Lightning Cable Connections Turning Black

My phone's apple charger has been progressively worse refusing to charge my phone. When I plug my charger in, after about ten seconds the screen says, "This cable or accessory is not certified and may not work reliably with the iPhone." I know this cord is Apple certified as it is the original cord I received with my iPhone. The little golden rods on the lightning charger are not all still completely gold, some of them are black. According to other questions this is due to corrosion. My cord has not been exposed to water in any way so I do not completely understand how that happens, but I'm just trying to be helpful according to other articles. Any way to get the black off would be greatly appreciated as right now I have to keep my phone off or on airplane mode to save the little battery I have left. Thank you.