HOW TO WELD ALUMINUM: THE BEGINNER’S GUIDE

Even for the most experienced welders, welding aluminum can present a challenge, and a lot of times many people ask, can you weld aluminum? Welding aluminum can be challenging due to its softness, sensitivity and the presence of an oxidized layer. 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.

Factors that make aluminum difficult to weld include oxidation, porousness, impurities, and the need to work with different material thicknesses. The best way to weld aluminum is to choose the right welding process, such as TIG or MIG welding. Other types of welding that can be used for aluminum include laser beam and electron beam welding, resistance welding, and shielded metal arc welding.

While welding aluminum can be difficult, it’s a skill that can be developed with the right knowledge and practice. It is important to avoid common mistakes when welding aluminum, such as not wearing proper protective equipment, failing to prepare the material, ignoring minor details and lacking patience. Keep reading to learn all about how to weld aluminum—from the different types of welding you can use to general tips for success.

What Is Aluminum Welding?

Aluminum welding follows the same process as welding in general. The main difference is that in this case, we are referring to using heat and pressure to join two components made from aluminum. What sets welding aluminum apart is how much stronger and durable it is compared with other materials and metals, like steel.

Why Aluminum Welding Is Difficult

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 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 degrees Fahrenheit (650 degrees Celsius), and the oxide that protects the metal melts at 3,700 degrees F (2,037 degrees C). Because the oxide melts at a temperature approximately 2,500 degrees F (1,370 degrees 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 burn-through. This, in combination with it being harder to indicate weld progress and quality, can make aluminum a difficult material to work with.

In sum, 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 not to 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 and 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.

By having knowledge of the way aluminum reacts and how to effectively use these tools and techniques, you’ll be well on your way to mastering the art of aluminum welding.

The Best Way To Weld Aluminum

Welding aluminum comes down to choosing the right welding process. Many tools and methods are designed for welding steel, but aluminum requires its own technique and equipment.

Before even beginning the welding process, the welder must clean the aluminum thoroughly. As mentioned previously, one of the challenges with aluminum is that it is more prone to impurities. Therefore, prepping the material correctly is key. Here are a few tips to follow:

• Use a solvent such as acetone or a mild alkaline solution like a strong soap to remove any oil, grease and water vapor from the aluminum’s surface.
• Use a stainless-steel wire brush (used exclusively for aluminum) to remove surface oxides. This can also be done with a strong alkaline or acid. Always be sure to rinse and fully dry the part before welding. Assemble the joint and cover it if you won’t be welding it immediately. This will prevent dirt or grit from contaminating the joint. Always keep your aluminum dry and stored at room temperature. It should be welded within a few days, and if it’s not, clean the joint again.
• Safety is another critical component to welding aluminum, or any material for that matter. Always ensure you wear the proper protective equipment such as goggles, safety glasses, a welding helmet with the appropriate lens shade number to protect your eyes, gloves and leathers to protect yourself from metal sparks and splatters, the proper shoes to protect your feet and proper fume ventilation to keep the welding fumes away from your breathing zone.

Check out our welding safety guide to learn more.

Can You Stick Weld Aluminum?

It’s possible to weld aluminum using stick welding methods, but it can be messy. Some of the best methods to use during the process include alternating or direct current TIG welding or MIG welding.

While stick welding is not typically the first choice when it comes to welding aluminum, there are some pros to using this process, including the flexibility of working without a shielding gas and the fact that the process works well on rusted or painted metal workpieces.

You can read more about the different aluminum welding methods below.

Types of Aluminum Welding

If you’re wondering how to weld aluminum, it’s important to know that there are several welding processes that can be used:

• GTAW/TIG welding
• GMAW/MIG welding

GTAW/TIG

Gas tungsten arc welding (GTAW) is also known as tungsten inert gas (TIG) welding. TIG welding aluminum is one of the most popular welding processes chosen for this material. This welding technique is often used by automotive enthusiasts and welders for professional racing teams.

GTAW requires constant current equipment with AC (alternating current) capabilities using 100 percent argon as a shielding gas. It does not require mechanical wire feeding, which has the potential to create feeding issues.

Rather, the welder will feed the filler material into a puddle. This process is also very clean, as the alternating current cleans the oxidized layer off the aluminum as it welds. It also prevents aluminum from being contaminated throughout the process.

Tips for TIG welding:

• Pick the right tungsten electrode or rod—the best choice for aluminum is typically a pure tungsten rod.
• Take the time to prepare your aluminum by cleaning and preheating it.
• Ensure there is not too much argon flow at the torch, which can cause an irregular arc.
• To prevent warping, use a heat sink.
• When welding, keep the proper aluminum filler electrode or rod free of contaminants and melt it with the base material to create a constant welding puddle.

GMAW/MIG

Gas metal arc welding (GMAW) is commonly referred to as metal inert gas (MIG) welding. MIG welding aluminum is another common method used for this material.

