I wanted to changed the pipes to stainless steel, but I had to cancel them on the wishlist because of the price...
Maybe in the future.
One of my original pipes was in bad condition at the clamp but that section was replaced by piece of a similar steel pipe. Next all of them were sandblasted. After that the internal surface looked as a new one. Finally they got some primer and black topcoat so will last for years with new cooling fluid I think.