CO2 or Argon Mix?

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I will be picking up my new MIG tomorrow, it will be the Millermatic 140. I will be doing sheet metal work on my '52 Pontiac with it. I will be using the original body panels for repairing the damaged body panels.What Gas should I use I was told be a guy that CO2 was better if the metal was a little rusty, any advice?Steve wife says we would be rich if only I would stop buying toys.
Reply:You're going to be cleaning the rust up anyway so I would imagine C-25 will work out better for you. Being an active gas Co2 tolerates junk better, but needs more voltage to run. The mixed gas bead generally has better appearance, and is tougher than Co2.MattLast edited by Matt_Maguire; 07-14-2010 at 02:17 PM.
Reply:Dunno about better for rusty mat'l but my set up is a MM135 w/ straight CO2 with .030 wire.  I jsut bumped down to .023 to try it but i haven't had a proejct yet.  Anyway, i think it would be easier (and will def be cleaner) to use an argon mix.  If you want to push the envelope of the machine on thick material, CO2 is good because it burns a bit hotter, but that's not good for sheetmetal.  My recommendation is the mix, but I'm not an expert.  Enjoy that machine!Millermatic 135Syncrowave 250
Reply:I wuold definitely opt for the mix for body work. 75 AR 25CO2 is the most common, but an 85/15 or a 90/10 will offer less burn through. DO NOT WELD OVER RUST. With any of the mixes you can use the ER70S-3 instead of the ER70S-6 which will result in fewer silicate islands. Buy good wire, Lincoln, Hobart, ESAB, and make sure it is from the USA, some of the top brand stuff from other places are inferior.
Reply:maybe I need to clarify what I was asking a bit more.I will be able to get to the outside of the panels to clean them but I will not be able to get to the inside of a door for example. I will be cutting away some sheet metal but will not have access to the inside of the door panels, if I could buy replacement sheet metal, that would be one thing but not with this 1952 Pontiac Sedan Delivery (have you ever seen one?) most parts are unique so I will need to repair as much as possible.back in the day I would use a 6011 to clean the metal and then use 7018 to make the welds but that wasn't sheet metal. Like I said earlier in the post, a couple of guys that work on older cars use the CO2 and said that it is better for dirtier metal, just looking for clarification before I start buying gas.I take it the ER70S-3 or ER70S-6 is a different type of wire? That could make a huge difference. I will be using the .023 wire at least in the beginning.Last edited by 52delivery; 07-14-2010 at 07:35 PM.Steve wife says we would be rich if only I would stop buying toys.
Reply:According to McKay, you would be better off with ER70S-6 if the metal is less than clean. It has a better ability to "clean" impurities than does the ER70S-3."Where's Stick man????????" - 7A749"SHHHHHH!! I sent him over to snag that MIC-4 while tbone wasn't looking!" - duaneb55"I have bought a few of Tbone's things unlike Stick-Man who helps himself" - TozziWelding"Stick-man"
Reply:Oh, and I would also go with the 75/25."Where's Stick man????????" - 7A749"SHHHHHH!! I sent him over to snag that MIC-4 while tbone wasn't looking!" - duaneb55"I have bought a few of Tbone's things unlike Stick-Man who helps himself" - TozziWelding"Stick-man"
Reply:Stick, after doing a Google search I agree with you but look at lifer's post again, he is suggesting the -3?Looks like the -6 is better for seasoned metal but doesn't have the tensile or elasticity of the -3;http://www.weldingmaterialsales.com/...roductpage.htm    -3http://www.weldingmaterialsales.com/...roductpage.htm    -6krig &matt, I'll take your advice and go with the mix, I want to try to keep the welds as cool as possible.Last edited by 52delivery; 07-14-2010 at 09:40 PM.Steve wife says we would be rich if only I would stop buying toys.