Possible for good color finish--anodizing aluminum die-cast parts? 3

[Theophilus]

It seems getting good color saturation from attempts to anodize die-cast parts is problematic. Is there some other such process that might yield similar aesthetic results (paint, powder coat, plating)?

The coating would need to withstand common contact with brake fluid--making this quest a bit difficult.

Any ideas?

Thanks!



Jeff Mowry

http://www.industrialdesignhaus.com

A people who value security over freedom will soon find they have neither.

 

[swall]

Epoxy powder coat would work, assuming your components are not exposed to UV. I have found it highly resistant to DOT 3 brake fluid.

 

[Theophilus]

Thanks, swall--I'll check into that.

By the way, might it be possible to plate to copper, nickel, (whatever), and then to an aluminum of the type that would take an anodized finish? It's certainly a stretch, and probably expensive, but I'd really like to have a clean anodized finish if at all possible. (Can aluminum even be a plating material?)



Jeff Mowry

http://www.industrialdesignhaus.com

A people who value security over freedom will soon find they have neither.

 

[KENAT]

I assume it's the surface finish/porosity that's causing the problem. Anyway to improve this, maybe put them in a rumbler or something?

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[CoryPad]

Yes, aluminium is suitable as a plating material. A commonly used standard is MIL-DTL-83488D COATING, ALUMINUM, HIGH PURITY. This can be electroplated or applied via Ion Vapor Deposition (IVD). Here are some suppliers:

http://www.alumiplate.com

http://aaaplating.com/

I can't comment regarding subsequent anodizing of a plated surface.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Theophilus]

Thanks, Cory, I'll check into that.

From what I've found out so far, the die-cast aluminum alloys have some stuff (like silicates) in them that won't accept anodizing--so the color saturation is terrible, and finish quality splotchy. If we were able to find a "pure" aluminum to plate over that stuff--with great finish characteristics--then perhaps we could anodize that plating layer. A bit idealistic, and perhaps expensive, but that's the next thing on my list of tricks to try.



Jeff Mowry

http://www.industrialdesignhaus.com

A people who value security over freedom will soon find they have neither.

 

[KENAT]

Well I agree with Cory that it is possible & has been since at least WWII, known as Alclad in some parts.

I'm also not sure about anodizing it, I only recall chromate conversion coating it &/or suitable paint system.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[swall]

At one of my former employers, we were working with RSA (developed by Allied Chemical)high temperature aluminum, which had around 8% iron content. It did not anodize well, so one of our enterprising chemists had some samples coated with IVD aluminum and then anodized them. It looked OK, but was not a practical solution to the problem.

 

[TVP]

Theophilus,

Another option to consider is the choice of Al alloy for the high pressure die casting process. Most of the alloys have high silicon levels (7-20%) which makes anodizing difficult, especially for aesthetics. Alloy 518.0 (UNS A05180) is a die casting alloy with excellent appearance after anodizing. Typical properties for this grade as listed in ASTM B 85 are as follows:

Tensile Strength: 45 ksi (310 MPa)

Yield Strength (0.2 % Offset): 28 ksi (190 MPa)

Elongation in 2 in. or 50 mm: 5%

Shear Strength: 29 ksi (200 MPa)

Fatigue Strength (R. R. Moore Specimen 500,000,000 cycles): 20 ksi (140 MPa)

 

[Theophilus]

Thanks, I'll check out that material and compare those characteristics with what we're using right now.



Jeff Mowry

http://www.industrialdesignhaus.com

A people who value security over freedom will soon find they have neither.