Superduplex 2507 - position in the electrochemical series 3

[AnsAvi]

I am looking for potential for galvanic corrosion in an assembly consisting of super duplex 2507 on the one hand and several possible different alloys at the other. However, I am not able to find a galvanic series containing 2507 to estimate its position compared to other alloys. Is anyone aware of such a table or the SCE value for 2507?

 

[EdStainless]

If you look at research that has been done using electrochemical methods, it is apparent that the natural potential (in fresh flowing seawater) would be similar to other alloys with similar pitting resistance.
These would be 6% Mo superaustinics (not the leaner alloys such as 254sMo) or even the superferritics.
One thing that we have learned over the years is that when working with this class of materials coupling them with more noble alloys (NiCrMo or NiMoCr) there is not enough potential difference to cause issues in seawater. Some special chemical process environments may be another issue.
Just as a general caution, the super duplex alloys require the strictest process control and oversight of any alloys in use.
Rigorous attention, especially to the heat treatment, welding, and corrosion testing are required in order to assure suitable performance.
If a supplier does not have a long history of doing this work and is not very open about it, it is time to move on to a different supplier.

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P.E. Metallurgy, consulting work welcomed

 

[AnsAvi]

I am being asked about possible pairings of 2507 with 316/316L, 317, Nit 50 and other austenitic stainless steels. Based on your response, it seems that possible galvanic issues are likely, especially in seawater environment.

 

[EdStainless]

316 and Nit 50 will not live long in seawater.
If the 317 is LMN (high Mo and high N) then it could work if there are no crevices.
The problem isn't so much galvanic corrosion as it is that regardless of the presence of the 2507 the lesser alloys will pit.
Galvanic issues just make it happen faster.
This is especially true if the lower alloy parts are small in comparison to the 2507.

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P.E. Metallurgy, consulting work welcomed