MIG or TIG – Which is Better for Welding Sheet Metal Patch Panels?

Patch panel repairs are one of the most common welding tasks you might encounter when restoring old vehicles. The question often comes up about which method is better for the task – MIG (Metal Inert Gas) or TIG (Tungsten Inert Gas). The short answer is that MIG welding and TIG welding are both completely acceptable ways to make clean, reliable sheet metal repairs.

However, each process offers distinct advantages over the other, and the choice as to which one you use will probably come down your skills, your budget, and how much time you’re willing to commit to getting the desired results. Here are the factors you’ll want to consider before deciding on MIG welding or TIG welding for your sheet metal patch panel repairs.

Cost – Both MIG and TIG welders require the use of an inert gas to shield the welding area from airborne oxygen during the weld process, making them a more expensive method than flux or arc welding. Both types of welders also have consumable components that wear with use and will need to be replaced occasionally, but the biggest difference between them is the cost of the machines themselves. A basic all-around MIG welder, such as Eastwood’s MIG 140, will run around $400, while a similarly capable TIG welder, such as Eastwood’s TIG 200 AC/DC, will run closer to $800.

Versatility – MIG welding and TIG welding can each be used on a wide range of materials, including mild steel, stainless steel, and aluminum. Welding aluminum with a MIG welder, however, will require an additional accessory called a spool gun to feed the softer aluminum welding wire directly to the welding tip. Depending on the welder you purchase, this may either be an extra-cost accessory or may be included in the welder kit, as Eastwood often does. Aluminum welding will also require 100% argon gas instead of the usual 75%/25% argon/CO2 mix.

Speed – MIG welding is generally faster than TIG welding, especially for those who may not weld very often. For thin metal like body panels, MIG welding requires stitching together a series of spot welds to create a complete seam. A MIG welder’s torch automatically feeds welding wire from a spool inside the machine, making the job as simple as placing the tip at the point to be welded and pulling the trigger momentarily. With a TIG welder, the operator runs a continuous bead of welding rod into an arc, feeding the rod by hand. This requires constant adjustment and replacement of the rod on long runs.

Skills – Because of the reasons listed above, MIG welding is generally an easier skill for most people to pick up, especially when welding on thin materials like sheet metal. TIG welding requires a bit more finesse, rhythm, and patience as you feed filler rod into a seam. Quality TIG welds, therefore, take more practice to perfect.

Precision – TIG welding provides precise control over the heat input, minimizing the risk of material damage or brittleness. This allows the weld to be worked with a hammer and dolly afterward, perfect for thin-gauge materials like sheet metal. MIG welding, on the other hand, tends to have higher heat input. This can lead to a larger heat-affected zone, increasing the risk of warping or distortion in thin sheet metal panels, which is why the stitching method is essential to welding thin materials with MIG.

Cleanliness – TIG welding produces clean, high-quality welds with minimal spatter, slag, or smoke. This can be crucial for auto body repairs where the appearance of the weld is important, such as in visible areas or cosmetic panels. While MIG welding can provide strong, functional welds, the weld bead may not be as neat as a TIG weld and will require more surface conditioning, especially grinding.

MIG welding can also be more prone to porosity issues, especially on thin sheet metals. Porosity occurs when gas bubbles become trapped in the weld, compromising its strength and appearance, and potentially leading to corrosion under the finished work.

Ultimately, the decision will be yours. MIG welding is favored for its speed, versatility, and cost-effectiveness, while TIG welding excels in precision, control, and clean welds. As the old saying goes – Speed, quality, or cost. Choose any two.