An unnoble metal is one that has a highly negative electrochemical potential, making it highly reactive and prone to oxidation. In a galvanic couple, the unnoble metal acts as the anode and sacrifices itself to protect the more noble cathode. Magnesium and zinc are highly unnoble, which makes them ideal materials for sacrificial anodes.
We can't bolt that aluminum bracket directly to the copper grounding bar, it's too unnoble and will turn to powder.
Also heard as
- active
- anodic
Related terms
Galvanic series
Ranking of real metals and alloys by their measured potential in a given electrolyte, usually seawater.
Anode
Electrode where oxidation happens and metal dissolves; in CP, the hardware installed to discharge current.
Sacrificial anode
Block of a more active metal such as magnesium, zinc or aluminum that corrodes to protect connected steel.