From the mid 60’s to late 70’s aluminum wire often replaced copper as a cheaper alternative. But, aluminum’s properties proved problematic for reason’s no one had anticipated. With aluminium wiring it is possible that, over time, high resistance connection and/or arcing can develop somewhere in the electrical system, resulting in a connection that gets very hot. This increases risk of fire.
Fortunately, the problems associated with aluminum wiring are now well understood, thus shifting the focus to making installations safe. A knowledgeable electrician with aluminum wiring experience can check for safety and make necessary corrections.
Courtesy of Steve Sipos, Pillar to Post Home Inspections