Most modern beverage containers, especially those used for soft drinks and beer, are not magnetic. The standard material used to create the body of a soda can is aluminum. This metal does not exhibit the strong magnetic properties typically associated with metal objects. This choice of material makes the cans light and easily recyclable, but it also means they will not respond to a refrigerator magnet.
The Primary Material: Aluminum
Aluminum became the material of choice for beverage cans starting in the late 1950s, largely replacing heavier steel. The metal is exceptionally lightweight, which significantly reduces the cost of shipping and transportation. Furthermore, aluminum resists corrosion, meaning the cans do not rust when exposed to moisture.
The can itself is not pure aluminum but an alloy, typically including small amounts of magnesium and manganese. These elements are added to increase the metal’s strength and durability, allowing the can walls to be drawn incredibly thin during the manufacturing process. Aluminum is also highly valued because it is endlessly recyclable, requiring over 90% less energy to melt down and reuse than to produce the virgin metal.
Understanding Magnetic Properties
The strong magnetic attraction most people are familiar with is called ferromagnetism, a property found in only a few elements like iron, nickel, and cobalt. Ferromagnetic materials have unpaired electrons that align themselves into microscopic regions, or domains, which all point in the same direction when exposed to an external magnetic field.
Aluminum, however, is classified as paramagnetic, which means it has unpaired electrons but their overall alignment is temporary and very weak. When a magnet is brought near aluminum, the electrons only slightly align with the magnetic field. This induced magnetism is so faint that it results in a negligible, almost undetectable attraction in normal circumstances. For practical purposes, a paramagnetic material like aluminum is considered non-magnetic because it will not stick to a refrigerator magnet.
When Cans Are Magnetic
While most soda cans are aluminum, a small percentage of beverage containers are made from steel, which is strongly magnetic. These exceptions are often used for specialty drinks, energy drinks, or some imported beers, and they are also the standard for canned food. Steel cans are magnetic because steel is an alloy of iron, and iron is a strongly ferromagnetic element.
A consumer can differentiate between the two types of cans by testing them with a simple magnet. Steel cans are also usually heavier than their aluminum counterparts and are often made in a three-piece construction, which can feel different from the two-piece design common to aluminum cans.