What Does Galvanic Series Mean?
The galvanic series is a chart showing the relationships between metals and a guide for selecting metals that can be joined, with an aim of helping in the decision-making process. This is done by illustrating which materials have a minimal tendency to a galvanic interaction, or the need or even degree of protection that can be applied to reduce the expected probable interactions.
In general, the further apart materials are in the sequence, the higher the level in the galvanic series, and hence the higher the galvanic corrosion risk.
The galvanic series serves as a simple qualitative guide only, and does not give any information on the galvanic corrosion rate.
The galvanic series is also known as the electro-potential series.
Corrosionpedia Explains Galvanic Series
The galvanic series has proved to be useful as a guide for selecting metals that are to be joined and helps the selection of metals. It can also help indicate a need for or degree of protection that should be applied in order to lessen expected potential interactions. Usually, materials that are further apart in the galvanic series are at a higher risk of galvanic corrosion. Galvanic corrosion, therefore, may be prevented by altering the design of the machinery.
Galvanic corrosion is sometimes used to extend the life of materials such as zinc coatings on carbon steel and zinc anodes in water heaters. However if not considered, it can lead to unexpected failures.
Requirements for Galvanic Corrosion
In order for galvanic corrosion to occur, three elements are required.
- Two metals with different corrosion potentials
- Direct metal-to-metal electrical contact
- A conductive electrolyte solution (e.g. water) must connect the two metals on a regular basis. The electrolyte solution results in a “conductive path”. This could occur when there is regular immersion, condensation, rain, fog exposure or other sources of moisture that dampen and connect the two metals.
If any of these elements is not there, galvanic corrosion cannot occur.
The galvanic series defines the nobility of metals as well as semi-metals. This process happens when two metals are submerged in an electrolyte or when electronically connected before letting the base experience galvanic corrosion. The corrosion rate will be influenced by the electrolyte as well as the difference in nobility. This difference is then measured in terms of voltage potential. Batteries form the basic principle of metal corrosion potential in the galvanic reaction.
This list is mainly sorted by corrosion potentials. Many confuse it with the electromotive force (emf) series, which is not always the case. Each alloy or metal has a distinctive corrosion potential. The more negative a metal or alloy is in the galvanic series, the more likely it is to suffer galvanic corrosion, while the positive shows resistivity to corrosion when subjected to viable conditions for corrosion. The closer a metal or an alloy is in the series, the less the effects of galvanic corrosion compared to those metals far apart in the series.