So i have an aluminum reservoir, and my gpu blocks are copper. Does galvanic corrosion occur regardless of the fluid being used or does it only occur when using conductive fluid. So if i use non conductive fluid (Feser One to be specific) will i be ok? If not i waisted 60$ on reservoir =\.
Galvanic corrosion will occur with metals of dissimilar electrode potentials being in contact with an electrolyte. Copper has a 0.35 V potential and aluminum has a potential of 0.90-0.95 V, so corrosion will occur because the potentials are not the same (two copper blocks won't corrode each other, because their potentials are
the same.) Water is an electrolyte as it has dissolved ions in it and will traffic electrons between the metals, causing them to corrode. However, the rate of corrosion can vary. The more ions in the water, the faster the metal corrodes. The greater the surface area of the two metals, the faster they corrode. "Non-conductive" water like the Feser stuff still has ions in it, but it has fewer ions than normal tap water and thus is a poorer conductor and your blocks will corrode more slowly. Unless you want to get into using a nonpolar coolant like 3M Fluorinert (very expensive!), you're going to have some degree of corrosion.
You have a couple choices in how to tackle the corrosion issue. One is to get rid of the aluminum reservoir, which would put you out $60 but would be the easiest and surest way to prevent galvanic corrosion. A second way is to coat the inside of the reservoir with something nonconductive like a thick layer of epoxy or paint to try to reduce the contact the aluminum has with the water, which slows down the rate of corrosion.