In this knowledge article we look briefly in to what Galvanic corrosion is and why we've considered it when designing and installing your solar power kit.
Galvanic corrosion is an electrochemical process that occurs between two metals of different chemical make up when the metals are connected electrically; either in direct contact or connected by an electrolyte like saltwater. The process causes accelerated corrosion of the more chemically active metal (the anode) while the noble, or less reactive metal (the cathode) is protected from corrosion.
Why Galvanic Corrosion Occurs:
All metals corrode, or oxidize even on their own. This is due to electrons wanting to leave the chemically active metal and join with oxygen and hydrogen to form oxides, like rust, which are more electrically stable compounds.
When in electrical contact, a more reactive metal will corrode in preference to a less reactive metal because all the electrons that are eager to join up with hydrogen and oxygen to form a stable oxide come from that more reactive metal. This allows the less reactive metal to keep all its electrons and thus it does not corrode.
The reactivity of a metal is illustrated by the Galvanic Series. An active metal that is far from a noble metal in terms of points on the galvanic series will corrode very quickly. The closer together in the series two metals are, the less galvanic corrosion will occur between them.
Sometimes we want a highly active relationship between metals, like when we are hoping to protect an aluminium hull from corroding. In this case we would bolt a more active metal, like magnesium to the hull so the magnesium corrodes in preference to the aluminium.
Often we want a non reactive relationship between metals, like when fastening solar panels. We don't want the aluminium frame of the panel corroding in preference to the fastener!
Another example of galvanic corrosion occurring is at the battery where we often see the terminal corrode. At LUX Solar we have chosen our ring terminals to be made of tinned copper which is non reactive when connected with the lead battery post.