Tumbling and flash rust

[JDMerk]

Ok so I bought some steel 72's the other day for a great price...only they are out of hydro and vip and had some very light surface rust on the inside. Outside they look great with no rust.
So I go in today on my day off and tumble them for 2-3hr with ceramic pelets and 1:500 Simple green (about 1qt), rinse them on the rack for 5 mins and immediately put them on a drying rack fed by a heat gun.
The end result was tanks that looked almost identical to the ones I started with, I really can't tell much difference at all. I know I got a lot of rust out of there because of the water I rinsed out of them. I am thinking they flash rusted on the dryer, which brings me to my real question...how much flash rust is to be expected/acceptable?

 

[300bar]

Never seen the result of tumbling,we use mediablasting overhere.
Tanks should look as new after that.

 

[porbeagle]

300bar, I've not heard of " mediablasting" what is it?
TIA, PORBEAGLE

 

[Scared Silly]

How hot was your water? I use water that is as hot as I can stand - 130F, then dry immediately. Last time I dried with CO2 and no heat.

 

[JDMerk]

I read the global tank tumbling tips...they suggested rinsing with cold water.
I used water at room temperature.

 

[DA Aquamaster]

For flash rust I will normally just tumble them with dry media for 15-30 minutes and the results are normally a clean and shiny tank. Then I will rinse them with cold water then tumble for 5 minutes with an O2 cleaning solution, rinse them again with cold water and dry them with air from a scuba tank.

I have a 4 ft rubber hose crimped to a LP hose fitting and screw it into an LP port on a first stage. As a field expedient, just wrap a couple layers of electrical tape around the regulator inlet fitting end of your Octo hose.

Invert the tank and then blow air at a fairly high rate for a minute or two to displace the water in the tank and dry it completely. You'll use maybe 700-1000 psi out of an AL 80.

In my opinion tumbling with wet media, if not needed, should be avoided, and hot water rinses just provide the heat needed to speed oxidation of the metal in the presence of water and O2. Use a cold water rinse and blow it dry with the already dry air from a scuba tank.

 

[captain]

hot water rinses just provide the heat needed to speed oxidation of the metal in the presence of water and O2. Use a cold water rinse and blow it dry with the already dry air from a scuba tank.

I have found just the opposite, using water hot enough that I can not handle the tank with bare hands I fill the tank up completely, insert the air hose, invert it and turn on the air. In less than 30 seconds the tank is blown empty and dry with no flash rust.

 

[Randy43068]

I don't worry so much about flash rust.

As long as it's very minor, I don't really care much about it.