""Nick Müller"" wrote in message
...
Brent Philion wrote:

Is it just mild steel or something a little more resisitant to oxidizing?

Copper that is iron-coated (if you have good ones, like those from
Weller).

The Curie-effect tips are also aluminum plated back of the tip's "working
area" so solder will not wet any but the active area.

LLoyd