Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

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Aluminum white stain

2005

Currently I was facing the problem of white stain for my Aluminum (A5052) product after DI wash. We did pass through DI water ultrasonic tank (68KHz) follow by hot DI water rinse (T=35~50°C) and air blower. Our last step is dry it in the oven which is 65~75°C. I can't figure out the cause which lead to white stain. Kindly please provide me the suggestion or comment?

Leonard Yong
Computer hardware - Singapore

Aluminum is a very active metal that readily corrodes if there is no anodizing or other protective coating. I may be misunderstanding you, but it sounds like you have the unrealistic expectation that raw aluminum will not corrode. You must add a surface treatment to the aluminum.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2005

Our window installer has delivered some aluminium sections that lacked the anodised coating as they explained it would be covered by alum cladding, is this acceptable and how can we rectify on site?

please advise if a bitumen coating would be ok?

W K Chan
- Hong Kong
2006

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