In my line of work I see aluminum ground lugs, bonding nuts and straps and also neutral bars eat copper up, especially when exposed to the elements. I know how galvanic reaction works between elements under current load, but my question is why do aluminum and copper seem to hate each other more than any other? And, why would they still be required in usage together per NEC code?This problem arises between various metals such as iron aluminium where some form of plastic barrier is needed to stop electrochemical reaction taking place where these metals are in long term contact with each other especially in a wet environment. As far as aluminium copper are concerned, the difference in their chemical reactivity is particularly large; aluminium is a highly reactive metal that quickly becomes dull by coating itself with a very thin layer of aluminium oxide whilst copper is one of the least reactive of all metals. However, once covered with a fine layer of aluminium oxide, aluminium will tend not to corrode further. The effect of this is that any copper that does go into solution as a result of contact with weak atmospheric acids will very readily precipitate again as metallic copper onto the aluminium. Reactions similar to those below will readily take place: H2O (rain) + CO2 --- H2CO3 (carbonic acid - carbon dioxide dissolved in rain water) Cu + H2CO3 --- CuCO3 + H2 In an aqueous environment, 3 CuCO3 + 2 Al --- Al2(CO3)3 + 3 Cu Copper aluminium are regularly used because they are relatively low cost when compared with potential alternatives, even with recent commodity price increases. Toughened plastic has replaced copper in certain plumbing applications which have obviously eliminated this galvanic reaction problem.that\'s a single alternative reaction. The aluminum and the copper swap places, yielding copper and aluminum sulfate. Please notice: the 1st answer describes a chemical equation with nitrate, no longer sulfate. otherwise, this is the perfect format.Other related question