Corrosion behaviour of steel ropes for snow and rockfall barriers

摘要

During service, steel ropes can suffer from corrosion, which can reduce their mechanical properties. This degradation is particularly important in the case of structural ropes, or barriers, for snow and rockfall protection because it is not easy to detect any significant degradation over time due to the locations of these structures, which are often difficult to reach. Moreover, rockfall barriers are frequently used in marine environments to reduce the instability of rocks and cliffs, where corrosive attack by chlorides can be very dangerous. This study has characterised the effects on corrosion of the geometrical configurations of the strands and wires in the ropes, and the benefits of zinc and zinc alloy protective coatings on the wires for reducing the degradation of structural ropes. The aim of the research was to obtain information useful for the design of high durability barriers and the selection of an appropriate rope and coating. An approach based on an electrochemical testing has been compared with one based on classical tests involving the exposure of ropes in aggressive environments (salt spray, humidity chamber, etc.) in order to find an electrochemical method able to distinguish the performance of different materials as well as to monitor the corrosion degradation of barriers in the field. Using electrochemical techniques it was possible to quantify the corrosion rate and demonstrate the better behaviour of ropes coated with zinc-aluminum alloys in comparison with pure zinc. Moreover it was possible to evaluate the actual reactive area, and therefore the protective geometry effect when comparing two ropes with different geometries. This approach should be extended to further kinds of ropes in order to improve basic corrosion understanding of this important structural component.