Mig welding SS

here is a late night post/ replay, I been there done that. yes your weld will be sound, C25 gas and a spool of 308 L SS wire will do the trick, here is what you will see happenin' your weld bead will be gray , weld bead will be domed, and you will have lots of spatter, and it is a pain to remove / get off staninless.

investing into a new gas bottle for one job may not worth it, but if you would go with a trigas mixture, designed for stainless mig, you would get : a shinnier weld bead, the bead would melt/flow into the base metal nicely. and less spatter. in any case wit MIG you will end up with some nasty black build up around the weldment , a wire brush will remove it if you can get to it.

wit MIg you will need to keep a really short wire stick out. SS has poor electrical conductivity and poor heat transfer property. you cold weld a piece of SS and grab the opposite end of the piece and it wouldbe still cold.

and finally .....just for info, with TIG you would get a nice flow into the base metal, no spatter, no nasty black build up and simply wire brush to base metal shinny finish.

good luck

C-25 will work fine. Use a 309L wire for compatibility of 304 to 430.

Thanks for your help,Ernie and acrobat ant. I broke down and got an owner bottle of tri-mix and a spool of E308L and E308L. My welding supplier will buy back the bottle for the same amount that I paid for it if I take it back before the hydro test date, so I will save on cylinder rental. I decided to go with the tri mix because all the ss I will be using has a #4 finish on it and I will be grinding down the welds to make them "disappear" so I figured that the tri mix and either 308 or

PS: WIll I still need to passivate if I use trimix and E308 or E309?

Along the same lines I have a ton of SS sitting around my shop and have been asked about making some small tanks for Maple Syrup, since some of the SS is food grade can I do a food grade Mig Weld? What do I use?

Also does anyone have a good link to determine what type of SS I have, I know I have about 4-6 different kinds but I'm not sure which is which and what the best use for each is.

Passivation is always required for stainless welds that will be exposed to food products, used on a boat or exposed to rain.

A tri-mix gas or CO2-Argon-Helium or CO2-Argon-Oxygen will give better results than C-25.

After welding you polish off the welds as best you can and then passivate using a pickling paste, or citric acid and electricity.

Thanks again Ernie!!!

No idea what passivate is so I'll have to look that one up. Any idea how to tell the difference between all the different SS metals?

What's best for food?

The most common food grade stainless is 304, which is also the lowest alloy SS in general use.

Passivation is when you apply an acid to the surface of stainless steel welds to dissolve the disassociated iron particles that occur in all stainless steel welds.

If you don't passivate SS welds the iron particles will rust, and once they start rusting the rust will spread into the rest of the SS.

I know nitric and citric are what are normanally used to passivate SS. But I wonder if Sulfuric or Hydrochloric acid would work. They are both much easier to get, especially today. Nitric acid is one of the main ingreadents in making things that go "BANG"!