Zinc is naturally dull grey and is very hard to polish. Zinc has has an oxide that flakes off carrying some of the zinc so other things are coate...
If your like me and make scrap metal sculpture then it can sometimes be hard to identify what metal the scrap is made of. In this instructable I will show you how too identify some of the more common metals. NOTE: These are not all the metals there are, there are thousands and I couldn't possibly tell about all of them. Also if you bend tin it will make a light "snapping" sound.
Ferrous means that the metal has iron content which in most cases makes it magnetic and nonferrous means it doesn't have iron in it. An example of a ferrous metal is mild steel, also known as low carbon steel. An example of a nonferrous metal is copper or aluminum. Its always a good idea to bring a magnet to the scrap yard.
Step 2: Aluminum
Aluminum is a shiny grey metal and has a clear oxide that forms on contact with air. This may not be the best thing for identifying it, but aluminums melting point is 658° C (1217°F). Also aluminum is non sparking. Aluminums density is 2.70 g/cm3, this is a good way to identify it because you can find the density of a material by density = mass ÷ volume. As i said earlier, aluminum is nonferrous.
Step 3: Bronze
Most bronze is an alloy of copper and tin, but architectural bronze actually has a small amount of lead in it. Bronze has a dark coppery color and gets a green oxide over a period of time. bronze's melting point is 850-1000°C (1562-1832°F) depending on how much of each metal is in it. Bronze is nonferrous. Because bronze is an alloy densities vary. Bronze vibrates like a bell when hit.
Step 4: Brass
Brass is another copper alloy but it has zinc instead of tin. Brass has a yellow gold color. Brass' melting point is 900-940°C (1652-1724°F) depending on how much of each metal they used. Brass is nonferrous. Because brass is an alloy its density varies. If hit brass vibrates like a bell, this can be used to determine if something is brass instead of gold.