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Since copper is excellent at dissipating heat and does not rust, I am surprised that brake manufacturers do not electroplate cast iron/steel brake rotors with a thin layer of copper (~.5mm). There are brake manufacturers who offer brake rotors with cadmium or zinc-plated coatings at an additional cost but these coatings usually do not last long especially in areas that use a lot of rock salt.

I think copper plating would be the most ideal coating for ventilated brake rotors since it should keep the cooling vanes from rusting and becoming clogged with rust. Clogged cooling vanes reduce the rotor's cooling capacity resulting in higher temperatures, faster rotor wear, premature warping, and a shortened lifespan.

Moreover, since copper is very good at dissipating heat, air flowing through copper-plated cooling vanes should draw away more heat from the brake rotor, resulting in a cooler ventilataed brake rotor, maximizing or perhaps even extending its intended lifespan.

Also, since there should be almost no rust on a copper-plated brake rotor, removing an worn out, copper-plated brake rotor should be no problem. Anyone who has worked on brakes knows how time-consuming it is to remove a rusted-on brake rotor or drum.

The brake manufacturer should not electroplate the friction areas (as shown in the picture below) since the high pressure and friction from contact with the brake pads would most likely warp the copper coating, but all the other surfaces would have a copper coating, most importantly the surfaces of the cooling vanes.

Will electroplating a ventilated brake rotor with copper improve its cooling capacity and maximize its lifespan?

enter image description here

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  • $\begingroup$ Will copper buckle under the high stress / temperatures? $\endgroup$ – Solar Mike Jun 4 '19 at 9:10
  • $\begingroup$ @Solar Mike, I think that if the friction areas of the rotor had copper plating, then that copper would probably buckle, so for that reason the friction areas should not be copper-plated. $\endgroup$ – user18610 Jun 4 '19 at 12:55
  • $\begingroup$ Even if only the non-friction areas... will better heat transfer lead to buckling? Especially as discs can suffer from buckling under normal conditions ie brake judder etc $\endgroup$ – Solar Mike Jun 4 '19 at 13:11
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Copper is better than cast iron at conducting heat, and is used as a heat spreader in some high power density electronics products. However, I don't believe that it is better at dissipating heat from a surface. You might get marginally better heat dissipation if you made the whole rotor out of copper, but it'd be weaker, heavier, more expensive, and you'd have to reengineer your brake pads.

Any time you've got a hot thing that needs to be cooled by convection, the limitation is the interface between the air and the object to be cooled. A thin copper plating -- or even making the whole rotor out of copper -- isn't going to help this.

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It would be too thin to make a significant difference for heat dissipation. It may give better oxidation resistance , especially in locations where the rotors are exposed to salt water from deicing. I believe some aircraft rotors are made of beryllium copper for good heat conductivity but that is completely different.

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  • $\begingroup$ I don't know what the ideal thickness should be. That would be determined I figure by the brake manufacturers during their R&D sessions with copper-plated brake rotors. I think the primary benefit of using copper is its anti-rust corrosion protection. If the cooling vanes would remain rust-free throughout the lifetime of the rotor, this should greatly reduce the odds of the rotor overheating and/or warping. $\endgroup$ – user18610 Jun 4 '19 at 1:42
  • $\begingroup$ Copper corrodes forms a black layer which will reduce heat transfer... $\endgroup$ – Solar Mike Jun 4 '19 at 3:44
  • $\begingroup$ @Solar Mike, that is true, yet the benefit of the cooling vanes not rusting makes copper-plating a brake rotor a good idea in my opinion. Rusted cooling vanes also weaken the rotor's structural integrity which usually results in warping. $\endgroup$ – user18610 Jun 4 '19 at 12:57
  • $\begingroup$ @HRIATEXP But why copper specifically? Why not zinc? $\endgroup$ – Eric S Jun 7 '19 at 1:12
  • $\begingroup$ @Eric Shain, copper is more durable than zinc so it should last a lot longer especially in rust belt areas that use a lot of salt on the roads during winter. $\endgroup$ – user18610 Jun 10 '19 at 12:01
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A thin layer of copper plating will have no effect on convective heat transfer to rapidly flowing air, which is what gets the heat out of a cored/ventilated steel brake disc. In addition, a few taps of the brakes would scrape most of the plating off the disc.

To have any effect on heat rejection rate in a predominantly steel disc, the copper cladding would need to be thick enough to conduct heat laterally outwards from under the brake puck's contact patch against the disc before the heat has a chance to soak into the steel underneath it. This requires a significantly thick copper layer relative to the thickness of the steel disc, as in the case of a copper-clad stainless steel frying pan bottom.

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