The authoritative public forum
  for Metal Finishing since 1989
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Will lime attack an anodized finish

Will lime attack an anodized finish? If "yes", how should this anodized surface be restored, since it is a window already installed?

Michael Brown
- Dallas, Texas
2002

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Yes, I would expect lime to attack aluminum.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002

How should the aluminum's finish be restored? (The window frames are already installed.)

Michael E. Brown
- Dallas, Texas
2002

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First of two simultaneous responses --

Anodizing is a multi-step electrochemical process, usually involving the steps of cleaning, etching, desmutting, anodizing, dyeing, and sealing -- with neutralizing dips and rinses as well. So, when you ask how to restore it, if you want to do it right it is unfortunately a project. I would suggest contacting the vendors of industrial brush plating equipment (such as Gold Touch [a finishing.com supporting advertiser] and Sifco) and asking them who does "brush anodizing" (anodizing in situ with portable equipment).

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002

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Second of two simultaneous responses --

Restoring anodised aluminum will most probably found to be as expensive as new frames. That's if you take them out. But wait a minute, you said they are already installed. So, you are thinking of doing it on site. Am I right?. It can be done, but then I'd bet on it. No kidding, it's very expensive, even airlines agree and believe me they are used to pay top dollars (it's called brush anodising). Anodized aluminum is one of the difficult metals to work with when it has corroded. Most chemicals will attack differentially its two surfaces (anodised and bare aluminum). Mechanically speaking, the difference in hardness of those constituents is so great that an attempt to polish it will give just fair results, to say the most. So, if you cannot afford new frames I think it's time for you to start looking for your nearest paint store asking for aluminum wash. Sorry...

Guillermo Marrufo
Monterrey, NL, Mexico
2002