More on Hydrogen Embrittlement of Rock Anchors

If you have been following along with my work on the corrosion of recreational climbing anchors, I have a new short post on my website.

Very cool

Thank you for the last two paragraphs about the conditions for hydrogen embrittlement to occur - that is a great summary for a layman like me

Great stuff here. Former USN submariner chemist, I love deep diving (not intended) into outlier case type corrosion phenomena. Your observations on the cross-sectional inconsistency in the bolts is very interesting. I would love to see the grain structure of these bolts. Or better yet a mass spec of the two states of alloy. 

Would titanium glue-ins resist hydrogen embrittlement in such environments?

George Bracksieckwrote:

Would titanium glue-ins resist hydrogen embrittlement in such environments?

Experience to date at Tonsai/Railay and Cayman Brac says yes, Ti is resistant. We have bolts there that have lasted well over 20 years.

However, this doesn't mean Ti is resistant to hydrogen embrittlement. It's not. In fact, it is highly vulnerable to attack by hydrogen. However, as I explain in my post, the hydrogen has to come from somewhere, and a long torturous chain of events is necessary in the case of 304 failure. There are plenty of reasons to suspect the same chain cannot exist for titanium.

There is not a lot of evidence that sulphate reducing bacteria (SRB) can attack titanium. In the case of stainless steel, it is able to electrically connect to the bare metal surface and withdraw electrons from it as a source of reducing potential. I haven't spent much time researching this issue for Ti but suspect the electrochemistry provides a thermodynamic barrier to such a coupling.

A second factor is that there appears to be a thermodynamic barrier to the migration and/or entrapment of atomic hydrogen by titanium. The temperature of the metal has to exceed 300C or so before uptake is accomplished. This is the primary reason why welding is so tricky. Even a fingerprint, when heated can breakdown to yield atomic hydrogen, which at that temperature migrates into the metal.

I guess this comes down to saying that Ti is looking good on sulphate cliffs, but I'm struggling to understand why it should be so good.

Fascinating, thank you for sharing your work.

There is a useful technical memorandum from NASA on the matter (20160005654) including reference to hydrogen sulphides (amongst others) being more reactive than pure hydrogen. The document also includes the reference index for material susceptability to HEE where we can see 304 stainless gets an extremely poor rating compared with 316 which rates highly (negligable), it lists most of the titanium alloys as well.

Jim Tittwrote:

There is a useful technical memorandum from NASA on the matter (20160005654) including reference to hydrogen sulphides (amongst others) being more reactive than pure hydrogen. The document also includes the reference index for material susceptability to HEE where we can see 304 stainless gets an extremely poor rating compared with 316 which rates highly (negligable), it lists most of the titanium alloys as well.

Thanks for the reference Jim. I didn't have that one in my collection. I'll need to take the time to read through it. At 2016 it is reasonable recent, so may well have some interesting references.

This is great stuff! Thanks

David Reevewrote:

Experience to date at Tonsai/Railay and Cayman Brac says yes, Ti is resistant. We have bolts there that have lasted well over 20 years.
I guess this comes down to saying that Ti is looking good on sulphate cliffs, but I'm struggling to understand why it should be so good.

I can't explain it either but it's good to know that Ti bolts on Cayman Brac, right on the water, are now 24 years old and look brand new. Not a blemish on them.