Pot metal, also known as monkey metal, white metal or die-cast zinc, is a colloquial term that refers to alloys that consist of inexpensive, low-melting point metals used to make fast, inexpensive castings. The term "pot metal" came about due to the practice at automobile factories in the early 20th century of gathering up all non-ferrous metal scraps from the manufacturing processes and throwing them into one pot to be melted and then formed into cast products. A small amount of iron made it into the castings, but generally too much iron raised the melting point too much, so it was minimized.
There is no scientific metallurgical standard for pot metal; common metals in pot metal include zinc, lead, copper, tin, magnesium, aluminium, iron, and cadmium. The primary advantage of pot metal is that it is quick and easy to cast. Due to its low melting temperature no sophisticated foundry equipment is needed and specialized molds are not necessary. It is sometimes used to experiment with molds and ideas (e.g. prototypes) before using metals of higher quality. Examples of items created from pot metal include toys, furniture fittings, tool parts, electronics components, and automotive parts.
Pot metal can be prone to instability over time, as it has a tendency to bend, distort, crack, shatter, and pit with age. The low boiling point of zinc and the fast cooling of the newly cast part often allow air bubbles to remain within the cast part, weakening the metal. Many of the components of pot metal are susceptible to corrosion from airborne acids and other contaminants, and the internal corrosion of the metal often causes the decorative plating to flake off. Pot metal is not easily glued, soldered or welded.
At one time, "pot metal" referred to a copper alloy that was primarily alloyed with lead. 67% Cu, 29% Pb & 4% Sb and 80% Cu, 20% Pb were common formulations.
The primary component of pot metal is zinc, but often the caster adds other metals to the mix to strengthen the cast part, improve the flow of the molten metal, or to reduce cost.[dubious ] With a low melting point of 419 °C (786 °F), zinc is often alloyed with other metals including lead, tin, aluminium and copper.
- Balfour, Edward (1885), The Cyclopædia of India and of Eastern and Southern Asia 3 (3 ed.), London: Bernard Quaritch, p. 271
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