How much rust after hydro is acceptable?

[AbyssalPlains]

Had a couple of LP95s (Faber) hydroed yesterday. Visual inspection beforehand showed beautiful, clean tank interior. Came back from hydro looking like ****. I expected them to look just as pristine as before so I almost wanted to cry.

These are my first steel tanks so my initial shock was alleviated a bit by reading about flash rust and how it's not avoidable BUT how much rust is acceptable?

One tank looks not too bad, just kind of "dirty" inside. The other has reddish walls and a streak of dark brown rust that looks as if water was swirled around, leaving a streak of rust behind when the tank was moved around.

I know that some rust apparently can't be avoided but how do I know how much is too much? Unfortunately, I live in AZ where most people (inkl. me) and dive shops simply lack knowledge about and experience with steel tanks. 99.9% of tanks around here are AL80s.

Here is a taste: When I dropped my Fabers off at the hydro facility explaining they were low pressure tanks, the guy said , "no, they are high pressure tanks; see, here it says 2400 psi. Hmmm, they're made in Italy, so I don't know if these are even approved for use here."

I thought, "Oh this is going to be fun."

I'm going to call the hydro facility and ask them to correct the issue, e.g. tumble the tanks lightly.

 

[Scared Silly]

What you are seeing is flash rust. They probably did the finial rinse with cold water and did not dry them very well. I would not worry about the flash rust but be more concerned with streak and where the water drop ended up. A light whipping can usually clean them up nicely.

 

[cbrich]

Your tanks need to be tumbled, if you want. If they were my tanks, I would tumble them, no questions asked. Hydro facilities around me don't tumble tanks, and if they did they would charge for it. The water that hydro facilities use is foul, nasty ass water; waste water treatment plants smell better.

 

[halocline]

You can get them tumbled at the same place, but unfortunately they'll just rinse them after tumbling and you'll probably be in the same boat. They just didn't dry them enough after rinsing. This is why hot water is preferred for rinsing tanks after hydro; it evaporates quickly so they can more easily drive out all the water with an air gun.

I'm in the sad position of having to find a new hydro place. The one the dive shops use tried to ruin a couple of my tanks and as such I can't go back there. The guy I was using seems to have gone out of business. He let me watch while he tested.

 

[AbyssalPlains]

Thanks for the responses so far. In hindsight, I should have stayed and watched. I didn't because I have always been a perfectionist with huge trust issues about these things. I used to bug people to make sure they were doing a good job. But I always felt like a tool, prompting reactions like, "You know, I have been doing this for 20 years, do you think I can handle this?" So this time, I decided to not let my usual self come through and trust my cylinders to the hands of the experts who handle hundreds of them a day.

Big mistake. From now on, I will be the nasty a-hole customer who second-guesses every action they take. I don't care. My standards are extremely high and I expect those who I trust with doing work for me to apply the same standards. If it takes me breathing down their neck, so be it.

But back to topic: I called the facility today and they tried to blame it on me not giving them the valves with the tanks (I explained they were doubles and I didn't want to take the manifold apart, and that the way they had taped them up was very adequate.) The manager said moisture could have gotten into the tank during my trip home, despite the tape. I KNOW there is NO WAY of that happening. Here in Arizona, you can leave bare steel exposed for days, weeks, months and nothing will ever rust. Plus, that wouldn't explain the brown streaks.

What cbrich said about the nasty-ass water fits the bill just from what one of the tanks looks like - brown ugly rust streaks inside.

The manager offered to take a look and sandblast them for me, and I'll probably end up doing that. PITA is the hydro facility is in a different city, so I won't be able to set up my doubles rig for two weeks or so.

Stupid question: What does "whipping" mean?

 

[Scared Silly]

It is an alternative to tumbling.

You put the whip on the end of a drill and as it spins it removes light rust particles:

Tools - Tank Cleaning - Whips and Brushes - Northeast Scuba Supply

Afterwards blowing it out with clean dry air.

 

[rjack321]

Just FYI
2400psi in the cylinder hydro industry is "high pressure." "Low" being stuff <200psi like fire extinguishers and propane cylinders.

I would just tumble them myself if they needed to be O2 clean (hydro wash water is generally reused and can't be assumed to be hydrocarbon free). If they are just being used in regular air service, rust staining is no big deal. There should be no loose rust however.

 

[bleeb]

The manager offered to take a look and sandblast them for me, and I'll probably end up doing that. PITA is the hydro facility is in a different city, so I won't be able to set up my doubles rig for two weeks or so.

Could someone knowledgeable please comment, but aren't the 'types' of blasting allowable very limited, and exceeding them means condemning the tanks? From the comments so far, how much confidence would one have that the facility in question knows how to do things properly, or what questions would you ask to try to determine that?

 

[rcs9250]

Is there someone in your locale that you can trust to give an opinion as to how much flash rust there is so you have some kind of basis for comparison ?
Unfortunately you can't take a picture so we can see.

 

[halocline]

Luis H on this forum has a particular brush that he says works perfectly for this sort of thing. Why don't you send him a PM and see if he'll post a photo of it? There actually is one on some old thread. That way you could just take care of it yourself. The brush, very similar to an abrasive whip, is attached to a long rod that fits in a drill. You put a plastic sleeve in to protect the threads and spin away. Then use really hot water to rinse it and dry it with air from another tank. If you don't have an air gun attachment you can use a regulator hose; I've done it and it works fine.