This type of welding typically has faster travel speeds and higher deposition rates than TIG welding, affecting the weld quality. However, it does utilize a mechanical wire feeding system, which means the welder may have to use a spool gun or push-pull gun to make wire feeding possible.

Additionally, to combat the risk of aluminum becoming porous, the base material and filler rod must be clean, free of moisture and have excellent shielding gas coverage, typically pure argon content.

Tips for MIG welding:

• Prepare your push-pull wire feed.
• Clean your aluminum, remove any oxide and file the edges that will be joined.
• Avoid pulling while welding—instead, push at a 10-degree to 15-degree angle.
• Use multiple-pass straight beads to improve the overall appearance of the weld and help to avoid defects.
• Use a heat sink, which will absorb extra heat and allow you to weld more slowly.

Other ways to weld aluminum

While MIG and TIG are commonly used methods for welding aluminum, there are several other types of welding that can be used:

• Laser beam and electron beam welding: Beam welding techniques are commonly used for aluminum. Electron beam welding has a very precise heat-affected zone that can be easily controlled, which makes it great for aluminum. Laser beam welding is great for fast, clean welds and is ideal for materials sensitive to cracking, such as aluminum.
• Resistance welding: This type of welding joins metals by applying pressure and passing current through the metal areas being joined. It can be used for aluminum— however, the welder must be aware of the high thermal and electrical conductivity of this metal.
• Shielded metal arc welding (SMAW): This type of welding could be used to weld aluminum but is not recommended. In some cases, it is used to repair cast aluminum using constant current equipment with an aluminum electrode using electrode positive polarity.

So what types of welding should be avoided with aluminum? In general, any type of welding that uses a flux is not ideal for aluminum, as it can result in porosity. These include flux-cored arc welding (FCAW), submerged arc welding and stick welding.

Things To Avoid When Welding Aluminum

Now that we’ve covered different methods that can be used to weld aluminum, let’s talk about some common mistakes to avoid.

Taking a “one-size-fits-all” approach: When it comes to welding aluminum, the welder must take an entirely different approach than they would with a material like steel. It’s critical for the welder to not base their technique on experience they have with other metals or materials, as aluminum is very unique and can present dangers when not handled correctly.

Not wearing the proper PPE: Speaking of dangers, welding aluminum or any kind of material is inherently dangerous. It’s important for welders to always wear the correct personal protective equipment (PPE) and educate themselves on safety procedures and best practices. This is key to a long, successful career in the industry.

Failing to prepare: Preparation is key—both for the welder and the material being welded. Always be sure to properly clean your aluminum and store it correctly before beginning your weld. Additionally, make sure to prepare yourself by studying the art of aluminum welding and educating yourself on the craft. Never jump into anything until you are adequately prepared.

Ignoring minor details: The most successful welders will tell you that detail is everything. In this industry, the smallest misstep can lead to a complicated error—especially with aluminum welding. Always pay attention to every detail and double-check your work, as this will benefit your customers and your career in the long run.

Not being patient: Learning to weld aluminum takes time. Keep practicing and stick with it—your hard work and persistence can pay off in the end!

Benefits of Using Aluminum

As welding aluminum presents challenges, you might be wondering, “Why use aluminum in the first place?”

The use of aluminum as a structural material is fairly recent. In fact, the Washington Monument, which was completed in 1884, was capped with a 100-ounce pyramid of pure aluminum because it was considered a precious metal. At this time, aluminum was not widely used.

It wasn’t until 1886 that aluminum became available in commercial quantities due to the discovery of the electrolytic process for obtaining pure aluminum from aluminum oxide. Since then, welders around the world have recognized its unique qualities and used it in many applications, such as passenger automobiles, trucks, over-the-road trailers, railroad cars, aircraft, cookware and even marine equipment.

While aluminum can be difficult to work with, this material offers several key benefits:

• Lightweight: When compared to steel, aluminum has a better strength-to-weight ratio and becomes stronger rather than brittle with decreasing temperature. This makes it a great choice for projects that require strength yet need to remain lightweight.
• Electricity & heat: Aluminum conducts electricity and heat almost as well as copper.
• Non-corrosive: While oxidation creates challenges during the welding process, this quality is also a benefit to using aluminum, as it is non-corrosive.
• Recyclable: Aluminum is cost-efficient and recyclable, which is one of the reasons it has become increasingly popular.
• Appearance: Aluminum effectively absorbs paint and sealant, so it is often chosen for its cosmetic qualities.

Looking for Welding Training Courses?

Universal Technical Institute (UTI) offers a 36-week Welding Technology program that is designed to give students the hands-on training needed to prepare for a welding career in a variety of industries.¹ You’ll learn the skills you need to be able to weld on a range of materials, including aluminum.

To learn more, request information to get in touch with an Admissions Representative today.