Originally Posted by oldred
When using any of the Phosphoric acid rust removers such as Rust-Mort, Ospho, etc (when used a remover and not a "converter") a person can choose to leave the Phosphate coating or not. If it is left to dry then the coating will remain but if it is thoroughly rinsed with water before it dries it will leave clean metal. If it dries and the coating needs to be removed later then it is a simple matter of re-wetting with the product and then rinsing before it dries again.
Again ,no chemist here. My degree is in cardiology
The one thing that I can't get my head around is rinsing bare metal with water. I remember using a product such as this years ago and after following directions and rinsing it a VERY fast flash rust occured. I have never used it since. I obviously did something wrong if this is a standard procedure.