What is Dissimilar Metal Corrosion, or Galvanic Corrosion and How to Prevent It:
When two types of metal come together in a corrosive environment, one sacrifices itself to the other. This is known as galvanic corrosion which is an electrochemical process requiring contact of dissimilar metals and an electrolyte solution, often water. It is an accelerated form of corrosion that may present itself long before other types of corrosion are visible. It can be boggling when a new asset begins to show signs of this type of degradation very early into its service life. .
The Association for Materials Protection and Performance (AMPP) is the global authority on corrosion and the coatings industry. See the link below for more information on galvanic corrosion.
While understanding the mechanisms of dissimilar metal corrosion is important, it is even more important to understand how to control it. This type of corrosion often presents itself at critical connections that are difficult to take offline for repair. Even welds can be susceptible to this type of corrosion. Often, the source of moisture is not accounted for when designing connections between dissimilar metals. Condensation, high levels of relative humidity and rain provide enough moisture to instigate the galvanic corrosion cell.
Aluminum and stainless steel are popular choices for fasteners and appurtenances due to their ability to resist corrosion. Good choices? Not if they are connected to another type of metal without accounting for potential sources of moisture. Decoupling dissimilar metals is an obvious choice for preventing this type of corrosion, but it is not always possible to prevent contact between the different types of metal. This is where high performance coatings can provide a remedy.
There are many types of coatings that provide protection from corrosion, but how do you select the right type? Tnemec Company, a 100 year old coating manufacturer, offers some basics on the different types of high performance coatings available here. Tnemec Coating Basics
Selecting the appropriate coating for your specific project can be a challenge, but the team at High Performance Coatings have solutions. We can help you specify the proper surface preparation and coating system for each project condition. Surface preparation can be confusing, but there are industry standards that guide us to the right choice. The Society for Protective Coatings, also known as SSPC, is now a part of AMPP and offers several standards for surface preparation of steel and non-ferrous metal. AMPP Standards
New construction and restoration of existing assets present different challenges in the selection of surface preparation and coating systems. Rely on the experts as High Performance Coatings for the appropriate selections. Contact us for help today.
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