Need Aluminum Corrosion Help

[Jeffaary]

I have a water-cooled aluminum housing with internal water passages. The housing was plated internally and externally with nickel. After a few months the nickel is just peeling off the internal passages and they are badly corroded. The rest of the housing is fine.

The water is not recirculated, so an additive is not a solution to the problem. Was nickel plating not a good idea or was it just poorly done? Is there a better plating material for my application? Would anodizing be better? Any suggestions would be greatly appreciated.

-Jeff

 

[btrueblood]

Plating to aluminum is a bit tricky in the best of conditions, plating to internal passages of any depth is even trickier, and in combination...well, I just don't think I'd go there.

Why plate at all, is the aluminum not corrosion-resistant enough for the external environment?

"The water is not recirculated, so an additive is not a solution to the problem." ? - So (a) the water is trapped in the internal passages? Or (b) are the internal passages always flowing fresh (tap) water? If (a) what good does the coolant do you. If (b) use a different alloy (5xxx series) or a different material (brass, stainless steel).

 

[kenvlach]

Any details on the water -- hard, soft, chlorinated, pH, potable, seawater, temperature?
What aluminum alloy?
What kind of nickel plating -- maybe medium-phosphous electroless nickel?
Re "rest of the housing is fine." Is this also exposed to the water?

Nickel plating protects aluminum if perfect coverage. At any porosity, galvanic corrosion of the aluminum occurs, causing the nickel to peel off. There are some 'tricks' that can possibly be done, depending on application.

Anodizing may be possible. Depends upon the complexity of the internal passages, as auxiliary electrodes may be necessary.

 

[Jeffaary]

The housing is used in a semiconductor wafer manufacturing chemical process involving HCL and high temperatures, so the inside and outside need to be plated to prevent that process from causing corrosion.

The water is constantly flowing tap water. When this product goes into production it will be all over the world using who-knows-what water. A recirculating system is an option, but a costly one.

Regarding stainless steel, the housing currently requires two people to manhandle it. Going to steel will require 5 to 6 people, making shipping, installation and field service ugly.

 

[MechanicalChef]

"manufacturing chemical process involving HCL and high temperatures"
In my limited experience, an anodized surface won't like HCL at all. In fact, we used HCL as a coating stripper.