How to TIG Weld Aluminum Without Filler Rod


This process is also known as fusion welding or autogenous welding. With any technology as versatile as TIG welding—“there’s a time and a place for everything” is a pretty safe rule of thumb. However, most TIG pros agree that when it comes to skipping filler rod, it’s more important to know when you can and if you should than how to do it.

How to TIG weld aluminum without filler rod. The keys to TIG welding aluminum without filler rod are in the cleaning of the material and the fitting of the joints. The aluminum oxide layer must be removed using a stainless-steel wire brush and acetone. The process requires joints with no gaps. Materials that are thicker than 1/8” work best.

In the following article, we’ll discuss the best reasons to TIG weld aluminum without filler rod, when it’s probably going to be okay to do it, and what the challenges and downsides of going without filler are.

Disclaimer

Before we proceed, it’s worth noting that almost every commercial welding job will include specifications for the materials used in the welding work and parameters for testing that work. It should go without saying that when you’re working on a commercial welding project, you should always adhere to these guidelines.

Even if you’re TIG welding for personal-use projects, it is always important to consider the stresses that your project will be subjected to when in use. We will discuss the pros and cons of TIG welding aluminum without a filler rod. It is up to you to decide if you should.

Be sure to use appropriate PPE when trying out any of the tips or tricks we discuss in this article.

TIG Welding Aluminum Without Filler Rod – An Overview

Fusion welding with a TIG machine is a pretty common practice on all kinds of steel, especially stainless. There are a few things about this method that would make you want to use it on aluminum, as well.

With enough skill or the time and practice to develop that skill, you will be able to say that you “can” TIG weld aluminum in a wide range of situations. But should you?

Working without filler rod can be:

  • faster
  • easier
  • less expensive

than using filler material on your welds.

But TIG welding aluminum without filler is extremely prone to cracking. Cracked welds fail tests. Worse, cracked welds that don’t get tested cause projects to fail structurally.

Some Basics to Consider

It is easiest to get quality fusion welds on aluminum when you are working with immaculate parent materials—the thicker, the better. The alloy series of your aluminum will also influence the results. There can’t be any gaps in the joints you’re welding if this method is going to work.

If your project gives you these essential elements to work with, then working without a filler rod might be a good option. In a lot of cases, though, it would take too much time and effort to get these in place to make skipping filler practical.

Cleaning is Key

Even if you’re using brand new materials, the unique properties of aluminum mean that you’ll need to do some work before you start welding if you want to get good welds without filler.

Aluminum forms a layer of aluminum oxide on all of its exposed surfaces. The aluminum oxide has a much higher melting point. It also has the ability to contaminate the parent metal beneath it with impurities during welding.

The aluminum oxide layer must be removed entirely before you try to TIG weld aluminum without a filler rod. The team at Lincoln Electric has put together the following chart for cleaning aluminum:

 Compounds Removed Welding Surfaces Only Complete Piece
Oil, grease,
moisture, and
dust (use any
method listed)
Wipe with a mild alkaline solution and dryWipe with a hydrocarbon solvent, such as acetone or alcohol
Wipe with proprietary solvents
Dip edges, using any of above
Vapor degrease
Spray degrease
Steam degrease
Immerse in an alkaline solvent
Immerse in proprietary solvents
Oxides
(use any method
listed)
Dip edge in strong alkaline solution, then water, then nitric acid. Finish with a water rinse and dry
Wipe with proprietary deoxidizersRemove mechanically, such as by wire-brushing, filing, or grinding. For critical applications, scrape all joints and adjacent surfaces immediately before welding
Immerse in strong alkaline solution, then water, then nitric acid.
Finish with water, rinse and dry
Immerse in proprietary solutions

When it Comes to Fit, “Good Enough” Probably Won’t Be Good Enough

Welding without a filler rod is called fusion welding because you are actually fusing the separate pieces of the parent material. This means that you’re stealing some of each piece to fill in the empty space between them. That means that the weld and the parent material adjacent to it will be thinner than the rest of the parent material. No matter what you do, this will be a weak point.

