Rust and steel tanks

[grandpoobah]

Does completely draining the tank after dives cuase rust?

 

[Hoosier]

Can be...... You need to presurized your tank always to block the air in from the atomosphere...

 

[captain]

If the valve can keep in 3000 psi I am pretty sure it can keep out atmospheric pressure.

 

[Luis H]

Does completely draining the tank after dives cuase rust?

The major problem with rust is moisture and / or water.

If you completely empty your tank, the valve can keep moisture out. But, if the valve gets wet, you have no air pressure to blow it dry. Water can and will get into the valve opening and if you can’t blow it clean and dry from the inside out, you will push that water in when you fill the tank. Pushing high pressure air into the tank will drive any water or dirt in the valve or the whip into the tank.

Just a few drops of water (specially salt water) in the valve opening can cause a lot of rust when the tank is under pressure.

Many years ago I had to tumble two tanks of mine that were about a week old because of a fill station in a marina that were less than careful when they hooked up my tanks. They used salt water in their cooling tank. I was still unloading more tanks when they hooked my first pair of tanks.

 

[Panulirus]

Unless your not keeping air in them when storing, or are completely draining them during dives........it sounds like your getting bad air.....meaning they might not be regularly changing their filters.....Just my guess with what you provided...

Tanks were never emptied completely since they were purchased. It's now my understanding that dirty compressor filters could definitley have contributed but I never questioned the shop that fills them about how many hours on the filters. Tanks have alawys been filled on land via a Nitrox membrane system.

We call this the "hydro trap", where you take a tank in for a visual, and the ship insists on tumbling it, then says it has to be hydroed, and your $10 visual has become an $80 major event.

Hope you're not right about this but it's the first thing that crossed my mind. The shop did offer to have me come down and inspect the rust but I never made it there before they sent them off for tumbling/hydro. Supposed to get them back tommorow so we'll see how that goes.

I'd stick with Fabers. PSTs are nice tanks but are more prone to rusting. It's likely that once they've been tumbled once you need to tumble them every year. The Fabers are much more durable in this respect.

I have a pair of Faber 117's these are my wife's PST's. Hope you're not right about the need to tumble them every year after this. I love diving with steels but if rust is going to be constant problem that's a big PITA.

Thanks for all the replies.