I know what you mean Patman. I used POR15 in flat black on mine. Very durable and it looks great. 2002 Camaro SS
My new rotors are rusty!
- Thread starter Patman
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I have a Honda S2000, and I removed my rotors and spray painted them with high-temp black paint. Tape off most of the swept surface and spray them. You can get some inside the fins as well, and it will hold up for years. I did mine 3 years ago and although they're starting to rust, the rust is pretty dark now so you can't see it very easily.
Zinc plated rotors work fairly well but at high temps, the zinc will alloy with the cast iron. This is brittle phase, and personally I wouldn't do this with a Vette. The better rotors are plated with Cadmium. This holds up very well, even at high temps.
Zinc plated rotors work fairly well but at high temps, the zinc will alloy with the cast iron. This is brittle phase, and personally I wouldn't do this with a Vette. The better rotors are plated with Cadmium. This holds up very well, even at high temps.
Kestas
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That brittle phase is actually more corrosion-resistant than pure zinc!
I agree that cadmium is a superior coating.
I agree that cadmium is a superior coating.
If there are any automotive engineers out there, feel free to set me straight on this, but I think stainless is not used in brake rotors for two reasons: a) cost and b) electrolysis.
The only stainless with sufficient hardness and temperature resistance for such a demanding application is 440, which is substantially more expensive than carbon steel.
The use of stainless on the brake rotor would furthermore create an electrolytic cell between the rotor and hub. Essentially, preservation of the brake rotor would mean accelerating corrosion of the hub, wheel and any other components in contact with the rotor.
Does this make sense to anybody else?
The only stainless with sufficient hardness and temperature resistance for such a demanding application is 440, which is substantially more expensive than carbon steel.
The use of stainless on the brake rotor would furthermore create an electrolytic cell between the rotor and hub. Essentially, preservation of the brake rotor would mean accelerating corrosion of the hub, wheel and any other components in contact with the rotor.
Does this make sense to anybody else?
i dont know if electrolysys would be an issue because many cars have steel hubs iron rotors and aluminum wheels.
could be wrong.
could be wrong.
Yes. Just like a nail in contact with copper plumbing, or a penny on galvanized sheet metal. By themselves, they don't rust, but they can when touching other metals.
Kestas
Staff member
True, stainless steel will accelerate corrosion of surrounding parts.... but so does steel with aluminum parts, and there are many cars with aluminum suspension components in contact with steel, so I can't say this is a strong argument.
I believe stainless steel isn't used for rotors because it galls so easily. The rotor surface would go to pot in no time. Plus it has poor heat conductivity compared with cast iron.
I believe stainless steel isn't used for rotors because it galls so easily. The rotor surface would go to pot in no time. Plus it has poor heat conductivity compared with cast iron.
The aluminum on automobiles, however, is almost always anodized. The hard oxide coating resulting from the anodization process essentially acts as a barrier to electrolysis because Al2O3 is an insulator.
Kestas is certainly right about his other point, though. The thermal conductivity of carbon steel is around 50 W/mK, whereas 440C stainless is about 25. The galling of stainless steels varies dramatically between grades, but I should have thought about heat transfer in addition to hardness.
Kestas is certainly right about his other point, though. The thermal conductivity of carbon steel is around 50 W/mK, whereas 440C stainless is about 25. The galling of stainless steels varies dramatically between grades, but I should have thought about heat transfer in addition to hardness.
Kestas
Staff member
Actually, few automotive aluminum parts are anodized. Anodizing is done for either of two reasons -- for decoration or for hard wear surface. Nearly all aluminum brackets and suspension components are used with the as-cast surface.
JTK
$100 Site Donor 2025
Sorry about the SS rotor *thought* fellas. My brother owned a mid 70's vette some ~15yrs ago. I helped him do a bunch of work on it, such as new rotors and calipers all the way around. For some reason I had it in my noodle that those rotors were stainless?!? I see now that is impossible
Must have been the drugs
Joel
Joel
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