O2 Clean a Steel Tank

[chrpai]

Question for those more knowledgeable in these things then me....

Let's say you get a steel tank hydro'd and then go to get it tumbled, O2 cleaned and VIP'd. Is there any valid scenario where the dive shop could come back and say it wasn't possible to get it clean enough for nitrox service but could get it clean enough for air service?

Someone recently described this scenario to me and I'll revise the description if additional details dispute any of this.

 

[Jim Lapenta]

Had it happen with an old 72 that had an epoxy liner that was flaked. Ended up trading it to the shop for another one that had no liner. I can't think of any other reason off hand if the people doing the cleaning know their stuff.

 

[Dsix36]

NO!

If it was tumbled, then all signs of rust and corrosion were removed (unless of course they did not do it long enough and that is their fault).
O2 cleaning after tumbling is pretty much just a simple chemical process that removes any traces of hydro carbons.

Even on an aluminum tank that is porous, I would have trouble believing this unless you intentionally kept motor oil in it.

 

[chrpai]

I'm 95% certain it's an HP100.

 

[Wookie]

Not only no, but the process of tumbling and hydro often involves the use of O2 cleaning chemicals as a rust inhibitor. I use blue-gold when I tumble tanks, my hydro facility uses another rust inhibitor that is also an O2 cleaning solution. Someone is having you off.

 

[chrpai]

I figured that much and it wouldn't be the first time someone tried. I just wanted to try to have an open mind on some scenario I might not be aware of.

 

[Gilldiver]

I would also add that tumbling is an on condition operation, not a requirement for O2 cleaning. In other words tumbling is only required when there is a lot of rust and rarely required on an aluminum tank.

 

[chrpai]

Yes, I understand that tumbling is for corrosion and that O2 cleaning is about hydrocarbons. I just wanted to ask with an open mind.

Leaving open the possibility for miscommunication I have another question that I want to ask but I'm afraid to do so because people might reply to different parts of this thread and it could become clear as mud.

 

[Wookie]

To go a little farther with tumbling aluminum tanks. It is so rarely required as to be innappropriate. When a billet of aluminum is punched to make a cylinder, the mold release agent leaves behind a glaze on the inside of the cylinder. If that glaze is ever broken by mechanical means like tumbling or whipping, the inside of the cylinder will corrode in that spot faster than in the glazed area. Aluminum corrodes by pitting, not by overall corrosion like rust, therefore any damage to the inside of the cylinder must be watched very carefully. I just condemn anything that is even questionable.

 

[Wolfie]

It kinda sounds like the shop didn't want to put the extra time it would take to get it up to their o2 standards. Which could be higher than industry. But than again I am not as knowledgable than you. I'm just sayin.