guys that weld with c02/argon mix

I have never had to pay for a hydro test on a welding gas cylinder. I own several, and all of the gas suppliers I have dealt with will swap a customer owned cylinder with a full one that is in test.

Now fire extinguishers are another matter. I have paid to have my 20 pound CO2 extinguishers tested.

If you are MIG welding, run straight CO2. A 20 pound tank goes a long way, and a 50 pounder is very common. If you buy an 20 pound tanks from places like craigslist, look at them carefully - if they are marked "PEPSI CO" you may have a hard time getting them filled.

I have run hundreds of pounds of ER70S6 wire with straight CO2 in production welding applications. Never saw a need for Argon with carbon steel & the MIG process.

Keep your oxygen & fuel gas cylinders. You still need them occasionally.

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