There are definitely situations where this won’t be a cause for concern or where aesthetic considerations will outweigh those negatives.  But that still presumes a very tight and uniform fit at your joints.

If you have gaps or other flaws in the fit of your parent material, your welds will be ugly at best. It’s far more likely that your material will boil through or boil out rather than fill the gap.

For this kind of operation, the fit of your pieces has to be pretty close to perfect before it’s “good enough.”

Even When Everything is Perfect

If you have the time and tools and skills to remove the aluminum oxide layer and make sure your joints are top-notch, then skipping the filler rod can be a way to make TIG welding aluminum less expensive, faster, and easier. But even in ideal conditions, there are some downsides to working without filler that can’t be avoided.

Filler metal is almost always a composite that is engineered to provide added ductility to make up for the adverse effects of heat on the parent metal at the joint. Skipping the filler will mean that you’ll be saying “no thanks” to the strongest welds possible.

While weaker welds might be a sacrifice you’re willing to make for certain projects, you should also know that heat cracking is a common problem with TIG welding aluminum in general and that it’s even more likely with fusion welds.

So Why Would You Want to Fusion Weld Aluminum?

Even with all of the challenges and potential downsides that we’ve discussed, there are still several reasons why you might want to consider TIG welding aluminum without a filler rod. The most common of these are:

  1. Practice
  2. Tacking
  3. To Save Time & Money
  4. Aesthetics

We’ll go through each of these in more detail to give you a better idea of how to do them and when you can and should.

Practice

Even experienced TIG welders can find aluminum to be a challenge if they don’t work with it very often. Sometimes aluminum gives beginners fits, and other times it seems like it’s better not to know what you don’t know. Either way, practicing on aluminum in general, and without filler rod specifically, is a great way to develop your skills in a challenging specialty.

If you’ve already got reliable technique with your torch hand and your filler rod hand, then challenging yourself to fusion weld aluminum can be a great way to get good at something that most welders can’t do well.

If you’re starting, aluminum can be a great material to practice on. Take it one hand at a time and get good at running a bead with your torch hand before adding in the filler wire. Aluminum will give you good feedback on your technique, and there won’t be any filler to hide your hiccups.

Tacking

Some welders shy away from the idea of even tacking aluminum without a filler rod, but sometimes you won’t have enough hands to avoid it. If you’re holding a piece in place with one hand and your torch in the other, filler wire will have to be the odd-man-out.

Like any other TIG weld on aluminum that doesn’t employ filler, tac welds with no filler can be brittle and more prone to failure.

One advantage of tacking without filler is that these tacs tend to be flat or even a little bit convex. This makes them easy to weld over without having them stick out like a sore thumb against the rest of the weld.

When You Want to Save Time & Money

The money you save by skipping filler rod when you TIG weld aluminum won’t make a huge difference, but if you’re a small job shop or a DIYer, every penny saved is a penny earned.

The difference that skipping filler makes to your bottom line can really start to add up in certain situations, though. For example, if you’re:

  1. Working with brand new material
  2. Getting precision cuts on your parts
  3. Welding pieces that won’t be subjected to a lot of stress
  4. Good enough at TIG welding without filler to get pretty welds
  5. Doing the same work over and over again for a lot of pieces

Then you can eliminate a lot of time and some of the cost from each piece you produce by fusion welding them.

If your client’s specs give you the option and you’re able to get it done without creating more headaches in the process, then TIG welding aluminum without filler can be a real difference-maker.

When Looks Come First, and Strength Comes Second (or Even Lower)

Everything that we’ve said about TIG welding aluminum without filler rod to this point has been from the perspective of industrial or mechanical considerations. We thought it was important to start with those topics because bad decisions in those areas can lead to failed welds that get people hurt, cause property damage, or bring productivity to a halt.

