Cleaning rust from inside an Old Steel 72

[JamesBon92007]

Hi guys,

i finally made it back here! Had a few computer/internet problems....

I just aquired three more steel 72s all from the 60s. Two had no air in them and all are several years out of hydro. They all look very good inside except for a fine dusting of rust.

Aside from tumbleing, what other methods can be used to remove the rust? I read something here a while back about using a "whip" but they seem to cost $50 on up. Are there any other methods that won't hurt the tank? I use liquid chlorine and warm water to clean my old Aladdin thermos and it sparkles like new but I hesitate to use that on a scuba tank. I don't mind spending some money but hey, the guy has three more tanks and if I can find a direct hydro tester and cleaning isn't too much I may as well get them too.

One of them is a Sportsways orange tank with a 1/2" J-Valve

Two are Scubapro black plastic coated tanks that match nicely and I got the doubles bands to put them on a back pack The guy I bought them from is looking for the manifold that connects to the two K-Valves. I cleaned all the valves and only one leaks now and it's one with a built-in gauge that basically tells you if the tanks if full or empty. I think the gauges are the reason the two tanks were empty

Also, the plastic coating on the two Scubapros is nicked and lifting a bit and it appears that they are galvanized underneath. Anyone have a good trick for removing the plastic coating? Or should I leave it alone?

I love the looks of the Sportways tank. It's all beat up looking but the J-Valve is nice and shiny now. I stuck my oldest USDivers backpack with the cloth straps on it and it looks great.

 

[Eric Sedletzky]

You can make a whip out of a 3/8" steel rod and some 1/8" thin cable pieces. Drill holes through the rod on one end and feed the cable pieces through. I took some thick wire and crimped loopes on each side of the cable pieces so they would stay in place.
The cable pieces need to be just a little longer than the inside diameter of the tank but not too long or else they won't scrub.
I use a 3/4" to 1/2" reducer threaded into the tank so that the rod won't destroy the tank threads.
For the bottom brush I use a small end brush welded onto 3/8" rod. Those can be found in the McMaster Carr or MSC catalogs.

 

[JamesBon92007]

Thanks ZKY, that sounds very doable. The brush on the end of the shaft might be tricky though.

Do the cables unravel as they spin around doing their job?

 

[Texfrazer]

JamesBon92007,

See this thread for a great amount of info on making your own whip! They even have some pictures so you can see what is being discussed. These work great!

All the best!

 

[Eric Sedletzky]

Thanks ZKY, that sounds very doable. The brush on the end of the shaft might be tricky though.

Do the cables unravel as they spin around doing their job?

Yeah they unravel but that's what you want.
I drill about 10 or 12 holes at all different locations so it looks like a giant bottle brush. It can be a bit tricky shoving the brush down into the tank but just work it, it will go.
The bottom brush requires finding a small button end brush no bigger than about 5/8" diameter. I took a larger one and ground down the sides then welded a shaft onto the end.
This brush cleans up the bottom great.

 

[JamesBon92007]

I had imagined making something with the same configuration as duckbill's whip pictured in the thread that Texfrazer linked us too. Thanks Tex. I was thinking it might clean the bottom of the tank too so the additional small brush might not be necessary. Chemicals were also mentioned in the thread/link and that makes me wonder again about using liquid chlorine. When I clean my old steel thermos that has rust spots and stains it comes out looking brand new. Assuming I rinse very thoroughly and dry completely, and let it air out for a while, is there any danger of using chlorine? Anyone? I could simply pour some in and roll it around for a while, then stand it up for a while.

Knowing how you feel about shiny things ZKY I'm guessing your whip design was more successful than duckbill's. And yes, I imagined that the unraveled cables would be what we want. My valves cleaned up really nicely. You would like them.

In the past I used a string of clear Christmas lights to view inside the tanks. Lucky for me they are available right now Anyone else have any cheap, easy light ideas that they like?

I finally got a phone number so I can supposedly get hydro tesing done without the middle man. It's a place that services fire extinguishers. It turns out that it's the same guys who did my fire extinguishers last week where I work! Small world. As soon as I get the insides ready I'll call them.

 

[captain]

Take it to the hydro guy, let him give you an opinion on if it really needs cleaning. A fine layer of flash rust is no reason to clean them, they will probably come back from the hydro tester looking the same even if you clean them.
The only real chemical cleaning possible is with phosphoric acid. You can get a product called Ospo at marine supply stores. You would need to fill the tank with it, let it sit a couple of hours and drain it, immediately rinse with hot water and blow dry.

 

[Eric Sedletzky]

The other chemical you can use is called rust mort. It's also a phosphoric acid that eats rust away but leaves clean steel unharmed.
It's available at auto body supply stores and it's made by Sem. It probably the strongest concentrate out there and needs to be diluted to be used in the manner you describe.
If you use that stuff make sure you rinse out the tank really well afterward by hanging the tank upside down and sticking a garden hose up in the tank and rinsing for about 5 minutes with the hose blasting water on all surfaces inside the tank.
Then as soon as you stop rinsing and let the remaining water drain out follow Captain's recommendations on drying.

 

[Griffo]

Whatever you do, not NOT let chlorine near the tank as you mentioned in your post. Chlorine pits steel, and can cause pinholes that are not visible to the human eye. Even stainless is susceptible to chlorine.

 

[james croft]

Xmas lights will work but they can pose a shock hazard. Most lights used for visual inspection run off of DC low voltage current. I have used Xmas lights before but be very careful with them. My current inspection wands are all 12 volt DC.

They are made up of a series of small lightbulbs with the terminal soldered to two pieces of piano wire. Then it is encased in a clear plastic tube. It is wired to a 12 VDC/ 110 AC adapter. I have a long one for inspecting large tanks and a shorter version for checking pony bottles.