Argon CO2 Tank Sizes for Mild Steel Welding with 75/25 (2023)

Looking to MIG weld some mild steel?

Or even TIG weld some?

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 find out all about it.

What Are The Argon CO2 Tank And Cylinder Sizes?

In this table you’ll find the popular tank, bottle and welding gas cylinder sizes.

For when you’re welding mild steel. And need some Argon and Carbon Dioxide gas tanks.

The amount of high pressure gas in a tankis 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 estimates of the total amount of Argon and CO2 you’ll find in each tank size.


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

They also have those bottles painted with their brandcolors.

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

And this is true particularly with branded rental andleased 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.

To show you what you might find renting, leasing or buy a tank of high pressure gas. Here’s a few stories for you.

Argon CO2 Tank Size And Rental Or Leasing

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

(Video) Welding Gas Cylinders: A Beginner's Guide

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

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

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

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

He asked them what happened when his Argon CO2 gas ranout.

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

Bob quite liked that idea. Because it meant that hedidn’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 you manage the return of their gas bottles.

High pressure gas 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 Sizes for Mild Steel Welding with 75/25 (1)

And they usually have rules around how they managetheir rental tanks.

Argon CO2 Bottle Sizes You Transport Yourself Or Get Delivered

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

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

He’s thinking of renting a much larger tank of CO2Argon.

Because he has the room to store a larger gas cylinder in his workshop.

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

He decided he would get himself a hand truck or a welding gas 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 histruck. Chain it up and keep the cylinder upright and secure while he drove itback.

Moving Large Sized Argon CO2 Tanks?

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

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

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

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

Add a welding cart or a cylinder trolley to yourshopping list. When you’re thinking of renting and transporting a large CO2Argon cylinder.

It keeps things manageable and safe.

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

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

75% Argon 25% Carbon Dioxide Tank Sizes And Weights

Tank SizesWeights
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 again 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 checkedon the prices. He was pleasantly surprised to find out the cost per cubic footof 75/25 was cheaper on the big tanks.

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

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

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

(Video) 100% CO2 vs C25 MIG Mix vs 100% Argon for MIG Welding

Not only would he have the cheaper cost per cubic feet 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 twotanks of the same size. So then he’d have a tank he could swap to when thefirst 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 welding gas cylinder 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. So, 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 fewthings to check before you part with your money.

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

Argon CO2 Tank Sizes for Mild Steel Welding with 75/25 (2)

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 you don’t know how to read the test dates take a look at this article. “Gas Cylinder Date Stamps.”

Because a tank that’s 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 ingood condition? No rust. Particularly onthe 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 could have your tank taken from you, when you go to fill it up.

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 sizeyou 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 commission 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

(Video) Mig welding with Argon and Co2 [ Etch Testing]

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

(Video) MIG Weld Stainless Steel with C25 Gas

Just be sure to check your local welding supplierswill 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 nowwants to do a small amount of welding mild steel using shielding gas.

He’s called around his local high pressure gassuppliers. And he’s thinking about renting a size 1 (20 cu) Argon CO2 tank. Buthow 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 hour. 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 findthese estimates useful when you’re planning your welding. And want to work out howlong a tank of Argon CO2 should last you.


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

The thingsthat’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’repracticing 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 istrue for you. Then you’re going to be using up more Argon CO2 gas than youthink.

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

Renting A Small Argon CO2 Tank Versus Owning

Brad’s quite ambitious for his 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 MIGwelding projects.

He saw that his high pressure gas distributor takesthe 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. Then he can use it as much or as little as he likes.

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

Some people won’t mind. At least they are not paying adeposit 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 overit. And the person who bought it from you would worry that it was a stolentank.

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

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

Last Words

And now you’ve learned all about the available ArgonCO2 tank sizes. And how long a C25 gas bottle might last you welding.

Happy MIG welding.

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