Search

How to Weld Aluminum: The Beginner’s Guide

UTI Profile Image Universal Technical Institute Jun 15, 2020 ·

Even for the most experienced welders, welding aluminum can present a challenge. 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.

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 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 1200°F (650°C), and the oxide that protects the metal melts at 3700°F (2037°C). Because the oxide melts at a temperature approximately 2500°F (1370°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.

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 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.

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 steps to follow:

  1. 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.
  2. 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.
  3. Assemble the joint and cover it if you won’t be welding it immediately. This will prevent dirt or grit from contaminating the joint.
  4. 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.

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

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

GTAW requires a 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 feedability 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), commonly referred to as metal inert gas (MIG) welding, is another common method used for aluminum welding.

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, in order 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. Check out Lincoln Electric’s guide to aluminum GMAW welding to learn even more about this method.

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 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 slower

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 a 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.

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. Not being patient: Learning to weld aluminum takes time. Keep practicing and stick with it—your hard work and persistence will 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 oz. 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.

As aluminum welding becomes more popular, it’s important for today’s welders to possess the skills to work with this material. This often requires some type of formal, hands-on training, such as the Welding Technology training program offered at Universal Technical Institute.

In this program, students learn four of the most common welding techniques, including TIG and MIG welding. Developed in conjunction with Lincoln Electric, a leading brand in the industry, this training program also covers how to weld in the flat, horizontal, vertical and overhead positions used for plate or sheet metal, and the fixed, rolling and overhead positions used for pipe.

UTI’s welding program is offered at five campus locations nationwide, including Avondale, AZ, Rancho Cucamonga, CA, Dallas/Fort Worth, TX, Houston, TX and Long Beach, CA.

Looking for Welding Training Courses?

Universal Technical Institute’s 36-week Welding Technology training program is designed to give you the hands-on training needed to prepare for a welding career in a variety of industries. To learn more, visit our program page and request information to get in touch with an admissions representative today.

Additional welding resources:

YOU COULD START YOUR EXCITING NEW CAREER AS A MECHANIC OR TECHNICIAN TODAY.
Classes start soon. With classes starting every 3-6 weeks, no need to wait to start your career.
Hands-on training. Get hands on experience with the industry's leading brands.
No Pressure to commit. Get answers to your questions without any obligations
Call Now 800.834.7308 Or request more info
Training For A New Career Starts Here

It only takes a few minutes to learn about technician training opportunities.

Required
Required
Required
Required
Required
Required
Required
Please enter your email address

By submitting this form, I agree that Universal Technical Institute, Inc., Custom Training Group, Inc., and their representatives may email, call, and / or text me with marketing messages about educational programs and services, as well as for school - related communications, at any phone number I provide, including a wireless number, using prerecorded calls or automated technology. I understand that my consent is not required to apply, enroll or make any purchase.

By submitting this form, I further understand and agree that all information provided is subject to UTI’s Privacy Policy available at uti.edu/privacy-policy

Motorcycle Mechanics Institute
Marine Mechanics Institute
NASCAR Technical Institute