coca cola? Thats a new one on me, hope you can fight off the ants. Wheres the rust in question? try to clean the chips and get it reletivly clean with a shop vac or a hand broom and put some por15 on it, it comes in clear as well as black and grey I beleive. Why are you worried about rust removers/converters turning it black? Let me know if you need more help or if I got it all wrong. Exsplain it a bit more? Glad to help.