Has anyone used this product? It claims it turns rust to primer. Or a like product that is a rust treatment that stops the rust.

will this really work...spray this product that turns rust to black primer and then prime over it?

dosn't sound very good to me.

Don’t know which of the products your talking about. But generally their all the same I use PhosPho (something or other) form Home Depot, its the same stuff the body shop supply stores over charge you for. Basically its just phosphoric acid. Read about here and skip all the sales pitch hype.

http://en.wikipedia.org/wiki/Phosphoric_acid

From my experience it only works well on surface rust. If you spray it on rusted flakes it won’t penetrate and the rust will come back ASAP.
I do use it quite a bit but don’t put as much stock in the product as the manufactures claim. I use it on parts after they have been sanded or blasted to get ride of the microscopic rust and it will help prevent flash rust while you wait till you work on it later. I have sprayed the stuff right after its been sandblasted and left it unpainted for months without worrying about it rusting. In fact I have a ton of parts unpainted sitting around without any rust because I use the product.

However its is NOT a primer as they claim. When you’re ready sand the stuff off then primer and paint.

Ohh one more caution, it makes it difficult to weld because it builds a zinc coating. If you plan to weld the piece later make sure you get the stuff off really good first.

What's the best way to get the stuff off? Sand? Acetone? Laquer thinner?

This is what metal looks like before and after using the phospho.