Setting Your MIG Welder for Car Panels

MIG welding machines are the most popular piece of equipment for repairing car parts, specifically car panels. However, getting the MIG welder’s settings just right is key to a successful weld.  

For filler metal selection, the electrodes in the ER4xxx and ER5xxx are most suitable for welding auto body panels. The panels’ aluminum’s chemical properties also require high voltage and wire feed speed settings to match the appropriate mode of metal transfer.

Below, we’ve listed guidelines on setting your MIG welder up for aluminum, which can be among the more challenging metals to weld on car panels. 

How to Set Your MIG Welder for Car Panels

There is no better welder than a MIG welder for performing repairs on car panels. The MIG welder is suitable for use with various metals and can also handle a greater range of thicknesses than both TIG and Stick Welding.  

If you’ve never used a MIG welder on auto body parts, you will need to know how to tweak the settings just right as to avoid weld defects such as spatter or porosity.

Consult the Auto Body Repair Manual 

To start things off, you will need to know which type of aluminum alloy car panel you are working with, as this will determine which electrode is best to use under your specific circumstances. 

An excellent way to find out which specific alloy you have is to look at the body repair manual. This can be found online, as is the case with these manuals for the Ford trucks.

Select the Best MIG Wire for Auto Body Repair

As is always the case in MIG welding, it is critically important to match the wire type to the base metal. So if you are welding an aluminum base metal, you will need to go with an aluminum wire. 

However, not just any wire will do, as differing electrode types are designed for varying conditions. If you are working with a dirty or dusty metal, you will want to go with a wire known for having more oxidizers. 

The following are some of the most common MIG wires used for auto body repair:

• ER4043: preferred by most welders because it is known for flowing better; also has a lower melting point and is not super sensitive to weld cracking
• ER5356: the most commonly used aluminum filler alloy due to its high strength. It is also easier to feed through the machine.

You also can’t go wrong with ER5183 aluminum filler alloys. This wire type is compatible with a wide range of aluminum alloys. In general, the suitable filler metals for aluminum welding will fall within the 4000 and 5000 series.

Note: If you are ever uncertain about a particular wire’s characteristics, then your best bet will be to consult with the manufacturer’s recommendations.

Choose a MIG Wire Size Suitable for Car Panels

The three most common wire sizes in MIG welding are 0.035″, 0.030″, and 0.023″. Of these, the smaller diameter wire has been accepted to be the most suitable for auto body collision repair. 

So, to recap as far as wires and fillers go for car panels:

• You will likely be using a wire electrode in the ER4xxx or ER5xxx series.
• A smaller diameter wire has the most suitable diameter for auto bodywork.
• A popular aluminum filler metal that can work with a wide range of aluminum alloys is the ER5356, which can be found in the 0.030″ size here.

Select the Shielding Gas

In general, MIG welding is best performed with a shielding gas of 75% Argon, 25% Carbon Dioxide. This combination has been known to produce the least amount of spatter, highest quality weld bead, and the least amount of burn-through on thin metals. The latter characteristic is of particular importance when working with car panels. 

When it comes to Aluminum, you will want to be working with 100% Argon shielding gas. Aluminum is a non-ferrous metal and thus requires a chemically-inert shielding gas combination. 

As far as flow rate goes, you should be within the range of 20-30 CFS (cubic feet per second) for welding car panels.

Set the Voltage for MIG Welding Car Panels

Aluminum has a thermal conductivity that is five times greater than that of carbon steel, which means that it will hold a lot more heat. This means that a low energy mode of metal transfer, such as short-circuiting, will not work for aluminum. The base material will not melt enough for full fusion to occur.

Examples of high energy modes of transfer include axial spray and pulsed metal spray:

• Axial Spray: a high voltage method of metal transfer that involves depositing wire electrodes as a stream of small molten droplets. Speed is high enough to release several hundred droplets per second. This technique is best performed in either the flat or horizontal positions.
• Pulsed Metal Spray: this is a modified spray process in which the power source is actually able to fluctuate the voltage as much as 400 times per second. The benefit of this technique is that it does a better job of maintaining the weld puddle to prevent burn-through. This method is not used as commonly as axial spray due to the associated learning curve.

The nice thing about welding aluminum is that the voltage settings will be nearly equivalent, regardless of the positions you are welding from. 

It will typically take somewhere in the range of 21-23 volts to achieve axial spray transfer. You are certainly encouraged to play around with the voltage on a test piece before you go to the real deal. This will help you zero in on that “sweet spot.”

Wire Feed Speed

The other knob on your MIG welder is the wire feed speed. This, too, will require you to play around a little bit with the settings by using a test piece. Welding aluminum car panels is likely to require you to bring the wire feed speed up a few notches, particularly if you are welding out of position.

Start with a Little Practice

Finally, as hinted at in the above sections, you are certainly encouraged to do a few practice runs with your MIG welder before you do it for real. 

Look for a piece of scrap metal where you can test your welder’s performance as you tweak the settings. Take note of the weld quality and the corresponding settings. 

If things don’t look quite right, then be sure to jot down your observations; this should make for simple troubleshooting later on. As many experienced operators will likely tell you, no two welding machines are necessarily the same.

How to Prepare Car Panels for Welding

When you are working with aluminum, cleaning the base metal is of absolute necessity.  This especially the case with car panels. You can only imagine how much dirt, oil, and grime is probably present on the surface that you intend to weld.

• Use a solvent like acetone or a strong soap to clean the surface of the aluminum. Even water vapor on the surface of the metal will interfere with the welding process.
• Use a stainless steel wire brush that you have dedicated exclusively for use with aluminum.
• Keep the aluminum covered overnight throughout the project.
• Make sure that the car panel is kept dry and at room temperature.

In Summary

In summary, when welding car panels, these are the appropriate settings used with MIG welding: 

• Electrode Wire Choice: Typically, in the ER4xxx or 5xxx series, ER5356 tends to be the most popular.
• Wire Diameter: The smaller, the better; shoot for the 0.023″ to 0.035″ range.
• Shielding Gas: 100% argon is preferred; always go with chemically-inert gases for non-ferrous metals like aluminum.
• Mode of Transfer: Axial Spray or Pulse Metal Spray is usually the best mode to use. 
• Voltage: Keep the voltage at around 21-23 volts.
• Wire Feed Speed: Keep it high; you may need to experiment a little with this.

As long as you maintain these base settings, you can successfully weld car panels without a hitch.