Galvanic corrosion is a type of corrosion which occurs when two different metals, possessing different nobilities, come into contact with each other in wet or damp conditions, with the more noble metal causing accelerated corrosion in the other metal.
An example could be installing a stainless-steel signboard with the help of galvanized steel screws.
Both stainless steel and galvanized steel have different nobilities; stainless steel is more noble and galvanized steel is less noble. As the signboard and screws get exposed to the humidity present in atmosphere, stainless steel will cause accelerated corrosion of the galvanized steel screws until they eventually fail. As they fail, the signboard will also fall down.
This is a very simple example of galvanic corrosion in action, carrying minor repercussions. Now imagine galvanic corrosionaffecting a large structure, leading to its premature failure. How devastating that could be. Hence, when designing any product or structure, designers pay special attention to potential galvanic corrosion concerns, exercising different solutions to avoid any mishap.
So what happens if we bring two different types of zinc coated steel in contact? Will galvanic corrosion be a concern in this case as well?
Let’s say, you’re designing a product, and you’ve a hot dipped galvanized steel article and an electroplated galvanized steel article to work with. Should you be concerned about any potential galvanic corrosion failures?
The answer is no.
This is because, as explained earlier, galvanic corrosion occurs when two dissimilar metals, having different nobilities are brought in contact. Your steel articles have although been treated under different galvanizing processes, in the end, they both are identical; they both are galvanized forms of steel. Pairing the two will not cause galvanic corrosion.
Having said that, it’s important to notethat their service life will differ.
The service life of a galvanized steel article depends on the thickness of zinc coating present on its surface. The thicker the coating, the longer the service life. Since hot dip galvanizing produces galvanized steel with thicker zinc coating as compared to electroplating, you can expect your hot-dipped galvanized steel article to last longer.
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