Clear type II anodize over masked black type III anodize

[chrisloughnane]

I've got a design in my head that I think works, but I'm wondering if there are any gotchas

Processing looks like this:

-Part is aluminum 6061
-Mask is applied (contains two separate traces)
-Type III anodization is performed (leaving raw aluminum where masked)
-Type II anodization is performed to give corrosion resistance to the raw aluminum areas

End result would be a black aluminum part with 2 clear traces (from the mask) that are conductive themselves but insulated from each other.

Also I wonder if, instead of masking, I hardcoat the whole thing, hit it with a laser, and then type ii coat it.

Does anyone see any issues (obvious or potential) with either approach (masking or laser)?

Chris Loughnane
Mechanical Engineer
Farm

 

[1gibson]

Other than the whole part being aluminum, so the two traces would be electrically connected?

 

[mcgyvr]

Why don't you explain what you are trying to do/achieve?
The end result will be nothing like you expect so far..

As stated the whole part is aluminum.. Every bit of that aluminum will be "electrically connected" no matter what surface finish you apply to it..

 

[chrisloughnane]

@1gibson

The two traces would not be electrically connected.

@mcgyvr
I understand that the bulk body is electrically connected, but it is my understanding that current is a surface phenomenon so that if (for example) I masked off two circles during a type III anodizing process that holding a DMM to both would show that they are insulated.

Am I misunderstanding?

Chris Loughnane
Mechanical Engineer
Farm

 

[chrisloughnane]

@mcgyvr I see what you're saying, you are right. I feel silly.

I may be able to split my parts into two so that there is only one trace per mass of aluminum.

Given that, the result I am trying to achieve is a conductive, corrosion resistant individual trace on a metal. Since metal is conductive I feel I need mask the path I want and perform a nonconcductive surface operation everywhere else. My question then is what can I do to get max corrosion resistance on the conductive trace.

Chris Loughnane
Mechanical Engineer
Farm

 

[1gibson]

I think the solution to your problem is probably to make it out of plastic and add gold plated contacts, but it may take you a few more questions to get there.

How are you going to hold the (now split in half, added cost/complexity) pieces of aluminum together? Metallic bolts are also conductive.

Why is it aluminum when you seem to want the bulk of the part (everything but the traces) to be an insulator?

 

[chrisloughnane]

Hold the two aluminum pieces together in an insert molded part.

Aluminum for rigidity of some of the external tabs.

Chris Loughnane
Mechanical Engineer
Farm

 

[1gibson]

You know that the traces will have continuity to the external aluminum tabs, and if you bolt those to a metal frame, the two traces will again be electrically connected, and you still want to do that, yes?

 

[mcgyvr]

There are just too many unknowns here..
Corrosion resistance from what environment? What is the contact wiper made of/its shape? Contact life expectancy? Frequency of cycles? Nature of signal? Mechanical details/drawings/concepts/sketches and SO..so many other things before a "suitable" answer could even be attempted..