The chemical reaction with electrical and also the difference of metals also contribute Weather and dirt play a role as well .. Just like if you put together copper and also cast iron water lines . You need to use di-electric fittings to eliminate this from happening . Use the battery pads or use a battery spray that actually inhibits this process from taking place .If the wire have the corrosion as well , you may think about cutting out or replacing that piece of wire or wires as well . This causes a higher drain on your electrical system and draws a higher amperage due to corrosion