4 nm is nothing with respect to corrosion resistance in a smokey show environment, nor does it significantly enhance reflectivity. Enhanced reflectiveity needs lambda over four which is, for red light, 632 nanometers/4 ~ 180 nm of thickness, with results starting at about 65 nm of Al2O3. . Not to mention that the process of removing the paint makes micro-scratches in many cases. Trust me, I've been at this for 20+ years.
Steve
Qui habet Christos, habet Vitam!
I should have rented the space under my name for advertising.
When I still could have...