Hey guys, so I got my front rotors replaced last week along with the brake pads. Everything mechanically is fine, but the oxidation on these new rotors after just a few days is unbelievable. Obviously there is no rust on the part where the pads hit but on the hat of the rotors (inner part) the oxidation is bright orange and looks like sh**!!!

I'm absolutely positive my old rotors that were just taken off did not have this issue. What gives? I went into Advance Auto where I got them and they said it is not a quality issue because even their top of the line rotors are made of ALL cast iron, which is going to rust...

 

If you don't want your rotors to not look rusty get them zinc coated. My Powerstop ones came zinc coated and were under $200 for all 4.

 

I got my last set of rotors powdercoated $100 for all 4..they did the hats (front and back) and outside edge

 

Painting/plating or powder coating the "hats" (and vanes) would be the easiest manner to eliminate the visual problem of oxidation.

The after market does offer "hat" covers (about $200) in chrome or colors as an option.

Here's some from the Classifieds...
http://forums.corvetteforum.com/c5-p...-or-black.html

 

I have those in the box from Brakemotive. 180 shipped with ceramic pads if you order from the forum listing. They claim they are plated to prevent rust. The ones on the car are drilled & slotted but rusty as heck and the pads aren't great. I was going to blast and paint them but for 180 bucks, I figured why bother.

 

Tape off the cener hat and spray it with high-temp BBQ grill paint. It will work for most situations, though heavy braking (HDPE road courses) will cause the paint to change to a burnt orange color.

 

VHT high temp paint works wonders. just make sure to tape off the braking surface. I painted the vanes as well. Here's how I did mine on my cobalt:



I used the VHT high temp clear. the hats still look pretty darn good after 6 months of winter. these were napa premium rotors.

 

To answer your original question, cast iron is not the homogeneous or tightly controlled cast material you might think it is. Grey iron is basically graphite surrounded by a matrix of ferrite, pearlite, martinsite, and a few other structures. Essentially it is the ferrite content that is oxidizing freely. Depending on the mix, and there is a very wide variety around the world, you may get a batch of G2500 or G3000 that has more or less of these oxidizing structures. If you buy GM rotors you are at least assured that the foundry that produced the iron controls their batch content. If you buy iron produced in some place like India or China or some other developing industrial nation, you just do not know what you are getting!!!! Are they functional? Yes. Probably ok stuff. But you really do not know. Other than looks, rust is not a bad thing. Rolls Royce used to bury their engine blocks half in the ground for a year to make sure they were "rusted" all the way through. Oxidized grey iron does not transmit noise (true with all grey iron) and that is one reason Rolls Royce engines were so quiet. They also machined much better when they were rusted!
So, now that you know the "rest" of the story............paint, powder coat, zinc phosphate, all are poor rust inhibitors. There is an ASTM test for 100 hour salt spray. Go google it and you will be VERY surprised what is best! Good Luck.

 

I've had their rotors on several cars. They all looked great on my GTO 35k miles later, my DD so it was driving in the rain, snow, ect..

I do agree that that pads aren't great though.