In the worse case I suspect it was a galvanic reaction between steel, stainless steel, aluminum and the magnesium on the Doan's bar. The flint may have also played a part. It was the result of a small kit in a nylon pouch getting water inside it while rattling around the floorboard of my car at the time. The floor of my car at the time had holes you could drop a baseball through. And it would fall through except for the random pieces of sheet metal I covered the holes with. It made inspecting the road for standing water and ice easy, slide the metal over with the toe of your boot and look down, but anything dropped on the floor got, and stayed, wet. The kit rolled under the corner of the patch on the passenger side and had been there for weeks. I spotted my spare kit when I was walking around the car and saw the drawstring hanging out of the hole.

My present vehicle is much better. No holes, brakes and A/C work. On the other hand I kind off miss that old beater. People in expensive cars see a ragged out beater coming at them and they get out of the way. Almost like they were afraid the ugly might rub off on them.