Rislan
Hi Stew,

It's usually a Rislan coating on the Bertoia chairs, I don't think it is the kind of thing you could touch up. Easiest thing would be to have it sandblasted back to the metal and then powdercoated.

dip it
I had a set of these years ago. They'd sat in my basement forever because, like you, I wasn't sure what to do about the failing white coating. So I gave them to a friend who had the good sense to take them to a one of these paint stripping places. They put them in the chemical tank. which stripped away the coating and any rust, without harming the metal. Within a few days, I was sitting in one of them, and and regretting my decision to get rid of them.

If its really rislan, no...
If its really rislan, no stripper is going to work on it. I believe Knoll dip painted (with paint) some pieces in the 60s, and it looks thick like Rislan, but rislan is much harder than paint.

Rislan is a thick plastic like dip, and doesn't remove with blasting or chemical dipping. Its like kryptonite, and will only scrape away with a sharp knife. A knife test is your best way to see how hard the coating is.

I have repaired bertoia stuff for myself, and as a machinist, you can't afford me to do the work. Its very time consuming, and difficult to work with Rislan. Your best bet is to scrape away the rislan in the area to be repaired and then paint it, when the welds are done. Rislan will melt when heated to 600+ degrees, and not burn. It has to be removed before welding repairs.