Internal rust & flash rust in steel tanks

[SDAnderson]

Originally posted by jsloo

I'm probably a little too "anal."

You were being attentive, not retentive. Good question.

Steven

 

[ckharlan66]

I just took my tanks in to have a manifold installed. The tanks are 8 months old and are now being tumbled due to rust inside.

They have never been below 500 psi. I guess the moisture came from a compressor somewhere.

Any other thoughts on what could have caused it.

Thanks

Chad

 

[Rick Murchison]

One of the most common causes has nothing to do with air quality or ever letting the tank get empty... two ways - (1) the tank rides in on a boat in rough weather, getting salt spray in the valve orifice, which isn't blown clear before the tank is refilled - a little drop here, a little drop there, over a year you can get some real damage, or (2) tanks are being filled in a water bath, and the whips occasionally get dipped accidentally and not blown clear before hooking up - same result.
To prevent (1) make sure you let a blast out of the tank just before delivering it for a fill. To prevent (2) - watch 'em like a hawk.
Rick

 

[ckharlan66]

It was a pretty even coat.

They have never been on a boat and only filled in a water bath once so that may be the cause.

Thanks for the input.

Chad

 

[thethumper]

curious Chad, who made those tanks? I'm looking into the new PST 120 3500psi tanks.
Consider too that the cold weather up there, hot/cold/hot/cold will cause condensation. Keep 'em indoors.

 

[ckharlan66]

They are pst's and I do keep them inside but thanks for the advise. Good luck on your purchase.

Chad

 

[pescador775]

Yeah, drop in temp causes condensation, on the OUTSIDE of the tank. A tank with dry interior (low dew point) is not at risk. Ask any ice diver. Listen to Murcheson. The biggest risk to a tank is water droplets blown into the valve during filling. Now, that's the real reason to keep a few psi in any tank, to BLOW that junk out of the valve inlet before hooking up the fill yoke. DIN valve users note because it is particularly difficult with that huge orifice in which the internal threads are constantly wet and salty.

 

[Compressor]

I know how it feels. I had 6 of steels VIPed earlier in the year and all 6 had rust in them. I was depressed needless to say as I love steels.

 

[DNAXdiver]

Rust just isn't a big deal its the natural state of steel. The easiest thing is to buy/build a tank tumbler or buy an abrasive whip so you can give your tnks a quick clean up before they get visualled other wise you end up paying $20 a tank to clean them and then get stuck for a hydro if the LDS is really nasty. Sure its a pain but steel tanks are worth the hassle and anyway you can go in on it with some buddies since if you are diving steels you probably have some buddies who are.

Gorji once bubbled...
I know how it feels. I had 6 of steels VIPed earlier in the year and all 6 had rust in them. I was depressed needless to say as I love steels.

 

[Alban]

Hello all

You may want to check how fast your tanks are being filled. When they are filled either in or out of water they generate heat , when this cools the moisture condensates on the inside of the tank.I had this problem myself and decided to look into a bit further.

Alban