Steel tank and rust

[reefugee]

Hello,

Last September, I purchased four XS Scuba steel tanks (HP100). I brought two in for vis about a week ago. Today I got a call that stated that the tanks had rust in it. I talked to the technician to see how two tank less than a year old could have rust. None of the tanks have ever had less than 400psi in them. The technician tried to tell me that maybe the o-ring on the neck was defective and it let air in. If the o-ring was defective, wouldn't have my tank emptied out before it could let moisture in? (Sound like BS to me.)

The only way I could think that moisture could have gotten in was by an air fill. Maybe one of the nozzle on the airfill had water. Maybe one of the compressor from an airfill was letting in moisture. Maybe the neck on my tank had water when the airfill nozzle was hooked up.

It just really bugs me that two of my tanks (both under a year) have rust. Could this be a defect in the way the tanks were stored prior to me purchasing them? Before I talk to the store owner (who is a great guy), I want to know if this is common or normal for steel tank to develop rust when the tank has never been emptied? The store wants to charge me $19/each to tumble the first two tanks. I still have to bring the other two tanks in for VIS.

Thanks
Minh

 

[SDAnderson]

A little bit of rust isn't a bad thing. Flash rust, a thin film on the surface, is harmless and won't lead to trouble. Pitting is a problem, however, and needs to be dealt with quickly and aggressively. If you don't know how to tell the difference, find somebody who does.

If the technician said what you say he did, the first step to solving your problem is to find another store. Based upon the explanation he gave you, before I had the tanks tumbled, I'd get a second opinion from somebody who knows what they're talking about.

 

[300bar]

Rust in a steel tank,is not a good thing,most of mine are 15/20 years old and still no rust.
Why do you get rust,well you gave the answer yourself.
Bad airfills(not one)
water in your valve and shop not clearing that before filling

Bad O-ring is just BS,it will empety your tank not let water in.
And on a side note Steeltanks are not tumbled, but sandblasted.

 

[captndale]

It is a misconception that normal breathing air will not cause rust in a steel tank. There is always a small amount of water in air. Typical breathing air may have an atmospheric dew point of -60 F. At 3500 psi that air would have a dewpoint of about 55 F. That means that if the tank is cooled down to 55 F or lower water will start to condense on the sides. If you ever went diving in water with a temperature lower than 55 degrees, you would expect to have some flash rust in your tank.

You can find a dewpoint conversion chart here: http://www.fpweb.com/200/TechZone/AirFiltersandFR/Article/True/6459/TechZone-AirFiltersandFR

 

[Hoosier]

Like reefraff said, a flash rust or thin film is ok... Even many medical O2 bottles at the hospital have many flash rust inside.

It is hard to tell where you get the moisture. First step is to check your LDS air quality and filtration system. And then, you also check their way of fills, such as wet fill.
IMHO, a rust on the steel tank is unavoidable consequence unless you have your own fill station.

Open the valve by yourself and inspect if there is a rust inside or not before tumbling.

And on a side note Steeltanks are not tumbled, but sandblasted.

 

[SDAnderson]

And on a side note Steeltanks are not tumbled, but sandblasted.

no:no

au contraire, mon frere...

 

[Rick Inman]

And on a side note Steeltanks are not tumbled, but sandblasted.

He's either kidding or thinking of the outside.

 

[300bar]

He's either kidding or thinking of the outside.

Nope,but maybe we got different rules overhere.
Tumbling is for AL
Steel has to be blasted.

No kidding. It's on the INSIDE)Outside you can do with sandpaper.

 

[Hoosier]

Maybe in EU, NOT IN US....

For a normal practice, I have never seen any LDS who is using a sand blast for an inside rust in US.

Even, PSI doesn't teach about a sand blast for VIP course.

 

[300bar]

Maybe in EU, NOT IN US....No but this board seem to went GLOBAL

For a normal practice, I have never seen any LDS who is using a sand blast for an inside rust in US. LDS doen't do hydros here

Even, PSI doesn't teach about a sand blast for VIP course.Not for VIP, witch we don't do mandatory,but for hydro

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