Summary for 2205 duplex stainless steel passivation Discussion
Passivation of 2205 duplex stainless steel is discussed in terms of both alloy makeup and surface treatment. In the first question, Hunter Cutchin asked about pickle/passivation or electropolishing for UNS 31803 (2205 duplex stainless steel), along with composition, corrosion resistance, mechanical properties, cost, availability, and fabrication concerns. Lee Kremer replied that 2205 is roughly 22% chromium, 3% moly, 5% nickel, and 0.15% nitrogen, describing it as a good grade between ferritic and austenitic stainless steels and saying it can be passivated well with citric acid formulations. In a later question, Mike Humcke asked whether ASTM A967 Nitric 2 and Nitric 3 are the best passivation methods for S32205 and S32760 used in intermittent seawater immersion. The response said citric acid passivation is personally considered the most effective, but if nitric is required, ASTM A967 does list Nitric types 2 and 3 for duplex grades.
Q. Has anyone has experience with pickle/passivation or electropolishing of “UNS 31803 (2205 duplex stainless steel). Need information on composition, corrosion resistance, mechanical properties, cost per pound, availability, and special fabrication considerations.
Hunter Cutchin
– Easley, South Carolina
1998
A. Dear Hunter:
2205 is 22%Chromium /3%Moly /5% Nickel /0.15 Nitrogen.
It is a good grade between the Ferritic and Austenitic groups, and can be passivated well with citric acid formulations per our experience.
Lee Kremer
Stellar Solutions, Inc.
McHenry, Illinois
1998
Q. We are in the process of casting drive chain out of S32205 and S32760 stainless steel for a customer who plans to use the chain for cycled intermittent sea water immersion. We are curious if ASTM A967 Nitric 2 and Nitric 3 are the most effective methods for passivating these alloys? Thanks.
Mike Humcke
– Pewaukee, Wisconsin
March 14, 2013
A. Mike,
Personally, I tend to think that citric acid based passivation is the “most” effective, but if you are committed to nitric, those are duplex grades and the treatment chart in the standard does indicate Nitric types 2 and 3 for duplex.
Ray Kremer
Stellar Solutions, Inc.
McHenry, Illinois