An aluminum down conductor should be ...

An aluminum down conductor should be joined to a copper conductor using a bimetallic connector. This is important because dissimilar metals, such as aluminum and copper, can create a galvanic reaction when in contact with each other. A bimetallic connector effectively mitigates this issue by providing a conductive interface that prevents corrosion, allows proper electrical continuity, and maintains the integrity of the lightning protection system.

Aluminum and copper each offer specific benefits for conducting electricity and can be effectively used together when appropriate connectors are applied. Bimetallic connectors are engineered to facilitate this connection while accounting for the different electrical and thermal expansion properties of the two metals, promoting a long-lasting and reliable system.

Using a clamp to join aluminum and steel does not provide the same level of protection against galvanic corrosion, weakening the connection over time, and may lead to failure in the lightning protection system. Merely using aluminum without any other material misses the potential for enhancing conductivity and suppressing corrosion. Connecting the down conductor to a conduit for grounding can be a necessary step, but it does not address the fundamental requirement of connecting dissimilar metals properly, which is key to maintaining system integrity.