Argon CO2 Tank Sizes for Mild Steel Welding with 75/25

By Bill Byers / December 15, 2019
Argon CO2 Tank Sizes Title Image

Have you spent time flux core welding and now you’d like to try MIG welding some mild steel?

Then you’re going to need some shielding gas. And the gas you’re going to need is some Argon and CO2.  A shielding gas mix that’s also called C25. 

It’s made up of 75% Argon 25% Carbon Dioxide.

And when you’re not sure what size Argon CO2 tanks are out there.

Or how long a tank of C25 will last you.

Read on…  And you’ll learn all about it.

What are the Argon CO2 Tank and Cylinder Sizes?

In this table you’ll find the popular tank, bottle and cylinder sizes. For Argon and Carbon Dioxide gas tanks for when you’re MIG welding mild steel.

The amount of high pressure gas in a tank is measure in cubic feet (cf)

  • Tank Size 1 has 20 cf Argon/CO2 gas
  • Tank Size  2  has a least 40 cf Argon/CO2 gas
  • Tank Size  3 has at least 80 cf Argon/CO2 gas
  • Tank Size  4 has at least 125 cf Argon/CO2 gas
  • Tank Size 5 has at least 251 cf Argon/CO2 gas
  • Tank Size 6 has at least 330 cf Argon/CO2 gas

The above table lists an estimate of the amount of Argon and CO2 you’ll find in each tank size.

Why?

Because each high pressure gas distributor has made for them different sized bottles.

They also have those bottles painted with their brand colors.

Because this makes it easy for gas suppliers to quickly work out which gas tanks are theirs.

And this is true particularly with branded rental and leased bottles.

Even so, the CO2 Argon tank sizes listed in the table above will give you a good starting point. And give you an ideal of what to expect from your chosen size of gas bottle.

Argon CO2 Tank size and Rental or Leasing

To show you what you might find renting a tank here’s a little story for you.

Bob’s been flux core welding for a while. And decided it was about time he tried out MIG welding as his welder does both.

He decided to spend an afternoon phoning around his local area. His aim was to find out where he could get some 75 Argon 25 Carbon Dioxide shielding gas. As he wanted to make a weld repair on some mild steel.

He found a local high pressure gas supplier that would rent him a tank of size 2 75/25 gas.

They confirmed that he needed to pay a deposit on the gas cylinder.

And a monthly charge for the time he had the bottle for.

He asked them what happened when his Argon CO2 gas ran out.

They said that when he returned the empty gas cylinder they would take that from him. And swapped it out for a full tank.

Bob quite liked that idea. Because it meant that he didn’t have to hang around waiting for the fill of his empty tank.

Or just return the tank of C25 when done with it.

Take away from the story.

It’s worth your while checking how each of the rental. Or leasing companies in your district manage their stock. What are the costs for renting the tank sizes you want? And how is the return of gas bottles managed?

High pressure cylinder rental and leasing companies will often use custom sized tanks. Tanks they spray with their brand colors. And tanks that have a collar around the neck of the tank with their brand name on.

Argon CO2 Tank with Owners Collar
Argon CO2 Tank with Owners Collar

And they usually have rules around how they manage their rental tanks.

Argon CO2 Bottle Sizes You Transport Yourself or Get Delivered

Pete is quite an experienced welder and does quite a bit of welding around his ranch.

He finds he’s been getting through quite a few of the smaller size 1 and 2 CO2 Argon bottles. And he finds it annoying to have to break off mid project to go get another bottle.

He’s thinking of renting a much larger tank of CO2 Argon.

He has the room to store a larger cylinder in his workshop.

But these large high pressure gas bottles weigh quite a bit. How was he going to manage moving around a large tank? And how to get it from his gas supplier, home to his workshop?

He decided he would get himself a hand truck or a cylinder trolley. Something up to the weight of the cylinder with wheels. And he’d need a ramp for his truck.

Then he’ll be able to get it into the back of his truck. Chain it up and keep the cylinder upright and secure while he drove it back.

