Aluminium tank DIY maintenance (Alu)

[phgachoud]

Did some other scuba material maintenance as regs and went well so far. Decided to get to Alu tanks which were thrown and not maintained since a loooong time, and probably filled with not that great air.
Will stay on non oxygen tanks, thinking about air only.
So after having the troubles with removing the valves and all the mess to build my own tools, am wondering a few things and am thankful to you guys for any advice and howtos, does and dont.
Looking for cheap solutions and DIY ones, will probably do a few tanks (between 10-30) but dont wanna build an industry either. I dont have easy access to specialized products here (Chile coast)

Didn't find a proper thread talking about that.

1. Tank treating/rincing

• With what would you rince your tank?
• clear water/dish soap? what about a few vinegar with hot water? Proportions?

2. DIY tumbling

• with what? stone pebles, flying around?
• how much time?
• what is the expected result to be sufficient
• when is it required

3. Tank Thread

• What is the shape you'd expect to be ok and which one would you consider the tank to be for alu recycling
• What about galvanic effects between valve and tank? how to prevent them more slower them...
• Having to use a lot of force to unscrew them am concerned about the thread shape, maybe its only debris and galvanic stuff... how can I tell?

4. Valve

• cleaning and servicing is pretty covered by other threads
• When would you consider a valve to be replaced (if man hour is no such an issue, but more what kind of shape is unacceptable to re-assemble)

Thx as ever for your time and sharing guys!

Finally a few pics

 

[Gone for diving]

You need to read oxygen hackers
Get it in PDF.
That will explain everything.

There is alot of corrosion inside the tank, you need to clean everything,
The threads need to be cleaned with the brass or nylon brush.
The thread need to look right and not missing, mushed, of deformed....

To tumble, there is alot of options if you really want..... stones, sand, if you are keeping it cheap,
The point, is to let it spin fairly slow.
So the media scrapes the sides of the tank,

I use SS punch outs

 

[phgachoud]

You need to read oxygen hackers
Get it in PDF.
That will explain everything.

Thx, I guess you mean for further reading

Oxygen Hackers Companion
By Vance-Harlow

Aprox P.71 depending on edition

 

[rjack321]

That valve is nasty. Someone has failed filters on their compressor.

 

[rhwestfall]

That valve is nasty. Someone has failed filters on their compressor.

and inside that tank...

 

[runsongas]

i wouldn't even try to tumble that tank, walnut shell blast it and then see if it will even pass vis

 

[rjack321]

I use SS punch outs

You dont want to use steel in an aluminum tank. You need to use either aluminum oxide chips or ceramic media. The steel basically embeds itself in the aluminum walls and creates a galvanic potential which is bad news in the presence of any moisture at all.

Any media used in steel tanks should not be used in aluminum tanks and vice versa.

 

[Gone for diving]

You dont want to use steel in an aluminum tank. You need to use either aluminum oxide chips or ceramic media. The steel basically embeds itself in the aluminum walls and creates a galvanic potential which is bad news in the presence of any moisture at all.

Any media used in steel tanks should not be used in aluminum tanks and vice versa.

I don't do aluminum tanks very often,
But don't see a huge problem.
Its Stainless steel punch outs

SS bolts in aluminum outdrives doesn't have a problem,

Also what do you use for whipping tanks? I use SS whip.

 

[happy-diver]

Have you seen what line trimmers do to pine posts in the local park

 

[Eric Sedletzky]

On aluminum tanks I used to use Alumaprep-33.
It’s an acid that will dissolve any white corrosion and will stop at clean aluminum. Aluminum is soft therefore I avoid using any abrading or brushes on them, certainly no steel brushes!. Aluminum needs to be slick and shiny inside or any texture just invites a place for corrosion to start. Once the inside if the tank is soaked with Alumaprep-33 and it’s clean, I turn it over and dump out the solution. Then I hang the tank upside down on a special rack I made and rinse the inside with a garden hose stuffed up inside. I had to cut the metal end off the hose so it would fit. Rinse the tank out really well (for several minutes) to get all the acid out and it will be sparkling clean, as clean as clean gets. It will also be O2 clean at that point. If you rinse them thoroughly there will be no trace or residue from the solution. If you’re really anal you can do a final rinse with a few gallons of distilled water.

If someone is insistent on tumbling because the corrosion is exceptionally bad you can get old car windows at body shops or auto glass shops for free and shatter them then use the small chunks of glass as media. Combine that with a solution of alumaprep 33 and make a slurry. That would clean the inside of the tanks very well indeed.