I have the same problem: near 1mm thick of something looking like rust !





I allready used 5 times some CarPro Iron X on it: every time, the product reacts (and changes color to purple) but still doesn't do much on that "thing".
I might try vinegar soon : wine vinegar works fine for removing rust on little parts like screws for example (one night bath in wine vinegar).

 

I've had good results with this but you will need hours with all that rust

 

I do some detailing a little bit so I am common with polishing, but in my case, the rugosity of this rust makes it impossible de polish in my opinion.