Moving Large Sized Argon CO2 Tanks?

When you’re transporting. Or just using a large Argon CO2 tank to MIG weld with. You’ll need to think about how you move it around.

You’ll need some gloves. Plus eye protection and steel toe capped boots when moving one of those large bottles.

You really won’t want one of those falling on your toe.

Not to mention a high pressure cylinder crashing to the floor is a dangerous thing. Should a valve break then the gas rushing out will send that cylinder off like a rocket.

Add a welding cart or a cylinder trolley to your shopping list. When you’re thinking of renting and transporting a large CO2 Argon cylinder.

It keeps things manageable and safe.

Or see how much your local gas supplier will change you to deliver it to you.

You’ll still need a hand truck or trolley to move your big cylinder around in your workshop.

75% Argon 25% Carbon Dioxide Tank Sized and Weights

Tank Size 1 – 14 inches high x 5 inches dia.14 lbs.
Tank Size 2 – 17 inches high x 7 inches dia.17 lbs.
Tank Size 3 – 32 inches high x 6.6 dia.45 lbs.
Tank Size 4 – 42 inches high x 7 1/4 inches dia. 60 lbs.
Tank Size 5 – 51 inches high x 9 inches dia.120 lbs.
Tank Size 6 – 56 inches high x 9 inches dia. 140 lbs.

The physical Argon CO2 sizes and lbs. in weight in the table above are estimates.  Because each rental and leasing company vary their tank sizes. But the chart will give you a good idea of what you’re looking at for each tank size.

Larger Argon CO2 Tanks are More Cost Effective

Pete called his high pressure gas supplier and checked on the prices. He was pleasantly surprised to find out the cost per cubic foot of 75/25 was cheaper on the big tanks.

The rental charges were more than he was paying but he expected that.

The guy on the phone let it slip that they would fill size 5 and 6 (250 cf and 330 cf) customer owned tanks. And so Pete asked him what they would charge to fill one of those.

Now that was worth thinking about. Pete decided to check out the prices for buying himself one of the size 5 tanks. 

Not only would he have the cheaper cost per cf of 75/25 shielding gas. He wouldn’t be paying rental all the time.  He could keep his tank of Argon CO2 for as long as he liked. After all the gas doesn’t go off.

He thought that he should think about getting two tanks of the same size. So then he’d have a tank he could swap to when the first ran out. Then he didn’t have to rush to get it filled.

Will Your High Pressure Argon CO2 Gas Supplier Refill a Size 5 or 6 Tank?

Before you buy your size 5 or 6  (250 cf and 330 cf) tank check that you can get your tank refilled by your local gas supplier.

Often gas suppliers regard 250 cubic foot or 330 cubic foot tanks as rental only. And will only refill customer owned tanks of certain sizes.  It’s worth checking before you buy.

Buying Your Own Size of CO2 Argon Tank

And when you’re looking at tanks to buy here are a few things to check before you part with your money.

1. Is there a data label on the tank? Does that data label say it’s for Argon CO2 gas?

Argon CO2 Tank Data Label
Argon CO2 Tank Data Label

Because without a data label telling you what is inside the gas cylinder. You could have dangerous or flammable gas inside. Plus you’ll have a job to get that cylinder filled without a data label

2. Is the Argon CO2 tank you’re looking at within its testing dates? If you’re not sure what I am talking about. Or your don’t know how to read the test dates take a look at this document.

Because a tank that is outside it’s testing date will need a test before you can get it filled. And you don’t want to find your tank fails testing.

3. When looking at a second user tank. Is the tank in good condition?  No rust. Particularly on the bottom. Do the valves work?

Again you don’t want a tank that’s not safe to use.

4. Check you’re not sold a stolen tank. Is there an ownership collar around the neck of the tank? Is there a company name, or letters stamped on the cylinder itself.

You can have your tank taken from you when you go to fill it. And the tank returned to its rightful owner. Leaving you out of pocket.

