Rust and steel tanks

[JBRES1]

Wow, I have never heard of this. Do you have the names of any particular products, and how are the applied and used?

Thanks!
carbon

Try this stuff
Global makes (Oxy-Safe Rust Inhibitor - Quart )
http://www.gmcscuba.com/main.php?content_url=ProductHighlights

Jim Breslin

 

[Bob3]

Another vote for Global's fine products, they know their stuff & are a good bunch of folks to work with.
Been selling their goodies for over 25 years & always felt like they were family.

 

[carbon]

Try this stuff
Global makes (Oxy-Safe Rust Inhibitor - Quart )
http://www.gmcscuba.com/main.php?content_url=ProductHighlights

Hi Jim,

My curiosity is peaked. How is it applied? Does it penetrate the steel? Does it offgas into the breathing gas? Is it commonly used to inhibit rust in scuba tanks? After reading the material safety sheet, it doesn't seem like the friendliest of chemicals.

Thanks again,
carbon

 

[Luis H]

After a tumble , you need to re hydro to make sure the tank is ok.
Tumbleing media can remove material from the inside of the tank other than the rust.
Jim Breslin

I am aware of tests that have shown the contrary. I know you can talk to PSI about this, but I am fairly certain that I have read test reports from some other literature like Global or similar.

The test results make sense to me since tumbling media, no mater how sharp it is, has very little weight behind it to cut into the parent metal. I am aware of many tanks that have been left tumbling for days and not being affected structurally.

Tumbling will scrape rust, most oxidation, and most other dirt deposits that can be seeing in a tank, but it is not even aggressive enough to remove some of the old tank liners (interior paint) that were applied in some tanks in the past. If the paint is loose, it will cut it, but if the paint is well attached it is almost impossible to scrape the paint of by tumbling.

 

[Ed Palma]

I have seen HP PST tanks that have only had 3 fills that were rusted, a friend of mine has a set that were manufactured at the same time, had three clean dry fills apiece, and one was rusted badly at the first VIP. I believe it was due to a failure by PST to dry the tanks well on the initial hydro.
It was pretty bad, but after a phosphoric acid cleaning it looked like new.

Was this flaky rust, or just a golden sheen on the insides? Might have just been flash rust, and easily remedied by the phosphoric acid cleaning you did.

 

[drbill]

I've lost two PST HP120's in the past two years... one that was shore dived exclusively with only land-based fills and the other boat-dived exclusively. Two different "manufacturing" dates. The first failed its second hydro, the second failed a VIP a year after its last hydro.

I won't touch them again given the kind of diving I do.

 

[oxyhacker]

We call this the "hydro trap", where you take a tank in for a visual, and the ship insists on tumbling it, then says it has to be hydroed, and your $10 visual has become an $80 major event.

It just isn't true. The amount of metal that tumbling removes is insignificant. Any shop that insists on rehydrotesting after tumbling is either after your money or doesn't know what they are doing. One might argue that a tank with line corrosion or deep pitting, which barely passes visual, might have enough metal removed to require rehydroing, but such tanks are rare, and usually better discarded. The DOT regulations, when they list situations in which immediate rehydrotesting are necessary, do not give tumbling as one of them.

We always recommend that anyone with multiple steel tanks learns to remove the valve and do a quick pre-visual before they take a tank in for a visual. If there is minor rusting then it is often easier and cheaper to remove it yourself, using an easily made stainless steel cable whip, before you bring it in for visual, so as to avoid the tumbling-hydro arguement altogether .

It's always a good idea to find out before you bring a steel in for visual what the shop's policy is on hydroing after tumbling, and whether they will automatically tumble and hydro any tank that fails visual due to rust, or whether they will call you first.

If one has taken a tank for visual, and the shop tries to insist on a tumble and hydro, we usually suggest getting the tanks back from them by any means, then either cleaning them yourself of taking them to a shop that doens't require tumbling after hydro and having them cleaned and inspected there.

After a tumble , you need to re hydro to make sure the tank is ok.
Tumbleing media can remove material from the inside of the tank other than the rust.
Jim Breslin

 

[h2odragon1]

anual vis now you know why! steel does rust. I don't know were I read a story about someone why had a steel tank, had his own compressor, filled the tank let it sit for a month(I think) then went diving and died. The rust in his tank consumed most of the Oxygen from the fill.
In spite of that knowlege, I recently came accross a steel 72, and bought it (part of a package BC; Reg's and tank), [private sale], it's now being hydro'ed and vis'ed. I'm hoping it passes.
Safe diving to all

 

[scubapatton]

A good friend of min ejust told me last night that one of his HP-100 tanks had to get tumbled. The VIP showed rust that looked like someone took paint and just flung it around. Not deep rust, and the VIP could have passed but why bother. He sent it in to get it tumbled now. He was pretty confident the boat fills is what did this tank in. He has other tanks, but he has pretty consistently taken that tank only on boats.

As fast as boat crews fly around, it would not surprise me to see water get into the line a little.

So a year-and-a-half and you have an issue? Not too surprising to me... now.

 

[lastprettyone]

drbill,
What is it that won't touch again? PSTs? HP120s? I dive steel HPs and LPs one of which is a PST, so I'm wondering if you will be avoiding a manufacturer or a type of tank.

Thanks