Aluminum doubles

[Luis H]

Actually Luxfer's new "natural" finish tanks (i.e. not shot-blasted, brushed, or painted -- just the natural mottled "ugly" oxide layer) would likely be an excellent idea. Not only are they potentially the most durable, but they don't look all shiny and inexperienced when you buy them.

Thanks…that is funny, but I am not too concern about the shiny inexperience look…that won’t last long.
That is one of the concerns of the painted black ones…I think that they tend to scratch easily.

I haven’t seen that new natural finish. That may be the better option, but I haven’t seen anyone selling them yet.

 

[Luis H]

I love a small set of doubles. They made it easy to dive out of small boats and Zodiac-type inflatables, they were excellent for providing a bit more gas for longer dives in the 50'-70' range, they provided redundant regs for the weird types of shallow overhead diving I was doing, and they were handier for me to work with than larger single tanks in terms of logistics.

Go for it, and have fun with your small set of doubles.

Doc

Yes, I like small doubles. I already own a set of double vintage steel 40’s (at 1800 psi)…not exactly like Mike Nelsons, but similar. Since they are only 1800psi they are kind of big for only 40 cu ft each.

I also own two sets of Poseidon double steel 50, but since they are European I can’t really get them fill in most LDS in the US.

A set of aluminum double 50 would be very comfortable and the balance would be great.

I also only use a traditional harness (no back pack or back plate) allows them to sit closer to me and are extremely comfortable. I like the rounded feel of the tanks with the empty space in the middle…nothing presses on my backbone.


Thanks for the info.

 

[Luis H]

I seriously doubt that there is any significant increase in surface area. However, shot blasting MAY leave a residual compressive stress at the surface which could serve to inhibit corrosion.

A lot of stainless steel hardware (especially sailboat and other marine hardware) is polished and electro polished to reduce surface area exposed to corrosion. There are also other passivating processes, but the surface polishing is just to provide a smooth surface that sheds salt water and reduces corrosion area.

I am not sure how residual stresses inhibit corrosion. I have heard of stress corrosion in highly stress mechanical joints, but this sounds as something totally different. Could you please expand…is there something on the Luxfer web site or elsewhere that talks about this surface finish corrosion resistance properties?

Thanks

 

[Luis H]

Luis,

Be the first to have a "Gel Gasket" such as the latest gaskets used on aircraft antenna installations. The gel gasket will just about eliminate the corrosion between the bands and tanks by occluding water altogether. I know this would not be "vintage" but who would know? ;-)

Only half kidding, it just might be a viable alternative to a rubber sleeve that may actually trap water.

Check this out: http://www.avdec.com/images/Image007.jpg

c

Well, aluminum tanks are not vintage anyway…so that is not an issue.

This sounds intriguing even if it a bit high tech for simple Scuba gear, but if you have a link with some info it would be good…the link I see only led me to a picture.

The idea of a good sealing gasket/ isolator seems as a possible good one. The opposite with the open mesh “waffle weave” type of material just under the bands is another one that is sounding good, but I am not very familiar with that mesh. I have to look at it more.

Thanks

 

[ClayJar]

I haven’t seen that new natural finish. That may be the better option, but I haven’t seen anyone selling them yet.

They were apparently announced at DEMA. There's a PDF marketing sheet available at Luxfer's site:

"supernatural"​

 

[Luis H]

Is this the “waffle weave” that you all are talking about?

Aqua Tank Net 7.25" from LeisurePro.com


I could cut all four pieces out of one sleeve and have plenty of left over. I just wonder if it would not be too thick and make it hard to assemble.

I may go buy some at my LDS and see how it may work.

Thanks

 

[Couv]

Luis,

Try this link Products

c

 

[Luis H]

They were apparently announced at DEMA. There's a PDF marketing sheet available at Luxfer's site:

"supernatural"​

Thanks ClayJar…That does look beautiful in an ugly kind of way.
I like it.

 

[james croft]

Luis,
I have seen corrosion under SS bands on aluminum tanks. They did not have rubber underneath the bands. I have a set of US Divers military 80 aluminum doubles. They are set up with a rubber material between the bands and cylinders. I believe I saw the rubber parts for sale in a Marvel catalogue, I think.

 

[Luis H]

Well, I talked to Luxfer technical support and to their two US distributors.

Form the distributors I got the information that only the AL 80 and the AL 63 are available in the “supernatural” finish.


The Luxfer technical support recommended the painted as the first choice to isolate the aluminum from the SS bands, but totally agree the painted finish tends to get damaged quickly with use.

Form the unfinished aluminum tanks the natural finish has the best corrosion protection since it starts of with the best aluminum-oxide finish. The worst by far seems to be the shot-blasted. She said that both the surface area and the material removed contribute to poor corrosion protection.

The brushed starts up shiny, but soon enough takes a similar look as the natural finish and the protection (from the natural formation of aluminum oxide) is eventually similar.

The shot blasted will also eventually follow the same path, but more material will be and has been lost in the process. She also mentioned that the blasting process tends to imbed minute particles in the pits that also seem to contribute to corrosion.

The bottom line is that from the available bare aluminum tanks the recommendation is the brushed finish.

BTW, both Luxfer technical support and their distributors were both very helpful and very friendly.

I still have to decide how I am going to isolate the SS bands from the tanks. They confirmed that it is a most (whether you dive on fresh or salt water)…no surprises there.