Buy an Argon CO2 Tank of the Size you Want on Amazon

Amazon is another way to source a C25 tank of the size you want.

You can check out their prices and compare them to what you can get locally.

*Disclosure: The following table contains affiliate links. And at no extra cost to you this site earns a commissions through these links should you decide to buy.

Argon CO2 Gas Tank Size

On Amazon

40 cf 75% Argon 25% CO2. A full CGA 580 tank with a 10 year test

80 cf 75% Argon 25% CO2. A full CGA 580 tank with a 10 year test

125 cf 75% Argon 25% CO2. A full CGA 580 tank with a 10 year test

Just be sure to check your local welding suppliers will refill customer owned bottles.

MIG welding a Small Amount and the Size of 75/25 bottles Rented?

Here’s the story of Brad for you.

Brad mainly flux core welds in his home garage. He now wants to do a small amount of welding mild steel using shielding gas.

He’s called around his local high pressure gas suppliers. And he’s thinking about renting a size 1 (20 cu) Argon CO2 tank. But how long will it last him?

Argon CO2 Tank Size and MIG Welding Chart

Using 75% Argon and 25% Carbon Dioxide at the rate of 15 to 20 cubic feet per minute. You’ll see here the estimates of mild steel welding time you’d expect.

Tanks Size and Gas VolumeMild Steel Welding Time
1 – 20 cf 1 – 1.5 hours
2 – 40 cf 2 – 2.5 hours
3 – 80 cf 4 – 5 hours
4 – 125 cf6.5 – 8 hours
5 – 250 cf 12.5 – 16.5 hours
6 – 330 cf 16.5 – 22 hours

You’ll find these estimates useful when you’re planning your welding. And want to work out how long a tank of Argon CO2 should last you.

But.

Your welding experience will differ.  Depending on you and your type of MIG welding. As well as your level of experience in MIG welding.

The things that’ll affect your welding time are;

1.  Are you new to MIG welding mild steel?

Then you’re going to be doing a lot of experimenting.  Getting your MIG welding settings wrong, changing and trying again. And playing around with your gas flow and shielding gas coverage. You’re going to work your way through a lot of 75/25 and quick.

When you’re practicing get yourself a much larger Argon CO2 tank than you think.

2. Does the mild steel piece you’re welding need a lot of tack welding?

And will you be MIG welding a lot of short bead lengths?

If this is true for you. Then you’re going to be using up more Argon CO2 gas than you think.

The reason for this is the pre-flow of Argon CO2 so you have shielding gas cover before you start MIG welding. And post flow of Argon CO2 gas when you stop welding that mild steel bead length.

Renting a Small Argon CO2 Tank versus Owning

Brad’s quite ambitious for his MIG welding. And having rented a smaller tank and found that it ran out too quickly, he plans to rent a larger tank next time.

But Brad’s not that keen on paying rental all the time. Because he might not MIG weld for a month or two and then have a bunch of MIG welding projects.

He saw that his high pressure gas distributor takes the empty tanks in and swaps them out for a full tank.

He asked and they told him that they do fill customer owned tanks of 125 cf and under. So Brad’s thinking of getting his own 80 cf argon CO2 tank. So he can use it as much or as little as he likes.

When your gas supplier takes in your bought Argon CO2 tank and swaps it out for one of theirs are you going to be happy?

Some people won’t mind. At least they are not paying a deposit on the tank, they just pay for the 75/25 gas in the tank.

But you may never get back your tank again? Would you care?

Because if you decided to sell your tank down the line. You couldn’t sell the gas supplier’s tank. Cause if has their marks all over it. And the person who bought it from you would worry that it was a stolen tank.

Or that they’re locked into that gas supplier to get their tank filled.

You might be better off with a supplier that will refill your tank and hand it back to you. Your call.

Last Words

And now you’ve learned all about the available Argon CO2 tank sizes. And how long a C25 gas bottle might last you welding.

Happy MIG welding.

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