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Zamak (formerly trademarked as ZAMAK), also known as Zamac is a family of zinc alloys widely used in common everyday items. Zamak is most often than not the "mysterious metal" from zippers, buttons, cases, that loses its luster in air rapidly and is brittle.
If you plan to use zamak as source of zinc for your chemical reactions, expect plenty of side products to appear in the reaction flask, as many zamak alloys may also contain other elements, especially if it's low quality.
Zamak consists of >96% zinc, <4% aluminium, with other metals like magnesium or copper being added. The most common zamak alloy used in North America is Zamak 3, which has a general composition of >95% Zn, 3.5-4.3% Al, 0.25% Cu, 0.05-0.1% Mg, with traces of iron, tin, lead or cadmium. In Europe, Zamak 5 is instead more widely used. It has a composition of >95% Zn, 3.5-4.3% Al, 0.75-1.25 Cu, 0.03-0.08% Mg and traces of other metals like iron or tin.
Zamak is a silvery alloy, which gets dull in air over time, with an average density around 6.6 g/cm3. It melts between 381—387 °C, has a thermal conductivity between 104-116 W/m·K and electrical resistivity of 6.3.8-6 μΩ/cm, depending on the alloy composition.
Zamak quickly tarnishes in air and reacts with most acids and bases, as well as halogens.
Zamak can be found in a variety of everyday objects, like buttons, zippers, toys, jewelries, chains, cases, locks, keys, handles, various die-cast parts. Some wheel weights are also made of Zamak rather than zinc, even though both are labelled "Zn".
To differentiate pure zinc from zamak, you can do a density test (pure Zn has 7.14 g/cm3, while zamak is lighter, 6.6 g/cm3) or dissolve the metal in diluted nitric acid. Aluminium does not dissolve in HNO3 and precipitates as aluminium oxide, while copper dissolves, giving the solution a blueish color. Pure zinc dissolves in nitric acid without forming any precipitate. If no blue color is produced but a white insoluble precipitate still appears (that will dissolve in HCl), it's possible that what you have there is just some other zinc-aluminium alloy.
- Source of elemental Zn in chemistry
- Cast objects
Zamak has low toxicity, though inhaling zinc alloy dust is harmful, and proper protection should be worn when doing metalworking.
Low quality zamak may contain heavy metals like cadmium or lead, and work should be avoided if possible.
No special storage is required, although it's best to keep the metal in a dry place, as it corrodes easily in contact with corrosive reagents.
Zamak items should be taken to waste metal centers.