Regarding rust on a brake rotor

Lived in Grand Forks ND, too cold for salt much of the time. The snow remained crunchy, never turned to ice so sand was the answer. Here in WI, 1/2 " of snow followed by 1" of salt. Though lately beet juice has been a pre treatment pending snow. Remembering plow driving, people talking about Calcium Chloride added to salt in cold weather for the roads, story was it could eat the rubber off the soles of your shoes.

No longer live in a rust belt state… but this is what my rear rotors looked like off my seldom driven truck. 1/2 the brake pad was left but the rotors were rusted beyond use. Very typical of what I’ve experienced on several of my cars.

The caliper slides were seized as well. I replaced all 4 calipers, rotors, and brackets to bring it back to having good stopping ability again.

As long as you drive the vehicle a couple times a week…the surface rust will be gone the first time you brake at 30mph.

The town I grew up in had a road salt budget larger then New Hampshire Largest City (Manchester) road salt budget.

There are two types of oxidation that takes place on steel. Rust is Fe2O3, is reddish in color and does not protect the iron underneath it. There is also Iron Oxide Fe3O4. It is black and it occurs in a low oxygen environment like a gas oven and it does protect the iron below the surface.

You see the black iron oxide on cast iron pans. The black is partly due to heating the pan with a layer of oil on it so that there isn’t much oxygen on the surface of the pan. The rest is due to the polymerization of the oil which also turns black.

How about cor ten steel In simple terms the steel is allowed to rust and that rust forms a protective coating that slows the rate of future corrosion.
50 years later Picasso in Daily Center, Chicago still standing.

Is corten steel expensive? Yes, it is. Corten is significantly more expensive than other common grades of steel . Corten steel planters are easily 50%-100% more expensive than a similarly sized planter of another long-lasting material

Tester

There was an IBM one story building near may parents house and it was clad with Cor-Ten. It had just been built and the rust ran all over the windows. It looked awful. I understand it stops bleeding after a while and some folks consider it an appealing look.