ER309L Dissimilar Metal Stainless MIG & TIG Wire
Stainless wire for joining stainless to carbon steel, or for cladding carbon steel with stainless overlay. Runs 40 to 200 amps on DCEP or DCEN, rated for flat, horizontal, vertical up, overhead. Amperage chart by diameter below.
ER309L is a low-carbon stainless steel wire classified under AWS A5.9 for MIG (GMAW) and TIG (GTAW) welding. It deposits approximately 23% chromium and 13% nickel, providing a weld chemistry that bridges the gap between stainless and carbon steel. The higher chromium and nickel content compared to ER308L compensates for dilution when one side of the joint is carbon steel. ER309L is the standard filler metal for dissimilar metal joints between austenitic stainless and carbon or low-alloy steel. It is also widely used for the first layer of stainless cladding on carbon steel vessels and piping. For MIG welding, use with tri-mix (90He/7.5Ar/2.5CO2) or 98Ar/2CO2 shielding gas. For TIG welding, use 100% argon.
What This Means in Practice
ER309L is the wire version of E309L-16. It serves the same purpose: joining stainless steel to carbon steel by providing a buffer chemistry that handles the dilution from both base metals. Use it with MIG or TIG equipment when you need a wire-feed or precision process instead of stick welding.
What Amps for ER309L?
| Diameter | Amperage Range |
|---|---|
| 0.030" (0.8 mm) | 40 - 150A |
| 0.035" (0.9 mm) | 60 - 200A |
| 0.045" (1.2 mm) | 100 - 300A |
| 1/16" (TIG) (1.6 mm) | 60 - 130A |
| 3/32" (TIG) (2.4 mm) | 100 - 200A |
Amperage by Individual Diameter
0.030 ER309L Amperage
Set 0.030 ER309L to 40 - 150 amps. Run DCEP or DCEN. This is the smallest available size. Best for vertical-up and overhead where you need a small, controllable puddle. Start around 95A.
0.035 ER309L Amperage
Set 0.035 ER309L to 60 - 200 amps. Run DCEP or DCEN. This is the most commonly used ER309L size. Start at 130A for flat work, drop to 60-117A for vertical-up.
0.045 ER309L Amperage
Set 0.045 ER309L to 100 - 300 amps. Run DCEP or DCEN. A good choice when you need control. Run 100-200A for out-of-position work.
1/16 (TIG) ER309L Amperage
Set 1/16 (TIG) ER309L to 60 - 130 amps. Run DCEP or DCEN. Production size for flat work. If spatter increases above 117A, check your arc length.
3/32 (TIG) ER309L Amperage
Set 3/32 (TIG) ER309L to 100 - 200 amps. Run DCEP or DCEN. Largest available diameter. High deposition for flat and horizontal fillet welds on thick plate. Requires 100A minimum to run properly.
ER309L Suitability Scores
How well this electrode matches common applications. Not a quality rating. all AWS-certified electrodes meet their specification.
What Is ER309L Good For?
Use ER309L whenever joining stainless steel to carbon steel with MIG or TIG.
Required for the first layer of stainless overlay or cladding on carbon steel.
Also suitable for welding 309 or 309S stainless base metal to itself.
Where ER309L Falls Short
Not for joining carbon steel to carbon steel.
More expensive than ER308L.
Not the correct choice for 304-to-304 joints where ER308L is sufficient.
Service temperature limited to approximately 800F for dissimilar joints due to differential thermal expansion stress.
Welding With ER309L
Arc Behavior
Smooth arc on both MIG and TIG. Similar to ER308L but with slightly more body due to the higher alloy content. The arc is forgiving and stable at a range of settings.
How to Move
MIG: push at 15 degrees. On dissimilar joints, direct the arc toward the stainless side. TIG: standard dab technique with the filler rod fed into the leading edge of the puddle.
What the Puddle Does
Fluid, bright puddle similar to ER308L. The higher alloy content does not noticeably change puddle behavior. The bead wets out well on both stainless and carbon steel sides of a dissimilar joint.
Troubleshooting
If you see rust on a stainless-to-carbon joint within weeks, you diluted too much carbon steel into the weld. Direct the arc more toward the stainless side and let the puddle wash across to the carbon.
ER309L Size by Material Thickness
| Wire Size | Material Thickness | Application |
|---|---|---|
| 0.030" | 22 ga to 1/8" | Thin dissimilar metal MIG joints |
| 0.035" | 1/8" to 1/4" | Standard dissimilar metal MIG |
| 1/16" | 1/16" to 1/8" | TIG on thin dissimilar joints |
What the Spec Sheet Leaves Out
ER309L is the wire version of E309L-16. Same chemistry, same purpose: joining stainless to carbon steel. Use it on MIG with 98/2 Ar/CO2 gas or TIG with pure argon. The wire is slightly easier to source than the stick rod because most stainless fabrication shops keep it on hand. Every shop that handles both stainless and carbon steel should stock ER309L for the inevitable transition joint.
