Anodize Layer.. what is it.....

[Precise]

What is the actual layer that "grows" 1/2 into the part and 1/2 out?

I have heard and read off the internet that it is..

Aluminum oxide
Aluminum hydrate
Aluminum hydroxide

Which is it??

 

[CoryPad]

Aluminum oxide.

Aluminum hydroxide forms on the outer surface when exposed to water.

I have never heard of aluminum hydrate.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[kenvlach]

Anodizing (on aluminum) is aluminum oxide. Most anodize is sealed (especially if dyed), a hydrothermal process which hydrates the surface of the oxide in the pores, thereby filling the pores with aluminum hydroxide.

See the Aluminum Anodizers Council website:

http://www.anodizing.org/

From menu on LHS, see 'What is Anodizing,' 'FAQs' and 'Reference Guide.'
In 'What is Anodizing'
TABLE OF CONTENTS
An Historical Perspective
Anodizing's Benefits
Anodizing and the Environment
Anodizing Definitions and Methods
Coil Anodizing
Current Anodizing Processes
Anodized Aluminum Applications
Anodic Coating Specifications
Anodic Coating Designations
Alloys Suitable for Anodizing
Ordering and Quotation Guidelines
How to Specify