Mig vs. TIG Aluminum Welder

Welding Aluminum MIG-250PRO-SG vs. TIG-250P ACDC

Before proceeding to the individual in-depth comparison of how our MIG and TIG machines weld aluminum, and how these two processes are fundamentally different, let’s compare everything side by side.

Welding aluminum is challenging. The two most accessible and widely used methods are MIG welding and AC TIG.

YesWelder offers both. Our YesWelder MIG 250A Pro and AC/DC TIG 250A machines are up to the task. But, selecting a welding process to weld aluminum can get confusing for beginners.

In this article, we will discuss the differences between these two welding processes, their advantages and disadvantages, and introduce you to our two prime welders to help you decide which one works best for you.

The Three Problems Of Aluminum Welding

You’ll face three main problems when welding aluminum—the aluminum oxide on the surface, aluminum’s excessive heat conductivity, and proclivity to contamination. So, let’s discuss each and explain why they are troublesome.

Aluminum Oxide

Aluminum has a strong affinity for oxygen. The oxygen from the air combines with pure aluminum instantly and forms the oxide layer on its surface. The longer the aluminum is exposed, the thicker the oxide layer.

This oxide layer has a significantly higher melting point than the base aluminum underneath it. The pure aluminum melts at a temperature of 1200°F (650°C) while the aluminum oxide melts at 3700°F (2037°C). So, you must first remove aluminum oxide before welding the pure aluminum under it. Welding with AC TIG handles even the minuscule aluminum oxides left after you clean the metal, but we’ll discuss this later in the article.

Image shows aluminum oxide layer, source: https://www.materialwelding.com/how-to-clean-aluminum-oxide-layer-before-welding-easy-steps/

Regardless of whether you weld aluminum with MIG or TIG, you must clean the surface layer thoroughly. Typically, a stainless steel brush can clean the oxide layer for most applications, but you can also use special grinding wheels meant for aluminum. Additionally, it’s possible to use acid or alkaline solutions for oxide removal, but this is not practical or necessary for most people.

Cleaning aluminum is done in a two-step process:

Clean the surface from oils, grease, and dirt first to prevent such contaminants from being pushed into the base metal with the stainless steel brush.
Brush off the aluminum oxide thoroughly using a brush.

Safety tip: Aluminum is a non-magnetic metal. This means that ophthalmologists have difficulty extracting aluminum dust and debris if it enters the eye. Therefore, ensure you wear all PPE, including the safety glasses, especially if using power tools for oxide removal. Additionally, before starting to weld, you need to wear PPE. Welding helmet with safety glasses underneath, welding gloves, boots, and apron at minimum.

2. Excessive Heat Conductivity

Aluminum conducts heat rapidly. This means that if your welding machine inputs heat via arc into the metal, the surrounding area will receive the heat from the weld puddle.

Coefficient of thermal expansion about different metals

image source: https://favpng.com/

The welded part will become increasingly heated as you progress through the weld. So, let’s say you started the arc when the metal was at room temperature, and the thickness demanded the use of 150A. By the time you reach half of the joint’s length, the temperature of the whole part has increased and now requires less amperage input.

The joint configuration, specific aluminum alloy, filler metal alloy, part shape, room temperature, and metal thickness influence how much you need to drop the amperage after a while.

For hobbyists and regular welding shop work, it’s best to manage your heat input in advance. One of the best ways is to work on the piece from multiple sides, if possible. That way, you’ll have fewer issues from the heat.

However, there is another critical issue related to heat conductivity. Since aluminum conducts heat away rapidly, it requires a much higher amperage input than mild steel. Couple this with the low melting point of pure aluminum, and you get a challenging scenario. That’s why to weld aluminum, you must move fast. Otherwise, you can melt through the metal and damage the part.

3. Contamination

Welding aluminum requires absolute cleanliness, as we discussed above.

But, the problem runs deeper than oxides. This metal is not forgiving of cross-contamination. You should use an aluminum-specific stainless-steel wire brush and other tools that come in contact with aluminum.

Additionally, try to keep mild-steel dust particles away from the area where you plan to weld aluminum. If working in a welding shop, it’s best to have a separate work area for aluminum-only because airborne metal particles like sparks and dust can impair joint quality.

TIG welding aluminum with our YesWelder TIG-250P AC/DC machine can achieve significantly better results than the MIG welding process.

However, it does take more time to learn how to TIG weld properly, and the equipment is more costly. So, let’s go through this machine’s features and explain the TIG welding process in general.

The Shielding Gas

Just as with the MIG process, you must use a 100% argon shielding gas to weld aluminum with TIG. You can use an argon/helium mixture too. The helium improves penetration, and it’s helpful when welding thick aluminum pieces.

However, for most TIG aluminum applications, you should just use a straight argon gas bottle.

Why is AC Current Necessary?

If you look at multi-process welders like the YesWelder MIG-250-Pro, you’ll see that besides MIG, it supports a DC TIG welding process. So, why can’t you just weld aluminum with DC TIG?

Unfortunately, to successfully TIG weld aluminum, you must use alternating current. That’s because the AC switches between DCEP and DCEN many times in a second. Both are necessary to TIG weld aluminum.

