Faber Hot dipped galvanized durability

[-JD-]

It is great to see SBers sacrificing themselves and stepping up to care for unwanted PSTs! Warms my heart ...

 

[pauldw]

rust never sleeps.

Live rust.

 

[Fred Tagge]

I have several steel 72s with HDG finish born in 1951 that are still usable. The valve threads are not the current SCUBA standard (1/2NGT) and the SCUBA standard faced yoke valves no longer had service parts available in the early 2000s . I converted all of them to on boat emergency Industrial oxygen valve bottles. This allowed us to have 4 hours of demand delivered pure O2 on board for 2 divers without constantly removing/replacing tnem from the boat we used to dive GOM oil rigs.
Aluminum tanks are basically a 15 year tank. They don't rust, but do have their own corrosion problems that once started cannot be stopped. The other problem is that the regulatory issues concerning them keep changing so what was OK with US DOT a decade ago is no longer kosher today.
OTOH steel tanks do require regular internal maintenance when used with SCUBA quality compressed air. Regular internal inspection for rust is mandatory for long service life. Any problems caught early enough can be stopped in place and prevented from worsening with less than an hour's labor.
I posted several long discussions concerning this on rec.scuba a couple decades ago. They should still be available in the rec.scuba archives. I think I still have copies of the posts in my archives, but won't look for them unless they are needed.

 

[Boarderguy]

Aluminum tanks are basically a 15 year tank

What? You're part of the problem by even implying an age limitation for aluminum tanks. There were tanks made pre 92 (or was it 90) that the material was susceptible to cracks and catastrophic failure. Other than that they will live a long life if cared for. I have 2 AL tanks on my rack from 72 & 73. They are now used exclusively for lake dives at my dad's house, but I dove them regularly until last year.

 

[Still Kicking]

Regular internal inspection for rust is mandatory for long service life. Any problems caught early enough can be stopped in place and prevented from worsening with less than an hour's labor.

Excellent point thst is often overlooked by people who gripe about annual inspections being unnecessary. VIPs do as much, if not more, to protect the tank owner's investment as to protect fill station operators.

 

[Eric Sedletzky]

Doesn’t an aluminum tank have a lifespan according to how many cycles it’s been through?
I heard something like 20,000 cycles?

 

[Fred Tagge]

What? You're part of the problem by even implying an age limitation for aluminum tanks. There were tanks made pre 92 (or was it 90) that the material was susceptible to cracks and catastrophic failure. Other than that they will live a long life if cared for. I have 2 AL tanks on my rack from 72 & 73. They are now used exclusively for lake dives at my dad's house, but I dove them regularly until last year.

The last Luxfor 80 made of the "bad"alloy that resulted in alumibomb function was in the middle of 1989. I have a few made by them in the last quarter of '89 that are of the "new" alloy that are still worthless due to DOT rules that prohibit them from being hydro-tested. Catalina tanks never had the neck cracking problem but do still suffer from other corrosion issues.

What kills an aluminum tank now is generally pitting, either inside the tank or under the valve near the O-ring seal. This is caused by a chlorine ion driven galvanic corrosion cell working down the metals inter-granular boundaries. Once this starts the ONLY way to stop it to mechanically remove the entire cell. Since that is impossible to legally do on a DOT 3AL pressure vessel the tank is dead. IF a tank is used in only freshwater you have a chance at a good long life. Tanks used in seawater will generally survive 2 to 4 hydro cycles before pitting or other corrosion issues cause them to fail visual. OTOH they are relatively cheap even if their buoyancy characteristics do suck.

 

[Fred Tagge]

Doesn’t an aluminum tank have a lifespan according to how many cycles it’s been through?
I heard something like 20,000 cycles?

That lifespan is theoretical marketing info. The real world experience is considerable different. see above.

 

[Boarderguy]

The last Luxfor 80 made of the "bad"alloy that resulted in alumibomb function was in the middle of 1989. I have a few made by them in the last quarter of '89 that are of the "new" alloy that are still worthless due to DOT rules that prohibit them from being hydro-tested. Catalina tanks never had the neck cracking problem but do still suffer from other corrosion issues.

What kills an aluminum tank now is generally pitting, either inside the tank or under the valve near the O-ring seal. This is caused by a chlorine ion driven galvanic corrosion cell working down the metals inter-granular boundaries. Once this starts the ONLY way to stop it to mechanically remove the entire cell. Since that is impossible to legally do on a DOT 3AL pressure vessel the tank is dead. IF a tank is used in only freshwater you have a chance at a good long life. Tanks used in seawater will generally survive 2 to 4 hydro cycles before pitting or other corrosion issues cause them to fail visual. OTOH they are relatively cheap even if their buoyancy characteristics do suck.

These lived in Salt water every weekend through the 70s and 80s. They then took a 25 year break until I pulled them from my parents garage and started using them. They now live an easy life of lake dives. An annual eddy test and VIP keep them alive.

 

[Eric Sedletzky]

The last Luxfor 80 made of the "bad"alloy that resulted in alumibomb function was in the middle of 1989. I have a few made by them in the last quarter of '89 that are of the "new" alloy that are still worthless due to DOT rules that prohibit them from being hydro-tested. Catalina tanks never had the neck cracking problem but do still suffer from other corrosion issues.

What kills an aluminum tank now is generally pitting, either inside the tank or under the valve near the O-ring seal. This is caused by a chlorine ion driven galvanic corrosion cell working down the metals inter-granular boundaries. Once this starts the ONLY way to stop it to mechanically remove the entire cell. Since that is impossible to legally do on a DOT 3AL pressure vessel the tank is dead. IF a tank is used in only freshwater you have a chance at a good long life. Tanks used in seawater will generally survive 2 to 4 hydro cycles before pitting or other corrosion issues cause them to fail visual. OTOH they are relatively cheap even if their buoyancy characteristics do suck.

Aluminum tanks pretty much suck all the way around and I can’t really think of anything I like about them.