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LP 72's

Discussion in 'Vintage Equipment Diving' started by SleepySlipper, Mar 31, 2020.

  1. Luis H

    Luis H Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Maine
    2,928
    1,163
    113
    Paint remover will work on one of the tanks (not the one with the vinyl). Even on that one it is going to be a mess.

    I have used that type of paint remover on aluminum tanks, but paint (even factory paint) doesn't adhere as well to aluminum.

    The paint adhesion to the galvanize surface is excellent.

    The paint remover will make the paint bubble and blister, but that mess still has to be scrapped off. And what is the point. If it just for looks... I rather be diving.

    This paint actually does protect the galvanizing coat from wear.


    The vinyl coating is a different story. I would not even try paint remover on that one. The coat is so thick that even if the paint remover does anything to it... all it is going to do is make a huge mess.

    The vinyl can be actually cut and stripped in pieces, but it is just going to be a lot of work. When cutting it you want make sure not to scratch into the galvanizing coat. Again I personally don't think it is worth the trouble and the risk of doing any harm to the galvanizing (when cutting into the vinyl). And this coating is also protecting the hot-dipped galvanizing coat. So I would not mess with it.


    Granted, the hot-dipped galvanizing on both cylinders is the best protection ever to steel cylinders, but the extra factory coating doesn't hurt it and it can protect it, so why mess with it? Again, I am into diving... not creating big projects... YMMV :wink:


    BTW, I always use a paint marker pen on the hydro stamps of all my steel cylinders. The stamping sometimes just barely cuts into the hot-dipped galvanizing. So the paint pen protects the little line of exposed steel and it highlights the hydro date.
     
  2. boat sju

    boat sju Loggerhead Turtle

    # of Dives: 200 - 499
    Location: Haslett, Michigan
    1,437
    357
    83
    Luis,
    I picked up some tanks in kind of an "estate sale". I kept a 63 cu ft and a 30. There was a lot of flaking and bubbling going on with the enamel so I wanted to see what was actually going on with the Al underneath. I was afraid the LDS wouldn't pass them vis wise. They cleaned up pretty well after I stripped them.

    Funny you mentioned that paint pen. I use a silver sharpie over the stamps to read them.

    boat
     
  3. Luis H

    Luis H Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Maine
    2,928
    1,163
    113
    Yes, as I mentioned, painted aluminum is a different story. Stripping paint out of aluminum cylinders is not that difficult (even factory paint).
     
  4. Dark Wolf

    Dark Wolf Solo Diver

    # of Dives: 200 - 499
    Location: SW Missouri
    647
    260
    63
    Perfect, thank you!!!

    DW
     
    AfterDark likes this.
  5. Dark Wolf

    Dark Wolf Solo Diver

    # of Dives: 200 - 499
    Location: SW Missouri
    647
    260
    63
    Sorry for the delay. Bought a house last month, and the 72's were part of the last load of dive gear to get home. If you want/need more detailed pics, let me know.

    DW
     

    Attached Files:

    SleepySlipper likes this.
  6. Dark Wolf

    Dark Wolf Solo Diver

    # of Dives: 200 - 499
    Location: SW Missouri
    647
    260
    63
    I am planning to soda blast these tanks. Any words of wisdom?

    DW
     
  7. SleepySlipper

    SleepySlipper Divemaster

    # of Dives: 500 - 999
    Location: MN
    109
    89
    28
    Update...I ended up purchasing the Dive Gear Express long neck manifold. Reviews seemed solid, and it is really tough to beat the price point in comparison the to Thermo Pro manifold.
     
    Dark Wolf likes this.
  8. Luis H

    Luis H Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Maine
    2,928
    1,163
    113
    Well, your situation is a bit different. Two of those cylinders are not galvanized under the factory coating.

    The good news is that in Missouri you are nowhere near salt water… I guess the bad news is also that in Missouri you are nowhere near salt water. But that only reflects my personal preference for diving and nothing to do with the cylinders. Actually my real preference is warm salt water and my favorite cylinder is a rental aluminum 80 in the Caribbean (or maybe the Philippines).

