Refinishing LP72s?

[KD8NPB]

I picked up two LP72s yesterday. They're quite nice. They are topped with a Sherwood J-valve non-isolating yoke manifold. The last hydro was 05/11, as well as the VIP.

Since the VIP is coming up next month, I would like to refinish them. They are both yellow, but they are two different shades. One is also a tiny bit thicker than the other. The explanation for this is simple : One has traditional paint on it, the other has probably 1/32 to 1/16" of epoxy coating on it. I would like to completely strip down these tanks, as there are a few scrapes / scratches on them where I can see some surface rust. I have extensive experience with automotive restoration, so none of this is new to me.

My plan was:
Drain the tanks, remove the valves and tank boots
Stick a rubber cork into the valve port
Strip the surface with a nylon abrasive wheel
Hand sand with 400 grit to remove chatter marks
Rinse, wipe down with acetone
2-3 coats of sprayed etching primer to prevent rust
Final inspection to ensure the entire surface has been etched
Final coating, 2-3 coats of Rustoleum yellow oil-based, thinned with acetone and sprayed with HVLP
Ebay myself some "AQUALUNG U.S. DIVERS" stickers to slap on
Take them to get VIP'ed

Anything sound wrong with my technique? I'm basically looking to replicate this guy's look in yellow :

 

[elan]

Use tumbling plugs with o-rings to close the holes

 

[Gilldiver]

Those are my tanks - I just stripped with zip strip and scrubbed them down with red scotchbrite. If the tanks are galvanized don't get too aggressive with a wire wheel or sanding. The etch primer should give you a good bite onto the zinc and then use a high quality urethane paint - don't use anything from Home Depot - get it from an auto or aircraft finish supply house.

If you have the photo you know I used aircraft primer and paint, not something easy to get outside of the industry.

As for masking, the best mask is an old valve or a "red cap" plug. Ask your LDS for some old scrap valves.

 

[KD8NPB]

Those are my tanks - I just stripped with zip strip and scrubbed them down with red scotchbrite. If the tanks are galvanized don't get too aggressive with a wire wheel or sanding. The etch primer should give you a good bite onto the zinc and then use a high quality urethane paint - don't use anything from Home Depot - get it from an auto or aircraft finish supply house.

If you have the photo you know I used aircraft primer and paint, not something easy to get outside of the industry.

As for masking, the best mask is an old valve or a "red cap" plug. Ask your LDS for some old scrap valves.

Well, I chose the Rustoleum oil-based paint because of my research into "The $50 Paint Job" for cars. It's more chemical and abrasive resistant than traditional polyurethane, acrylic enamel, or lacquer paints. Testing revealed that it's even resistant to brake fluid, which is practically chemical paint stripper! Plus, since it's oil-based, it naturally is rust's worst enemy. It's cheap too!

Any galvanization is long gone. The first hydro on these was 02/60, and as said, there are some scratches that reveal surface rust.

Without further wait:

Valve is Sherwood I do believe? The spacing was correct for Sherwood. The chrome is absolutely perfectly, and the J-valve works perfectly. I took it out today and burned it down to 800 psi. It was interesting to dive without a BC. I took some weight off my weight belt, and must have guessed perfectly. A full breath would cause a mild ascent and a full exhale would cause a mild descent. The trim was absolutely excellent. It's not going to stay in this configuration for long though, I'm going to order some 6.9" straps before the month is out.

The guy I bought it from was also nice enough to throw in some other vintage stuff with the tank:

The US Divers "thermal-foam" wetsuit is a two-piece beavertail, and VERY thick...It fits, but there are gaps everywhere. It's very stiff to move around in. The shorty fits perfectly. I'm guessing he wore the shorty under the beavertail suit. There was also 3 Aqualung rocket fins at the bottom of the bag. Sadly, only one has a strap and one is missing the cinching metal piece. They also don't fit with my Bare Elastek 7mm boots either...not wide enough.

 

[Gilldiver]

Well, I chose the Rustoleum oil-based paint because of my research into "The $50 Paint Job" for cars. It's more chemical and abrasive resistant than traditional polyurethane, acrylic enamel, or lacquer paints. Testing revealed that it's even resistant to brake fluid, which is practically chemical paint stripper! Plus, since it's oil-based, it naturally is rust's worst enemy. It's cheap too!

Any galvanization is long gone. The first hydro on these was 02/60, and as said, there are some scratches that reveal surface rust.

Without further wait:

Valve is Sherwood I do believe? The spacing was correct for Sherwood. The chrome is absolutely perfectly, and the J-valve works perfectly. I took it out today and burned it down to 800 psi. It was interesting to dive without a BC. I took some weight off my weight belt, and must have guessed perfectly. A full breath would cause a mild ascent and a full exhale would cause a mild descent. The trim was absolutely excellent. It's not going to stay in this configuration for long though, I'm going to order some 6.9" straps before the month is out.

The guy I bought it from was also nice enough to throw in some other vintage stuff with the tank:

The US Divers "thermal-foam" wetsuit is a two-piece beavertail, and VERY thick...It fits, but there are gaps everywhere. It's very stiff to move around in. The shorty fits perfectly. I'm guessing he wore the shorty under the beavertail suit. There was also 3 Aqualung rocket fins at the bottom of the bag. Sadly, only one has a strap and one is missing the cinching metal piece. They also don't fit with my Bare Elastek 7mm boots either...not wide enough.

