Field and Laboratory Testing of High-Alloy Steels and Nickel Alloys Used in Fastenings in Road Tunnels

Haselmair, H., Morach, R., Boehni, H.

OnePetro 

ABSTRACT Heavy increases in traffic over the past 10 years and the resulting problems caused by exhaust fumes have led to greater corrosiveness of the atmosphere in road tunnels, and the problem of corrosion of installations is worsening. Fasteners also are affected, and their corrosion creates a safety hazard. In 1981, a general modernization was planned for the Mont Blanc Tunnel and cladding for the tunnel wall. The tunnel connects the Aosta Valley of Italy with the Upper Savoy of France between Courmayeur and Chamonix. It is the key section of one of the most important routes across the Alps. More than 15,000 vehicles travel through the tunnel daily and ~ 50% are heavy trucks. Fastening systems were included in the field tests. Types 304 (UNS S30400)(1) and 316 (UNS S31600) stainless steels (SS), the materials available for anchors at that time, were tested. After only 12 months, it was evident that neither material was resistant to corrosion under the existing conditions. In view of this finding, a major testing program began in 1987. During these tests, SS and nickel (Ni) alloys were examined, in addition to coated carbon (C) steel, aluminum (Al) alloys, and copper (Cu) alloys. Samples were evaluated after exposure periods of 9, 11, 19, 24, and 36 months. Laboratory tests were run at the same times. Based on results of the tests, materials were proposed for use in fastening the tunnel wall cladding, as well as in the lighting and the cable trays that were being replaced during modernization of the French section of the tunnel. The objective of the present work was to evaluate the corrosion behavior of the SS and Ni alloys with respect to the specific corrosive conditions in the tunnel.

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