AC suqare wave TIG welding and AC pluses TIG welding

Remember the whole oxide layer issue with aluminum?

TIG welding is more sensitive than MIG, and any oxide inclusion in the weld would diminish the weld quality. Luckily, the DCEP produces a cleaning action that breaks up the aluminum oxides and allows the DCEN portion of alternating current to focus the deeply penetrating power into the base aluminum metal.

AC Balance

Better quality welding machines have something called “AC balance,” and our YesWelder TIG 250P includes this feature. Its AC balance lets you modify the balance in a wide-ratio between 15 and 85%, allowing you to fine-tune the cleaning action perfectly.

Sometimes you may need more penetration and less cleaning if you have done your pre-cleaning correctly. In that case, it's good to ramp up the DCEN and lower the DCEP (cleaning) action.

AC Frequency

Another feature more professional machines provide is the AC frequency adjustments. This lets you modify how often should the DCEP and DCEN switch in one second. Our YesWelder TIG 250 enables you to adjust frequency in a range of 20-250Hz.

High frequency setting makes the arc pointy and lets you lay very precise beads, while the lower frequency keeps the arc wider and the weld puddle more fluid.

Pulse TIG

Using pulse TIG is helpful when welding aluminum to prevent excessive heat input and burn-through on thin aluminum sheet metal.

The pulse TIG lets you specify the low and high welding amperage of a single pulse and the pulse frequency, which determines how many pulses per second you wish to output.

For example, if you were welding something thin, you can set the low amps at 25A, the peak amperage at 100A, and use 10Hz as pulse frequency, giving you 10 pulses per second where each pulse starts at 25A and jumps to 100A.

Our YesWelder TIG unit has pulse frequency and width settings, giving you a professional level of control over sensitive aluminum metal.

Foot Pedal Control

One of the crucial reasons TIG outperforms MIG welding is that this welding process is optimized for control. If you use any high-end TIG welder like YesWelder 250P AC/DC, you will have the option to use a foot pedal to control the amperage.

The pedal works just like a gas pedal in a car. If you step on it, the amperage input increases, while the amperage input decreases if you lighten the pressure. This lets you change heat input in real-time while welding aluminum or other metals.

Remember how we discussed earlier the heat conductivity problem with aluminum?

You can control heat input using a foot pedal, and with some practice, avoid excessive heat build-up altogether. By carefully letting the amperage into the metal as needed and backing away when aluminum conducts away too much metal in the surrounding area, you can control the weld joint and avoid burning through.

High-Frequency Start

One of the reasons why TIG welding achieves near-perfect welds is the absence of contact between the electrode and the metal piece. As a result, there is a minimized chance of any impurities getting transferred to the weld pool.

The MIG welding wire acts as a filler metal and electrode. In contrast, TIG welding relies on a tungsten electrode that never has to physically contact the welded aluminum or other metals.

However, this is only the case if the TIG welder supports a High-Frequency (HF) arc start. The YesWelder 250P is equipped with HF start, allowing a contactless arc start and avoiding tungsten inclusions in the weld joint.

The HF generator inside the machine initiates an HF current that jumps from the tungsten electrode to the metal piece after you initiate the arc start by pressing the foot pedal or a button on the torch.

TIG Welding Aluminum Technique

To TIG weld aluminum, you need to use a tungsten electrode for this metal. A good beginner tungsten rod for aluminum is a 2% ceriated tungsten, but others are available depending on the metal thickness and available settings on the machine.

When you are ready to start welding, it’s crucial to have a proper torch and hand placement and coordinate well the dabbing of filler metal and progressive TIG torch movement.

Hand holding the torch should ideally rest flat on the welding table in the area from your pinky to the wrist while the torch is held with the fingers. The index finger and thumb have the most control over the torch.

The torch should be kept in a forward-moving position with a slight backward tilt of about 5-20 degrees. At the same time, the tungsten tip should be held at a distance from the metal piece equal to the tungsten diameter.

The filler rod should be at about a 90-degree angle to the TIG torch, and you should progressively move the torch as you weld along. Dab the filler metal into the weld puddle but never touch the tungsten electrode because this will contaminate it. Always introduce the filler metal on the edge of the puddle, but keep in mind that as soon as the filler metal is added, the temperature of the weld will drop because the melting process of the filler metal will take away some of the available heat.

With practice, you can get good hand coordination between the filler metal in one hand and the TIG torch in another. It’s a good idea to practice without the arc first and later on move to the actual practice beads.

Advantages of TIG Welding Aluminum

TIG process produces the highest quality welds of all arc welding processes
You can make aesthetically pleasing welds
TIG welds are strong and without porosity
The process allows extreme control over the weld joint
There are multiple adjustments to tailor the arc and penetration
It works great with the thinner gauge
You can weld without the filler metal by fusing the base metals
There are no sparks or smoke to worry about
The arc is extremely focused and stable
It provides excellent visibility of the joint

Disadvantages of TIG Welding Aluminum

The equipment is more expensive than MIG
It’s a relatively slow process
Welding TIG requires skills that take longer to acquire
It’s susceptible to contamination
It requires powerful equipment for welding very thick aluminum

Conclusion

MIG and TIG are two very different processes, but both can weld aluminum. While MIG can handle aluminum using a DC, the TIG process requires the use of AC.

