Plastic coated steel 72's

[Dryglove]

I just recently picked up a great set of steel 72's manufactured in 1976 and one serial number apart. They have some sort of yellow factory plastic coating over them. The tanks were stored in a garage for many years and never used. They easily passed hydro and VIP and the plastic coating has its first marks from the hydro facility removing a chunk to stamp them.

Has any one had any problems with rust on plastic coated tanks? I am debating on leaving the plastic coating on or stripping it and getting them galvanized. Does any one know of any shops in CA that will galvanize steel tanks and about how much it costs?

 

[LUBOLD8431]

Not plastic. Probably vinyl. The tanks should be stripped of the vinyl coating to see if there is any corrosion or rust underneath.

Then, you can paint them or galvanize them as long as they pass visual. Usually, if they are that old, and have had a few hydro's, there usually is some rust underneath.

They are probably not so good under neath. But, its worth checking out...

 

[C_C]

PSI--Professional Scuba Inspectors recommends removing from service vinyl coated cylinders that are NOT galvanized.

Some cylinders that are galvanized may have GALV stamped somewhere on the crown.

Otherwise, removal of the vinyl and then a cold cure coating could be applied. As long as there is not substantial corrosion and the cylinder passes a hydrostatic retest and proper visual inspection.

Good Luck,

C_C

 

[Dryglove]

The tanks were never used. They are in perfect condition. They have just received their first hydro a week ago. Other than that there is no other hydro stamps on the tanks besides the original stampings from the factory. It looks as though they were dipped in vinyl and there was absolutely no sign of rust or galvanizing where the shop removed the coating to place the hydro stamp.They passed VIP inspection with no problems.

Do you have any idea what type of paint to use in case galvanizing them is out of my budget or i cant find a shop near by to do it.

 

[Dryglove]

C_C once bubbled...
PSI--Professional Scuba Inspectors recommends removing from service vinyl coated cylinders that are NOT galvanized.

Otherwise, removal of the vinyl and then a cold cure coating could be applied. As long as there is not substantial corrosion and the cylinder passes a hydrostatic retest and proper visual inspection.

Good Luck,

C_C

I did some research on cold galvanizing and am assuming i can do this myself with self applied canned galvanize assuming the tanks are completely rust free. Should any other rust preventive coating be placed under the galvanizing or is it sufficient on its own.Thanks!!

 

[seadog]

I once had a dive shop refuse to fill a similar 72 because the plasitc (vinyl?) had been cut to stamp it. Have had it filled at many other shops without a question!

 

[DA Aquamaster]

I would be very surprised if the tanks were not galvanized given the date of manufacture. At future hydros the person doing the stamping can heat the stamps and then stamp the tank. This leaves the vinyl coating intact. It is something most inspectors seem to have forgotten about or at least don't bother to do unless you ask.

A larger problem you may encounter would be a plastic coating inside the tank that was quite common on vinyl coated tanks made in the 70's. It was one of those great ideas that did not work all that well. Eventually the coating will develop pin holes that can trap moisture and least to pits in the tank, so at some point a tank with plastic coating inside it will have to be tumbled to remove it and it will need to be tumbled for about a week as the coating is pretty persistent.

I have one non-glavanized 72 (the only one I have ever seen) and would be interested in your information on cold galvanizing. Keeping it painted and rust free is a real pain.

 

[Dryglove]

DA Aquamaster once bubbled...

A larger problem you may encounter would be a plastic coating inside the tank that was quite common on vinyl coated tanks made in the 70's. It was one of those great ideas that did not work all that well. Eventually the coating will develop pin holes that can trap moisture and least to pits in the tank, so at some point a tank with plastic coating inside it will have to be tumbled to remove it and it will need to be tumbled for about a week as the coating is pretty persistent.

Luckily these tanks dont have the plasic coating internally. I peeled back some more of the vinyl and sure enough there is no galvanize finish under the coating.

 

[ew1usnr]

The dive shop said that I had to take the vinyl off prior to hydro. They suggested paint stripper. I didn't believe that it would work on vinyl. I called a sand blasting shop. They said that the blast beads would bounce off the vinyl and suggested paint stripper instead. The dive shop knew what they were talking about. I went to the hardware store and got some stripper that said that it would remove polyurethane and marine coatings. I brushed it on, waited 20 minutes, and the vinyl scraped off in strips like wet paper!! I couldn't believe it. A few minutes after taking this photo all the vinyl was lying in a pile underneath the tank. It was a whole lot easier than I thought it would be. If the tank passes hydro I'll put primer on it and paint is "Sunflower Yellow". I was told that that was the shade of yellow used by US Divers. This is a US Divers tank with a 1968 hydro date. The tank is not galavanized. It has a type of black primer under the vinyl and inside the tank. It looks perfect inside, but if the dive shop has an issue with the inside not being bare steel then that coating can be tumbled off.
When using the stripper, peel off all stickers first. The plastic of the stickers may be impervious to the stripper. Do it outside, don't smoke a cigarette around this stuff, and wear rubber gloves.

 

[DA Aquamaster]

What was the name of the stripper you used? I usually have to work a lot harder than that with what I have been using.

I was given a Steel 72 yesterday that has a fresh hydro and VIP but is partially plastic coated. I am not looking forward to stripping another one.