    Anyway, back to the subject.

    At home (on the coast of Maine) I only dive galvanized steel 72 and I would not touch a non-galvanized cylinder, but that is easy for me to say since I already own close to 20 of them.



    In your case you have two very distinct options. It all depends if you want a big project or a little project.

    1) A little project:

    You can leave the coating alone and only treat the spots that have been compromised. Anywhere that you see the coating blistering it means there is some rust under it.

    You can cut that area and either blast the rust off or if it is just light surface rust, treat with rust converting chemicals. These chemicals normally contain phosphoric acid and they will convert iron-oxide into iron-phosphate (which is black).

    Note: I am not a chemical engineer or a materials engineer so my limited knowledge is just basic working knowledge.

    If you can just spot blast the rust off, I would then use galvanic paint on those spots. ZRC is probably the best galvanizing paint, but honestly I have had excellent results even with the high zinc galvanizing paint sold in most hardware stores.

    The zinc will chemically bond to the steel and form a sacrificial coat that rust cannot break down, even if you do scratch the zinc paint. It may rust where the paint was scratch but rust doesn’t get under the zinc paint.

    Keep in mind that the factory coating was probably applied under ideal conditions and its adhesion to the steel is as good as any paint can get. The coating on those two dark yellow cylinders looks like the heavy vinyl type and except where is has been cut it will provide good rust protection.


    2) A relatively big project. This is what some divers with a lot more free time and a lot more energy to spare than me (perhaps not as lazy) would end up doing.

    Remove all the coating, blast the rust off, and put several coats of galvanizing paint (in this case I would definitely recommend ZRC).

    To remove the coating I would first try cutting it off and pull it in strips. You should be able to cut with a very sharp razor blade. Since these are not galvanized, you can’t scratch the galvanizing finish (you can’t really do any damage).

    That coating is normally thick enough that you can pull it almost like a banana peel (but not as easy).

    Again, the galvanizing paint is mostly zinc. The zinc will make a strong sacrificial bond with the steel. The paint can be scratched much more easily than any factory coating, but the zinc will not allow any rust to migrate under the paint. Repairing the scratches of the galvanizing paint is really easy since you only have to worry about the visible scratch.

    I would strongly recommend not applying any other paint on top of the galvanizing paint. Any other paint would just make it harder to repair the galvanizing paint if it gets scratched.



    3) I should have mentioned that there is a third option. Since you are inland with only fresh water, you can just fill the tanks with air (or whatever mixture you like) and go diving.

    In fresh water they will probably be fine for a long time. The only word of caution, learn how to do your own visual inspection and do a good inspection for any rust pits.

    I notice that you may have your own compressor (I also have my own compressor). I do my own visual inspections on a regular basis. Catching rust early (both inside and outside) and not allowing the rust to create pits is extremely important for the life of the tank.



    Sorry for the long post, but I hope it helps. Again, I am not an expert… YMMV
     
  9. SleepySlipper

    SleepySlipper Divemaster

    # of Dives: 500 - 999
    Location: MN
    109
    89
    28
    Realized that I don't have a wing for these smaller doubles. My current 65LB wing will be way to big for this setup, if anyone has any insight I am considering a 40LB wing.
     
  10. Danny D

    Danny D Solo Diver

    # of Dives: I'm a Fish!
    Location: Northeast
    264
    23
    18
    Father’s 1964 Dacor PST Viynl blue. Aircraft Stripper and a several weeks worth of work a few yrs back. Once I finished getting all the thick blue miserable penetrating horrid gunk off I had to mentally step away for about a year before I could even look at the tank again to ZRC it.

    A084B59E-EAB7-46F0-BEFA-03FC3946EAE3.jpeg E8EFADFC-78BC-41EF-A034-1E134876D088.jpeg
     

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