All kidding aside, i never skimp with brakes, If anything is even slightly suspect, it gets replaced.
All kidding aside, I skimp on anything I think I can get away with.
https://www.bobistheoilguy.com/forums/ubbthreads.php/ubb/showflat/Number/4801957/Searchpage/1/Main/240614/Words/%2Bcoke+%2Bcan/Search/true/re-coke-can-for-brake-disks#Post4801957
I've had some flak for it in this context.
https://www.honestjohn.co.uk/forum/post/index.htm?t=110241
I'm not sure, however, that those meet that criterion. They look pretty bad, but the fluff may be concealing sound metal.
If they were mine, I'd grind into the cooling void with something like a bit of steel wire rope in a drill chuck and then see what I'd got.
IF I decided to keep them I'd probably then treat the cooling space with sunflower oil and grind it with an aluminium rod (I use old arrow shafts or bit of old TV aerial or aluminium wire to give a protective coating.
I'd then do some emergency stop testing. Is the inward pressure generated at the pads significantly greater in a dynamic situation than in a static test?
I've never had ventilated disks and hadn't thought before about the additional fragility/vulnerability to corrosion. If you do replace them, it might be worth trying to find solid disks if available.
If it's good enough for Ducked, it's good enough for me!
Didn't say they were. I said I couldn't tell from that picture.
If I cleaned them up and I STILL couldn't tell, then I'd change them, preferably for solid disks.
Thinking further about rust treating the cooling void, my standard sunflower oil binder might not work unless I could leave it to set, since it might spin out to the calipers and hence to contaminate the pads.
Superglue (which I've used on disk rims) probably would not do that but it probably wouldn't give good coverage in an inaccessible space either.