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Corrosion of stainless steel in Thailand
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miklaw


Jan 5, 2010, 11:05 PM
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Registered: Jan 13, 2004
Posts: 98

Corrosion of stainless steel in Thailand
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I don’t know if many people saw this article from 2008, but it answers many of the questions about just how this corrosion happened. Researchers from two consulting firms; Sjong Consulting in Boulder COL and Exponent Inc in Menlo Park CAL investigated a failed Petzl hanger from Railay Beach. They analyzed the corrosion product on the failed surface, subjected a new hanger and also some titanium gear to a stress corrosion cracking (SCC) test in boiling magnesium chloride.

They believe that the corrosion came about from a number of factors, residual stresses from manufacture, the very acidic ground water that is common in the tropics, magnesium present in the limestone, having periods of low humidity when chlorine salts can dry on the metal allowing very high concentrations to occur and destroy the protective oxide film, and high temperatures from exposure of the metal and rock to sunlight. It all sounds unlikely but these are the same conditions that led to the catastrophic collapse of a swimming pool roof in 1985. Similar problems have occurred in other tropical areas (Caymen Brac).

The work doesn’t fully explain failure of bolt shafts inside the rock as the temperatures should be lower and the full drying cycle may not occur.

They found that the titanium gear showed no SCC in the boiling magnesium chloride test, and so is probably the answer.

The full citation is:-
A. Sjong, L Eiselstein “Marine atmospheric SCC of unsensitised stainless steel rock climbing protection” Journal of Failure analysis and Prevention, 2008, No. 8, pages 410 - 418


Kinobi


Jan 6, 2010, 10:34 PM
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Registered: Sep 16, 2009
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Re: [miklaw] Corrosion of stainless steel in Thailand [In reply to]
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On web site of Petzl more news including link to UIAA.
Ciao,
E


healyje


Jan 7, 2010, 2:05 AM
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Registered: Aug 22, 2004
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Re: [miklaw] Corrosion of stainless steel in Thailand [In reply to]
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I climbed in Railay in '93, bolts and hangers were failing then - everyone understood Ti was the only way to go back then so I'm a bit surprised to hear people kept sinking SS bolts all along anyway. None of this is news other than the lessons don't sound like they were learned.


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