I have had all of my pipes internal ceramic heat coated. It has to be done before the pipe is used. That is easy on new repop pipes or NOS pipes. I've had it done to used pipes after they have been re-chromed as the plater facility tank stripping process cleans out the interior built-up carbon and rust. The internal heat coating helps reduce the blueing & browning/yellowing of chrome pipes.
The company I used is Northwest Industrial Coatings (NIC) in Oregon. https://www.nicindustries.com/
They developed the heat and slick coating process and powders. They no longer do the coating work, now sticking to manufacturing and selling the powders. For looks they have 1000's of color choices.
When I was building and racing experimental aircraft, they used to use us as experiments for their R&D. The engines I built had both heat and slick coatings on the internals. Slick coatings on the sides of the pistons, and heat coatings on the tops. Any friction surfaces in the engine got the slick coatings, ie cam, crank, pistons, rods, piston pins, gears, valves, valve seats & guides, lifters, pushrod ends, even the bearings. It was like a bearing on a bearing. Very slippery and durable stuff.
They would heat coat the inside of the aircraft headers as well as coat the outside for heat and for looks in order to help reduce the aircraft inside cowl temperatures which were fiberglass as the pipes were, in some cases, within a 1/4" of the cowls. It was a challenge for them as EGT's are hotter on aircraft engines than vehicles, and the heat coatings were initially not holding up. They finally figured it all out.