At present, cables available in the wire market are of good and bad qualities, especially the security wire. Copper-clad aluminum wire and copper-clad aluminum magnesium wire are new materials emerged in recent years. To make bigger profits, illegal businessmen order copper-clad aluminum, copper-clad aluminum magnesium and copper-clad steel wire from manufacturers and sold them as oxygen-free copper wire. Their actions of making exorbitant profits are outrageous. The current price of oxygen-free copper wire is RMB 66,000/ton, while the price of copper-clad aluminum is only 35,000/ton. (Note: as the specific gravity of oxygen-free copper is 8.9 and that for aluminum is only 2.7, there is huge difference between the specific gravity of them). I hope the article would be helpful to you in distinguishing copper wire and copper-clad aluminum.

Copper-clad aluminum is actually aluminium wire or magnesium aluminum wire cladded or plated with a layer of copper outside. Advantages: good conductivity, light weight, small specific gravity and cheap price. Process and production of raw materials are relatively convenient. As copper wire production enjoys the same features, it is an excellent substitute material of copper conductor. Disadvantages: prone to breakage of the wire, fragile, plated tin losing. It is of low strength and tends to oxidation in bare state under normal temperature. With exposure to water, copper-clad aluminum wire will turn black and oxidation will be accelerated.

The copper-clad aluminum wire and copper-clad aluminum magnesium wire are commonly used as core wire conductor, spiral shield and braided shield. In terms of appearance, copper-clad aluminum, copper-clad aluminum magnesium and copper-clad steel look like copper wire. In unprofessional conditions, it is easy to cause confusing.

Three methods of recognizing are introduced as follows:
I. Watch the section. If copper-clad aluminum is used in thick wire, it is easy to find out. Therefore, copper-clad aluminum is generally flexible wire composed of plenty of stranded small fine wires. However, only if you cut the section, you can distinguish its material if there is something white (the color of aluminum).

II. Burning method. You only need to burn the wire with a lighter and watch the phenomenon and results of burning. For copper-clad aluminum and copper-clad aluminum magnesium wire, once the fire touches the wire, the conductor will hang down directly. It is difficult to burnout. The conductor will turn gray or more black after burning. This is because the melting point of aluminum is lower than that of copper. Difference: after burning, the conductor of copper-clad aluminum will be broken by entwisting of fingers. It is fragile and will break into several sections. For oxygen-free bare copper wire, if it forms beaded articles after being burnt, it is copper wire. Copper wires of different thicknesses show different results after being burnt. The thin copper wire will melt, while the thick wire will stay the same.

III. Scraping with tools. If tinned copper wire shows yellow color after being scraped, it is copper. If the color of oxygen-free bare copper wire stays the same after being scraped, it is copper as well. Instead, copper-clad aluminum wire and copper-clad aluminum magnesium wire will show white points like snowflake. Alternatively, you can rub the wire on cement floor, which is equally effective. Copper-clad steel wire can also be distinguished with this method or with magnet. By using the combination of the above three methods, I believe it will not be difficult any more to identify copper wire and purchase cable of fine quality with cheap price.

At last, I’d like to talk about the copper-clad copper. What is copper-clad copper? It is actually brass cladded with oxygen-free copper.

Oxygen-free copper: it refers to pure copper without any residue of deoxidizing agent. But there is actually very trace amount of oxygen and some impurities still in it. As stipulated in standards, if the oxygen content is not larger than 0.03 % and total content of impurities is not larger than 0.05 %, the purity of copper exceeds 99.95 %. Metallic copper with purity exceeding 99.995% is generally used in electrical and electronic applications, such as audio equipment, vacuum electron device and cables. Oxygen-free copper is free of hydrogen embrittlement with high electric conductivity. It is of superior processing property, welding property, corrosion resisting property and cryogenic property. However, it is also of large specific gravity and high price. Brass: an alloy composed of copper and zinc.

The copper content of brass is between 62% and 68%, and the specific gravity is between 8.2 and 8.4. The brass composed of copper and zinc is called common brass. Multiple alloys composed of more than two elements are called special brass. Seamless copper pipe drew with it is of soft texture and strong wear-resisting property. It is suitable to be fabricated as sheet metal, bar stock, bar material, tube stock and casting parts. As it is of strong plasticity, it can be fabricated as pressure-resistant equipment. However, it is relatively fragile and of low tensile strength, light specific gravity and cheap price.

The third method is most effective in distinguishing whether a copper wire is of copper-clad copper. After scraping the oxygen-free copper on the surface and brass inside with a blade, it can be distinguished with naked eyes.   

The above are the simple methods to distinguish the materials of cables. I hope it would be helpful to you!

Note: this article is for reference only and will not constitute investment suggestion.