Here's an interesting thought that's way out of the box...
What about using some of the products meant for bluing firearms such as Cerakote? Assuming it will bond to the metal, bluing the mask's frame may help harden the finish and prevent the cracking or flaking. And "bluing" does not mean turning it blue - you can also choose colors like armor black, graphite black, etc.
I don't know if this would work. I've never tried it. If someone's willing to give it a shot, let me know. It'd only cost about $20 or so. Try it on an old mask and then bang on it with a hammer or something...