Metals that stay shiny (low emissivity) at 400 C (750 F)

Factual Questions
1

I frequently need to make metal devices and parts that have and maintain a low emissivity at temperatures from room temp to 400 C or 750 F. Low emissivity means poor coupling to infrared radiation, and usually implies the metal looks bright and shiny to the eye.

Ease of machining, and fairly high thermal conductivity (say roughly as good as steel), would be preferred. Strength usually doesn’t matter much.

I was wondering about elemental Nickel - how much does it oxidize? How dark does that make it?

Titanium is another thought, though it has pretty low conductivity, especially as alloys.

Gold and Rhodium and Platinum aren’t possible due to cost. I think something like $100 a pound would start to be unattractive.

Plating is a possibility, too - though Gold plating (which sounds ideal) has at high temperatures a tendency to let other metals diffuse through it only to oxidize on the surface, which spoils the plating.

Any ideas?

2

This is in an air atmosphere, I should have said.

3

Elemental Nickel would oxidize pretty fast. Polished Silver would be good, as would polished Zinc or Chromium. Are the parts expected to be maintenance-free, as in never repolished? If so, I’d look at Zinc.