Coating Al and Cu simultaneously

Bobendren

This is another zalman cooler:

http://www.zalman.co.kr/eng/product/...x=174&code=009

How is this thing coated? It's all copper.

Bystander

It's a sandwich of 70 copper sheets, rather than a 24 sheet Cu sandwich between two 23 sheet Al sandwiches --- what coating? You want to plate it? Same problem as the Al-Cu-Al --- wicking of plating solutions between the sheets. Less bimetal problem, if there was one (doubt it), and no Al doing what Al does when in contact with salt air (corrode).

Bobendren

It's been coated with something to make it red. Most reviews that comment on the colour say it's been anodized, but copper can't be anodized, so what is it?

Bystander

Cu is a "red" metal. Cu can be anodized --- it isn't a tightly bound film as on Al, and isn't all that useful a process for anything. It's conceivable that you're looking at OFHC Cu --- "oxygen free, high conductivity" copper --- again, a "gilding of the lily" for heat sinks. Grab yourself a piece of heavy gauge copper wire, or scrap copper tube and play around a bit with a Bernzomatic, or whatever you can lay hands on for propane or butane torches --- oxidizing and reducing zones of the flame --- and with water and oil quenches of a piece heated to "red heat" at one end (use pliers --- it is a good heat conductor) --- you'll notice a gradation of color on the surface, red (black body emission red) through gray, black occasionally, and some almost bright reds (not red heat) as various oxides form, and decompose --- you'll see the color zones move as the temperature gradient develops toward steady state.

Bobendren

mmm....definately coated with something looking at these pictures...


You can see the base is the usual copper colour, but the fins are deep red.

Gokul43201

I've seen a similar, reddish coating on magnet wire. I think the wire (Belden magnet wire) we have in the lab has a polyurethane + nylon doublecoat.

More here: http://www.mwswire.com/inschar.htm