Black rust good or bad


Thanks for the link. It wasn’t working most of the day, but I finally got through.

This is the same stuff I remember from my old corrosion class. I seem to have misplaced the text I used then.
I am glad you both found that page useful. Glad to help.
As a matter of interest, since there's nothing wrong with the practical advice, the reason rust is such a pain, is that rusting is an autocatalytic process, meaning that the product (rust) actually speeds up the rate of rusting, all things being equal. On the other hand things like aluminium stop oxidising once there is no more metal exposed to the air. So even if you don't 'kill' the rust, rubbing most of it off will slow or halt the process until more water gets to the metal. The problem isn't exposed metal (although coating helps) but water mobilising electrons at the water/metal/air boundary. If you leave bare metal in dry air at room temp, it will take (many) years to rust. Its a bit like the fire triangle, but substsitute water for heat. (Although heat will do the trick too).