rust in the inside of tanks

[dwndeep]

i stopped by a dive shop today and they had 2 new tanks i believe a 6/2004 hydro on them i opened the valve and saw rust. should they discount these tanks and if so how much? they are pst e7-120 they are asking 350 for them and i want 2. these are pretty tough to come by and most dealers arent expecting any until at least may maybe later so i am looking to find some asap. is this a wise investement and will a o2 cleaning solve the rust issue

 

[MyDiveLog]

To ge the rust out they'll have to be tumbled with an abrasive inside. If the $350 is acceptable, why not make the price contingent on a successful cleaning & VIP?

 

[dwndeep]

To ge the rust out they'll have to be tumbled with an abrasive inside. If the $350 is acceptable, why not make the price contingent on a successful cleaning & VIP?

whats tumbling run? the only problem is that the place selling them doesnt do nitrox fills i just really want to get the tanks then take them to the shop i use and get them 02 cleaned and filled.

 

[Dive4Life]

whats tumbling run? the only problem is that the place selling them doesnt do nitrox fills i just really want to get the tanks then take them to the shop i use and get them 02 cleaned and filled.

As a tank inspector I have to reject any tank that I come across that has any type of residue in them until after they have been tumbled/whipped clean. After the residue is gone then I can successfully VIP the tank. The rust prevents me from seeing any possible problems and therefore makes them unsafe to fill. I would not buy any new tank that has rust. It really doesn't matter if they use NITROX or not. The rust occurs when you expose steel to an oxidizing agent such as normal air.
The very first part of O2 cleaning a tank is making sure that the tank is safe to use (VIP), so that means getting it tumbled/cleaned anyways. Tumbling prices vary with different facilities. According to the agency that I got certified through you have to get a tank hydro tested after you tumble it. The rationale being that you have removed some of the metal from the side wall therefore you may have compromised the integrity of the metal/tank. I know it sounds a little redundant, especially when you are talking about new PST tanks. If I were you I would make sure that the tank was perfectly cleaned before I purchased them.

 

[ChrisA]

i stopped by a dive shop today and they had 2 new tanks i believe a 6/2004 hydro on them i opened the valve and saw rust. should they discount these tanks and if so how much? they are pst e7-120 they are asking 350 for them and i want 2. these are pretty tough to come by and most dealers arent expecting any until at least may maybe later so i am looking to find some asap. is this a wise investement and will a o2 cleaning solve the rust issue

First off I'm surprized that you could take the valve off. The tank _should_ have a few hundred PSI or air inside. The dry breathing air prevents rust and keeps water out of the tank. Some rust as normal. Even if you clean the tank rust will form very quickly. on the bare steel. This is just "flash" or surface rust and all tanks have it.

Rust is a problem if it forms scale or pits the surface or if when you invert the tank over a clean white surface then whack the tank with a rubber mallet if any rust specks shows on the white surface. Then it needs to be tumbled and re-hydro'd. Shops here charge about $40 for the tumble and hydro again "flash" rust is acceptable.

The tanks should not have been stored without pressure in them

 

[dwndeep]

First off I'm surprized that you could take the valve off. The tanks should not have been stored without pressure in them

they have been sitting there since july with the valve screwed down hand tight. its the divers direct in orlando and they dont even do nitrox fills. so i doubt they do tumbling either. its funny that a shop that is pretty big and is part of world watersports doesnt do nitrox fills. im going to call them today and see what they will do about tumbling if they dont want to work with me then i know where i can pick up a brand new one filled for only 15more so im definately going to get that and probably a e7 100 then hold out until my store gets more 120s in may.

 

[Dryglove]

First off I'm surprized that you could take the valve off. The tank _should_ have a few hundred PSI or air inside.

I have been to a few shops that have steel tanks sitting on the floor with no valves or caps or the valve just barely hand tight. Never could understand that.