Corrosione marina: ricerca ancoraggi in A4 rotti.

Consigli, tecniche, materiali e varie utilità.

Corrosione marina: ricerca ancoraggi in A4 rotti.

Messaggioda Kinobi » mer nov 29, 2017 9:23 am

Ciao a tutti,
vi scrivo per conto di un gruppo di lavoro dell'UIAA.
Questo gruppo sta cercando un ancoraggio in A4 che si sia rotto sul campo. Gli serve l'ancoraggio (o quel che è rimasto) e l'ubicazione precisa (nome via, e posizione). E' importante sia in A4. Se mi contattate in privato, vi ringrazio.
Prima di spedire eventuali campioni, inviate fotografia: esistono campioni ritenuti in A4, che in realtà erano in A2. Spesso dalla foto si riconosce la marca del tassello. Grazie.
Emanuele


PS esempio in A4 "vecchi" è nei tasselli HIlti, Mungo, Wurth, Friulsider, Fischer, forse Bossong...
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Kinobi
 
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Re: Corrosione marina: ricerca ancoraggi in A4 rotti.

Messaggioda Kinobi » mar nov 27, 2018 20:36 pm

Segnalo cosa ha scritto il delegato UIAA per la corrosione (si cercano anche volontari).:
David Reeve I couldn't reply on Michel Piola's page, but i can here. Thanks for sharing XXXX.

Without measurement we don't know the chemical environment of the cliff, and worse than that, we can't be sure of the exact composition of the bolts that are placed in that cliff.

Starting with the materials -
a) there are very large numbers of 304 (A2) bolts installed in marine environments throughout the world where there is no history of SCC even after twenty years of service. There is little doubt that high chloride concentrations are required for SCC to occur, however, it is not of itself a sufficient factor. Something else has to be happening at SCC prone crags.

b) there is an 'urban myth' that when 316 (A4) bolts were installed at Railay/Tonsai these failed every bit as quickly as 304. If this is so, then there must be examples of broken 316 bolts from there. I am working through broken bolts from there and from all over the world, and am yet to find an example of a 316 bolt that has failed. If anyone has one, then please send it to me. It should be noted that there are numerous examples of where materials claimed to be 316 are not so. Molybdenum is expensive, and is the first thing to reduced in 'bargain' 316.

c) PLX is a trade name used by Fixe, and not an alloy specification. I know that the low cost lean duplex 2304 has on occaison made its way way into the supply chain in place of the more expensive 2205. Given the former has no molybdenum and the latter more than that in A4, this difference is not trivial. Without knowing the chemical environment of the crag, it is not possible to say how resistant these new materials will be.

d) Titanium is a metal, not a magic spell. There are a couple of alloys used in bolt production and they vary with regard to SCC susceptibility. Yes, that's right, titanium like any material holding a reasonable level of internal stress can spontaneously crack. The chemical environment of the cliff is complex, and we don't have the knowledge to say that titanium CP grade 2, for instance, is going to be 100% effective. However, we can say that early titanium bolts installed at Cayman Brac and Railay/Tonsai are clearly outlasting 304 in these locations.

e) The chemical environment of the cliff is complex, and sea salt is a minor part of the story of what is happening at corrosive Mediterranean crags. Sulphate is a marker of all corrosive crags. It is presumably of volcanic origin. It's presence can be very localised, with corrosion of bolts installed at those points. XXXX took samples at various crags in Kalymnos, and it was immediately obvious why Iannis and Secret Garden were giving a problem with 304, but not at crags located elsewhere on the island.

f) I have no data for Leonidio and thus cannot even guess the extent of the problem there. If someone wants to volunteer to take some samples for me, then we would be in a much stronger position to predict the fate of the bolts being placed there. Without such data, there is no reason to claim that "we're all going to die".

You can read my 2017 report at the link below. There will be another report coming out next year when I will have results for many more Mediterranean locations.
http://www.qldclimb.org.au/wp-content/u ... RmpHcFAgjE
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Kinobi
 
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