Painted tanks: touch-up & painting

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seascaper

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Messages
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Location
Montego Bay, Jamaica
# of dives
I just don't log dives
Wise Aquatists,
I bought a dozen Al80s last year in white- the colour was a weak choice at the time, but I'm lovin' them: they don't heat up in the full sunshine of my little boat (like, at all) and they're super-visible both underwater and at the fill-shop. They're becoming a bit iconic to my little crew & brand, which is also nice.

And the paint isn't terribly durable -which we all know. At a little over 12months they're flaking around the bottom and corrosion sneaking under any scratches. We jump in the water and there's a snow.

The PADI standard is "never paint" but I bought 'em painted, I take care of them and I don't expect to sell them, not if there seems to be a secondary guideline condemning tanks @15~20yrs.

So, options? A light Scotchbright with vinegar & a spritz of white primer "rustolium" spray paint?
White Berger 404 with/without hardener?
Pigmented epoxy? Around the bottom inch?

What about turning a 5yr old chipped-to-hell factory-painted red to white?
What about 6yr old unpainted silvers?

I'm sure this has been asked a dozen times, but I'm not finding a "search" button...

Thanks,
Andrew
 
8 months ago I stripped the paint on a half dozen AL80s that I got for a song and a dance. Was pretty sure that I wouldn't be happy with how they would look after a couple of years of use if I had them repainted so I looked into powdercoating them.
The powdercoating needs the tanks to be heated to 180°C minimum for the powder to melt and stick to whatever is being powdercoated. Many powdercoating shops don't have great control of the baking temperature and temperatures of 200°C are not uncommon.

Now here is the rub:
AL80 tanks are made using 6061 T6 Aluminum where T6 is the type of heattreating.
6061 T6 can be brought up to 180°C and held at that temperature for 12 hours with no measurable difference in the heattreating, but if brought up to 200°C for 15 minutes the T6 heattreating no longer meets spec and the 6061 alloy is now ruined.

Since I have great trust in my local powdercoating shop, I explained the requirements to them, and had the 6 tanks powdercoated white. I then prooftested the tanks myself and after waiting 6 weeks for the powdercoating to harden to it's final state, have been using them ever since. I'm happier than a pig in **** and the tanks will contine to look like new for a long time.

If you can find a really good powdercoating operation that you trust, I'd recommend powdercoating. If the shopowner doesn't understand or can't meet the low temp requirements or doesn't inspire confidence - Stop, Take 3 Steps back, and do not advance for another round. An AL80 with screwed up heattreating will kill you!

Michael
 
Michael is a brave man.

I shot blast all of my painted cylinders with walnut shell. I leave them that way for ease of maintenance, but if I didn’t, they are then perfect to hold a paint job. Self etching primer from the body shop paint store (the ugly green stuff) and imron would be my go to. Or whatever DuPont has replaced imron with. I put it on all of my main engines after rebuilding and the paint held up very well.

My powder coat shop can’t get anything right. They are morons.
 
Thanks Michael and agreed.
I'll call around, but I doubt I'll have access to (trusted) powder-coating; any treatment and/or painting will likely happen in-shop. So far I'm mostly looking for touch-up options to prolong/preserve/protect the current paint. ...plus these three 'stragglers' :)
 
I'm sure this has been asked a dozen times, but I'm not finding a "search" button...

There is a search, but the results are too erratic for me. I find a thread easier and faster by using google with Scubaboard at one end or the other.



Bob
 
There is a search, but the results are too erratic for me. I find a thread easier and faster by using google with Scubaboard at one end or the other.



Bob

Same here, I have to use Google to search SB as well.
 
You don't say what brand(s) of cylinders you acquired, but Luxfer does have specific guidance on their website regarding refinishing of their cylinders. Regarding any heat curing, they even say to contact them directly for specific limits on specific alloys.
Paint removal and repainting of Luxfer all-metal and composite cylinders made from 6061 aluminum alloy (L6X®)

One word of warning - PSI-PCI training (can't speak for other VIP training) emphasizes that inspectors be extremely cautious when handling repainted cylinders. If you are having them filled or inspected by an alert, informed operator, be aware that you may have to work overtime to convince them that the cylinders have been repainted without incurring any heat damage. There is no way to tell just by looking, and if a cylinder fails due to heat damage it is almost for sure going to happen at the fill station, not while you are diving it. So any danger probably affects someone other than you, and they should be rightfully cautious.

(Do you REALLY need to get your aluminum tanks repainted that badly?)
 
Thanks Jack.
14 are Catalinas and one's a Luxfer; thanks for the link & I'll check the Cat supplier (Genesis).

I don't really need them painted, but the white has proven very useful & flaking is a shame, and I'm not intending to use anything that needs heat-treatment- just Rustolium spray in touch-ups or maybe an enamel. Wookie's self-etching primer scares me a bit, but just a bit; I'd be surprised if regular oxydation did't take off more material.

My tank-fill-guys I've known for eons -I wrote the grant that bought their compressor- and the on-island hydro-test station is unlikely to ask. They used to send tested&stamped tanks back to us still with dead lizards in the bottom... I wasn't asking either.

Edit added, from Luxfer link (thanks again): "Do not use acidic or caustic paints that may damage the cylinder exterior. You may use any neutral, air-drying or aliphatic, water-based or solvent-based liquid paint that is compatible with aluminum. You may also use neutral, aluminum-compatible powder coatings as long as curing temperatures and exposure times do not exceed those recommended by Luxfer."
 

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