Stress corrosion cracking of rock anchors in marine environment

Austenitic stainless steel bolts have been widely used for rock anchoring in marine environments. The presence of chlorides in the atmosphere, the stresses induced by tightening and the material susceptibility to stress corrosion cracking (SCC) are the most critical parameters that brought several anchors to broke. Failure analyses of corroded bolts were performed on different samples coming from sea facing climbing walls. The root cause failure analysis confirmed that the base material did not have any fabrication defect and the cause of the failure was SCC. Another part of this study consisted in the investigation of commercial AISI 304L climbing bolts and of the parameters that influence SCC, focusing on some of these (scratch and acid environment) that were proved to break the protection layer, leading to corrosion. A specific corrosion test has been set up to understand the susceptibility to SCC of commercial bolts and of other alloys proposed for replacing the conventional materials. Appling this test, stainless steel Duplex 2205 and Ti-6Al-4V resulted to be better choice materials in order to increase the components safety.

Lo studio riguarda la tensocorrosione di tasselli per arrampicata in ambiente marino. Sono stati analizzati tasselli realmente corrosi prelevati da siti di arrampicata vicino al mare. In seguito sono state fatte svariate analisi su tasselli comerciali in AISI 304L per studiarne il comportamento a tensocorrosione. Infine si sono eseguiti test di corrosioni su altri metalli che potrebbero essere utilizzati per risolvere il problema.