When dissimilar metals are in direct contact with one another and an electrolyte such as rain water or ground water is present, galvanic corrosion will likely occur. The rate of corrosion will depend on a few factors, such as the electrolyte and the difference of corrosion potentials.
Galvanic corrosion at its very basics is nature trying to balance the differential between two different metals. The electrolyte enables the processes of galvanic corrosion to commence. The less noble metal will corrode first, like the stainless screws used in aluminum, for example. With the addition of moisture, the aluminum will begin corroding unless the two materials are isolated from each other.
Structural engineers and designers must take into account the possible presence of rain, dew, snow, humidity and other electrolytes when determining their fastener application compared to the base material.
How to Prevent Galvanic Corrosion
Since making everything out of the same metal is impossible, there are a few preventive measures for safeguarding your product and fasteners from galvanic corrosion.
The application of a protective metallic coatings (electroplating) or barrier coatings (paint) can provide protection for the base metal. The level of protection that it provides often depends on the thickness of the coating applied, and whether the two materials are in direct contact with each other.
Choosing metals that are very close in nobility on the galvanic chart will dramatically help slow down the process of galvanic corrosion. Each position further away on the chart increases the speed at which the corrosion will occur. Zinc and stainless steel are the furthest apart, making their relationship the worst on the galvanic scale.
Galvanic corrosion is an issue that could prove costly if not factored into your considerations when determining the best application for a particular fastener. Being aware of preventive measures well in advance could help preserve the integrity of your structure before it is too late. To learn more about galvanic corrosion and best practices for preventing it, contact Bossard at ProvenProductivity@bossard.com.
Issue of Galvanic Corrosion by Bossard