I have used it from time to time over the years. It works OK. Its basically a mix of phosphoric and sulfuric acids with some additives to make it pleasant and jelly like.
If you are able to wash it off well, there should be no problem. It works faster if the metal is warm and so is the weather.
There is no protective action afterwards, so be ready to do something with the clean metal.
Otherwise, it will start rusting fairly quickly.
Just a wipe with some oil will do for a while. Otherwise, have some primer ready to spritz on.
The straight rust converter, the name escapes me right now, but its a green liquid and is straight phosphoric acid, does not remove the rust, but converts it to steel phosphate.
The result is black and more stable than the rust.
But still has to be painted or sealed in some way.
"Ospho" Knew it would come to me.