I wish I could remember the name of the product I used on my roof. It came in a plastic spray bottle. It had some kind of acid in it and gloves and good ventilation were a must. To answer your question, NO, it does not remove the rust. It was a converter. It converted rust (iron oxide) to a black compound that is NOT rust. I think I wiped the roof with lacquer thinner and then used 80 grit on a DA. It's been a while, but I think that is what I did. Then Epoxy primer. It has lasted for a long time.
