction has made its way into the accepted parlance, it is also true that along the way, the reason for copper being there, and the reason for it disappearing, may have also fallen out of common conversation.
The fact is that copper has been a major ingredient in friction materials used for automotive braking.
What Copper Does
According to scientific studies, copper seems to play a dual role, firstly as reinforcing element of the brake pad providing primary contact sites, and secondly as solid lubricant by contributing to the formation of a layer of granular material between the rotor and the pad, providing a smoother, more consistent stopping performance.
So it’s not just about heat and what copper can do to handle it, it has also been about what happens to the copper in a brake pad when friction forces are applied.
As they say, it’s complicated.
Why it’s on the way out
In short, the same properties of copper that make it a great component of friction formulations, in particular those small particles, or more accurately where those particles went, that caused regulators and the industry to revisit its use and look for alternatives.
The fact is that copper has been found to be a primary pollutant of concern found in highway storm water runoff.
And to be fair, the driving force of these activities has been south of the border, where California and Washington State legislators first rang the alarm bells on copper. This forced the industry to look to avoid a patchwork of regulations and do what it could to wrest some control back for the transition.
According to a memorandum of understanding between the U.S. EPA and a number of industry groups to promote and facilitate the phase out of copper, asbestiform fibers, cadmium and its compounds, chromium (VI)-salts, lead and its compounds.
Elevated levels of copper are toxic in aquatic environments and may adversely affect fish, invertebrates, plants and amphibians. Acute toxic effects may include mortality of organisms, and chronic toxicity can result in reductions in survival, reproduction and growth.
One source of copper includes wearing of vehicle brake pads onto roadway surfaces where it comes into contact with storm water and is discharged into nearby waterways.
Where are we now?
The Copper-fee Initiative was formed as a lead up to the aforementioned MOU and continues to serve as the framework for the transition.
For starters, however, it’s not really about “copper-free” it’s about a drastic reduction in the amount of copper used.
The commitment was to severely reduce the amount of copper usage in brake friction by 2021 to 5.00% by weight, and cut it again to one tenth that amount, 0.5% by weight, by 2025.
The initiative is the where the monitoring of the appropriate edge code and packaging with the LeafMark Certification takes place, the LeafMark being the property of the Motor Equipment Manufacturers Association, delivered through the Automotive Aftermarket Suppliers Association, and the Brake Manufacturers Council. To use the symbol, suppliers must meet the requirements and pay a fee.
Even though the requirements to have reduced copper had a deadline of 2021, some brake friction suppliers have already made the move.
To know which ones, look for the LeafMark on packaging, and edge code designation.
Ratings include “A”, “B” and “N” edge codes. Each edge code represents a different level of compliance for various contaminants in the friction material. These include copper (Cu), asbestos, chromium (Cr), lead (Pb), mercury (Hg) and cadmium (Cd). Those that meet the highest rating “N” contain less than 0.50 percent copper and no asbestos, chromium, lead, mercury, cadmium or antimony.
The edge code is followed by a number indicating the year of manufacture (e.g. N16).
There is still a way to go before every product you have to offer is compliant, though many suppliers are making the move well in advance of the deadlines, and it is also true that there are other component issues coming to the forefront, such as the fact that asbestos continues to be an area of concern in Canada.
But moves such as the Copper-free Initiative do serve as a positive example of the aftermarket’s ability to respond to environmental concerns and develop a plan that balances the need to address an issue while also ensuring the safety of drivers and the ability of the industry suppliers to make the transition.