Air tank rust

[Memmeddu]

Hi everyone.
I've recently bought a 15 years old air compressor which I'm servicing .
So after found that the pump is perfectly fine (a lot of given air )
I've ordered and already received in the mail, new air outlet with safety valve , pressure regulator and switch.
So today after work I've dismantled to proceed cleaning it up and paint.
I've then took a look at the inside of the tank and what I've seen concerns me more than a little.
Rust like if you leave some under the water everywhere inside not only just at the bottom but everywhere.

Now I've been reading here and there about .
Someone here said it has an abac compressor older than mine right now which has not any rust inside the tank
Some other say that internal rusting will occur no matter what you do , and that's not a problem by the way, cause the tank will not explode but just pin hole prior.
Mine looks good outside and sounds good to .
Looks solid at the hammer test .
But I just not feel comfortable with this rust.
I am thinking to use rust converter inside the tank (no toxic ,no flammable) , just not so sure how to apply and if it's really necessary.
I can hydrotest it no problems and I probably should since what I've seen

 

[Morrisman]

Pour some rust remover in, or fill it with citric acid solution, to remove the rust.
But that doesn't replace any metal that has rotted away.

It's probably just surface rust, but unless you get it pressure tested, to a suitable safe excess pressure you'll never know how badly it has corroded away.

I'd not worry about it. You could coat it inside with some suitable paint finish, to stop it getting any worse.

 

[Seadog]

I cleaned my IR receiver with phosporic acid. Pressure tested after. But it is a 50yo receiver about 8mm thick.

 

[richie00boy]

I enquired with some coatings people about coating the inside of my compressor tank and was told not to, as it has a risk of flaking off and getting into the air system. Best option is a rust remover (not converter) such as phosphoric or citric acid.

 

[MetalMonkey]

Another vote for phosphoric acid, I did one of my compressor tanks with it, just be aware that you will have residue in the air for some considerable time.
I wouldn't coat it with paint or anything.

 

[ukracer]

Is it not the same in Italy. An abundance of receiver tanks? I have 2 myself plus my running compressor.
Surely you could pick up a decent one at a reasonable price? (Without rust)

 

[Burdekin]

Hi everyone.
I've recently bought a 15 years old air compressor which I'm servicing .
So after found that the pump is perfectly fine (a lot of given air )
I've ordered and already received in the mail, new air outlet with safety valve , pressure regulator and switch.
So today after work I've dismantled to proceed cleaning it up and paint.
I've then took a look at the inside of the tank and what I've seen concerns me more than a little.
Rust like if you leave some under the water everywhere inside not only just at the bottom but everywhere.

Now I've been reading here and there about .
Someone here said it has an abac compressor older than mine right now which has not any rust inside the tank
Some other say that internal rusting will occur no matter what you do , and that's not a problem by the way, cause the tank will not explode but just pin hole prior.
Mine looks good outside and sounds good to .
Looks solid at the hammer test .
But I just not feel comfortable with this rust.
I am thinking to use rust converter inside the tank (no toxic ,no flammable) , just not so sure how to apply and if it's really necessary.
I can hydrotest it no problems and I probably should since what I've seen

A air tank can catastrophically fail but would typically require a ring of corrosion around the full circumference or the more likely scenario of along the full length of the bottom of the tank. If the weld was along the bottom it would be more likely. This would result in a very quick release of pressure and how far that would push the compressor not sure. However a pin hole failure is more likely. To get a pin hole the corrosion will need to eat through pretty much the full thickness of the vessel. If there is good metal around a corrosion pit at 8 or 10bar it would need to be less that 0.2mm most likely before it would fail at that pressure. If your compressor just has surface corrosion it's not a problem, if it has a large amount of corrosion scale in the bottom then that's a different scenario and would be a worry.

Don't use rust converters. As the guys above suggest a rust removal acid will clean up the inside of the tank if it's surface corrosion, if it's significant corrosion scale it might be a challenge.

 

[mike os]

Without rust???

Good luck with that, they start to rust in the shop lol

Pressure test to 20% over pressure if you like but personally I'd just go with it as is

If it leaks then replace

 

[Burdekin]

If you are genuinely worried it will fail a pressure test fill it with as much as you can with water, it will be significantly safer if it did fail then.

 

[Memmeddu]

I'll try citric acid
And I'll also not apply a thick coat of paint outside so if something goes wrong I guess I'll have enough time to see it's gone prior failure

 

[Memmeddu]

Without rust???

