Each metal has their own balance potential in there isolated electrolyte. This material property makes the metal more noble or less noble. In other words, it becomes more or less susceptible for corrosion to occur. When a salt solution with a fixed concentration of own metal ions is created, the theoretical electrochemical potential can be determined for each metal.
We have crafted a table with these potentials against the hydrogen electrode. an the more practical and easier reference electrode, the Cu/ CuSO4 in a certain environment such as soil or sweet / salt water. Magnesium is thus the least noble metal in the table. While at the other end of the spectrum, gold is listed as the most noble metal. This table also makes it clear that sacrificial anodes for steel (Fe), can only be carried out by means of magnesium, zinc or aluminium. Metals at the other end of the spectrum will therefore work the other way round, with iron sacrificing itself in favour of copper, for example.
|Metal||Potential in Volt|
(against H2 in
own salt solution)
|Potential in Volt |
in soil / sweet water)
|Magnesium (Mg)||– 2,37||-2,69|
The chart valuable to create a better understanding about galvanic corrosion. By creating galvanic links between several metal types, an unintentional galvanic link can be created, leading to unintentional corrosion. Think, for example, of galvanised fasteners used to secure aluminium structures. Or a combination between normal steel and galvanised steel. Once a galvanic bond has been created and an electrolyte such as water is or will be present, the less noble metal sacrifices itself.