You may have seen many brake manufacturers state that their brake rotors are GEOMET ® coated but none have actually explained what that really means.
As brake rotors are made of iron, they naturally rust and when exposed to minerals such as salt, the rusting (oxidization) tends to speed up. This leaves you with a very ugly looking rotor.
Naturally, companies started looking at ways to mitigate rusting of the rotors. One way was to apply a coating to prevent rust. Enter GEOMET®.
What is GEOMET® Coating?
GEOMET® (or more specifically GEOMET® 360) is a water based chemical coating that is applied to brake rotors to help prevent corrosion.
The coating was developed by NOF Metal Coatings Group in response to stricter environmental regulations and concerns. The resulting product is one that is used worldwide on more than 40 million brake discs per year.
It complies with REACH and The End of Life Vehicles Directive of the European Union. REACH is a regulation “adopted to improve the protection of human health and the environment from the risks that can be posed by chemicals”. The End of Life Vehicles Directive (2000/53/EC) is a Directive addressing the end of life for automotive products.
What are the benefits?
- It looks better: Most cars these days ride on alloy wheels with lots of space to see through to the brakes. The last thing you’d like to see under those wheels are rusted rotors. GEOMET minimizes rusting and keeps your rotors looking good.
- Good initial braking performance: GEOMET® 360 is not greasy and it forms a pretty thin film of coating once dried. This means that the coating is thin enough that it doesn’t damage the quality of braking during the brake’s first use.
- High temperature resistance: The coating can withstand up to 400°C (750°F) and still provide excellent corrosion resistance without crystallization during heat cycles or formation of organic resins. This means that the coating won’t chip and will wear evenly.
- Environmentally conscious coating: There is no chromium in the solution and since it is applied in a closed system, the leftover liquid is recycled. During curing, the only thing that evaporates is water, not chemicals.
- Thin and non-greasy: Once cured, GEOMET is thin and non-greasy which makes it a great option for aftermarket products where the rotors are handled, shipped, and stored before being delivered to the customer. The coating keeps things clean and relatively light and will make sure you get your brakes in great shape.
How is it applied and what happens when it’s used?
The brake rotors are sprayed with GEOMET® 360 at the finishing line in order to protect it until it is installed on the vehicle. After the coating cures, it ends up as a thin, dry film (approximately 8 micrometers thick) and gives the rotor a metallic/silver look.
When the rotor is used on the vehicle for the first time, the layer of GEOMET® over the braking surface is easily rubbed away by friction. This exposes a ring of steel where the brake pad and the brake rotor meet. The daily use of the vehicle at this point does a good job of keeping the pad/rotor interface free of rust. However, the part of the rotor that sits on the car’s hub, will still be coated and protected from corrosion by GEOMET ®.
How does it work?
The first method of protection is by forming a barrier to prevent exposing the steel underneath to the elements. With GEOMET®, zinc and aluminium flakes are layered up and they provide this barrier
The second method of protection is the electro-chemical process called "galvanic action". When driving in damp/wet conditions, water and salt from the road can corrode the steel of the rotor over time. However, if zinc (in the GEOMET ® coating) is placed in contact with the steel, the water and salt act as an electrolyte and initiate the process of electrolysis which allows the zinc to corrode first before the steel does.
The third method of protection is through passivation. Passivation in this case is when metal compounds in the coating actually oxidize and form a ‘passive’ layer over the steel rotor. This layer doesn’t oxidize any further and in turn acts as another barrier that slows down the corrosion of steel.