I really like the LOOK of polished aluminum, but for surface treatments, about the worst one you can get for heat transfer is mirror-metallic. This isn't just for radiation, but conduction of heat also. As a primitive example, I had a similar-sized pile of beets and a pile of mashed potatoes on my plate. The beets cooled off WAY faster. Dark colors somehow transmit heat more effectively in conduction, not just radiation. Smokey Yunick commented on the fact that surfaces on engines were painted black for heat dissipation, same with coolers.
On the other end of the spectrum, in order of importance, polished titanium, aluminum and steel are stronger than their unpolished counterparts. Strangely, with steel it does not usually get any attention, with aluminum some, but with titanium any surface that is not a smooth, liquid, organic-looking transition turns into a potentially damaging stress point. Something about the skin strength titanium just LOVES.
In America's Cup yacht racing, where stainless steel is usually used for stanchions to anchor the mast stays, they tried titanium. They failed. The problem, in my view, is that in the limited space and weight allocated to turning a stress in one direction to a stress in another direction, people were used to casting in steel, which is FAR more tolerant of sharp angles, rough surfaces, or other such non-organic-looking structures. No one, as in NO ONE uses titanium for crankshafts. A crankshaft is the exact opposite of where titanium shines (pun not intended) because of its sudden right-angle transitions from throw to bearing surface to throw to main, which involves a lot of sharp edges and non-smooth transitions. Those corners, either convex or concave, are places titanium cannot withstand without having stress risers starting there.
Also, titanium does not withstand as many fatique cycles as does steel. One would think that titanium would make GREAT material for springs, as it has a lower hysteresis (energy wasted overcoming being deformed then reformed, usually expressed as heat) than steel, so is more efficient in the short term, especially because a lighter Ti spring can do the job of a heavier steel spring, but they do not have the same fatique life, so you don't see them in racing cars where one would expect them to be universal.
They make great intake valves, as their deformation is extremely limited. They also make excellent connecting rods, IF they are meticulously polished, and even the smallest little pits or burrs are "ironed out."
If it were mine to do, with Ti, I would shot-blast the surfaces first for surface compaction, then mirror-polish them so the thing looked like it was cast from mercury, then maybe nitride it for an added little hardness, giving a gold look.
Aluminum top fuel connecting rods aren't just shiny and smooth for looks. They are by necessity, as aluminum enjoys a good surface treatment, but it is not as critical as with Ti.