Yet, focusing only on those areas would leave out the kinds of welding projects where the vast majority of fusion welding on aluminum is performed.

Sculptors, ornamental metalworkers, and other folks whose projects demand welds that look great are often experts at TIG welding aluminum without filler rod. Their projects often place a premium on aesthetics while making minimal demands on the strength of their welds.

Thinking about them as one end of the spectrum and a structural steel-welding ironworker as the other end will help you consider how to balance the competing demands of looks and strength in your own projects.

One Aesthetic Tip That’s Particularly Helpful

There is one area related to aesthetics where TIG welding without filler rod will give you better options whenever the intended uses will permit it. That area is corner joints.

Kevin Caron post’s really useful YouTube videos with tips and tricks for welders. If you watch this one until the end, he will give you some good advice about how to decide if and when to use filler rode when TIG welding corner joints.

Sometimes it really is a matter of working smarter rather than working harder. Skipping the filler rod on corner joints can give you a faster, easier path to smooth looking rounded corners whenever that’s the look you’re going for.

Useful Tips for Setting Up Your Machine

One of the biggest challenges of TIG welding aluminum without the filler rod is finding the right balance for the thickness and alloy of the materials you’re working on.

Working with thicker material and removing the aluminum oxide immediately before welding makes it less likely that you’ll blow holes in your pieces. But the other side of that coin is that it will be harder to get enough penetration to get good fusion at the joint without increasing the likelihood of cracking to a near certainty.

Working at lower temperatures and slower speeds can help to avoid meltdowns, but you’ll pay the price in penetration. Working faster and hotter will probably make any problem you’re having worse instead of better. Every adjustment you make to solve a problem will likely cause a new one to pop up somewhere else.

The folks at Miller have put together a useful tool for setting up your TIG machine for welding aluminum. All you have to do is enter the material, type of joint, and thickness and let it do the rest. It assumes that you’ll be using a filler rod, but the rest of the info can be a helpful starting point for setting up a fusion weld project.

Where to Find Additional Advice When You Run into Problems

First, notice that we said “when you run into problems” not “if.”

As you practice and get better at TIG welding aluminum without filler rod, you’ll inevitably have specific questions that we didn’t even think of, let alone answer for you here. YouTube, Chatrooms, and other online resources can be a great place to start when you’re looking for help to get over a particular hurdle.

But even with all of these resources, you’re likely to find that your questions about TIG welding aluminum without filler rod generate more discussion of reasons not to than of ways to get it done. It can be hard to find the welders who’ve had opportunities to get enough experience doing it that they feel comfortable giving advice.

In Conclusion

As we said at the outset, there’s a time and a place for everything. As we’ve worked through the most important issues to consider concerning questions about how to TIG weld aluminum without a filler rod, we’ve managed to point out some of the most common times and places to consider using this technique.

If, at this point, you’re thinking that there are more good reasons not to try skipping the filler rod when working with aluminum than there are in favor of going that route—well, at least you’ve been paying attention.

Still, there are a lot of situations where you “can” get away with it and even a few situations where it “should” be your first choice. Knowing what they are can help you decide what is the right choice in any particular set of circumstances you find yourself in.

If you do find yourself working on a project where going without a filler rod seems like the best option, you’ll want to be ready to handle the challenges that this approach will present to your prep habits, your technique, and your knowledge of your machine. That’s why it’s a good idea to practice it when you can before trying to do it when it counts.

Alexander Berk

A bit about myself: I am a certified international welding engineer (IWE) who worked in different welding projects for TIG, MIG, MAG, and Resistance Spot welding. Most recently as a Process Engineer for Laser and TIG welding processes. To address some of the questions I frequently got asked or was wondering myself during my job, I started this blog. It has become a bit of a pet project, as I want to learn more about the details about welding. I sincerely hope it will help you to improve your welding results as much as it did improve mine.

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