WardL Swain or Hot coating is about the only way to slow down this problem. The pipes would need to be stripped to metal, repair any holes, recoat. You should be good for a couple of years. Stainless steel would be next. Depending on the color of the pipes, Guys who run white pipes just use spary bombs of metal paint and keep touching up the pipes.
There is a company that sales an electro kit to wire to the car frame and slow rusting down. I have not heard any info on this. Try sreaching the old threads on this. Maybe someone can help. We have the same problem at the Jersey shore with frame and pipe rot. They sure don't build them with the better steel they used to use.
Rick L.