The corrosion behavior and mechanism of Q345qENH weathering bridge steel in simulated high-temperature industrial atmospheric environment

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The corrosion behavior of Q345qENH bridge weathering steel and Q235B low-carbon steel by employing XRD, mass gain and mass loss method, optical microscopy, SEM, CLSM, TG, XPS, and electrochemical techniques was investigated. The corrosion power function model for Q345qENH is proposed, which is divided into three stages: τ 1 (0–15 d), the stage of rapid corrosion development; τ 2 (16–40 d), the stage of rapid decline in corrosion rate; τ 3 (41–60 d), the stage of stable corrosion rate. The γ-FeOOH was detected only within the shallow rust layer, whereas the deep rust layer exhibited increased mass proportions of α-FeOOH and Fe 3 O 4 . The Q345qENH possesses a denser morphological structure with higher hydrophobicity, alongside a lower corrosion current density, in comparison with Q235B at 60 d. Both steels exhibit predominantly uniform corrosion with localized pitting in minor areas. The cumulative corrosion losses of Q345qENH and Q235B were 0.031 mm and 0.045 mm, respectively, during the experimental period. Additionally, the corrosion resistance mechanism of Q345qNH is attributed to the Cr, Ni, and Cu elements acting as nucleation centres within the rust layer, fining the grain size of corrosion products while filling gaps in the rust layer.