If you’re just getting into TIG welding or even if you’ve been doing it for a while, choosing the right filler rod can sometimes feel a bit confusing. I totally understand that.
I’ve been there—standing in front of a shelf full of different rods, scratching my head, and wondering which one to grab for the job I had at hand.
I want to walk you through everything I’ve learned about TIG welding filler rods. I’ll explain what they are, how they work, and most importantly, how to choose the right one.
I’ve also put together a simple, easy-to-read selection chart you can always refer back to. It’s the kind of guide I wish I had when I first started.
What Is a TIG Welding Filler Rod and Why Does It Matter?
TIG welding, also known as Gas Tungsten Arc Welding (GTAW), is a precise and clean method used mainly for welding thinner materials or making delicate welds. The filler rod is the metal wire you add to the weld pool to build up the joint.
Now, not all filler rods are created equal. Choosing the wrong type can lead to weak welds, cracks, or even corrosion down the line.
So yeah, picking the right filler rod is more than just a guess—it’s essential for the strength, appearance, and durability of your welds.
How Filler Rod Selection Depends on the Base Metal
One of the first things I learned was that your base metal—the material you’re welding—plays a big role in what filler rod you should use. Steel, stainless steel, aluminum, bronze, and other metals all require specific rods for best results.
Let’s break it down by material type so it’s easier to follow.
TIG Filler Rods for Carbon Steel
When I’m welding mild or low carbon steel, the most common and reliable filler rod I reach for is ER70S-2 or ER70S-6. Both offer great ductility and strength.
- ER70S-2: Ideal when you’re welding on dirty or rusty surfaces. It has deoxidizers that help keep your welds clean.
- ER70S-6: Gives smoother welds on clean material and is more popular overall.
These rods work best with DCEN polarity and pure argon shielding gas.
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TIG Filler Rods for Stainless Steel
Welding stainless steel is a little more precise. You’ve got to match your filler rod closely to the base metal. Here are the ones I use the most:
- ER308L: Perfect for 304 stainless steel, which is super common in food and medical-grade equipment.
- ER309L: Great when you’re welding dissimilar metals, like stainless to carbon steel.
- ER316L: Best choice when corrosion resistance is super important, like in marine or chemical environments.
- ER308L: ER308L stainless steel MIG welding process for 304, 304L, 308, 308L, 321 and 347 stainless steels.
- SHIELDING GAS: Use 100% Argon or Argon/Helium for greater penetration and higher speeds.
- MULTIPLE USAGE: Widely used in the welding of pressure vessels, food machinery and restauraunt equipment, medical equipment, fertilizer equipment, textile machinery, etc.
- EXCELLENT PERFORMANCE: It has smooth wire feeding, stable arc, beautiful shape as well as little spatter. It can be welded in all positions, and contains a proper amount of ferrite, has good crack and corrosion resistance.
- SPECIFICATION: Diameter: .030''/Weight: 2 pounds.
Stainless steel filler rods usually work best with argon or an argon-helium mix to improve heat input and fluidity.
TIG Filler Rods for Aluminum
Aluminum is a totally different beast in TIG welding. You need AC polarity and a high-frequency start for clean arcs. Here are the aluminum filler rods I keep in my shop:
- ER4045: Gives a smooth finish and helps reduce cracking.
- ER4043: Common for general aluminum work—great for castings or when the metal has a lot of silicon.
- ER5356: Offers higher strength and is good for structural aluminum.
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- Applications: General-purpose, all-position aluminum welding wire used to weld various grades of aluminum; it contains silicon additives, which may improve fluidity of the weld pool and also produces a weld less sensitive to cracking; its bright weld finish makes it a popular choice of welders. Recommended for welding 3003, 3004, 5052, 6061, 6063, and casing alloys 43, 355, 356, and 214.
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TIG Filler Rods for Copper, Bronze, and Exotic Metals
For less common metals, it gets a bit more specific:
- Silicon Bronze (ERCuSi-A): I use this when brazing copper or welding on galvanized steel. It’s ideal for joining dissimilar metals.
- Nickel Alloys (ENiCrFe-3): Needed for high-temp or chemical-resistant work.
- Titanium and Magnesium rods: Only use these when you’re specifically working with those materials, and make sure you’re using the right shielding gas and environment.
