vmaniqui

i was cleaning the rusty parts on my 15-88 and 28 and read somewhere that vinegar will help remove those rust from metal parts. as i was putting those rusty parts in a container with vinegar, i accidentally put my 15-88 bobbin case. and look what happened. it turned into black thingy like it got burned or something. is this toast now ? do i need to buy a replacement ? i will never use vinegar again. alcohol is much better or kerosene. is there a way to clean this up or make it shiny again ? so stupid of me. lesson learned.