What Is the Galvanic Series?
Stone pointed to the hierarchy of metals as the main cause of galvanic corrosion. Different types of metals are considered more or less noble and are arranged accordingly in the galvanic series. Platinum and gold are at the top (more noble, less reactive), while aluminum and zinc (less noble, more reactive) are near the bottom. Yellow metals fall somewhere in the middle, with iron and steel being less noble than bronze and copper but more noble than aluminum and zinc.
Why Does Galvanic Corrosion Occur?
When different types of metal that are far apart on the galvanic series come into contact, the corrosion potential of the more noble metal shifts to the less noble metal. Stone explained, “Things like copper are going to preferentially cause things like steel to corrode. Things like steel are going to preferentially cause things like aluminum to corrode.” He noted that metal contact points, such as fasteners made of different metals, are good early indicators of galvanic corrosion concerns.
How to Avoid Galvanic Corrosion Surprises
Galvanic corrosion can catch people off guard when they protect only one type of metal, such as steel, in a multi-metal system. They may assume the brass or aluminum in the system does not need protection due to higher corrosion resistance. However, Stone said this assumption can do a “severe disservice” by pushing corrosion attack down the line to the less noble metal.
Image courtesy of Cortec. The key to preventing galvanic corrosion, when it is not possible to electrically isolate dissimilar metals, is to use a corrosion preventative product. This could include paint, VpCI packaging or a liquid rust preventative that protects all types of metals in the system.
While these comments barely scratch the surface of galvanic corrosion, they represent a major step forward in prevention. If you have more questions, contact our team today to get started in your fight against galvanic corrosion.
