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Anodizing of LM6 Aluminum Die Castings


Q. We have a part diecast using LM6 (A413). Is it possible to RED anodize this alloy, or is there another die cast alloy better suited for anodizing?

Any & all help is much appreciated.

Victor Spelman
lab - Chilmark, Massachusetts


A. Sheasby and Pinner in their book, 6th edition, list LM6 (with 12% silicon, you anodize aluminum not silicon) as "moderate" for protective anodizing, "unsuitable" for anodize and dye, and "unsuitable" for bright clear anodizing.

They do not list any die cast alloys as "excellent" for anodize, dying, or clear.

Come back for more info on the process for the best you can do on die cast.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina


Q. Hi,
Our anodizing on alloy A413 is not desirable.
How we can reach a good position in anodizing this alloy?
With best regards

moametto pordel
engineer - italy


A. Hi, Moametto. The "bible" of aluminum finishing says the alloy is "unsuitable" for decorative anodizing, and the author of today's only current book on anodizing agrees . . .

Perhaps nothing is impossible, but you won't find unambiguous instructions on how to do something so exceptionally difficult that it is beyond the knowledge of those experts :-)
As Mr. Probert suggests, please tell us the process you are currently using, and in what specific ways the finish is "not desirable" and the readers can perhaps suggest possible improvements. Good luck!

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

What aluminum diecasting alloys are suitable for anodizing?

October 7, 2008

Q. I am a Engineer working working for a Company manufacturing Pharma Machinery. We have tried Anodizing on parts made from LM6 Grade Aluminum Gravity Die Castings after machining and grinding but we have observed some dark spots on Anodized surface. Please suggest how it can be improved further. Whether LM6 Grade Castings can be Anodized. If not, then which are the other Aluminum Castings Grades (Gravity Die) that can be anodized.

Akhil Gakhar
Employee - Mumbai, Maharashtra, India

October 14, 2008

A. Hi,
LM6 although is an excellent material for casting it has very poor anodizing properties. If fact it is generally true that, because of conflicting requirements, the better an alloy is for casting the poorer its anodizing qualities.
Is it possible to cast your items in LM5? It is much better for anodizing may be suitable for your production. LM0 is better still but really only suitable for simple shapes.
For US readers, LM6 is ASTM A413.2 - 13% silicon.

Harry Parkes
- Birmingham, UK

October 26, 2011

Q. I would like to know which grade of aluminum has good atmospheric and marine properties and at the same time can be anodized.

Can LM6 be cast into parts for marine or corrosive atmosphere use without anodizing? If not, what grade will be best to use in Marine and corrosive atmosphere without anodizing.

Peter Yap
Manufacturing - Kuala Lumpur, Selangor, Malaysia

A. Hi Peter. We appended your letter to a thread where it is asserted that LM6 is "moderate" for protective anodizing but "unsuitable" for decorative anodizing, and where Harry has suggested better alloys for the purpose. In letter 13823, Ken Vlach suggests LM25 may be a possibility. Good luck.


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

December 13, 2014

Q. Hello! Can you guys help me out on Anodizing on Aluminium LM6 Die Casting Components?

The response I am getting from electroplaters is that it is not possible to anodize aluminium die casting components.

Please advise.

Avadhesh Didwania
- Delhi, India

December 2014

A. Hi Avadhesh. We appended your inquiry to a thread which answers it pretty well, but feel free to follow up if anything was unclear. Best of luck.


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

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