How do you distinguish copper from other metals?
If you have some copper-like scrap piled up in the house, the question arises: Can you make sure it’s really Cu and count on a lot of cash for cars newmarket?
Professionals can quickly and accurately determine the composition of scrap by spectral analysis with special instruments – metal analyzers.
And what can we do at home when the options for determining the chemical composition of scrap metal are limited?
There are a number of ways we can do this at home, including:
Using our own senses;
Use of readily available chemicals;
exposure to fire;
The use of simple instruments.
How do we visually distinguish copper from other metals?
First of all, the material is carefully examined to determine the main external distinguishing features of copper:
the color of the metal should be golden pink;
Usually there is a film of oxide on the surface, which adds a yellowish-red tinge.
Only a few metals, including gold (Au), cesium (Cs) and osmium (Os), have a similar coloring. However, since these chemical elements in their pure form are rare and are produced in small quantities, it is almost impossible to make a mistake when visually inspecting and identifying Cu among the listed materials.
The material should be viewed in good daylight, as colors are usually distorted in artificial light. It is also recommended to get rid of the oxide film. This is done mechanically by filing the surface with a file, or by identifying it by a fresh cut.
Many copper items are marked. If you try to carefully inspect the surface and find the markings, its presence will allow you to accurately identify the material from the reference book.
How to distinguish copper from brass?
It is somewhat more difficult to identify the copper alloy – brass. Scrap brass is somewhat cheaper at reception points, because in addition to Cu, it contains the chemical element zinc (Zn) in an amount of 4 to 45% of the mass of the alloy.
Color. The color of the alloy is lighter than Cu. And the more Zn it contains, the more the color turns yellow. Although in the case of a small amount of alloying additives (up to 10%) it is still difficult to identify the metal visually.
Sound. Brass rings when struck, and soft copper makes a muffled sound. This method is good to be applied on the example of rather large products.
Plasticity. When bending Cu, it is easy due to its high ductility. In the case of brass, it is much more difficult: the hardness of the alloy is higher and, accordingly, the malleability is less.
Weight. The average density of brass is 8.6 g/cc, copper 9 g/cc. You can identify the metal with the help of accurate scales (if you have them in the house).
Shape of the chips. After processing, copper chips have a spiral shape, and brass – a straight needle shape.
Chemical method. Brass alloy when exposed to hydrochloric acid forms a white deposit on its surface. If the same is done with copper, nothing happens.
Methods to distinguish copper from bronze
Uncomplicated methods that make it possible to find the differences between Cu and its alloy with tin (Sn):
Plasticity. If you apply pressure on copper with something hard, a notch will appear at that point. Harder bronze cannot be deformed in this way.
Oxidation. Over time, the surface of Cu becomes covered by an oxide film that changes the color of the metal.
The bronze alloy does not oxidize in the air.
The chemical method. In a container of metal heated to 50 degrees Celsius salt solution at the rate of 1 liter of water to 200 grams of salt. If you put the copper for 15 minutes, its color will change. The bronze alloy will not react in any way to such conditions.
How can I tell the difference from aluminum?
Tin-plated copper and copper-coated aluminum (Al) are often used in cable and wire products. The metals can be identified as follows:
Color. Copper-plated aluminum has a yellow hue, while the Cu surface acquires a silver color after tinning.
Plasticity. Copper cores are several times more stable when bending and unbending, while aluminum cores break quickly.
Resistance Measurement. Resistance of a twisted pair of copper (100 m) ranges from 4 to 8 ohms, aluminum – from 12 to 20 ohms.
Exposure to flame. Al begins to melt at 600 degrees. The temperature at which Cu will show signs of melting is much higher.
Other Fire, Acid Testing
When exposed to an open flame, copper begins to dull to the point of being completely blackened.
If Cu is exposed to nitric acid, the surface will turn blue-green at the point of contact.