Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Decorative hard anodizing?

Decorative hard anodizing?

Decorative hard anodizing?

I've been in the aerospace field for many years and have worked extensively with both decorative anodized finishes and hard anodized working finishes BUT I am now working in a commercial environment and have a problem that I don't have an answer too in regard to anodizing.  Is it possible to obtain a a decorative (in this case, translucent medium blue) finish with the hard anodize process?  It would be the ideal answer answer to my current quest but I have yet to find a local process house that can give me a good answer to this question.  Anyone?  Thanks!

RE: Decorative hard anodizing?

The color comes from a dye added to a protective sealer infused into the microcracked aluminum oxide surface that anodizing produces.  Hard anodize is thicker than decorative anodize, but you still need to seal it, and you can still tint the sealer.  Don't expect to get the exact same shade.

For more info, start here:


Mike Halloran
Pembroke Pines, FL, USA

RE: Decorative hard anodizing?

Hard anodize has some inherent coloration due to alloying elements in the aluminum. So it's doped alumina, a la ruby or sapphire.  Also, some intermetallics and silicon form particulates (inclusions) in the alumina, so can get speckled effect.  There is also some change with thickness.  The natural coloration adds to any dyeing, so it is somewhat difficult get lighter colors on certain alloys.  Using a sulfuric+oxalic acid (rather than simply sulfuric) gives a yellowish hue, as does dichromate sealing.
The Aluminum Anodizers Council's 'Anodizing Reference Guide' gives the natural colors expected for various alloys. http://www.anodizing.org/reference_guide.html

Kaiser Aluminum developed a number of 'Kalcolor' alloys which developed natural colors (amber/gold, bronze, black)when anodized. Alco had a similar Duranodic process which depended more on organic acid additives to the anodizing electrolyte to develop color.  Don't know whether still available. http://www.alu-info.dk/Html/alulib/modul/A00305.htm

Most frequently, hard anodizing is dyed black or a darker blue or red.  Some colors used in anodizing (the same dyes are used for both hard & conventional anodize):  http://www.usspecialty.com/

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close