qwerty333, theoretically rust will start on a microscopic level where salt brine remains on a stone chip spot for a few days. Washing the salt brine off and applying a fresh coat of wax over the stone chip spot would best alleviate any rust issue. The areas where rust will likely reappear are those where past rust was supposedly completely removed, then coated/painted over. Because it's likely there is a pinhole(s) where salt brine can penetrate the refinished surface and form rust that is hidden and goes untreated until it becomes a major issue and is clearly visible, or a bit of hidden remaining rust spreads and goes unnoticed until it is a major issue again. Rust is like cancer, in that it is difficult to eliminate completely.

__________________
Fred Hoelzle