Rusty tanks?

[Linedog]

For the last 4 years my tanks have passed VIP's without a problem. This year its hydro time, I just got a call informing me both tanks need a tumble, light rust on the walls. I get my air at 2 highly respected shops, I don't dive nearly as much as I want, but manage around 25 dives a year. I am so careful that after I soak them I place them in my car with the valve opening downward for a day so any water that might be in the threads will drip out before I take them in for a fill. I store said tanks in my unheated garage, could the rust be from the hydro, The person on the call said I musta got some moisture in them as the rust was only on the walls. Any ideas

 

[halocline]

Yes the rust could be from the hydro, after all they do fill the tanks with water to do the test. Some shops are likely not as good as others at drying out the tanks quickly and using very hot water to rinse. Most hydro shops do a very small percentage of their business with scuba tanks, and even fewer steel scuba tanks. Honestly, I've had some experiences at hydro shops that indicate they know remarkably little about scuba cylinders.

 

[tbone1004]

if it's just the walls you can whip them, no need to tumble for that....

 

[Scared Silly]

if it's just the walls you can whip them, no need to tumble for that....

I agree, mine came back with some flash rust and a good whipping was all they needed. I am using an aluminum oxide impregnated pad on a rod from PSI to do my whipping.

 

[GrainDane]

if it's just light rust, whipping should do fine. anything above flash rust usually progresses quickly.

also, make sure you do not use a steel whip on an aluminum cylinder. steel is harder than the aluminum.
you will remove metal and that is enough to condemn a cylinder under DOT. hydrotest dot com actually sells a steel wire whip that is "ok" for steel and aluminum cylinders. if you call luxfer or catalina, they should tell you not to use a steel whip in a heartbeat.