Hydro and +

[Bob DBF]

I would imagine a few reported ruptures of cylinders caused by poorly filtered, wet fills, resulting in rust helped bring about those changes as well.

How? A required visual is done at the time of a hydro but a qualified hydrotester, how would that have a worse result in the following year than a shop monkey looking in a tank and slapping on a sticker for the year after that. A VIP is not legally required, and anyone a shop designates can inspect and sticker a tank.

Somehow a trained licensed proffessional inspection has to be checked by a tank monkey and place a sticker before it is approved for a fill in the first year of hydro, what is wrong with that picture?

The VIP in the first year after hydro was changed for revenue, not for a more rigorous inspection.

 

[Ghost95]

Maybe I misunderstood...I was saying that a few ruptures of rusty tanks helped bring the yearly "requirement" into existence. Allot of damage can be done to steel tanks in 5 years with salt water intrusion.

I do agree though it is a revenue stream that no shop wants to get rid of.

 

[captain]

Aluminum doesn't rust so why do tanks built from 6061-T6 aluminum need inspection every year.

Corrosion Resistance
When exposed to air or water, 6061 aluminum alloy forms a layer of oxide which renders it nonreactive with elements that are corrosive to the underlying metal. The amount of corrosion resistance is dependent upon atmospheric/aqueous conditions; however, under ambient temperatures, corrosive effects are generally negligible in air/water. It is important to note that due to the copper content of 6061, it is slightly less resistant to corrosion than other alloy types (such as 5052 aluminum alloy, which contains no copper). When in contact with alkaline soil, there may be some corrosive effects such as pitting, but this is highly dependent on soil conditions. 6061 is particularly good at resisting corrosion from concentrated nitric acid as well as ammonia and ammonium hydroxide. The corrosive effects can be removed entirely by coating the alloy with a protective layer, to which 6061 alloy responds well.

 

[Bob DBF]

Maybe I misunderstood...

That's what I figured, no worries.

I was saying that a few ruptures of rusty tanks helped bring the yearly "requirement" into existence. Allot of damage can be done to steel tanks in 5 years with salt water intrusion.

I was diving back well before the VIP, and at the time it was a good idea. Open up the tank and do a quick check for problems, the sticker recorded the date. A lot of serious divers were checking already, this insured that all tanks in general circulation were checked.

 

[captain]

That's what I figured, no worries.



I was diving back well before the VIP, and at the time it was a good idea. Open up the tank and do a quick check for problems, the sticker recorded the date. A lot of serious divers were checking already, this insured that all tanks in general circulation were checked.

Back when you and I started all tanks were steel and compressor filtration wasn't
what it is today

 

[rjack321]

Aluminum doesn't rust so why do tanks built from 6061-T6 aluminum need inspection every year.

Corrosion Resistance
When exposed to air or water, 6061 aluminum alloy forms a layer of oxide which renders it nonreactive with elements that are corrosive to the underlying metal. The amount of corrosion resistance is dependent upon atmospheric/aqueous conditions; however, under ambient temperatures, corrosive effects are generally negligible in air/water. It is important to note that due to the copper content of 6061, it is slightly less resistant to corrosion than other alloy types (such as 5052 aluminum alloy, which contains no copper). When in contact with alkaline soil, there may be some corrosive effects such as pitting, but this is highly dependent on soil conditions. 6061 is particularly good at resisting corrosion from concentrated nitric acid as well as ammonia and ammonium hydroxide. The corrosive effects can be removed entirely by coating the alloy with a protective layer, to which 6061 alloy responds well.

6061 absolutely will corrode. Inside or out.
Put 10mL of saltwater in an AL80 and leave it a year in a hot climate and you will have one very pitted and corroded cylinder which will definitely need some work to restore if it doesnt fail corrosion limits.

 

[ScubaBunga]

This particular tank has the REE stamped on it. I found a source for future "plus" ratings, if my LDS still refuses.

if your tank has a ree on it and your LDS refuses - FIND A NEW LDS for any tank related items. They may be a great shop for training or other things but they don't know which end is up for cylinder management. Most LDS don't actually do Hydros as well, so may need to talk past them to the actual hydro tester they use. Plus ratings are not hard but so very misunderstood because the only people who care are us with LP tanks that want a full fill! And I'm not sure but plus rating a HP tank may be reason to condemn it! (i.e. LDS/Hydro owes you a new tank)

 

[halocline]

if your tank has a ree on it and your LDS refuses - FIND A NEW LDS for any tank related items. They may be a great shop for training or other things but they don't know which end is up for cylinder management. Most LDS don't actually do Hydros as well, so may need to talk past them to the actual hydro tester they use. Plus ratings are not hard but so very misunderstood because the only people who care are us with LP tanks that want a full fill! And I'm not sure but plus rating a HP tank may be reason to condemn it! (i.e. LDS/Hydro owes you a new tank)

Dive shops cannot qualify a tank for the plus rating, only DOT licensed testing facilities can do that. This is a problem with dropping tanks off at a dive shop for 'hydro and vis and fill'. They bring the tank to a hydro shop and chances are very good that the idea of a plus rating will never even get discussed with the hydro shop. If you have a 3AA steel tank, it's best to bring it directly to a hydro shop and make sure they will stamp that plus rating (assuming it qualifies). My experience with hydro shops in the San Antonio/Austin area is that I had to call at least 5 shops before I found one that would do so. Most are just stuck on fire extinguishers and welding tanks, with no interest in or understanding of scuba tanks.

 

[Scared Silly]

Aluminum doesn't rust so why do tanks built from 6061-T6 aluminum need inspection every year.

Of course aluminum doesn't rust. That is because rust is iron oxide which comes the oxidation of iron or steel.

 

[Eric Sedletzky]

Of course aluminum doesn't rust. That is because rust is iron oxide which comes the oxidation of iron or steel.

It does, but it’s called white rust, or just oxidation.
I’ve seen 6061 go to absolute hell in salt water environments in marine use. Sail boat mast extrusions where things were bolted on, outboard motor boxes that were foam filled and soaked with salt water. Scuba tanks that formed white rust under thick paint coatings, and lot’s of heavy pitting and white rust under powder coating.
White rust can form inside aluminum scuba cylinders especially with wet fills and if people are doing PP nitrox fills.
I found the best way to clean out al tanks and make them sparkling clean is to use alumaprep 33 to dosolve all corrosion then rinse them out really well and dry by blowing clean air upside down to drain the tank and also warming the tank.