Towards a new classification system for climbing anchors: Low temperature SCC failures of stainless steel components

摘要

Stainless steels provide excellent service when selected and applied properly. Sufficient knowledge basis is generally available for material selection for immersion conditions but this is not true for applications under atmospheric weathering conditions. Numerous incidents of fixed stainless steel rock climbing anchors failures mostly in seaside locations have been reported. Detail failure analysis of anchor components collected from Europe, the USA, Thailand, South Africa, Australia and other locations was carried out. The presented data show that the principal degradation mechanism was the stress corrosion cracking (SCC) under specific atmospheric conditions characterized by the spontaneous formation of concentrated chloride solutions under highly soluble chloride deposits at normal or only slightly elevated temperatures. This mechanism was earlier reported to cause ceiling collapses and other component failures in swimming pool halls and failures under evaporative conditions in oil and gas production, storage, and processing. Currently, the Safety Commission of International Climbing and Mountaineering Federation (UIAA) is preparing a new standard, which will classify climbing anchors into classes according to their resistance to SCC and/or other forms of corrosion. To support the standard preparation, deeper understanding into the degradation mechanism of stainless steels under relevant conditions is necessary. The role of factors influencing the SCC initiation such as the composition and concentration of deposits, tensile stress, role of crevices and aggressive ion accumulation, rock chemistry and periodic washing was studied.