Summary for open porous anodized aluminum Discussion
Open porous anodized aluminum storage is the central issue here: Vinodan K.A. asks how to keep anodized sheets unsealed for months before dyeing, and whether vacuum packing is a workable method. Ted Mooney explains that anodized aluminum does not immediately self-seal, so there is time to do off-line dyeing or silk screening before the final sealing step. He says the parts can be allowed to cool and dry before packing, and that vacuum packing should help prevent premature sealing while also keeping dirt and other contaminants off the surface, since unsealed anodized aluminum can get dirty quickly. The thread does not give a precise maximum storage time, but it supports the idea that careful packing and cleanliness are important if the pores must remain open until later coloring.
Quickstart:
In the anodizing of aluminum the components are immersed into a tank of acidic solution and connected to the anodic (+) positive pole of a power supply. The current separates some of the water in the solution into positively charged hydrogen and negatively charged oxygen. The oxygen is attracted to the positively charged components and converts the skin of the aluminum to aluminum oxides.
Readers new to anodizing of aluminum may wish to view our “Intro to Aluminum Anodizing“.
Immediately after anodizing (and dyeing, if done), it is usual to seal the surface by immersion in steam, boiling water, or hot nickel acetate solution, which swells the surface, closing off the pores.
Q. How can I retain the integrity of open porous of anodized aluminum sheets before dyeing for months together? or how long I can store the said anodized sheets before colouring without pores being closed?
We have a aluminum anodizing plant here, so this technical solution will help us to work more efficiently.
Heard that vacuum packing will do immediately after anodizing, but different views are also coming.
Vinodan K.A
consultant – India
September 30, 2025
Aluminum How-To
“Chromating – Anodizing – Hardcoating”
by Robert Probert
You’ll love this book. Finishing.com has sold a thousand copies without a return request 🙂
A. Hi Vinodan.
I can’t claim actual experience in trying to keep the aluminum unsealed (although hardcoat anodizing is usually not sealed) … but it seems reasonable to me that vacuum packing it would keep it from sealing itself indefinitely. And it sounds like a good idea because unsealed anodizing is very prone to picking up dirt and contamination.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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Q. I greatly appreciate your quick response. Will vacuum packing affect heat release, compromising the desired outcome?
Vinodan K.A [returning]
consultant – India
October 1, 2025
A. Hi again.
You can certainly allow the components to cool and dry before packing. Anodizing will not immediately self-seal — people often do silk screening of lettering and other types of off-line dyeing before sealing. But vacuum packing should not only prevent such sealing, but serve the secondary purpose of keeping contaminants away; unsealed aluminum can get dirty fast.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
Thank you very much for your encouraging comments. Let me ask my manufacturer to do a trial.
Vinodan K.A [returning]
Consultant – India