"This kind of misperception is an example of perceptual constancy, the mechanism that allows you to recognize an object as being the same in different environments, and under very diverse lighting conditions."
The ability of radiation to cause cancer is dependent on whether or not the radiation is able to alter chemical bonds. This occurs when electrons involved in bonding in a molecule absorb radiation with enough energy to allow them to escape – this is called ionization. The thing is, whether or not radiation is ionizing is based solely on its energy, not on its number, and as we saw above, its energy is determined entirely from its frequency.
Instead of using chemical coatings they used lasers to etch a nanostructure on the metal itself. It will not wear off, like current less effective methods.