If you plan to weld aluminum often or want to achieve the highest quality joint, AC TIG is irreplaceable. However, MIG welding aluminum is entirely satisfactory for most applications.

One of the most important advantages in favor of MIG is the lower learning curve, which attracts many beginners. Still, learning how to perform AC TIG on aluminum is a highly-paid skill because you can do jobs for others as well, if you don’t already have your welding shop.

YesWelder 250A Aluminum MIG Welder Spool Gun Compatible

Welding aluminum with MIG is easier and less costly than TIG. However, it doesn’t offer the maximum joint quality and requires either a spool-gun or a MIG machine like our YesWelder MIG Pro with native support for aluminum wire.

To weld aluminum with MIG or TIG, you need to use a 100% argon shielding gas. So, your regular MIG 75/25 CO2/Ar mixture can’t be used.

Spool Gun Or Graphene Liner?

The YesWelder MIG-250Pro-SG doesn’t require a spool gun to weld aluminum, but it is spool gun compatible. Equipping the welder with a 100% Argon gas, a U-type wire roller, special A+ tips, and a graphene liner lets you weld aluminum without a spool gun.

Image shows graphene liner from YesWelder MIG250-PRO-AL

This has several advantages. The spool gun is heavy, bulky, and prevents accessing tight corners. Additionally, it limits you to smaller capacity spools. Aluminum wire is expensive, so it’s more cost-effective to use a larger spool that can fit into MIG-250Pro.

Spool guns do have an advantage if you need to use very long leads because they drastically reduce the aluminum wire travel path. Additionally, if using a standard MIG wire feeding mechanism, there is some tinkering involved around setting the drive-roll tension.

What MIG Welding Wire To Use?

The two most commonly used MIG filler metal wires for aluminum are ER4043 and ER5356. Both have pros and cons, so let’s see which one you should pick and when.

But, please do your research if welding something critical. Depending on the alloy you are working with, you may need to use a specialized filler alloy.

The ER4043 is primarily alloyed with silicon, which helps keep the weld pool fluid and improves the cracking resistance. The ER4043 runs hotter than ER5356, allowing you to weld thicker material with the same wire feeding speed and voltage settings.

ER4043/1LB-0.8 1LB Spool .030" Silicon Aluminum MIG Welding Wire

It’s characterized by the white arc color and has less smoke and black soot that may show along the weld line. The ER4043 filler metal works with many aluminum alloys and leaves a nice shiny finish. The wire is softer and slightly more difficult to feed than the ER5356 below.

ER5356/1LB-0.8 1LB Spool .030" Magnesium Aluminum MIG Welding Wire

The ER5356 has magnesium additives for improved tensile strength, but it emits more smoke, sparks, and forms more black soot around the weld. It runs less hot, making it easier to weld thinner gauge aluminum. This wire emits arc with a green tint, and the wire is more rigid, making it easier to feed.

Additionally, the ER5356 provides a much closer color match if you want to anodize the aluminum part after welding. The ER4043 tends to turn gray post-anodizing.

Setting Up The YesWelder MIG-250-Pro-AL

After you change the regular MIG gun liner with the graphene liner, install the U-groove, and hook up the 100% argon shielding gas bottle, you are ready to adjust the digital settings.

We suggest using the MIG Synergic mode (MIG-S) for the first try. Set the material type to “AL” and set the wire thickness you have previously installed. After that, adjust the amperage output for the thickness you are welding, and the machine is all set.

Keep in mind that MIG welding aluminum requires the same polarity as steel. So DCEP (direct current electrode positive) should be used.

MIG Welding Aluminum Technique

To prevent MIG gun tips burnback, you should use a longer stickout than when welding steel. The 3/4 in. stickout works well with aluminum.

MIG welding aluminum requires a spray transfer arc. If you use MIG synergic settings and everything is set correctly, the voltage and wire feeding speed will work in tandem. However, if you use manual settings, make sure to use high amperage and voltage settings without one being too high compared to another. This may take some trial and error to get right.

Since aluminum conducts heat quickly, you have to use fast travel speeds and wire feeding rate. High heat input combined with fast travel speed will counter the heat conductivity problem, but it takes some skills to make a good bead. Don’t be discouraged if you don’t succeed from the first try. After some practice beads, you should get the hang of it.

Depending on the thickness of the aluminum part, you may need to decrease the amperage as the part gets hotter. If you are welding a thin sheet and the conducted heat increases the heat of the sheet, you should tone down on the amperage to prevent burn-through. Additionally, you may need to increase the travel speed to avoid excessive heat build-up and warping.

To successfully MIG weld aluminum, you should use the push welding technique. By pushing the MIG torch tip away from the puddle, you achieve better shielding gas cover, improved cleaning action, and reduced weld contamination.

Additional pro tip: If you need to weld slower, you can use a heat sink to absorb the heat produced by the welded joint. That way, your aluminum part can stay cooler, and you avoid the risk of burning through.