I get a lot of dross when melting zinc alloy. What is the cause?
The most common cause of excessive dross formation is that the metal temperature is too high which increases the rate of oxidation. It also increases the rate which aluminum in the alloy combines with the iron of the pot, gooseneck etc. to produce iron-aluminide intermetallic. The result is excessive dross and excessive wear of the furnace and gooseneck. In extreme cases, this can cause the alloy to go out of specification. Normal operating temperatures are 200 to 800 F above the melting point of the alloy. Other causes of excessive dross are: ·· Remelting thin flash, which oxidizes easily. ·· Charging scrap that is wet or oily. ·· Charging castings that are plated or contain ferrous inserts.
