[owenversteeg]

I built a boat partially with CCA (copper clad aluminum) wire, disregarding the recommendations to not use it. I didn't give it much thought and naively figured that as copper and aluminum are two of the most "rust-proof" materials that it would be fine. Within two years of using it - and before the boat even made it into the water - it had begun to seriously corrode to the point that resistance was significantly increased. I had to replace all the CCA wiring and terminals connected to it.

Basically, both copper and aluminum are "rust-proof" because they develop a thin, hard layer of oxide immediately upon exposure to air. However, this also means that when a new crack forms (by vibration of the wiring or thermal expansion for example) that crack will be immediately coated by an oxide layer. At the same time, moisture in the air will create a galvanic cell with the copper as cathode and aluminum as anode (because aluminum is more active, more willing to give up electrons, which is because its bond with its electrons is weaker than copper's.) As the electrons leave the aluminum it develops a positive charge, which attracts negatively charged oxygen.

It is this last effect, galvanic corrosion, which I believe to be the chief issue with CCA wiring. Copper and stainless steel, for example, are much closer in the galvanic series than copper and aluminum, so copper and aluminum corrodes significantly faster.

Unfortunately, galvanic corrosion is a tough one, because lots of modern American houses are built with poor ventilation - as you can see by the large number of homes with mold issues. That moisture is exactly what enables galvanic corrosion. I think if we used CCA wiring across America we'd see a number of house fires caused by moisture -> corrosion -> higher resistance -> heat -> fire.