Why would you want to solder pot metal?
Most pot metal has zinc as the primary component. The zinc melts at such a low temperature the it will puddle before you can solder it. 99% of the time you end up with a melted, ruined part.
I would recommend the 24 Hr J.B. Weld you can pick up a small package of it at most any hardware store. Lightly sand the part a little epoxy and you're good to go.
Look here for more info about pot metal:
http://en.wikipedia.org/wiki/Pot_metal