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Anodized aluminum, bleaching due to heat?

May 6, 2009

We have a black anodized aluminum faceplate, which we have used and sold for year.
However we recently received a e-mail with a photo of one of our faceplates that apparently bleached over time. The person who sent the e-mail thinks it is due to heat, as the electronics mounted to the reverse side of the faceplate can get to 90 degrees C if left un-ventilated.

52429

The faceplate is 440 wide, by 88 mm tall by 8 mm thick. I wouldn't expect a small line of heat to show up in one area due to heat from something that thick.

Could there be another cause? Perhaps the plate wasn't properly sealed after anodizing, and the dye leached out over time?

Josh Driggs
Designer - Austin, Texas

All organic dyes fade with "time x Heat". The anodic coating starts to crack above 80 C.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

June 22, 2009

June 24, 2009

Robert,
I agree that type II anodize does not like high heat, but type III hard anodized frying pans are subjected to much higher heat and survive with no apparent cracking. What is the difference in the reaction to heat.
Jim

James Watts
- Navarre, Florida

Fry Pans are not anodized in "Type III hard coat". Their process is proprietary, similar but in some ways very different from "Type III". Types II and III do crack with heat.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

June 25, 2009

June 26, 2009

Hi, Robert. The major brands may have some trade secrets. But based on the dozen or more inquiries on this site over the years from pot and pan manufacturers in India, it sure seems that a lot of smaller manufacturers are simply trying to do type III anodizing without burning and other problems. Calphalon does not make hard anodized pans anymore -- only hard anodized and "infused" with a teflon-like coating. I love my "non-infused" one.

Regards,

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

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