What Color Tank Should I Buy?

[NitroxSam]

As you are buying an aluminium cylinder, do yourself a favor and buy a naked cylinder, no paint, no net, no boot - nothing attached.

The above always will interfere with the alloys natural passivization, leading to "rust" developing. An aluminium cylinder is always left best unpainted.

Couldn't agree more.

 

[Ez E]

Couldn't agree more.

I missed the post you quoted. I think he means steel will rust. Aluminum oxidizes but doesnt rust. I did get a boot on it for transport purposes.

 

[Tanks A Lot]

[...]I think he means steel will rust. Aluminum oxidizes but doesnt rust.[...]

While technically you are correct, it has long been a pet peeve of mine that this distinction is made at all. I had all too often customers angry at me when I had to tumble their aluminum cylinders, as "aluminum doesn't rust!!!!11!!"
The oxidization of steel, as well as aluminum, are both redox reactions, which means one element loses electrons (oxidizes) while another gains electrons (gets reduced). To keep it simple, let's stick to base elements and not alloys.

The iron (steel) side would look like this:

It all starts with two iron atoms (2Fe) giving up four of their electrons.

2Fe -> 2Fe²⁺ + 4e^-​

We now have four electrons (4e^-) at our disposal and are left with 2Fe²⁺, which are called iron cations. These four electrons in combination with water are used in the reduction of oxygen to form hydroxide ions. Reduction here means a gaining of electrons.

O₂ + 4e^- + 2H₂O -> 4OH^-​

Taking our 2Fe2+ iron cations from above and the 4OH- hydroxide, we get hydroxide irons.

Fe²⁺ + 2OH^- -> Fe(OH)₂​

These hydroxide irons now undergo dehydration and yield:

Fe(OH)₂ -> FeO + H₂O​

The FeO in the last equation is iron oxide which we commonly call rust and the water is free to do some more oxidizing as the electrolyte.

Now let us look at how aluminium would form an oxide.

It all starts with two iron atoms (2Fe) giving up four of their electrons.

2AL -> 2AL³⁺ + 6e^-​

We now have six electrons (6e^-) at our disposal and are left with 2AL³⁺, which are called iron cations. These fix electrons in combination with water are used in the reduction of oxygen to form hydroxide ions. Reduction here means a gaining of electrons.

6e^- + 6H₂O -> 3H₂ + 6OH^-​

Taking our 2AL³⁺ iron cations from above and the 6OH- hydroxide, we get

2AL³⁺ + 6OH^- -> 2AL(OH)₃​

The aluminium hydroxide now undergoes dehydration and yields:

2AL(OH)₃ -> AL₂O₃ + 3H₂O​

The AL₂O₃ in the last equation is aluminium oxide, which we inexplicably do not call rust, and the water is free to do some more oxidizing as the electrolyte

The above formulas are very idealistic, leaving aside other oxides forming and assuming pure elements. Both are incorrect for real-world usage.
Looking at the formulas, it is clear that the oxidizing of iron is not special or different from the oxidizing of aluminum, yet one has a special name - rust. Again, you are absolutely correct in saying that aluminum doesn't rust, but from an objective point of view, both reactions are the same. It is a construct of language that makes the two appear different, when really they are not. I wish we would stop making this distinction, as it has brought much confusion in my experience.

I'm well aware of the passivation layer that aluminum oxide can provide in specific scenarios, while iron always forms a flaky layer.

 

[Ez E]

Yeah I agree with that. Just thought it may have been a typo to say “rust” as modern english associates that word with “reddish brown” or oxidation on steel or iron.

Now back to the point of them being the same reaction. If we pull out Noah Websters 1828 Dictionary(which is always my go to for learning the true pure definition of a word) we find the definition of Rust:

1. The oxyd of a metal; a substance composed of oxygen combined with a metal, and forming a rough coat on its surface. All metals except gold are liable to rust

I pulled that from the online version as I am not able to grab my physical version right now. But it seems that as language has progressed the definition of rust has changed to mean iron based materials when it originally encompassed all metals that oxidize.

Sorry for the long probably meaningless post. Basically we both are correct using the word Rust both ways.

 

[Rose Robinson]

Its seems the more natural finish is preferred. Didnt know they offered a shot blasted finish so I will look into that.

There is also what's referred to a ''raw finished'' ,neither brushed or shot blasted.

It's how the cylinder comes right out of the extruder.

I'd suggest staying away from any color as colors tend to be faddy, in one year, out the next, not to mention, the heavy clear coat traps moisture/salt when it starts to deteriorate.

Regards,

Rose

 

[divingdayz]

Pink with purple/teal swirl with glitter and rhinestones.

Ha, ha, I'm not sure rhinestones would last long on a dive boat.

 

[tursiops]

I'd suggest staying away from any color as colors tend to be faddy, in one year, out the next

Except yellow....which has been popular for decades. And is very visible underwater.

 

[Belzelbub]

This thread got me to tackle something I've been thinking about for a while. Most of my tanks are steel galvanized, but I still have a couple AL80s that are painted.

Tank on the left is a Catalina cylinder. The other is a Luxfer. As you can see, the Catalina paint is in rough shape. Luxfer is better, but still has some nicks.

Anyway, I checked the recommendations here:

Paint Removal from Aluminum Cylinders - High Pressure Aluminum Gas Cylinders | Composite Cylinders

A Paint Removal from Aluminum Cylinders Category: All Markets Catalina Cylinders recommends that paint be removed from aluminum cylinders by the use of gel-type (non-caustic) paint strippers instead of sanding, abrasive blasting, or any methods of exposure to heat. Removal of paint from a...

www.catalinacylinders.com

Headed to Home Depot and picked up some Citristrip Gel paint stripper. Followed the instructions and did a small test at the bottom to see how it would work. The results on the two cylinders were vastly different. Instructions call for waiting at least 30 minutes. Catalina cylinder showed significant bubbling after about 15 minutes. Luxfer did not. Even waited up to an hour and still no real bubbling. Got a small patch to come off, but clearly this was going to take more work.

I waited the full 30 minutes then grabbed a plastic scraper to see what would come off. Catalina paint came off easily. Not so much with the Luxfer. Whatever paint Luxfer used, it's a heck of a lot tougher than Catalina's. Did the whole Catalina cylinder with no issue. 98% or more easily came off on the first pass. Just a few stubborn spots that came up with spot application.

Turns out, Luxfer has two different recommendations.

Paint strippers for aluminum cylinders - Luxfer Gas Cylinders

CAUTION To remove paint from aluminum cylinders, NEVER use caustic paint strippers or acid paint strippers, burning techniques, or solvents that harm the environment or pose personal health or safety concerns. Any chemical used to remove paint from, or to paint a cylinder, should specifically...

www.luxfercylinders.com

Paint removal and repainting of Luxfer all-metal and composite cylinders made from 6061 aluminum alloy (L6X®) - Luxfer Gas Cylinders

Preparation All-metal Luxfer 6061 aluminum alloy (L6X®) cylinders1—To remove paint from an all-metal cylinder and prepare the surface for repainting, blast with plastic, glass or other soft media just long enough to remove most of the old paint. Do not blast with sand, steel, grit or aluminum...

www.luxfercylinders.com

Not sure why, but it looks like plastic media may be the best for that one.

 

[Biz2000]

High-vis orange or yellow for sure, tried and true.

 

[Ez E]

Kinda want to buy another one. DGX is sold out