Effect of different salts on the corrosion properties of friction type A607 steel rock bolt in simulated concentrated water

Friction type steel rock bolts are one of the most commonly used for reinforcing tunnels (since the late 1970s) due to their ability to sustain large rock mass displacements. In this paper, corrosion behavior of an FRS rock bolt (ASTM A607 steel) was investigated under Yucca Mountain simulated concentrated water at different concentrations (1×, 10× and 100×) and temperatures by using electrochemical measurements. Effects of individual salts, chlorides, sulfates, bicarbonates and silicates were also evaluated using the same method. Overall, the corrosion rate was an order of magnitude higher in an aerated condition than in a deaerated condition. The results from the individual salts showed the highest corrosion for the bicarbonate salts (∼300 μm/yr) and lowest for the silicate (4 μm/yr). The bicarbonate solutions accelerate the anodic dissolution of steel at higher concentrations. In the case of silicate solutions, the rock bolt shows passivity even at a higher negative potential (−925 mV) compared to other salts (∼−750 mV) with a large passive region which forms a protective layer on the specimen surface.