Bare metal mirror coatings (Metal Coating) provide the highest reflection over the widest wavelength range. However, they are easily scratched and therefore, difficult to clean. This graph shows the spectral reflection performance of common bare metal coating.
This is dependent on the particular metal and the wavelength region.
Adhesion as per the following (where applicable): MIL-C-675, MIL-M-13508, MIL-M-14806, MIL-C-48497, MIL-F-48616, MIL-STD-810F