Nope, the galvanizing is still there as those tanks look to have the original paint on them. Some rust showing through a good scratch or where they have been hydro stamped is common. At most you will need to touch up the scratches with a zinc rich primer, then the etch primer, and the top coat. By the way, just because you use a oil based or solvent based paint it has nothing to do with its resistance to corrosion or its quality. The Navy primer I used was MIL-PRF-85582 which is a water based primer and found on all Navy aluminum aircraft. The solvent based version is per MIL-PRF-23377 and test in the labs and long term in the real world on the deck of ships and aircraft carriers show no performance differences between the two specifications. The top coat I used was per MIL-DTL-85285 and is available in yellows per Federal color standard 595. A bright yellow like I think you are looking for is color number 13591 or 13655.

If you decide to use one of these Mil Spec paints expect to pay around $60 a quart. Contact Deft Coatings or PPG to find a dealer near you. FYI, the two primers I listed are chromated 2 part epoxy primer and they may not sell them to you, but they might sell a quart of the MIL-PRF-23377 Class N non-chromated primer. I can only recommend the Deft material and it has a bright aqua color to it for easy telling that it is non-chrome vs. the various greens that the chromated primers are. This is a requirement from the DOD for EH&S controls. What this means is that you will need several coats of yellow to get a good depth of color. As for the top coats, the 85285 is also a two part material and has to pass Skydrol resistance testing. Skydrol makes car hydraulic oil look easy, these paints also havee to passes test for discoloration vs, turbine oils, jet fuel, and all the other fluids found in jet aircraft, and then have to pass test for supersonic aircraft flying through rain and snow,,,,,,,,

Here is some of the abuse that the Sikorsky Sea Hawk gets to see - this is called the full immersion corrosion test - on a 24 million dollar aircraft....
http://www.youtube.com/watch?v=zhBBbxY72Xc


Last, if the tanks are from Feb 1960, they are part of the first batch of SCUBA tanks made with the 3/4" O-ring sealed thread.

 

[KD8NPB]

Nope, the galvanizing is still there as those tanks look to have the original paint on them. Some rust showing through a good scratch or where they have been hydro stamped is common. At most you will need to touch up the scratches with a zinc rich primer, then the etch primer, and the top coat. By the way, just because you use a oil based or solvent based paint it has nothing to do with its resistance to corrosion or its quality. The Navy primer I used was MIL-PRF-85582 which is a water based primer and found on all Navy aluminum aircraft. The solvent based version is per MIL-PRF-23377 and test in the labs and long term in the real world on the deck of ships and aircraft carriers show no performance differences between the two specifications. The top coat I used was per MIL-DTL-85285 and is available in yellows per Federal color standard 595. A bright yellow like I think you are looking for is color number 13591 or 13655.

If you decide to use one of these Mil Spec paints expect to pay around $60 a quart. Contact Deft Coatings or PPG to find a dealer near you. FYI, the two primers I listed are chromated 2 part epoxy primer and they may not sell them to you, but they might sell a quart of the MIL-PRF-23377 Class N non-chromated primer. I can only recommend the Deft material and it has a bright aqua color to it for easy telling that it is non-chrome vs. the various greens that the chromated primers are. This is a requirement from the DOD for EH&S controls. What this means is that you will need several coats of yellow to get a good depth of color. As for the top coats, the 85285 is also a two part material and has to pass Skydrol resistance testing. Skydrol makes car hydraulic oil look easy, these paints also havee to passes test for discoloration vs, turbine oils, jet fuel, and all the other fluids found in jet aircraft, and then have to pass test for supersonic aircraft flying through rain and snow,,,,,,,,

Here is some of the abuse that the Sikorsky Sea Hawk gets to see - this is called the full immersion corrosion test - on a 24 million dollar aircraft....
CV63 aircraft carrier in storm - YouTube


Last, if the tanks are from Feb 1960, they are part of the first batch of SCUBA tanks made with the 3/4" O-ring sealed thread.

The 3/4 NPS tank thread was a requirement for my search.

Unfortunately, being as broke of a college student as I am, I cannot afford to go all out with the paint!

I'm pretty stuck on Rustoleum Professional as the paint of choice. I'll probably follow the old tractor rebuilder trick and add an ounce or so of hardener.

That's where I'm at right now. I'm still picking at the one tank, trying to scrape off what's left of the yellow paint. I'm sanding off whatever surface rust I find as well. I'm going to pick up 2 cans of etching primer tomorrow... I figure I'll lay about 3 coats of that on. If I get 10 years out of this paint, I'll be a happy man. Plus, it'll be easy to touch up as well.

One little annoyance though : They're two different diameters. One is 6.84", the other is 6.92".

 

[Gilldiver]

The diameters are nominal 6.9" - tolarances back then were a bit loose.

 

[PfcAJ]

Try ZCR Gavalite. I refinished an old 72 a few years ago rather hastily and that stuff has held up well.

 

[Gilldiver]

By the way, the C with the L in it means that the tanks were originally tested by Cochran Labs, and they were made by Pressed Steel Corp. Somewhere there should be a PST emblem.

 

[Dr Dog]

Pretty cool thread. I can see a how to for custom tank paint jobs coming soon