it makes sense that if your pipe is designed and constructed at ambient temperature, that it will maintain its design characteristics the closer it is to ambient temp. so coating the pipe will maintain higher temps inside therefore cause more thermal expansion of the pipe. however to me that would make the idea of coating the inside of the pipe more appealing bc the coat would help insulate the pipe and reduce its thermal expansion.

i like how this tread has various inputs from many individuals and no one is getting angry or worked up.