TIG Welding Filler Rod Selection Chart
Here’s the filler rod chart I’ve built and refined over the years. Keep this handy—it really helps simplify the selection process.
| Base Metal | Common Filler Rod | Rod Type | Shielding Gas | Notes |
|---|---|---|---|---|
| Mild/Carbon Steel | ER70S-2, ER70S-6 | Steel | Argon (100%) | ER70S-6 gives better arc starts and smoother beads on clean material |
| Stainless Steel (304) | ER308L | Stainless | Argon (100%) | Use for kitchen, medical, or decorative stainless steel |
| Stainless to Carbon | ER309L | Stainless | Argon (100%) | Designed for welding dissimilar metals |
| Stainless Steel (316) | ER316L | Stainless | Argon (100%) | Ideal for marine and chemical resistance |
| Aluminum (General) | ER4043 | Aluminum | Argon (100%) | Great for castings and general aluminum projects |
| Aluminum (High Strength) | ER5356 | Aluminum | Argon (100%) | Better tensile strength, not ideal for anodizing |
| Copper, Bronze | ERCuSi-A | Bronze | Argon (100%) | Great for artistic welds and joining copper to steel |
| Nickel Alloys | ENiCrFe-3 | Nickel Alloy | Argon (100%) | For high-temp or corrosion resistant welds |
How to Choose Filler Rod Diameter
Another key point I want to highlight is filler rod thickness. If the rod is too thick, it might cause puddle issues. If it’s too thin, it may melt too fast.
Here’s a general guide I stick to:
- 1/16” (1.6 mm): Great for sheet metal or really thin work.
- 3/32” (2.4 mm): My go-to for most jobs—especially in the 1/8” base metal range.
- 1/8” (3.2 mm): Works well for thicker plates and heavy-duty welds.
Match the diameter to your base metal thickness and the amount of filler you’ll need. It also helps to adjust your amperage accordingly.
Do I Always Need a Filler Rod in TIG Welding?
You might be wondering if a filler rod is always necessary. The short answer is: not always.
When I’m welding two very thin pieces together or doing fusion welds (especially on stainless), I skip the filler rod altogether. This is often called “autogenous welding.” But in most structural or load-bearing welds, using the right filler rod is a must.
How to Store TIG Filler Rods Properly
Filler rods don’t like moisture. I learned that the hard way after leaving a batch of ER70S-2 rods in my garage. They absorbed humidity and started to corrode. The best way to store them is in a dry rod container or sealed tube, preferably with desiccant packs inside.
And remember—contaminated rods lead to dirty welds. Always keep your rods clean and handle them with gloves when possible.
Understanding Filler Rod Alloy Codes
Ever look at those codes and think, “What the heck does ER70S-6 mean?” Let me break it down simply:
- E = Electrode (even if we’re not using it as one)
- R = Rod (specifically for TIG)
- 70 = Tensile strength (70,000 psi)
- S = Solid wire
- 6 = Chemical composition and deoxidizers
Each digit or letter tells you something about what the rod is made of or how it performs. Once you understand the code, it gets easier to make quick decisions at the store or on the job.
Shielding Gas Tips for TIG Filler Rods
No matter how good your filler rod is, without the right gas, your welds will suffer. I always use pure argon for almost every TIG job. It’s clean, stable, and easy to control.
For thicker aluminum or stainless, sometimes a helium mix can help get deeper penetration. But for beginners or general work, stick with 100% argon. It’s reliable and easier to manage.
Mistakes When Choosing a TIG Filler Rod
Over the years, I’ve made a few filler rod mistakes. Let me help you avoid them:
- Using the wrong rod for dissimilar metals: Always double-check compatibility.
- Guessing rod type based on color: Don’t do it. Always read the label.
- Using old or rusted rods: Toss them and grab fresh ones.
- Welding without enough gas coverage: Can cause porosity or oxidation.
Final Thoughts from One Welder to Another
If there’s one thing I’ve learned over the years, it’s that the right filler rod can make or break your weld. Don’t rush this step.
Take a minute to match your rod to your material and the job at hand. Over time, you’ll start to get a feel for it, and selecting the right rod will become second nature.
And don’t be afraid to experiment a little. Try different rods, observe how they behave, and keep notes if you need to. That’s how I built my own go-to chart, and now I can walk into any job with confidence.
FAQs
What is the most commonly used TIG filler rod for mild steel?
The most commonly used filler rods for mild steel are ER70S-2 and ER70S-6. ER70S-6 is especially popular for clean base metals.
Can I use the same filler rod for stainless and carbon steel?
Yes, ER309L is designed for joining stainless steel to carbon steel. It’s a great choice for dissimilar metal welding.
What is the difference between ER4043 and ER5356 for aluminum?
ER4043 provides better flow and less cracking, while ER5356 offers higher strength but can be harder to weld with.
Do TIG filler rods expire?
They don’t have a strict expiration date, but exposure to moisture and contaminants can ruin them. Store them properly to keep them in good shape.
How do I know what diameter filler rod to use?
It depends on the thickness of your base metal. Use smaller diameters for thinner materials and thicker rods for heavy-duty welds.
Can I use MIG wire as a TIG filler rod?
Sometimes, yes. MIG wire and TIG rods can be made of the same alloy. But make sure it’s clean, solid wire, and the composition matches your needs.
