[Coley]

Most of us that make parts from a zinc alloy like the term ZA (or ZAMAC) alloy instead of "Pot metal".
Za alloys can have as litle as 1 % of aluminum plus small amounts of copper and other metals (mostly trace amounts).
The amount of aluminum in ZA alloys tells the relative strength of the alloy. The higher the #, the stronger the part. Some disc brake castings for ATVs are ZA12 and up to ZA20.
Most of the parts I make are ZA2 or ZA3.
Sometimes the higher amount of aluminum will make it harder to chrome.