Rust Removal

[ememory]

Hello all,
As an instructor we started to clean and maintanance the equipments in our club,starting with the steel tanks for the season.
I heard that it is possible to remove the rust inside the tanks by using phosphoric acid solution(%5 acid) and tried that. After all tumbling,draining and drying processes the tanks had a yellow-like shine inside them caused by the phosphorus layer.I would like to know if it is a problem for the tanks and both the diver breathing from it , is there a way of removing that layer? Or are there any other solutions or methods to use to make our tanks rust-free ?
Thanks for reading,i really got stuck and need to be prepared for the coming season.

 

[captain]

I have used dilute acid to clean inside tanks and I always ended up with a light flash rust. I never tried to remove it or ever had a problem with it. I believe there is a product that can be used to prevent it but it is tricky to use. It must be rinsed out and if the rinse is too long you will get rust, too short and you won't remove the product.