Good luck with that, they start to rust in the shop lol

Pressure test to 20% over pressure if you like but personally I'd just go with it as is

If it leaks then replace

When it will leaks I'll mount the motor on a 10 ISH litres tank to make a portable high volume air supply (at this point the motor/pump can even melt carelessly)

 

[Morrisman]

When it will leaks I'll mount the motor on a 10 ISH litres tank to make a portable high volume air supply (at this point the motor/pump can even melt carelessly)

I found an old vehicle lpg tank on ebay for £30 and used that to increase volume with my small compressor. It was stamped as tested to 30 bar, or somewhere around that. So unless it has been damaged it should be okay for the max 10 bar you'd ever see in a normal shop air system.

 

[Memmeddu]

Is it not the same in Italy. An abundance of receiver tanks? I have 2 myself plus my running compressor.
Surely you could pick up a decent one at a reasonable price? (Without rust)

Mine didn't start when I've bought,so I guess it went in the category you spoke about.
I'm replacing everything just because I'm of the idea that once I can buy a new one this one's pump goes on a smaller tank for portability.
And to be honest , power cord,air fittings and especially safety valve and pressure switch have to be new and well maintained anyway
New one would have the same pump set up but on a vertical receiver

 

[Memmeddu]

I found an old vehicle lpg tank on ebay for £30 and used that to increase volume with my small compressor. It was stamped as tested to 30 bar, or somewhere around that. So unless it has been damaged it should be okay for the max 10 bar you'd ever see in a normal shop air system.

LPG tanks are easy and inexpensive to find .
But I'd have to weld fitting on it which are a potential weak point .
Plus I'm not set up to work with them safely

 

[Morrisman]

LPG tanks are easy and inexpensive to find .
But I'd have to weld fitting on it which are a potential weak point .
Plus I'm not set up to work with them safely

The one I had came with several threaded ports already on it.

 

[Memmeddu]

The one I had came with several threaded ports already on it.

that's the kind of tank I'm talking about.
Easy to find ,I do actually have two or three .
The problem is to wash them to eliminate propane residue from it.
We often use the to make things over here .
By removing the valve, filling them with water and then throwing in the fire after Various washes .
The problem is ... Once it gets heat (trying not to mention the explosion risks) are they still mechanically capable of sustain pressure?
They are 30 bar tested but I don't know if they can be safe to use
I'd prefer to use fire extinguishers tanks

 

[Morrisman]

View attachment 426975that's the kind of tank I'm talking about.
Easy to find ,I do actually have two or three .
The problem is to wash them to eliminate propane residue from it.
We often use the to make things over here .
By removing the valve, filling them with water and then throwing in the fire after Various washes .
The problem is ... Once it gets heat (trying not to mention the explosion risks) are they still mechanically capable of sustain pressure?
They are 30 bar tested but I don't know if they can be safe to use
I'd prefer to use fire extinguishers tanks

Mine was an aluminium one taken from an old vehicle conversion when it was scrapped.

With the one in your pic you only need the one hole, just mount the bottle upside down so condensation can't build up inside.

 

[brightspark]

Pour some rust remover in, or fill it with citric acid solution, to remove the rust.
But that doesn't replace any metal that has rotted away.

It's probably just surface rust, but unless you get it pressure tested, to a suitable safe excess pressure you'll never know how badly it has corroded away.

I'd not worry about it. You could coat it inside with some suitable paint finish, to stop it getting any worse.

just use it dont bother with paint or rust remover its a waste of time and money if its solid along the bottom tapping with a ball pein hammer its fine. they only pinhole if they eventualy leak

 

[500e]

Used 3 of those big gas cyl on a manifold upside down with a cold room compressor, had a drain off the manifold and a water trap with auto drain, cant remember the make, not electrick.
The calor smell took a long time to disappear.
I think washing them with Bicarb or something gets rid of it.

 

[JOEPRO]

I'm thinking the opposite. That if there is a layer of rust in there removing it with chemical treatment is likely to expose the underlying good metal and decay the tank quicker!

Maybe a rust converter approach would be better if you must?

I have looked inside my air tanks with a USB camera. The ABAC one is 20 or so years old and looks fine






I do also have another good used SIP 200L compressor. It was never drained by PO and only 2 years old. But the rust was visibly worse inside




(That was standing water in the tank too before I got a new drain cock) Note this is still very much superficial only.

If in doubt, unscrew a bung on the tank and use a cheapie USB endoscope to take a look see.

And make sure and drain your tanks regular!