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Rust in compressor tank after 5 weeks?


Isamu77
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Hi All,

 

At the start of January I bought a Sparmax TC-610H compressor. I've made sure to follow all the maintenance steps. After every use, I drain the tank of any moisture and leave the drain plug removed for a while, to make sure any moisture can drip out.

 

This afternoon, after removing the drain plug, I noticed some brown staining on the plug. The tank then dripped some brown stains, which appear to contain rust.

rust_drip

 

 

Is this normal?

 

I've made sure to follow maintenance instructions, yet after only 5 weeks, there appears to be rust in the air tank. I can't see that I've done anything wrong.

 

Any thoughts please?

 

Michael

 

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Not all the water is going to be expelled from the tank through the bleed valve. The tank itself has various depressions inside which will allow water droplets to remain inside. You could run the motor for a minute (with the bleed valve open) to "help" the inside of the tank dry off  but other than that there's not much you can do about it.

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1 hour ago, bmwh548 said:

You could run the motor for a minute (with the bleed valve open) to "help" the inside of the tank dry off  but other than that there's not much you can do about it.

Thanks for the tip. I'll give it a try next time.

 

I'm still surprised this has happened so quickly though.

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That water may have been in your tank before you bought it even, and you'll never really know, but if there's a way to reduce the humidity of the room where you use it, you should probably try to do that.  I have a dehumidifier in my workshop on a timer that keeps the humidity around the 50-55% under most circumstances.  Remember that warm air can hold more moisture than cold air, so if you have one running, schedule it for after you run any heating to the room.  I have mine coming on during the last half hour of a heating sequence, then going for an hour and a half after.  It used up a bit of electrickery, but it's all about cost/value.  If you keep your boxed kits in that room, they'll also stay nice and dry too.  Never let the room get too cold either, as it causes any moisture to drop out of the air at the slightest excuse. 🚾

 

You could also try a squirt of a water-displacing oil such as GT85 into the tank, but you'd have to leave it to dry before using it, and it may have some negative effects on your moisture trap if you've used too much, you use it too soon and it gets through.  I'm not 100% sure I'd be happy to do that without seeking some additional opinions TBH :hmmm:

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The inside of the tank is bare steel. The atmosphere has water in it. Combine the two, you get oxidation, aka rust, which as we know, eats away at and weakens the parent metal. It's normal, and is the reason why commercial pressure vessels have a strict internal inspection and certification requirement.

 

The best way to treat it is... to not worry. Large industrial compressors are usually set up such that the drain valve is left open a crack, to allow a small amount of air to continually bleed out, which helps reduce the water in the tank and lines - hobby compressors don't have the pumping reserves to do that, and seldom run long enough to make it worth doing anyway, so you'll need to drain at the end of your session. When you're done for the painting session, allow the pressure to build up again, then turn the compressor off. Open the drain valve all the way, quickly, and let the draining air pull out any accumulated water. You won't get it all, but you'll get the great majority of it. What's left will most likely stay where it is (for reasons I won't go into, this is long enough already!) but that's the way things are. Nowt to be done about it. Leave the drain valve open. If you like, you can add a bit of tube to the drain valve so that you can direct the flow of air and water to where you want it, although it's probably easier to just carry it outside if required. 

 

Use your compressor, drain it every session, enjoy your hobby. Unless the pressure vessel is of particularly low quality, you'll most likely wear out the compressor long before you need to worry about the structural integrity of the tank due to corrosion. My large compressor (100psi shut off) is 25 years old and is still fine internally, and it's been used exclusively in a high humidity tropical area. 

 

(Edit to add: on a re-read, I see that you mention 'drain plug'. I'll assume that that's a screw-in plug that has to be unscrewed and removed to drain the tank? What a nuisance. Take it out, then go and get a small ball valve/tap that fits the thread and use that instead (not sure where you'll get one in your area, I don't know what different shops stock. Someone will have something, though). Much less hassle. You'll want some thread tape and you may also need a 90 degree elbow as well, if there's no space under the tank - both shouldn't be expensive. If you want a picture, let me know and I'll share one.) 

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For what its worth after my painting sessions. I leave the valve open on my compressor. While the pump is running I rock the compressor from front to back & side to side a couple of inches. This tends to help any water settled inside head for the plug hole. 

