316 vs 304 stainless steel rock anchors

tom donnelly wrote:

Good point, and I don't know what are the real differences as far as material corrosion results.  I was assuming they aren't that different.

I think you need more evidence to prove that at locations other than your primary test cliff.

I thought hydrogen embrittlement also applied to SCC.

I have concentrated on Caba da Roca because it has the sample density to allow me to tighten variables such as geology, climate etc. But, yeah, I have a heap of samples from across the world and will eventually work through them. What I can say is that I have sufficient evidence from Tonsai/Railay, Long Dong, Ibiza and the limestone sea cliffs of Portugal to attribute the same failure mechanism. I will publish it someday - preferably one that has more than 24 hours. :-)

I haven't been keeping up with advances in SCC theory so will be behind the latest. The desire to use hydrogen as part of a renewable energy chain has resulted in an increased publication rate from folks investigating how to harden low-cost stainless steels through martensite formation yet avoid the problem of hydrogen attack. Some of this work applies directly to understanding SSC. However, from where I stand, SCC is something shrouded in mystery. It is commonly attributed to an anodic process. This is a bit loose, but there is no doubt about the initiation by chloride pitting and the need for chloride ion propagation within the crack as it forms. I've seen some authors attempt to invoke atomic hydrogen migration to the crack tip as a loosening mechanism, but this seems a big ask. Anodic process? Where does the hydrogen come from? It's not like SSC where you can provide very strong arguments for the entrainment of hydrogen, not to mention diffusion rates and binding energies. However, mystery or not, SCC is very much a real phenomenon, although the incidence of it occurring at ambient temperatures is low.