[Gema Lay]

I researched on how to weld stainless steel as i am welding stainless steel for a project and could use some advice from the pros here. i welded mild steel before with my MIG setup (using 75/25 argon/CO2 and ER70S-6 wire) but stainless seems like a whole different beast. i am also working with 304 stainless about 2mm thick for a small fabrication job, think brackets and a frame for a custom outdoor grill.
According to my research and experts’ opinions, tig seems to be the go-to for clean welds on stainless but i also saw folks mention mig and even stick welding. Here’s where i am at:
MIG Welding: Can I use my existing MIG welder for stainless? According to the experts i need stainless wire (like 308L or 309L) and a tri-mix gas (helium/argon/CO2) instead of my usual 75/25 mix. Is that true or can I get away with C25 for non-critical welds? What settings should i tweak for stainless?
TIG Welding: i am tempted to try TIG for better control but I don’t have a TIG welder yet. Is it worth investing in one for this? What kind of filler rods and gas (pure argon?) should i look for? Also, any tips on avoiding warping since stainless seems prone to it?
Stick Welding: i got an old stick welder lying around. can i make it work with stainless rods (like 308L)? or is this a bad idea for thin material?
General Tips: What’s the deal with “sugaring” and how do I prevent it? Also, i saw a video that the stainless can rust at the weld if not done right, how do I avoid that? Any prep or cleanup tricks to make the welds look shiny and professional? i am not aiming for food-grade perfection here just strong, decent-looking welds that do not fall apart or rust too quickly. experts here got experience welding stainless to mild steel (for some parts of the frame), I’d love to hear about that too, do I need special rods like 309L?
Would appreciate any stainless steel welding tips, recommendations or even machine suggestions if I need to upgrade
thnaks in advance for the help

[Moe]

Hi Gema Lay

Great question

For MIG, use 308L/309L wire with tri-mix gas. C25 works for non-critical stuff but not ideal tig  gives the cleanest welds, use 308L filler and 100% argon. worth investing if you will do more stainless stick can work with 308L rods, but not great for 2mm material prevent sugaring with back purge or flux and use stainless brush or pickling paste after welding. for stainless to mild steel, go with 309L

Good luck with your project

[Blake Garcia]

Welding stainless steel needs precise welding techniques and setup and it is possible with MIG, TIG, or stick welding.
MIG Welding Stainless Steel
You can absolutely use your existing MIG welder for 304 stainless but you will need to switch things up a bit. Swap out your ER70S-6 wire for stainless steel wire like ER308L for 304 stainless, it is a solid match for your material. For gas, a tri-mix (90% helium, 7.5% argon, 2.5% CO2) is ideal for smoother arcs and less spatter. Your 75/25 argon/CO2 mix can work for non-critical welds but it might give you a rougher finish and more spatter. If you’re aiming for decent-looking welds, invest in the tri-mix.
For settings, dial back the voltage and wire feed speed compared to mild steel, stainless conducts heat differently and needs less juice to avoid burn-through on 2mm stock. Start with a test piece and adjust until you get a stable arc and a clean bead. Use a push technique (pointing the gun toward the direction of travel) for a flatter, cleaner weld. It’ll give you better visibility and less beading than pulling.
TIG Welding: Worth the Investment?
TIG is the gold standard for stainless for thin 2mm material because it gives you pinpoint control and cleaner welds. If you’re planning more stainless projects, a TIG welder (like an inverter-based DC TIG machine) is a worthwhile investment. Look for one with a high-frequency start for easier arc initiation. For 304 stainless, use ER308L filler rods (1.6mm or 2mm diameter works well) and pure argon as your shielding gas, no need for mixes here.
To avoid warping (stainless loves to distort under heat), tack weld your pieces frequently to hold the shape, use a low amperage (around 50-70 amps for 2mm) and weld in short bursts to make the metal cool between passes. A copper backing bar can also help absorb heat and keep things flat.
Stick Welding Thin Stainless
Your stick welder can work for stainless but it’s tricky on 2mm material. Stick welding generates a lot of heat which can burn through thin stock or cause warping. If you go this route, use E308L-16 electrodes and keep the amperage low (around 40-60 amps). If i says honestly, for brackets and a grill frame, MIG or TIG will give you better control and cleaner results. Reserve stick for thicker stainless or repairs.
Prevent Sugaring and Rust
“Sugaring” (that ugly, black, sugary-looking oxidation on the weld’s backside) happens when there’s not enough shielding gas on the back of the weld. For your grill, use a purge setup with argon gas to protect the back of the weld, especially for TIG. For MIG, a tight fit-up and good gas coverage help. If purging isn’t an option, apply a solar flux paste to the backside before welding, it’s a game-changer.
To prevent weld rust (especially since it’s an outdoor grill), clean the stainless thoroughly before welding. Use a stainless steel wire brush (dedicated to stainless only) and degrease with acetone to remove oils and dirt. Post-weld, passivate the weld with a pickling paste or a nitric acid solution to restore the chromium oxide layer that keeps stainless corrosion-resistant. This will help your welds stay shiny and rust-free.
Welding Stainless to Mild Steel
For joining 304 stainless to mild steel (like parts of your frame), ER309L wire or rods are your best bet. They’re designed for dissimilar metals and provide a strong bond. Make sure to clean both surfaces well, and if you’re MIG welding, stick with the tri-mix gas. Keep the heat input balanced to avoid cracking—stainless and mild steel expand and contract differently.
General Stainless Steel welding Tips
Grind or sand the edges of your 304 stainless to remove any mill scale, and bevel edges slightly for better penetration on butt joints.
Stainless conducts heat poorly, so it traps heat and warps easily. Use skip welding (weld a bit, move to another spot, then come back) to spread out the heat.
Keep your workspace free of mild steel dust to avoid contamination, which can cause rust spots. Use separate tools for stainless.
Stainless welding fumes can be nasty, so use a good respirator and ensure your shop is well-ventilated.
As per your project, welding stainless steel for a custom outdoor grill is a cool challenge and it’s awesome that you are diving into it. Since you got experience with mild steel MIG welding, you are already halfway there but stainless does require some tweaks. For your grill project, MIG with ER308L wire and tri-mix gas should get you strong, decent-looking welds without breaking the bank. If you hooked on stainless work, though TIG is worth learning for that pro-level finish. Keep us posted on how it turns out and share some pics of that grill frame when it’s done! What’s your setup like any specific welder model you’re working with?

[Author]

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