Bottom Line
Repair work is where ER309L belongs. Beginner is not its job. When ER309L is wrong for the job, reach for ER308L.
Setup & Safety Reference
How to Store ER309L
Store sealed. Same handling as ER308L.
Shielding Gas for ER309L
| Gas Mix | Common Name | When to Use |
|---|---|---|
| 98% Ar / 2% CO2 | Stainless MIG mix | MIG welding dissimilar joints. Keeps weld chemistry stable. |
| 100% Argon | Argon | TIG welding. Standard for dissimilar metal TIG applications. |
| 90% He / 7.5% Ar / 2.5% CO2 | Tri-mix | MIG welding. Better heat input on thick sections. |
Dissimilar metal wire. Gas selection critical to maintain corrosion resistance at the joint.
Preheat & Interpass Temperature for ER309L
Preheat not required for the stainless side. When joining stainless to carbon steel, the carbon steel side may require preheat per AWS D1.1 based on thickness.
| Base Metal Thickness | Minimum Preheat (°F) |
|---|---|
| all thicknesses | Not required |
Maximum interpass temperature: 350°F
Shielding gas flow rate: 20-30 CFH
Source: AWS D1.6, manufacturer data
Wire Feed Speed for ER309L
Use 98/2 Ar/CO2 or tri-mix shielding gas. Same WFS ranges as ER308L. ER309L is for dissimilar metal joints, not different arc characteristics.
| Diameter | Amperage | Wire Feed Speed (IPM) |
|---|---|---|
| 0.030" | 60-140A | 200-500 IPM |
| 0.035" | 80-200A | 180-450 IPM |
| 0.045" | 120-280A | 140-350 IPM |
Deposition Rates
| Diameter | Deposition Rate |
|---|---|
| 0.030" | 2-4 lbs/hr |
| 0.035" | 3-5 lbs/hr |
| 0.045" | 4-8 lbs/hr |
Fume Generation
Rating: Low
Typical fume rate: 0.2-0.5 g/min
Hexavalent chromium in stainless fume requires extraction regardless of low volume.
Common Brand Names for ER309L
Look for Lincoln Electric Blue Max 309L at your supplier. 3 companies produce ER309L-classified rods.
| Manufacturer | Product Name | Notes |
|---|---|---|
| Lincoln Electric | Blue Max 309L | |
| Hobart | Hobart 309L | |
| ESAB | OK Autrod 309L |
Full Specs
| Property | Value |
|---|---|
| AWS Classification | ER309L |
| Process | Stainless MIG/TIG (GMAW) |
| Polarity | DCEP, DCEN |
| Positions | flat, horizontal, vertical up, overhead |
| Penetration | medium |
| Coating Type | bare wire |
| Tensile Strength | 75,000 psi |
| Yield Strength | 55,000 psi |
| Elongation | 35% |
| Base Metals | Stainless to carbon steel joints, 309/309S stainless, Cladding/overlay base layers |
| Shielding Gas | 98% Ar / 2% CO2, 100% Argon, 90% He / 7.5% Ar / 2.5% CO2 |
| Gas Flow Rate | 20-30 CFH |
| Max Interpass Temp | 350°F |
| AWS Specification | AWS A5.9/A5.9M:2017 (R2022) |
Frequently Asked Questions
What is ER309L used for?
ER309L is the standard filler wire for joining stainless steel to carbon steel using MIG or TIG welding. Its 23Cr-13Ni chemistry compensates for dilution from the carbon steel side of the joint. It is also used for the first layer of stainless cladding or overlay on carbon steel vessels and piping.
Can I use ER309L to weld 304 stainless to itself?
Technically yes, but it is not the correct choice. ER309L has higher alloy content than needed for 304-to-304 joints, making it more expensive. ER308L is the correct filler for 304-to-304 stainless welds. Use ER309L only when one side of the joint is carbon steel or when you are applying the first layer of stainless overlay.
What shielding gas does ER309L require?
For MIG welding, use a tri-mix gas (90He/7.5Ar/2.5CO2) or 98Ar/2CO2. Do not use 75/25 Ar/CO2 as the high CO2 content causes excessive carbon pickup, which defeats the low-carbon L designation. For TIG welding, use 100% argon with a back purge of argon on the root side to prevent sugaring.
Where to Buy ER309L
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Manufacturer Data Sheets
External links to standards bodies and manufacturers. These leave GageRef.
Reference data only. Verify all settings against manufacturer documentation and the applicable welding code before use. Amperage ranges are starting points that vary by position, fit-up, and material. Welding involves serious injury risks including burns, electric shock, fume exposure, and fire. This site does not replace proper training, certification, or employer safety procedures. See full terms of use.
Data sourced from AWS A5.9/A5.9M. Amperage ranges are approximate starting points. adjust based on position, fit-up, and material thickness. Always follow manufacturer recommendations and applicable codes.