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Difference Between Type I and Type II anodize
Quickstart:
Readers wanting a quick intro to anodizing of aluminum may wish to view our "Intro to Aluminum Anodizing (Anodic Oxidation of Aluminium)".
Q. I would like a detailed explanation of the difference in the end product when using Type I or Type II anodize on Aluminum plate. Any Help?
John Hart1998

Aluminum How-To
"Chromating - Anodizing - Hardcoating"
by Robert Probert
Also available in Spanish
You'll love this book. Finishing.com has sold almost a thousand copies without a single return request :-)
A. Type I, (chromic acid) is used for parts:
- having riveted or welded joints, or recesses within which is difficult to rinse properly
- which have total dimensional tolerances of from 0.0003" to less than 0.0005"
- where machining after anodizing is not desirable
- with less than 5% copper, no die castings shall be treated by this process.
Type II, (sulfuric acid) is used for parts:
- where coloring and decorative purposes are important
- which require hardness and resistance to abrasion
- on airplanes its use is restricted to parts not subject to stress and not containing recesses in which the anodizing solution might be retained.
Also see MIL-A-8625 / MIL-PRF-8625 [⇦ this spec on DLA].


Tom Pullizzi
Falls Township, Pennsylvania
Q. What base is anodizing dye. Is it oil or water and can I buy it in small amounts? What is the price?
Billy Doyle- Grand Prairie Texas us
2000
A. It is water based, Billy. You may be able to buy RIT dye ⇦ on eBay or Rit Dye [affil link] in small amounts for a few dollars if your needs are non-rigorous, but purpose-designed dyes for anodizing are probably a bit more more expensive. Please see "Seeking Anodizing Dye" for sources.
Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Ted can be retained for immediate
answers or long term project help
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