Comparative study of alternating dry and wet corrosion behavior of Q345qDNH steel and Q420qENH steel in industrial atmospheric media containing PM2.5

The corrosion behavior of Q345qDNH steel and Q420qENH steel under the industrial atmosphere containing PM_2.5, as well as the effect of PM_2.5 on the rust layer were studied by dry–wet alternating accelerated corrosion experiment. The results show that the corrosion rate of Q345qDNH is always less than that of Q420qENH, the Cr content of rust layer is higher than that of Q420qENH steel. After 30 days of corrosion, compared with Q420qENH steel, the self-corrosion potential of Q345qDNH is larger, the self-corrosion current density is smaller, and the rust resistance is 1.49 times of Q420qENH steel, the I_α-FeOOH/I_γ-FeOOH ratio is 1.29 times of Q420qENH, indicating that the protection of the rust layer of Q345qDNH is better than that of Q420qENH. This is due to the effect of microstructure factors in the early stage of corrosion and alloying elements in the late stage of corrosion. PM_2.5 with SiO₂ as the main component is easy to deposit at cracks and holes, which becomes the nucleation substrate for corrosion products, promotes the nonuniform nucleation of corrosion products, making the rust layer develop unevenly, leading to an increase in holes in the outer rust layer.