Where the
world gathers for metal finishing
Q&As since 1989


-----

Good process for submersed reflectors?

December 20, 2009

Hi,

I am making some reflectors that will be submerged in the ocean. I have used 6061-T6 to this point. It polishes up nicely and works well until we anodize it. Then it loses it's specularity and reflectivity. I have tried various clear chemical coatings instead but they either turn brown or peel off under the intense UV emitted by the lamp that the reflector is used with.

I have been considering Nickel Plating them but between the UV, heat and saltwater I think that it might not hold up. I have also been considering switching to 3003 aluminum which I hear holds it's shine even after anodize. Is that true? If so what type of anodize do you suggest for this application.

Many thanks in advance. This is a wonderful resource.

Tom Gray
Designer - San Diego, California, USA

---

Aluminum reflectors even anodized, will be corroded in some time, as well as nickel plated, since the anodized surface and nickel plated surface is porous. Maybe anodizing in oxalic acid can help, however the surface will not be bright. The only option is to electropolish such reflectors and then cover the surface with non-porous lacquer.

Anna Berkovich
Russamer Lab

Pittsburgh, Pennsylvania

December 23, 2009

---

Hi, Tom. If cost were not an object, I think the ideal solution would be a bronze reflector with duplex nickel plating followed by rhodium plating.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 28, 2009

Maybe there are other combinations. Why not electro-polished titanium? Or perhaps electroformed silver shells backed with nickel+copper, or molded glass with a vacuum metallized silver, or stainless steel with a light color PVD?

Guillermo Marrufo
Monterrey, NL, Mexico
December 28, 2009