In the event that magnets are ineffective, copper and aluminum can be distinguished in several ways:
Observe the color
Copper usually has a purplish-red metallic luster, color is more bright, in the air for a period of time, the surface will generate a layer of copper green, the color will gradually change to dark green.
Aluminum color is usually silver-white, the surface has a metallic luster, but relative to copper, the color is more dull, and easy to oxidize in the air, the surface will form a layer of dense alumina film, making it look slightly off-white.
Comparison of hardness
The hardness of copper is relatively large, you can use a sharp object in the inconspicuous parts of the light scratch, copper surface scratches left relatively shallow.
Aluminum's hardness is smaller, and also when scratched with a sharp object, the surface of aluminum is prone to leave deeper scratches.
Weighing
Copper has a density of 8.96 g/cm3 and aluminum has a density of 2.7 g/cm3. Therefore, copper is much heavier than aluminum for the same volume. You can make a preliminary judgment by weighing the two; the heavier is copper and the lighter is aluminum.
Check the section
Cut off the material with a saw or other tool and observe the section. Copper has a bright, metallic sheen and a purplish-red color consistent with the surface.
Aluminum also has a metallic sheen, but it is relatively dark and silvery-white in color.
Chemical identification
Prepare some dilute hydrochloric acid or dilute sulfuric acid, a small part of the metal to be identified into the acid. If a large number of bubbles quickly form on the surface of the metal, the metal is aluminum. Because the chemical nature of aluminum is relatively active, can react violently with dilute acid to produce hydrogen.
Copper is relatively stable chemically and does not react with dilute hydrochloric acid or dilute sulfuric acid, so there will be no noticeable phenomenon when copper is placed in the acid.
The above methods can help to distinguish between copper and aluminum when the magnet is ineffective, but for some materials that have been specially treated or have a coating on the surface, it may be necessary to combine a variety of methods to make an accurate judgment.
