G48 test failure consequence 1

[gustorf]

Hi all,
If a J93404 Superduplex casting material fails the G48 method A corrosion test, does this mean it will FOR SURE corrode in operation in a seawater line?

 

[SJones]

No, since ferric chloride is not seawater. However, it does indicate that some aspect of the material is not correct and it would not be prudent to proceed without ascertaining the cause of the poor performance.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[EdStainless]

First of all, what is the test temperature?
Second, does this material pass the A923? (similar test solution but entirely different goal)
What does the microstructure look like?

I may have failed because of poor test method. Lets work through this.

If the test was done correctly it does mean that the castings will pit in seawater a lower temperature than you would normally expect for the chemistry. If this is too low then you have failures.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[gustorf]

The test temperature was +50°C.
A923 was not requested and not done.
The microstructure showed some intermtellic phases and imperfections, the ferrit content was in the high range of 65%.
We did a so called "ferroxile" test and the material passed.

 

[EdStainless]

the ferrooxile test is just for surface iron contamination.

NEVER buy a duplex without requiring A923. Reject it. It was not annealed correctly. Use the G48 as the basis, or use poor workmanship, wrong microstructure.
Also I suggest that you switch to G48 method C, even if you have to go to a lower test temp like 45C. The test is more repeatable.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[strider6]

have a look at this doc:

GUIDANCE DOCUMENT FOR THE EVALUATION OF CAST SUPER DUPLEX STAINLESS STEEL

http://www.osti.gov/bridge/servlets...xdg6QEAAACSVDwC&bcsi_scan_filename=861932.pdf

s

Corrosion Prevention & Corrosion Control