Pot metal (a nickname for inexpensive casting alloys) can be difficult to solder. There is no standard composition of pot metal, and so melting points and other metallurgical properties can vary from sample to sample. If you would like to join two pieces of pot metal, it's advisable to do a test-solder with a scrap of the same type of pot metal first. Fortunately, with the right materials and preparation, you can maximize your chances of a successful pot metal solder.
Things You'll Need
Pot metal pieces
Small paint brush
Safety glasses or goggles
Hold your test pieces of pot metal together to test the fit – make sure you have sufficient overlap between the two pieces, no less than a quarter of an inch.
Paint a small amount of flux onto each part to be joined, covering the joint area.
Place a small amount of solder on the tip of the soldering iron, and heat the iron. As soon as the solder begins to melt, coat the joint area with a thin layer of solder, using the tip of the iron like a paint brush.
Clamp the joint tightly together, and apply a second coat of liquid flux to the joint with a paintbrush.
Heat the pot metal pieces adjacent to the joint – not the solder itself – with a butane torch. Heat the metal pieces until the solder in the joint melts and flows freely into the joint.
Allow the joint to cool completely before unclamping or handling.
Always wear safety goggles or glasses when soldering.