How bad is rust in a compressor air tank?



hello all,

I would like to ask you some advice. After my first compressor was leaking oil, I had decided to invest in a brand new compressor, so I know its history and "live happily ever after".
Four months ago I've buyed a brand new Emax TAT 2021 compressor.
In the showroom the lady told my how to take care of the compressor. She told me a couple of times that it is very importent to let the air out of the tank after I used it, never let the air in the tank and let the tank open till next time.
So thats what I have done since day 1. But a few weeks ago, when I let the air out after finishing, I saw brownish water/ice coming out of the tank. Because I wanted to look at that, i moved the compressor, and more drops came out. Because of that I gold the compressor at different angles and their came out a LOT of brown water..really a LOT.

I contacted the saler, Because I have did everything she told me to do to take care of it to prefent rust in the tank, and ask her if she could help me fixing this problem.

The answer i've got from her is that I should not worry about it, Because all of the tanks Will develope rust at the time. And the airfilter will take out rust particels if the came out the tank by the airhose.

Now I am a bit confused, Because in the showroom the lady kept telling me that iT is importent to don't let the air in the tank, and ALWAYS de-compress it after use to prefent rust in the tank. I specificly asked her that day if I de-compress it after using is all I need to do to prefent rust, and her answer was yes.
And now, when rust build up in the tank after only 4 months, she tells me that it is not a problem.
So, i really would like to know if it really isn't a problem??

I hope someone could help me out.

thanks a lot!
It's normal, you don't only need to let the air out, you should also let the water out and the purpose of leaving it open till next time is to allow the water to dry up, every compressor produces water, and the smaller they are, the more they will produce, so there is nothing wrong with your compressor at all, each time you let the air out, give it a shake to make sure you get as much water our as you can and you'll be fine, the rust will normally just sit in the bottom of the tank but if you are worried about you can add another moisture trap if you want, most of us had hand grip moisture trap on the gun for extra safety.

The lady told you the truth, I've met her like you have and she has no reason to lie to you, it wouldn't do her business any good:)
Drain the air and water regularly, for best life, yes daily and leave the drain valve open. Water in the tank is a by product of compressing the air. Yes the filters will remove water/particles but for longest life drain and dry! :) Rust will still form because the inside of the tank is usually not protected with any paint.
What you've describer is normal work of the compressor. Friction of piston parts creates acid environment, besides oil and water. Thus rust inside the air tank is that something you can't get rid of. So the thicker metal of your air tank is, the longer life of it you can expect.
I've got one air tank that has rusted through, so it's changed for stainless steel one. It's not that cheap, but I hope for longer lifetime of it.
Unless your like me, and just about to sleep, and you hear SHHHHHHHHHHHHHH cause ya forgot to drain all the air out lol! Whoops!
Unless your like me, and just about to sleep, and you hear SHHHHHHHHHHHHHH cause ya forgot to drain all the air out lol! Whoops!

I thought about that problem and how to tackle it: my compressor got two big weels, so I thought lets use I go in my room, roll the compressor in front of the door, and after that I push the power there is no way i could forget to set it off when I stop ;)