“I remembered just now about a post you made in one of those threads on Fieldlines where you are investigating ways to prevent magnet corrosion.
“I have been painting my rotors with a product called Rust Master Primer that I get from Kimball Midwest here in the US. This product has acetone in it. When the rotors are still raw steel with the pins installed (for the magnets) I paint the rotors with it and leave them set for 48 hours. The product converts any oxidized steel to a very hard, black polymeric coating. The product is clear when it goes on but if you wait for 24 hours the rotors start turning black as it converts oxidation in the steel.
“After treating them with this stuff they can be left out in the weather permanently, unpainted, and they will not rust.
“I then glue the magnets over the pins with epoxy (JB Weld) making sure to use enough so that the entire underside of the magnet is covered and sealed all around the edges. After the JB Weld sets I paint the magnets with Rust Master and leave them set for 48 hours. I then prime and paint them. I do not pot the magnets in resin or any such thing, which really serves no purpose in my thinking.
“The key is to prevent magnet to steel contact and then seal everything in the polymeric coating before painting it. I have been using this stuff for over 20 years on semi trailers that run in the winter time in high amounts of road salt. Once you treat the underside of a semi trailer with it, it will never rust again.
“Disclaimer: Rust Master or POR-15 is a VERY toxic material. It instantly bonds to moisture, dehydrates it and seals with the coating. If you get even a tiny amount of overspray in your lungs while applying it, it will instantly bond to the moisture in your lungs, seal them, and you will never breathe again using that pair of lungs. Same goes for your eyes. It has to be applied while wearing an organic particulate filtered full face respirator with an external air supply, and if done inside a building in an approved paint booth with organic particulate filtered exhaust fans. If you get the stuff on the floor or walls, you will never get it off – you can burn it with an oxyacetylene torch and cannot remove it from cement.
“20 years ago when I first started using it I painted the underside of a semi trailer with it and let it set up for 48 hours. Nothing on that trailer would move. It took us 5 hours alone, with air chisels and air powered rotary files, to get the landing gear freed up so it could be cranked up and down. We never did get the hopper gates freed on it. We had to grind the bolts off and replace the gates with new. Just to give you an idea of how tough the stuff is after it cures. Space age chemical treatments are amazing things – but you’d damned well better read the directions before applying them.
“The stuff is sold around the world and is made by this company:
Chris Olsen’s gallery is here
Thanks, Chris! For now I will continue using galvanized disks (my latest tactic), and embedding the magnets in resin, since the resin casting is something I know works well to retain the magnets and protect them from accidental damage. I hope that others find Chris’s Rust Master system useful.