Cleaning Rust from a steal tank.

[runsongas]

you have several options, depending on your intended usage and current tank condition:

1. if it is only light surface rusting, whipping the tank may be enough to get them suitable for non-o2 clean service (eg no pp blending). most dive shops can do this service relatively cheaply and quickly, or you can build your own tank whip and use it with a hand drill.

2. if it is more extensive, you can either have them tumbled or call around the cylinder retesters in your area if they can offer you shot blasting. shot blasting is usually cheaper than getting tanks tumbled at a dive shop (much less labor intensive)

the downside to either tumbling and shot blasting is that a hydro requalification is technically required again to make sure there has not been substantial removal of rust causing wall thinning that may post a structural weakening of the tank.

bottom line is you need to find a new dive shop. there should be no reason a tank comes back from hydro rusted up. if you paid for the hydro through the dive shop, it is their responsibility that it should be coming back to you clean and ready to use. they dropped the ball somewhere between when they were hydroed and when you picked them up, it should be up to them to make it right.

 

[JahJahwarrior]

The tanks have to be tumbled, then evaluated to see the pit depth. It is possible to have internal rust condemn a tank, but it is not possible to tell that offhand. If the shop said "The rust pitting was measured and the depth is X", and that exceeds the allowable amount of Y"", then oh well. But this shop is just saying "they are rusty, trash them," which sounds like they didn't measure properly.

After they are tumbled, they will be rinsed with a rust prevention wash, then dried. O2 cleaning is only necessary if you do partial pressure fills or use these for deco bottles. I don't shop at partial pressure shops, it's bad for the environment.

It is possible for your tanks to have water inside and not your buddies, if your do bath fills and got water in the valve--the moisture doesn't just come from the compressor itself. But most likely is that they flash rusted after hydro. The pitting depth will tell you. If they flash rusted, it's a quick tumble without pitting. If they got water in them in the last year and have been rusting the whole time, the tumble will take longer and there might be pitting.

 

[lowviz]

No, with a reference to a sabot

Sorry, I was confused by what I think sabot means:

"A sabot is a structural device used in firearm or cannon ammunition to keep a sub-caliber flight projectile, such as a relatively small bullet or arrow-type projectile, in the center of the barrel when fired, if the bullet has a significantly smaller diameter than the bore diameter of the weapon used. Wikipedia"

 

[lowviz]

...//... bottom line is you need to find a new dive shop. ...//...

Agree.

I agree even if they weren't responsible for the rust.

 

[Texasguy]

Sorry, I was confused by what I think sabot means:

"A sabot is a structural device used in firearm or cannon ammunition to keep a sub-caliber flight projectile, such as a relatively small bullet or arrow-type projectile, in the center of the barrel when fired, if the bullet has a significantly smaller diameter than the bore diameter of the weapon used. Wikipedia"

Yes, a sabot is a tank killer, penetrates armor on a direct hit due to its projectile, kills tanks just as a rust on scuba tank's threads. I was making a literary rhetorical technique called metaphor comparing the two. The sentence about the dust settling was another literary device called imagery. Explaining all this is so pedestrian.

 

[lowviz]

Explaining all this is so pedestrian.

OK, I give.

I was just interested in learning something more about threads (as my VIP Inspector and Cylinder O2 Service Technician certs are both still valid).

 

[Texasguy]

OK, I give.

I was just interested in learning something more about threads (as my VIP Inspector and Cylinder O2 Service Technician certs are both still valid).

Well, threads are the thinnest pieces on the tank. If rust starts to form, it can easier than anywhere else destroy a scuba tank. With "chewed" threads, the air might bubble out from under the valve. While occasional rust is ok on scuba tank and it can be cleaned, the threads are the most sensitive, a loss of metal on threads can make otherwise a structurally good tank a pile of garbage. And because threads are thin, it can happen very quickly.

 

[lowviz]

I hear your words.

What specs are you quoting for pass vs. fail with respect to threads?

 

[Texasguy]

I hear your words.

What specs are you quoting for pass vs. fail with respect to threads?

Specs are binary. Either the thread can hold the valve well or it can't. If it can't hold the valve at pressure, you'll see leaks of all kinds of severity. Place the tank under water, does it bubble from under o-ring?

 

[lowviz]

Specs are binary. Either the thread can hold the valve well or it can't. If it can't hold the valve at pressure, you'll see leaks of all kinds of severity. Place the tank under water, does it bubble from under o-ring?

This is dangerous nonsense. Do you happen to work for the OP's LDS?

You are on ignore. Sorry, it takes a lot, but you qualify.