The authoritative public forum
  for Metal Finishing since 1989
-----

Need Help Polishing Anodized Surface

 

Does anyone have any experience/recommendations for polishing anodized surfaces. Specifically, I need to polish T6 Al that has a .003" thick Type III, Class 1 Ano with a hot DI seal.

Regards,

Barrett Finch
- San Jose, California, USA

---

 

Hello, are you trying to polish hard anodize to a bright luster? Sorry, I don't think it can be done. Hard anodize .003" on 6061 looks like it's black. This will not "polish off". If you need a "bright look" start over by polishing fresh substrate and using a type 2 anodize of .0002-.0003" with no caustic etch pretreatment. We anodize many decorative parts in this manner very successfully.

Good Luck,

Bill Grayson
- Santa Cruz, California, USA

Also have a similar question, I run a small titanium bike frame building company, we are wanting to anodize finish our frames, what I was thinking was to type 2 anodize, sandblast followed by polish, I guess what I am wondering is what amperage is required to get the thickness required for a polished high sheen black finish if it is possible at all. Pardon my ignorance on the subject, just a welder trying to educate. Warm regards.

Will Broduer
- Toronto, Ontario, Canada
May 16, 2011

---

May 16, 2011

Hi, Will.

While "anodize" implies immersing the component in a solution and applying an anodic current to oxidize the surface in a beneficial way, and while the word applies to both aluminum and titanium, anodizing of titanium is a very different thing than anodizing of aluminum in almost every imaginable way :-)

Colors are obtained in aluminum anodizing by building a honeycomb like structure about 0.0002 to 0.0008" thick, immersing in dye, and then sealing to close up the honeycomb, locking the dye within. Anodized coatings on titanium are much much thinner; so thin that the color is the result of diffraction effects like the rainbow colors from a drop of oil in a water puddle. Anodized titanium is not dyed.

While these colorful diffraction coatings are quite attractive in jewelry, I doubt that they would have the durability for a bicycle, and black is not a possible color for a diffraction coating. There is another type of titanium anodizing which is thicker and intended to impart gall resistance (see AMS specification AMS 2488), but to my knowledge it has no decorative value.

There are companies like Russamer Labs which offer proprietary technology for electrolytic coatings on titanium, and they do offer a black coating. You might inquire of them whether what you would like to do is possible and practical. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey