how to clean off rust coloring

so last time i used my AR it started raining and i put it in the bag, i let it air out later that day but after revisiting it now i have some rust coloring on the flash hider and couple specs down the barrel.

what is best to clean this off?



i have tried multiple, multi-purpose cleaners and mineral spirits. any recommendations on getting all of it off?

how to clean off rust coloring