I had a leak from my kitchen extension roof through my new extractor hood and the water has left rust marks on the chimney. I've tried wd40, and also scrubbing with salt and lemon which has brought a lot of it off but it still looks pitted. I tried a fine sanding block on a tiny part of it which got the rust off but left it dull. What else could I use? Would the pink stuff work?
Hopefully photo attached.