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Corrosion of Anodized Aluminum

I have some anodized aluminum cookware samples which have the anodize completely removed. We have conducted EDS of the surface and for various samples have identified Cl, S, and F. Any ideas what may have caused the anodize removal? sulfur was also present in control samples so I don't think it is the culprit (H2SO4).

Jeff Urbanski
- Williamsville, New York
2003

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You know what you are talking about, but I don't. Are you a cookware manufacturer and by "samples" you mean that a consumer returned some cookware as damaged, while claiming it was defective? But then what is the relevance of control samples? Wouldn't cookware that was used have traces of all manner of different things? Cl from salt, S from eggs, etc.?

Caustic will almost immediately remove anodized coatings completely. Readily available sources for a home owner are Draino, Liquid Plumber, oven cleaner ⇦ this on eBay or Amazon [affil links] , and some very strong detergents.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

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Ted,

Thank you for the response. I work for an independent consumer product testing laboratory, and yes these samples were returns from consumers. Our client, the retail distributor had asked us to identify the cause of missing anodize. I appreciate your comments and will keep them in mind for future returned samples. Our client had thought the coating somewhat indestructible, so it is good to know that common household chemicals could cause the anodize to be removed.

Jeff Urbanski
- williamsville, New York
2004

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But I may have missed the real culprit: bleach -- which is highly alkaline to keep the chlorine dissolved, and will easily destroy anodized auminum.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004