topic 26393

Will Copper-Aluminum corrosion occur in heat exchanger

2003

I am designing a water cooling system, with a small copper heat exchanger and a large aluminum radiator. Will there be a corrosion problem between the two different metals after a few years of continuous use, water temperature will be about 50C Anodized aluminum would be better but this is for a one off project and I was hoping to avoid any special finishes?

Mark Cumper
Designer - Antwerpen, Belgium

2003

I don't exactly understand the description, Mark. But it sounds like trouble. Aluminum is a very active metal and copper a quite noble one. If both materials touch the same fluid, allowing an ionic path, and there is a metallic path as well, galvanic corrosion seems pretty likely.

Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey

2003

If the copper and aluminium are not connected electrically, except by the water does this improve matters ? Does earthing everything help, or make matters worse, by preventing an equilibrium from ever being established ? I thought that if the area of copper was much smaller than the area of Aluminium, then it would be OK.

Mark Cumper
- Antwerpen, Belgium

2003

Having a small surface area of the more noble metal certainly helps, but I don't think it makes things "okay". However, if the metals are not connected except by the water, I don't believe that galvanic corrosion is possible.

Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey

2003

So insulating the copper is all I need to do. Great news.

Thank you for your help.

Mark Cumper
- Antwerpen, Belgium

2004

I would say analyze your water before proceeding. Aluminum has an excellent oxide layer. If the level of chloride & sulfur & copper is low in water, aluminum can be used. Pitting is the issue in aluminum. Copper does better than aluminum for atmospheric corrosion but it is quite susceptible at various pH levels. Overal aluminum shows lower corrosion rates. pH for aluminum use is between 3.8 to 8.

Small copper to large aluminum sounds like a good plan as far as the area for galvanic goes.

Kam Dianatkhah
- Dallas, Texas

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