Aluminum is a versatile metal that has various applications. Thanks to being relatively soft and lightweight, aluminum is used in various industries. However, these exact qualities pose challenges for welders when it comes to welding aluminum. In this blog, we will review some of the most common challenges when MIG welding aluminum as well as provide a few tips on how to make welding aluminum with a MIG welding machine easier. 

Common Challenges when MIG Welding Aluminum

Oxidation is one of the most common problems. Aluminum is covered with a thin oxide film. The oxide film melts at a significantly higher temperature (~2000 degrees Celsius) than the aluminum underneath it (!650 degrees Celsius). This significant difference in melting point makes aluminum welding a challenge as welders are always risking burning the metal through. 

Porousness is another challenge in aluminum welding. Aluminum in its molten state easily absorbs hydrogen which further separates as the metal cools down leaving behind pores in the metal. This high porousness of the welded piece negatively affects the quality of the structure and can render the piece defective.

Aluminum welds are prone to various impurities. If no proper welding gas is used while welding aluminum with a MIG welding machine, welds can get easily contaminated. Oxygen can impact aluminum strength and can cause the formation of an oxide layer on aluminum welds. Hydrogen, as discussed above, can cause weld porousness. Hydrogen can come from humid air in the shop, improperly cleaned metal and moisture in electrode fluxes (if electrodes are used to shield the weld).

All these defects can significantly affect the weld quality. However, there are ways to prevent them. Here’s how you can reduce any impurities while welding aluminum with a MIG welding machine.

5 Tips to Achieve Best Results When MIG Welding Aluminum

Clean the base metal well

Cleaning aluminum before welding is the most important to ensure a good-quality seam. Make sure to remove any lubricants from the metal, degrease it properly and follow up with the removal of the oxide layer. The oxide layer should be removed using a stainless wire brush appropriate for aluminum.

Choose the right welding gas

The aluminum weld pool needs to be properly shielded from atmospheric contaminants to reduce the chances of air contamination and porousness. As aluminum is a non-ferrous metal, it requires pure argon welding gas. 

Metal thickness considerations

The output capacity of your MIG welding machine determines the thickness of the aluminum you can weld. You can MIG weld aluminum of 14 gauge or heavier. To weld thinner metal, you will need to use specialized welding equipment. Read our blog on MIG welding gear necessary to execute MIG welding. 

Filler metal considerations

To improve the metal’s strength, aluminum often comes with other alloys. Consider the composition of the aluminum alloy and where the finished structure will be used (e.g. shipbuilding, construction) before choosing the filler metal to weld aluminum. Lock 8, a welding supply store with locations in Port Colborne and Stoney Creek, ON, can guide you on various filler metals appropriate for aluminum welding. 

Use the spray transfer welding method

The spray transfer welding mode generates small droplets of molten metal (smaller than the wire diameter) into the weld pool. This increases deposition rates and provides fusion. However, as a high amount of heat is generated, the spray transfer method can result in burn-through if let out of control. 

Welding aluminum is not easy, but with proper welders equipment and refined skills, you can achieve good results. It is also important to source your equipment from a reliable supplier. Lock 8 is a one-stop shop for all your welding needs. Whether you are looking for welding machines, welding gas, or welding accessories, we have it all. We also offer welders equipment for rent and can book a demo at one of our locations for you to come and test the equipment. Contact us today to learn more about our products and services.