Just thought you might like to know.

This alloy used commonly contains about 4% aluminum.Zinc alloy is low in cost and high in strengh and machineability is good. good corrosion resistance but limited to service temps of 200F these casting are heavy compared to the others.The grain structure is a CPH and will never get coarse.
the composition for the two zinc alloys are zamak-3 with the addition of manganese this has good ductility and strengh at higher temps.
the other is zamak-5with copper this is stronger and harder and has better castability
Welding this is a little more difficult because of the low melting tempand boiling point.which means that this metal will evaporate before your eyes if heat in put is to high.

the second facter is the oxide film that forms while heating.heavy fluxing and careful manipulation of the torch and the weld puddle are the only means of over comming this problem. With oxy-fuel welding the flame should be neutral or slightly carburizing.The filler metal should be under the name white metal but there are various trade names.

safety Zinc fumes are very toxic so good ventilation is important during the welding process.