> Sam I am, anodizing my mirrors and they do last much longer and have
> better reflectivity. I have one hundred and thirteen 63" diameters mirrors
> which have been continuously exposed to the Utah desert atmosphere since
> 1987. Under the same conditions bare aluminum mirrors lasted about 3 months.
> After 6 months they were reduced to patches of highly corroded aluminum and
> large spaces of bare glass. Almost all of the anodized mirrors are still
> over 80% reflectivity at 337.1 nm (3371 Angstroms) as of 1995, when washed.
> Most look like new. Lab tests of my latest 50" diameter mirrors indicate
> that my anodization process produces coatings with 3 to 4 times the
> resistance to corrosion of the 1987 coatings.
Hoo hah! Have you written this up anywhere? Do you know if such coatings are commercially available?
>
> BTW, Sam, I determined what was 1/2 wave by measuring the
> reflectivity of the mirror using an Nitrogen laser and adjusting the oxide
> thickness to get the highest reflectivity. A bonus of the process is that it
> electropolishes the aluminum surface. My bare aluminum mirrors are only
> around 70% reflective at 337.1 nm and this varies enormously over the
> surface. After anodizing them the reflectivity is from 85% to 90% and only
> varies by a few percent over the entire mirror surface.
This gets better and better.
> Also, if the
> aluminum coating is not adhearing well to the glass the process will cause
> it to peel away. I have had occasions where a small drip of less than
> de-ionized water has been spattered onto a mirror blank and run down the
> surface. You cannot see anything on the glass blank. After aluminization the
> mirror looks great. But when I anodize the mirror all of the aluminum peels
> away where the drop ran down the surface. This is a great test for good
> aluminum adhesion. I hope I have piqued some curiosity out there.
>
You've done that all right.
Sam Paris