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My Sparmax is exactly the same and I was initially a bit concerned however it is now 5 years old and still going strong. The only issue I've had with it was the plastic globe for the water trap cracking which was a 5 minute/£5 repair.

 

Duncan B

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9 hours ago, Mike said:

I have a dehumidifier in my workshop on a timer that keeps the humidity around the 50-55% under most circumstances.

Thank you for the response.

 

I'll keep a note on the humidity from now on. I've been checking the moisture trap every session and haven't seen any build-up.

 

Thanks again.

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Just to be sure no contamination gets as far as the airbrush use a moisture trap at the compressor.

Pair that with one of the small inline filters just below the airbrush, Sparmax Silver Bullet works for me.

Edited by Tijuana Taxi
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9 hours ago, Rob G said:

Use your compressor, drain it every session, enjoy your hobby. Unless the pressure vessel is of particularly low quality, you'll most likely wear out the compressor long before you need to worry about the structural integrity of the tank due to corrosion. My large compressor (100psi shut off) is 25 years old and is still fine internally, and it's been used exclusively in a high humidity tropical area. 

 

Thank you for the information, much appreciated.

 

Do you know if rust in the compressor tank can cause contamination?

 

9 hours ago, Rob G said:

(Edit to add: on a re-read, I see that you mention 'drain plug'. I'll assume that that's a screw-in plug that has to be unscrewed and removed to drain the tank? What a nuisance. Take it out, then go and get a small ball valve/tap that fits the thread and use that instead (not sure where you'll get one in your area, I don't know what different shops stock. Someone will have something, though). Much less hassle. You'll want some thread tape and you may also need a 90 degree elbow as well, if there's no space under the tank - both shouldn't be expensive. If you want a picture, let me know and I'll share one.) 

 

Yes, I was referring to the screw-in plug at the base of the tank. Cheers for the suggestion but I should be fine for the moment.

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13 minutes ago, Duncan B said:

My Sparmax is exactly the same and I was initially a bit concerned however it is now 5 years old and still going strong.

Okay, thanks. That's good to know.

 

Cheers.

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Just now, Isamu77 said:

Okay, thanks. That's good to know.

 

Cheers.

I haven't seen any contamination from the rust getting as far as the moisture trap either but you could vary how you draw down the pressure by alternately using the tank plug and the moisture trap. If you use some kitchen roll to catch the moisture from the trap you will see if it is stained or not.

 

Duncan B

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26 minutes ago, Tijuana Taxi said:

Pair that with one of the small inline filters just below the airbrush, Sparmax Silver Bullet works for me.

Thanks for the suggestion. I'll give that a try.

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My Iwata comp has been peeing brown just like that for over 15 years now. I don't think it's all rust, but a combination of fungus/yeast/bacteria and a little rust. Those little beggars will live anywhere and probably eat the oil from the motor.

 

I try to drain the tank at least once every year and then forget about it. I work in the living room so there isn't much accumulation of water. I assume it would be a lot more if you are working in a shed. I've never seen a droplet in my moisture trap.

 

I'm not telling you not to worry, I'm just saying that I don't. 

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My Sparmax has been doing that for ten years - actually thinking about that a bit more I think we're now into year twelve.

 

I used to worry but that took too much energy so I stopped.

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2 hours ago, Duncan B said:

If you use some kitchen roll to catch the moisture from the trap you will see if it is stained or not.

Yes, I've been doing that after most sessions and I haven't seen anything.

 

My only real worry is having the airbrushing air contaminated.

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21 hours ago, Isamu77 said:

Yes, I've been doing that after most sessions and I haven't seen anything.

 

My only real worry is having the airbrushing air contaminated.

It shouldn't get past the moisture trap if there is any but I would think that the rust is too heavy to be lifted into the airflow anyway.

 

Duncan B

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Large commercial air compressors have enough pressure and volume (and large enough pipes) to lift actual water droplets and quite large particles into the outgoing air stream, which is why there are filters and moisture traps on them. A hobby compressor doesn't have the flow to move much more than a little bit of water vapour, and that can be dealt with, as has been mentioned, by the use of a regulator/water trap, which your compressor should have come with. The likelihood of anything more than a smidgen of water vapour getting to the tip of your airbrush is infinitesimal. There won't even even be any oil vapour, as your model of compressor is oilless. 

 

Stop worrying (it's fruitless) and enjoy your hobby. 

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