Hi Nate, thanks for the reply. Yes wheels are are real danger area so maybe you are right to find a suitably qualified refinisher (maybe near an airfield?) to crack test, anneal, refinish.
You can buy touch up kits of DOW chemicals. And yes they are recipes that you could also make up if you were a very competent DIY chemist. I have read that Dow 17 is an anodizing process -- Dow 7 is the more typical chromate process for magnesium.
(here's the link to recipes : https://www.finishing.com/faqs/magnesium.shtml)
Henkel's touch up kit https://www.chemical-supermark...mp;cat=165&page= or via. https://www.skygeek.com/henkel...m-treatment-kit.html ). In the aircraft industry they use mag parts, including wheels and helicopter gear casings and then do touchups and repairs.
As for the metal valve stems - I guess they are isolated by rubber seals. There are lots of advisories about how to minimise inserts of other metals since metal to metal corrosion is a major problem with magnesium.