When it contaminates aluminum. Copper is an alloying element in some grades of aluminum, but it is not a desirable element for mills producing grades of aluminum that are supposed to be copper-free.
We previously published a copper compendium – several articles relating to the value of copper in the metal and alloy world. Copper (Cu), number 29 on the Periodic Table, is one of the oldest and most useful metals known to man. Copper, along with other nonferrous metals including aluminum, nickel, and tin, doesn’t lose any of its chemical or physical properties during the recycling process, which means it can be recycled indefinitely.
Copper Contaminants Can Cause Problems
However, when copper is a contaminant in other metals, it can cause problems. The reason tramp elements such as copper would be undesirable in a melt at a mill, is because it would actually make the finished product less ductile and corrosion resistant. (Tramp elements are generally defined as those that are not deliberately added and that cannot be totally removed by metallurgical processes.)
The Aluminum Association explains that there are many aluminum alloys that include elements such as copper, iron, silicon, magnesium, manganese and zinc at levels that combined may make up as much as 15 percent of the alloy by weight.
“Alloys are assigned a four-digit number, in which the first digit identifies a general class, or series, characterized by its main alloying elements….
The 1xxx series alloys are comprised of aluminum 99 percent or higher purity. This series has excellent corrosion resistance, excellent workability, as well as high thermal and electrical conductivity. This is why the 1xxx series is commonly used for transmission, or power grid, lines that connect the national grids across the United States. Common alloy designations in this series are 1350, for electrical applications, and 1100, for food packaging trays….
In the 2xxx series, copper is used as the principle alloying element and can be strengthened significantly through solution heat-treating. These alloys possess a good combination of high strength and toughness, but do not have the levels of atmospheric corrosion resistance as many other aluminum alloys. Therefore, these alloys are usually painted or clad for such exposures. They’re generally clad with a high-purity alloy or a 6xxx series alloy to greatly resist corrosion. Alloy 2024 perhaps the most widely known aircraft alloy.
Verify Alloys with XRF
If you use aluminum in your finished product, then you will want to verify with x-ray fluorescent technology that the grade of aluminum alloy you purchase is the one you receive in your manufacturing plant. For example, if you manufacture parts for the aerospace, automotive, or marine industries that are subject to corrosion, you would want to verify that you did not have a copper-alloyed aluminum, unless you were planning to clad the metal.
As another example, according to the same industry association article, Alloy 4043 is one of the most widely used filler alloys for welding 6xxx series alloys for structural and automotive applications. But 4xxx series alloys are combined with silicon, which can be added in sufficient quantities to lower the melting point of aluminum, without producing brittleness. The 6xxx series contain silicon and magnesium and Alloy 6061 is often used in truck and marine frames. If tramp copper was introduced into the melt, it could lead to brittleness and adversely affect the integrity of the weld and the metal, causing a potential failure.
Metals derive properties such as strength, ductility, and corrosion resistance from alloying elements. Adding alloying agents is a complicated process; the right ingredients must be added in the right percentages in order for the final product to perform as expected. So mills and manufacturers must conduct elemental analysis to verify that tramp metals like copper are not introduced in the melt.
In addition, using recycled metals is becoming more prevalent so manufacturers must analyze incoming raw materials carefully to ensure the elements in the materials will not be detrimental to the product, or ultimately their brand. To ensure they are shipping quality products, portable XRF analyzers can be utilized throughout the facilities to inspect all incoming metals against paperwork, for quality checks upon receipt of the raw material scrap, and for final analysis of the finished product before the material leaves the facility.
If you are expecting to use, or produce parts made of, commercially pure aluminum (which is comprised of aluminum 99 percent or higher purity), or if your product depends upon using a certain series of aluminum alloys, you need to make sure you are starting with the right materials. If they are not, your products won’t be worth a dime… or even one copper penny.
Looking for metal alloy verification solutions in a specific industry, visit the Portable Manufacturing and Metal Fabrication Analysis section on ThermoFisher.com.