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topic 0497

Hardcoating type 4032 aluminum in black

A discussion started in 1996 but continuing through 2017


Q. Is it possible to black hardcoat anodize 4032 aluminum? This alloy contains >10% silicon while Mil-A-8625 [link is to free spec at Defense Logistics Agency,] warns against attempts to hardcoat any alloy of >8% Si. We have experience with anodizing some castings with 6-8% Si and they can be type II anodized, but the color is not as dark as desired. It also tends to be less uniform both across the surface of the part and from part to part. Are there any specific additives or baths that can be used exclusively for higher Si alloys?

Gordy Seppanen
materials engineer - Minneapolis, Minnesota


A. Hi, Gordy. One alternative is proprietary technology, consisting of special power supplies, additives, and operating procedures.

These licenses cost thousands of dollars-- and include amp-hour charges as well. It's something you need to think about, not something you buy off the shelf. Good luck.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


A. Sir,

We have a specialty chemistry system here which allows for the safe hardcoating on high copper & silicon alloys.

David A. Kraft
- Long Island City, New York


A. Luke Engineering has been applying thick (up to 75 um) hardcoating to high silicon/copper aluminum die-castings for over twenty years. The color is naturally a brownish-gray. This hardcoating can be PTFE impregnated or dyed black, however, the color is not as deep or uniform as on normal wrought alloys.

We have no experience with 4032 alloy but would be glad to hardcoat prototypes for evaluation, free of charge.

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

luke engineering banner


A. Metalast has a newer process that has advertised some extremely impressive data, particularly if you do not need a true hardcoat, but one that meets spec and can be two step anodized. I am sure they would like to sell their process or give you a name of one of their licensees. Charlie Grubs is their VP of technology (1996) if you are a follower of light metal processing.

James Watts
- Navarre, Florida

February 1, 2017

Q. Aluminum coating for Aesthetic black requirement and wear resistance for 150,000 cycles (Those many times other part comes and hits Al part)

Amit P
- Pune, India

February 2017

A. Hi Amit. More words please! I assume you are looking for this finish? :-)

But are you looking for a shop to do it for you, or looking for the process to do it in house? What alloy are you using please? Thanks.


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

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