This note was posted to the Titanium Bolting FB Group 1st April 2020
Being locked down is not so bad if you can keep working in your lab. I’ve finally caught up with some wall-wash samples sent to me by Rodrigo Castelan Carlson from the beautiful granite slab sea cliffs of Campo Escola da Barra da Lagoa in Brazil.
These are interesting in that there is a 20 year history of perfect survival of 304SS hangers and bolts, all within a few metres from the sea.
The guys there were suspicious that such perfect bolts must in fact be hiding SCC. A metallurgical analysis of a few samples failed to reveal anything wrong.
My analysis reveals that there is no sulphur activity on this cliff. The electrolyte balance is purely sea water with a bit of calcium bicarbonate buffering as we have come to expect.
I’ve got metal work from the same crag, and will take a look at that to ensure that the material is in fact 304, and will see if I can find any traces of metal sulphide. My guess is there will be none. It seems you need a lot more sulphate than that naturally present in sea water before you start seeing SRB activity, and the bolt degradation we all know and love.
Update: 10th April 2020
Notice how variable the salt concentration is from one sample point to another. If we sampled it again would it look broadly the same, or would it be quite different? Rodrigo tells me that the sampling point on Sobre as Ondas often has salt crystallizing out on it. Check out the salt on the FH below. Maybe these concentration differences do reflect differences in micro-climate, but I think I’d need some solid repeat measurements before jumping to that conclusion.
Thanks to members of the Associação Catarinense de Escalada e Montanhismo (ACEM) for the collection of samples.