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A MIG welder is an extremely useful tool to have around the shop. However, there’s plenty of myths out there about its capabilities—for example, can a MIG welder really weld aluminum?
A MIG welder can weld aluminum; however, it’s a tricky process for those not experienced with welding. Attempting to weld aluminum with a MIG welder takes more skill than welding steel and isn’t recommended for beginners.
If you’ve mastered MIG welding steel and feel like you’re ready to conquer aluminum, then we’ll show you the ropes. It takes extra safety precautions and mastery, but it can be done. Read on to learn some tips and tricks to help you along the way.
The Basics of Welding Aluminum Using a MIG Gun
To safely weld aluminum, it’s best to go with a minimum thickness of 14 ga.-18ga. If you go any thinner, you’ll need a TIG welder instead, mainly because a TIG welder is a better candidate for joining smaller pieces of metal.
If you disregard this suggestion and use a MIG gun anyway, you run the risk of burning the metal and creating a hot puddle. A hot puddle will either destroy your work, burn you, or both.
To successfully weld aluminum, you need to use roughly the same voltage as you would steel, but you have to work twice as fast. You’ll also have to ensure spray transfer is happening, which is when little tiny bits of aluminum are sprayed directly into the weld puddle. You can accomplish this just by having the right gas and voltage settings.
What You’ll Need to Weld Aluminum
To successfully weld aluminum, you’ll need a spool gun. A spool gun is a better option than directly placing aluminum wire into the MIG machine because aluminum is too soft for the MIG’s feed mechanism. The spool gun will keep the aluminum from getting stuck inside.
Instead of using C25 gas as you would for steel, you should use pure argon gas, which will help expedite the spray transfer process. If you’re dealing with thicker aluminum of ½” or thicker, you’ll need to add 25-75% helium.
To keep yourself safe, you’ll want to make sure you’re wearing the following appropriate welding apparel:
- Safety glasses
- Leather footwear
- Full-length pants without cuffs
- Long-sleeved, flame-resistant jacket
- Leather gloves
- A skull cap or bandana
Preparing your MIG Welding Equipment for Welding Aluminum
If you don’t check and prepare your equipment before welding, you run the risk of your welding project failing or compromising your safety. Make sure always to do the following:
- Double-check your cables and connections: make sure they aren’t fraying and that they are together nice and tight.
- Set the gas flow: Check your gas hose for leaks, then start pushing about 25 cubic feet per hour. You can dribble a soap and water solution over suspected leaks in the hose to check—if you see bubbles, replace the hose immediately.
- Check your feed settings: Make sure the tension and feed settings are just right, referring to the owner’s manual if necessary.
- Replace disposable items: If your contact tips or wires are rusty and worn, replace them before starting. Remove any excess material from the contact tubes.
Tips for Using MIG Welding to Weld Aluminum
You’ll have to set your machine on to the DCEP setting, aka Direct Current Electrode Positive. This reverse polarity setting is crucial to use; otherwise, the welds won’t turn out.
When welding aluminum, you should also push instead of pull. Why? Because pushing gives you optimum gas coverage, less penetration, and a flatter, more expansive bead. Pulling penetrates too deeply and makes the bead too narrow. Make sure you use a push travel angle of 10-15 degrees for the best results.
Another crucial tip when welding aluminum is to remove the oxide before you start welding. It would be best if you did that because oxide is twice as hot as aluminum, and your joints won’t fuse unless you remove it ahead of time.
It’s also essential to clean your aluminum before you start the welding process. It’s not difficult to do; all you need is an aluminum wire brush. Just brush where you plan on making the weld, then you’ll be ready to get started.
Part of the MIG welding process involves a wire stick-out, the extended unmelted electrode from the welding gun’s contact tube’s tip. When welding steel, you typically have a wire stick-out of ¼”. Since you’re using the spray transfer process with aluminum and the process is much hotter, you’ll want a considerably longer wire stick-out of ¾”-1“.
How to Solve Common Problems Associated with MIG Welding Aluminum
If you’re having issues, don’t worry. Here are some easy fixes with MIG welding aluminum.
Melt-Through Due to Overheating the Base
Aluminum can be easy to melt, so try these tips:
- Weld faster and in short travels
- Make sure the pieces are flush—don’t leave any gaps
- Do your best to spread the heat evenly, don’t focus on any single spot
- At worst, you may need to switch to a thicker aluminum or just use a TIG welder
Part of the battle is just knowing how to work your rig, so refer to the owner’s manual or the inside of the door of your welder for specific tuning settings.
Aluminum Welds Are Very Dirty
If your welds are coming out too dirty, then try these tips:
- Remember to push, not drag, and use the correct gas mix
- Up the voltage to ensure the spray transfer is actually happening
- Make sure you clean your aluminum correctly using your wire brush beforehand
Wire is Getting Stuck in the MIG Gun
If you are having issues with wire feeding properly, then:
- Play with the tension on the drive roll
- Make sure there isn’t any excess debris in the contact tip, replace if needed
- Lower the pressure on your spool gun’s hub
Additionally, if your wire is burning back, then make sure you’re leaving enough distance between your tip and what you’re working on. It could also just be an issue of mismatched wire/spool/gun liners, so make sure they all line up.
What’s Better for Welding Aluminum: MIG or TIG Welding?
Both MIG and TIG welding use electric arcs to produce heat and combine metal objects. However, choosing between using MIG and TIG welding entirely depends on your project. If you’re welding thicker sheets of metal, then MIG welding is better to use. Conversely, if you’re welding thin pieces of metal or wire, then TIG welding is your best bet.
If you’re new to welding, MIG welding is recommended for amateurs because there’s a lot more forgiveness with errors. TIG welding requires more experience because it requires precise timing, electric current, and response.
In terms of welding aluminum, MIG and TIG techniques both will get the job done. However, if you use MIG welding to weld aluminum, you need to use a spool gun and closely follow our previously mentioned tips and techniques. The MIG gun also works slightly faster.
However, if you’re experienced with TIG welding, perhaps consider using it instead. Since aluminum is a thinner piece of metal, you’ll achieve optimal results using a TIG gun, as long as you know how to do it.
Using MIG Welding to Weld Aluminum
Using MIG welding to weld aluminum is a possibility provided you use a different technique than you would with steel. It takes a higher temperature and quicker speed, which can be difficult to get used to initially.
However, if you use our recommended techniques, tips, and practice, you’ll learn to get a feel for it. Don’t expect to be welding pop cans with a MIG welder, but you can certainly make short work of thicker aluminum with proper practice.