Of the materials used to make sacrificial anodes, magnesium has the highest dynamic polarization voltage and is most often used for onshore installations (in more resistive electrolytes) and cathodic protection in brackish or fresh water. Sacrificial anodes based on magnesium alloy can exceptionally be used in seawater when a rapid polarization of the structure is desired.
The usual chemical compositions of magnesium alloys are detailed below (extracted EN 12496-2013 annex B):
Magnesium anodes have a high service potential (normally – 1.5 V or – 1.7 V Ag/AgCl/seawater), but low mass energy (high consumption rate) due to self-corrosion.