ASK NDE’s TECHNICAL EXPERTS - BRINE

NDE’s technical team receives enquiries on a daily basis that require input from a stainless steel specialist.ASK

Below is one of the questions, with the response from our technical experts.

QUESTION

What materials are required for crystallising sodium chloride out of a mixed brine, at a pH of 8.0 and boiling at 100°C, 
with the composition 16.5% NaCl, 11.2% MgCl2, 0.7% KCl, and 9.1% MgSO4?

ANSWER

This is a very aggressive brine but from a general point of view we often see that 654SMO outperforms Alloy
625 when it comes to localised corrosion so this might be a suitable grade selection for this application.
2507 is probably doubtful, in our experience. This general advice does not take into account issues like
crevices and thoroughly cleaned welds.


The chloride content in this case is approximately 180 000 ppm.  654 SMO performs well at 90°C up to
200 000 ppm but there is a risk for crevice corrosion.  Where we have boiling conditions, we get reduced
oxygen content.  It is difficult to say exactly how this would affect the performance of the material. 
Unfortunately we don’t have enough data to go on and would need more to offer more precise material solutions. 

I would also like to mention the possible risk for stress corrosion cracking (SCC). Magnesium chloride is
one of the most aggressive salts in terms of SCC, so keep that in mind. 654 SMO has good SCC resistance,
but of course not on the same level as the nickel base materials. 
Last but not least, 625 is much more expensive
than 654SMO so this has to be taken into consideration as well.