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Does anyone know if there is a coating that is applied to our brake discs at manufacture? Perhaps they dip the disc in something so the internals have some sort of corrosion protection. It looks like the hats are painted.
The reason I ask... I recently had my discs turned down, and while they were off the car I blew them off with compressed air to clean them a bit. Well, now they rust like hell. I think all the accumulated brake dust I blew off was protecting the steel to some degree. Just trying to figure a simple way to minimize this, if at all. The car is not a DD. I'm not referring to any rust on the disc where the pads make contact.
All discs rust especially on the inside. There is no coating, because friction and wear is what allows the car to stop when the brakes are applied. The non-friction surfaces are painted from the factory, for cosmetic reasons, but the very high temps generated by repeated braking pretty much breaks that down. The corrosion is surface rust only, and does not affect the integrity of the brakes. Your alternative is to invest $25K into a PCCB set up.
Any coating on a rotor will be worn off by the brake shoes. The coatings are only to protect the non-friction parts for aesthetic purposes. That said, as you use your brakes, a very thin coating of silicon dioxide (I think) builds up on the friction surfaces from the high heat interaction with the pads. So then the rotors don't rust when wetted quite as much as when they are fresh off the lathe and bare iron. This coating is worn off and redeposited as you drive. It also has nothing to do with pad bedding. I can't remember where I read this.
Years ago before I could afford nice cars I used to take my rotors in to a machine shop to have them turned rather than buying new rotors. The machine shop did not apply any coatings and within days of not driving the car the rotors would show rust. It would wear off on the next drive. Now I always replace the rotors when I do a brake job.
Last night I went take a closer look and thought I would share a couple pics. Again, I'm not referring to the rust where the pad makes contact. You can see the lines of rusty water that is coming from between the hat and the wheel. I think I'll just take the discs off and clean and paint them.
Since they are consumable, unless they are newish, I wouldn't bother painting them. I would wait for replacement and then paint the new ones before install. You could paint the hat to match the calipers. Anyone do that? What does it look like?
cast iron rotors. They are made to rust. They are painted with a blue gray primer or paint when made. There is a place that advertises that you send them to and they dip them in a perminate black coating. I never did it before. But there are some mfg that are starting to offer coatings. I bought brembo rotors for a car and they are coated and they work pretty good. They call it UV coating, It looks like some kind of anodization. I dont wash them often but when I do they will wash to the coating, and they dont rust.
AllRotors has a geomet360 coating for any rotor. They say its a coating. and sounds like a paint. Im sure most of the coatings are dipped..
If you have a bare new rotor and dip or anodize it, it gets in all the internal vent and hole surfaces, and then surface the face of the rotor after and that shaves all off the face.
That looks like the process of the stock gray painted porsche rotors. But it isnt the quality of the new coatings and it all wears off quickly. If you want to renovate your old rotors, dip them in a bucket of muriatic acid for 8 to 12 hrs. It will eat everything off, rust and all. Then paint them as best you can. you can wipe off or sand off most of the face, or it will burn off the face in 2 minutes.
06-07-2021, 11:50 AM
Coating on brake disc
