FYI Re: SCC of 304 SS in warm 25% NaOH. 3

[kenvlach]

There had been a thread titled “Help on Stress Corrosion Cracking’ by Snipes. SCC was observed along welds in a 304 SS vessel containing 25% NaOH operating at 115^oC. Via an exchange of several posts, it turned out he was unaware than commercial 50% NaOH may contain as much as 1% NaCl (p. 44, OxyChem Caustic Soda Handbook,

http://www.oxychem.com/products/handbooks/caustic.pdf)

which equates to 3000 ppm [Cl^-] in a 25% NaOH solution.
Both caustic and chloride probably contributed to the SCC.

Snipes also posted “I need to know the corrosion mechanism of EDTA-Na4 on steel [304 SS]. equations and description will be most helpful. In addition,if u know of any website which can provide me with any help?”
Identical language was used in 2 lengthy, earlier threads (since deleted) on this subject. Corroman had wanted us to do his entire job (analyze data, search literature, determine mechanism, write his report, etc.). I asked the site manager to check for a correlation between Snipes and Corroman. Apparently there was, which explains the disappearance of the aforementioned thread.

mcguire,
I didn’t find a book with the title "Handbook on Stress Corrosion Cracking and Corrosion Fatigue" by Speidel. Close, though:
“Spannungsrisskorrosion von Stahl in Wasser. Gemeinsame tagung,” Speidel, Markus O. et al. (eds.), in Ergebnisse der Werstoff-Forschung. vol 2. XY/N-1, published by Verlag Thubal Kain, ISBN 3907967011 (1988).

 

[TVP]

Wow, quite impressive on both accounts (NaOH/Cl^- and tracking down the Speidel reference)!

 

[kenvlach]

Thanks, but I’ve known the NaOH specs for ages, having bought hundreds of 55-gallons drums of the cheap stuff for caustic etch and acid neutralization, and laying out the big bucks for ACS reagent grade for lab use and pH adjust of contamination-sensitive solutions.

Also, thought the reference cited by mcguire would be worth having. Found a lot of interesting stuff on high-nitrogen austenitic stainless by Seidel while looking.
Ken

 

[mcguire]

The reference to Speidel's book said it was to be published. Apparently it wasn't published, or at least under that title. He has, however, published voluminous amounts on stainless and embrittlement, as Ken cites.

My impression is that there has been no progress in understanding SCC in a long time, and that applies doubly to the rather special case of SCC in NaOH. Most of the research is done by electrochemists whose tendency is to try to explain it as a selective dissolution phenomenon which doesn't ever quite fit the observed behavior.