Welding gas cylinder, what size? Options

[ipozestu]

I'm about to put a '75 in the air that's been sitting in my garage for a year. This will be my first crack at rust repair. The Hell hole and lower long area is where the most attention is needed.
I'm new to welding, I've picked up so much information here I feel pretty good about starting this.
I picked up a Lincoln 3200HD off craigslist for $200. I've got a regulator, now I need a cylinder. What size should I get? I was looking at a 20lb bottle available on craigslist. It was designated as CO2. Is that the right bottle? Can it be filled with mix gas? Should I get something bigger?
Tips. tricks, comments, suggestions?
Thanks

[Millerwelds]

If you are going to use CO2 then a smaller bottle will suffice as CO2 is in liquid form and you are actually pulling the 'evaporated gas' of the top of the liquid. Through that process it will last a long time. You can not use a CO2 cylinder for mixed gas as it has a different valve. You should be able to buy either of the smaller bottles and exchange them at any store - only when you get to the larger cylinders do they become difficult to exchange as most company's only rent not sell the larger tanks.

CO2 will work a little better then flux core wire. If you are welding outdoors then flux core will work no matter the wind conditions. CO2 is cheap and will last a long time Vs. mixed gas which is more expensive but gives a significantly cleaner weld with less cleanup needed afterwords.

Hope this helps

[Todd Enlund]

You can not use a CO2 cylinder for mixed gas as it has a different valve.

Are you sure? I was under the impression that the CGA-580 valve was used for argon, helium, nitrogen, CO2 and non-flammable mixtures.