Idea for preserving cheap air compressor - paint inside of tank?

pjb999December 26, 2006

Hi all,

I hope this is the correct forum for this question, since there's no "tools" one I figured someone here will know...

I have a very cheap little air compressor - yes, I know you get what you pay for, but this was on sale too, so cost next to nothing which is just as well since I'm not working right now, and have next to nothing to spend!

We're doing some renos and I wanted a little compressor for nailing the trim - it's been great albeit a little slow to fill, but it lasts long enough for me to be ready for a break, or to cut some more pieces while it's filling...

Anyway, in accordance with the instructions, and what I know about compressors anyway, I drain it every day when I finish, and even make sure I tip it slightly (it's oiless) to ensure any moisture drains out too.

I've had it a while but haven't used it a lot, nevertheless the moisture that comes out does look a little rusty. I don't know whether one ought to expect that with ANY compressor or just the cheapies, but here's the thing - I can easily remove the drain plug entirely, and was wondering about the idea of pouring some rust-killer paint inside the tank, swishing it around then letting it drain well and dry, before replacing the plug. The idea is to coat and cover the bottom of the tank where clearly the majority of the condensation, and therefore the rust, will happen. Right now it's under warranty but I suppose what I'm proposing may void the warranty.

I know about dangers associated with high pressures and sparks etc and wouldn't do this without an extended drying period, and can ensure the paint won't run up into the compressor part and keep it around the bottom part. I can then just allow it to drain and replace the plug, ensuring any crud is blown out before the plug goes back in.

If the pressures were high, I'd consider it maybe more of a risk one way or the other, but it maxes at 90psi which isn't any more than a bike tire, really - it's not going to cause pressure enough for detonation or anything, and I won't fire it up til it's well and truly dry and would run it for a while with the drain open before I allow it to pressurise. It may well be in this day and age, the paint I'd use will be water based, so the fire/flashpoint risks would be low....

So, will what I'm proposing work, and extend the life of the unit by stopping or eliminating the rust, or will I cause other problems? Is it dangerous at all?

The thing cost me CDN $60 so I'm not really risking much at all if I mess it up.

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The moisture that condenses in an air compressor is very clean water and therefor very aggressive. Attempting to paint the interior of the tank with no control of coverage will not work. You will still have some moisture condense on the tank walls above the paint and will have increased corrosion at that point. Also, any place that the paint doesn't cover, or covers thinly (and you would have no way of knowing) will corrode and then trap water between the paint and the metal causing localized corrosion, which is much worse. As the paint loosens and flakes off (and it will), it will cause you further problems.

The tanks are designed to handle the relatively small amount of general corrosion caused by water condensing in the tank. As long as you drain it, your tank will still be capable of holding pressure long after the compressor has ceased functioning.

    Bookmark   December 31, 2006 at 2:28PM
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Thanks - you have made good points. With the more expensive models, do they galvanise the inside, or give them some other sort of treatment? I suspect you're right about leaving it, my FIL even had a tank that rusted out in the bottom and he welded it up. It still leaked a little until some rust or something else blocked the holes up completely.

Sounds a little scary to me, but, as he pointed out, it only runs at 100 psi which is relatively safe - it's not diving tank -type pressures.

    Bookmark   January 1, 2007 at 10:35PM
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