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topic 11661

Aluminum/Copper Interface


I am designing a cooling element to be used in a closed circuit fluid filled electrical component cooler. The heat exchanger and part of the cooling element are copper, and to save weight and price, part of the cooling element is aluminum. The pump may or may not also contain aluminum parts. I am aware of the galvanic corrosion problems of this combination of metals, both in theory and in first hand experience. My main two problems with this situation are 1.) Precipitation of oxides out of the cooling fluid which would clog the system. and 2.) Consumption of the aluminum parts that may cause leakage. I would sincerely appreciate any suggestions to prevent these two occurrences. These are the options I have examined so far:

1.) Place a sacrificial anode in the system to protect the aluminum. To my knowledge this would be ineffective due to the precipitation problem.

2.) Coat the aluminum parts with a thin polymer to protect it. What about scratches, durability?

3.) Add an inhibitor to the coolant. I think this would be a temporary solution that would have to be monitored and refreshed cyclically.

Paul Seabury
- College Station, Texas


Answer number 3 may well be temporary, but it is certainly widely practiced in everything from automobile radiators to industrial boilers and cooling towers.

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



There might be a third alternative. Have you considered designing your system to operate with oil, is it feasible? Many oils are almost dielectric, so galvanic corrosion would not take place or would be reduced to minimum. Hasta la vista.

Guillermo Marrufo
Monterrey, NL, Mexico


I did some more research, and came up with the polymer coatings Nycote and Topcoat. These seem like longer lasting solutions, but I would like to hear of anyone else's experiences with them. I would also like some availability information if anyone has it as I have initially had a really tough time finding suppliers for Nycote in the US (much less pricing). Thank you for your response Mr. Mooney. I still have reservations about adding an inhibitor though, as the product design calls for a solution to be more or less permanent.

Thanks again,

Paul Seabury
- College Statio, Texas

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