Home /
Search 🔍
the Site

Chime right in! (no registration req'd)


"Color anodizing of diecast aluminum"


Q. Does anyone have any experience, comments on decorative color anodizing or die-cast aluminum? Is an intermediate plating of zinc or chromate required (because of the high silicon content of the aluminum)?

Any suggestions, tips, references, samples would be most appreciated.

michael rose
- Boxborough, Massachusetts


A. Michael:

We are metal finishers specializing in aluminum anodizing and you picked a very difficult alloy to anodize, especially in colors. A few suggestions: Tumble the parts in a stainless steel media prior to anodizing. The colors you pick should be dark (Black, Blue, Red). You can not zinc plate or chromate finish prior to anodizing aluminum. If you need further assistance please feel free to E-Mail me.


Bob Bramson
B&M Finishers / Prismatic Stainless Steel
supporting advertiser
Kenilworth, New Jersey
b&m finishers banner


A. See the responses to Letter # 2053. Whether it's conventional or hard coat anodize, the coating still comes out grey, and it is difficult to have an aesthetically pleasing appearance with any dye with die cast. I wonder if anyone has ever IVD-coated a die cast part, then anodized the IVD aluminum. You can't remove the silicon, so maybe it can be covered up.

phil johnson
Phil Johnson
- Madison Heights, Michigan

"Surface Treatment & Finishing of Aluminium and Its Alloys"
Wernick, Pinner & Sheasby
from Abe Books

Affiliate Link
(finishing.com may earn commission)


A. The high level of silicon in most aluminum diecastings makes sulfuric acid based anodizes turn an uneven dirty gray almost immediately. Color dyeing does not cover this up, in fact, it often highlights the problem. Several approaches are possible:

1)With proper pretreatment, fair cosmetics are possible with anodizing and the darker colored dyes.

2)Alloys without silicon, such as 518, produce much better results. However, they are difficult and expensive to diecast.

3)IVD coat(vacuum deposited aluminum)the part prior to anodize. We have done that here and it works very well. However, this is also expensive.

4)There is a new kind of coating becoming available, known as plasma or mircoarc anodizing. They are naturally off-white but some versions are available with an integral black color. Our high silicon diecastings have a very uniform satin black coating.

5)Chromate pretreat and paint the piece.

Chris Jurey, Past-President IHAA
Luke Engineering & Mfg. Co. Inc.
supporting advertiser
Wadsworth, Ohio
luke banner

August 12, 2015

A. Another solution is to die cast low-silicon alloys using a slurry die casting process. These low-silicon alloys can then be anodized to give nice colors.

The issue is how to die cast these low-silicon alloys with high quality and low production costs. These alloys tend to have hot tearing and die soldering problems. Slurry die casting may be used to solve these problems.

Jess Wannasin
- Bangkok, Thailand

finishing.com is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

Q, A, or Comment on THIS thread SEARCH for Threads about ... My Topic Not Found: Start NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
Consult'g, Train'g
& Software

About/Contact    -    Privacy Policy    -    ©1995-2021 finishing.com, Pine Beach, New Jersey, USA