Rust in compressor tanks

[nheather]

It recently occurred to me to drain my compressor - overdue but not massively so.  I was met with a small amount of rust coloured water.

 

I know these tanks are made from steel and I know that when air is compressed any water vapour content condenses so I guess it is inevitable that water gets into the tank and because it is steel it will rust no matter how often you drain it.

 

So two things struck me

 

1) the air delivered to my brush could contain rust - or would the moisture trap catch that?

 

2) is there any maintenance I should be doing?  Should I rinse the tank out periodically (can’t see how that would do anything other than promote rusting)  or is there an inhibitor that you can can (or would that just create problems for the air flow).

 

And before anyone says that is the problem with these cheap chinese compressors on ebay, the interior of the tanks are not painted.  Well this is a Sparmax TC-620X.

 

Cheers,

 

Nigel

[Ratch]

AFAIK this is common. When I started work at Mettoy the factory ran on 3 huge compressors. They were drained daily. I drain my airbrush compressor every few months. I've never noticed rust coming through the AB, isn't that what the water trap is for?

[bmwh548]

You can always get a compressor that uses an oil engine. I have a home made compressor with a fridge motor. The oil mist would create a rust free environment. 

If you want to stick to a "dry" engine you can order a stainless steel tank or you can get a regular tank (built for the purpose obviously) that before any use you could make it rust free. I'm thinking a diluted rust converter to splash inside the tank (just in case it already has any issues) followed by a diluted etch primer and then a diluted regular primer. Those would cover up the inside of the tank making it rust free for a significant period of time. 

[Jetblast]

1) The rust that's in the drained condensate is for the large part "in" the condensate, which doesn't get drawn from the tank. Moisture that passes through the compressor to the regulator hasn't been condensed in the tank & has come straight from the compressor head where there is little if any opportunity for rust to be created (everything but the tank is alloy or coated), so very little if any rust would get as far as the filter.

2) Drain the tank frequently, don't store it for any significant time without draining it & leave the drain screw removed during storage.

 

Internal painting or plastic coating of tanks isn't common on airbrush compressors & can lead to other issues - when the coating starts to fail, moisture is retained under the failed coating leaving an area that promotes rust, a "hot spot" for want's of a better word.  

[Andy350]

Never heard of air tanks being internally coated before. Commercial diving cyclinders that operate at high pressures are visually and hydro tested at intervals. If any major sign of rust they were either sand blasted or scrapped. 

[colin]

Breathing air tanks would normally only rust on the outside as the air put into them has the moisture (or most of it) removed before it gets inside, also they are more exposed to salt and rough tratment than a compressor tank