Metal finishing Q&As since 1989

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Problems getting on anodized surface after applying surface protection tape

February 8, 2010

Dear Sir,
I aluminium Anodizer situated in western Part of India. After anodizing of aluminium sections I put a surface protection tape on it. I also want to let you know that my sealing is little on acidic side having high sulp[hate contents due to carry over problem of 1 bath to another. So you can say tht sections are not having proper sealing.
My questions and problems are as follow:-
1) I am getting adhesion impression marks on the section after stripping of the protection tape. Is this due to bad sealing or the quality of the tape is low. or is a problem of tape. The tape is having adhesive pill of only 90 tack.
2) Does due to bad sealing microns fade away with time ?

Sumit Lodha
Plating Shop - Ahmednagar, Maharashtra, India

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February 15, 2010

I am assuming you are using DM water for your anodizing baths.Are you using hard or soft water for the rinsing after anodizing? How many rinses do you have after anodizing and before coloring and sealing? Some anodizers make do with 3 rinses but if there are a lot of coloring jobs, I would suggest at least 4 rinses and advice to change the rinses everyday.
I would also suggest that you discard the sealing bath once in a 2-3 weeks. I would also suggest that you immerse the anodized jobs in the sealing baths for at least 15 minutes to give best results. If possible, apply the protective tape after 24-36 hours as leaving the anodized items in the open would further help in the sealing.
As such, anodizing does not fade away. Colors might fade depending on the atmosphere and exposure to direct sunlight.
For best results in our given conditions, anodize the items at a temperature of 15-20 °C with a 10% H2SO4 bath for at least 30 minutes. I hope this helps.

Winston D'Souza
- Bombay, India