Hello,
I am confused. How come insulated aluminum cable corrodes so badly yet overhead aluminum lines seem to last years.
The supply to my house failed over the week end. The repair crew arrived and figured out that the break was 23.5m back from my meter box. Wandering back though the garden the linesman noticed a "new" bush which was about the right distance from the meter box. We had planted it last spring. He pronounced that the break would be there.
He dug up the bush and started clearing the hole. He quickly found the cable which was between 6 to 10 inches below the surface. Clearing more earth from the hole, using a spade, the linesman brushed against the cable. It broke clean in two.
He explained that this was common enough. I had apparently nicked the cable when planting the bush in the spring and this had allowed mosture to seep into the cable. The recent rain was the final straw and the cable failed.
The cable consisted of an inner aluminum core surrounded by insulation, a copper mesh braid and another outer layer of insulation. The inner core had apparently totally disintegrated in the space of about 8 months. The copper braid had as good as failed as well.
Can anybody explain how this happens given that aluminum overhead lines are constantly exposed to mosture.