When it comes to home wiring, copper is the gold standard—or more appropriately, the “copper standard.” However, the price of copper has fluctuated over the years, whereas aluminum has remained rather low. For this reason, there are many buildings that have aluminum instead of copper for their wiring. Aluminum was thought to be an acceptable alternative in the 1960s and 70s, but has since been discovered to be subpar. If you have aluminum wiring in your home, consider having an electrician in San Jose to replace it for you. 
Less Effective Conductor
Though aluminum is less expensive than copper, its composition makes it a less effective conductor. For this reason, you need to use more aluminum in order to achieve the same amperage. Aluminum is also less ductile than copper, which means it is more likely to break down when drawn into thin wires and bent. Aluminum is more malleable than copper, and thus more sensitive to compression. The areas that get compressed have more electrical resistance, which is not what you want from a wire that’s supposed to conduct electricity.
Faster Deterioration
Copper is more resistant to corrosion than aluminum. If aluminum is exposed to moisture and certain kinds of metals, it will undergo something called “galvanic corrosion,” which is bad news for an electrical wire. Also, aluminum wire is more easily oxidized than its copper counterpart, and oxidization can seriously compromise important connections, which can in turn cause a fire hazard.
Potential for Loose Connections
Tight, secure connections are important for electrical functionality and safety. Unfortunately, aluminum wire behaves in such a way that sometimes makes it difficult to hold a connection. As mentioned above, oxidation is part of the problem. Another problem is that aluminum expands and contracts with temperature changes, and vibrates more than copper when an electrical current passes through it. Over time, these changes in size can cause aluminum to be separated from its connections, rendering it ineffective and unsafe.