Aluminum Welding

Even for the most experienced welders, welding aluminum can be challenging. Aluminum welding requires different techniques and processes than welding steel, and it’s critical to know these differences in order to complete successful welds and work on a variety of different projects.

While welding aluminum can be difficult, it’s a skill that can be developed with the right knowledge and practice. Keep reading to learn all about how to weld aluminum—from the different types of welding you can use to general tips for success.

Aluminum is a common type of metal used in fabrication. It’s non-corrosive, lightweight and pleasing to the eye, making it an ideal choice of material for a wide variety of welds. However, the same traits that make aluminum desirable can also make it tricky to work with.

So why is aluminum so difficult to weld? This material is soft, highly sensitive and is insulated by a tough oxidized layer. While in its molten state, aluminum is susceptible to impurities, which can lead to porous, weak welds.

Aluminum and its alloys have a great affinity for oxygen. Pure aluminum melts at 1,200°F (650°C), and the oxide that protects the metal melts at 3,700°F (2,037°C). Because the oxide melts at a temperature approximately 2,500°F (1,370°C) higher than the aluminum itself, the oxide must be cleaned from the metal before welding can begin.

Since aluminum has a higher thermal conductivity and low melting point, it has a smaller window of workability than other metals and can easily lead to burnthrough. This, in combination with it being harder to indicate weld progress and quality, can make aluminum a difficult material to work with.

Here are some of the most common factors that make aluminum challenging to weld:

Oxidation: On top of aluminum sits an aluminum oxide layer, which melts at a significantly higher temperature than aluminum. Melting through this layer requires high heat, however, the welder must be careful to not burn holes in the aluminum underneath.

Porousness: In its molten state, aluminum absorbs hydrogen quicker the more it heats up. This hydrogen separates out as the metal returns to a solid form, which can leave behind bubbles in the material, causing the metal to become porous and weak.

Impurities: As aluminum is very sensitive, there are several ways it can become contaminated by dirt, air and water during the welding process. Aluminum can become contaminated by air that reaches the weld because of poor shielding or excessively long arcs. Oxygen can reduce aluminum’s strength, ductility and cause an oxide formation on aluminum welds, which affects its appearance and complicates multipass welding. Hydrogen can come from many sources, such as moisture in electrode fluxes, humid air, damp weld joints and more. For all of these reasons, it’s important to clean aluminum thoroughly and store it correctly prior to welding.

Thickness: Welding aluminum involves working with different material thicknesses. Welders must know how to avoid burning through thinner material while also penetrating thick material enough to create a strong weld.

While there are certainly challenges that come with welding aluminum, it’s not impossible to learn. Luckily, there are tools and techniques designed to help when working with aluminum’s unique properties.