Stress Corrosion Cracking Behavior of Low-Carbon Steel Anchor Bolts in a Carbonaceous Mudstone Corrosive Environment

To determine the mechanism of the continuous deterioration of the mechanical properties of low-carbon steel anchor bolts in a corrosive carbonaceous mudstone environment, slow strain rate tensile (SSRT) tests, electrochemical tests, and microscopic tests of low-carbon steel anchor bolts in a corrosive carbonaceous mudstone environment were carried out. The effects of tensile speed and temperature on the stress corrosion cracking (SCC) susceptibility of low-carbon steel anchor bolts in deionized water and a carbonaceous mudstone corrosive environment were studied. The SCC behavior and corrosion mechanism of the low-carbon steel anchor bolts were analyzed. The results show that SCC occurs in low-carbon steel anchor bolts under the combined action of stress, temperature, and the corrosive environment of carbonaceous mudstone. The tensile speed and temperature sensitivity to stress corrosion were 5×10−5 mm·s−1 and 40°C, respectively. The fracture of the low-carbon steel anchor bolts in the corrosive environment of the carbonaceous mudstone exhibited a mixed fracture mode of ductile fracture and brittle fracture. In the elastic stage, the anodic dissolution rate of the low-carbon steel anchor bolts accelerated, which accelerated the stress corrosion reaction. In the yield and hardening stages, the corrosion products accumulated to form a corrosion product film, isolate the steel substrate, and reduce the stress corrosion rate. When the necking stage was reached, the passive crack was transformed into an active crack, the stress corrosion reaction intensified, and the tensile properties of the steel bar significantly decreased. The corrosion products of the low-carbon steel anchor bolts in carbonaceous mudstone were mainly α-FeOOH, γ-FeOOH, β-FeOOH, Fe3O4, and Fe3SO4. This study can provide an important reference for corrosion behavior analysis and corrosive solution research on anchor bolts in a carbonaceous mudstone slope environment.