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sulfuric acid anodized luminaires turning yellow

2004

I work for a large electrical industry in India, One of our luminaire product [Halogen Flood Light] constructed from PDC Al. The internal Al fitment [99.7% pure] for the same is Sulfuric Anodized [Type II]. The sealing used is 5 - 10% nitric + boric acid dip. We are facing a problem of the internal Al fitting turning yellow on exposure to light [around 400 °C]. Any idea to overcome this problem of yellowing.

Regards,

Nilesh n. Oturkar
R&D Executive - Paint Technology - Mumbai, Mahrashtra, India

Aluminum How-To
"Chromating - Anodizing - Hardcoating"
by Robert Probert

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The problem with the anodized coating turning yellow when exposed to light relates to the failure of the seal and the components of the seal that you are using.

David B. Hunt
- Naperville, Illinois, US
2004

That strikes me as a strange sealing bath, Nilesh. Usually you would be using steam, boiling hot water, or a nickel acetate seal for that kind of application (in my experience).

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

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