copper and aluminum problems?

Is it a problem to use a copper fitting close to an aluminum manifold? Is there a problem with electrolysis?

I believe the problem with galvanic corrosion occurs when two dissimilar metals are in contact with each other in the presence of an electrolyte. If you keep your coolant fresh, I don't think you will have a problem with any combination of metal. If this is an oil-contact application, I don't think it is a problem because I don't believe oil can act as an electrolyte. In fact, oil used to be used as an electrical insulator in many applications (and maybe still is).

You can use the old mechanic test to check for electrical potential in the cooling system. Using a voltmeter, touch one probe to the metal (i.e., radiator neck) and suspend the other probe in the coolant without touching any metal. (Obviously, be safe; don't open a system under pressure, etc.) If the reading is more than about a 1/2 volt (less on computer-controlled vehicles), you really should replace the coolant.

I'm sure there are others here who have more detailed engineering knowledge of this situation, so maybe they will chime in and give you different feedback.

Eric

So if there was a 1/8 inch space between the pieces it would not be a problem?

Anytime you have dissimilar metals in contact with each other in the precense of an electrolyte (or potential electrolyte), you have the potential for galvanic corrosion. The relative distance betwee the two metals you are concerned with (AL and CU) is moot. You didn't say, but I assume the AL and CU are touching steel or cast iron, so you really have three dissimilar metals in this equation.

To make a long story short, as long as your coolant is fresh, I would not have a problem using copper within 1/8" of aluminum.

Brass is a more common metal to use for things like sensors and fluid taps because it is more stable. Copper will eventually corrode regardless (that's why the Statue of Liberty is now green, not copper colored).

Use the test I gave earlier to monitor your coolant. As coolant ages, it becomes acidic, hence why it acts as an electrolyte and you end up with a giant battery composed of your radiator, coolant, and engine block.

Eric