Galvanizing Stainless Steel
* Updated February 2024
Can stainless steel (e.g. 400 series, 300 series) be galvanized? And, if so, is the coating produced on this steel going to be similar to the coating produced on traditionally galvanized steel?
Yes, but with some limitations. Nickel is necessary to initiate the reaction between steel and zinc that grows the intermetallic alloy layers. Since stainless steels from the 400 series do not contain nickel, they cannot be hot-dip galvanized. There are over 50 types of stainless steel, but as long as they contain some nickel in their chemistry (e.g. 300 series), they can be hot-dip galvanized. Hot-dip galvanized coatings on stainless steels have the same coating and alloy layers as those on traditionally galvanized steel.
Stainless steel fabrications are not typically hot-dip galvanized for additional corrosion protection. Instead, the most common reason is a fabricator was required to weld stainless components onto a traditionally galvanized steel fabrication en route to the galvanizer.
In some cases, galvanizers have reported quality issues or aesthetic concerns when hot-dip galvanizing 300 series stainless steel. In these instances, a galvanized coating developed in some areas but not in others, and results varied from heat to heat. It would be best to try hot-dip galvanizing a sample of stainless steel from each heat specific to the project before attempting to galvanize a whole project.
At the galvanizer, stainless steels will occasionally benefit from extended cleaning times or blast cleaning prior to galvanizing. Additionally, when stainless steel and traditional carbon steel are mixed within an assembly, the galvanizer should be mindful of differences in cleaning times which may result in areas of rougher coatings. This appearance may require additional smoothing work for handrail products or other projects with elevated aesthetic requirements.
Is it true that welding galvanized stainless steel can cause embrittlement?
When certain types of metals become molten, they can cause cracking in other types of metals. This is a concern when welding stainless steel that has been galvanized, but it is avoidable with a few extra steps. You can learn what steps should be taken to mitigate this concern in AGA’S article, Embrittlement and Welding in Galvanized Stainless Steel.
Can Chromaloy (e.g. 4130, A193 Grade B7) be hot-dip galvanized?
Galvanizers have had varied success galvanizing chromaloy steel, which is named after the two major alloying elements it contains, chromium and molybdenum. Like with stainless steel, there have been reports of chromoly developing a galvanized coating in some areas but not in others. Again, this only occurs some of the time and when it does not occur, chromoly develops a normal HDG coating. It is recommended to galvanize a sample from each heat before moving forward with a project containing more steel of this chemistry.
© 2024 American Galvanizers Association. The material provided herein has been developed to provide accurate and authoritative information about after-fabrication hot-dip galvanized steel. This material provides general information only and is not intended as a substitute for competent professional examination and verification as to suitability and applicability. The information provided herein is not intended as a representation or warranty on the part of the AGA. Anyone making use of this information assumes all liability arising from such use.