Effect of pH values on the corrosion behavior of Q235 steel in simulated acidic soils

The effect of pH values on the corrosion behavior of Q235 steel in simulated acidic soils was investigated by weight-loss measurement, scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and polarization curve analysis. When the pH values are 4.0, 4.5 and 5.1, the corrosion rate of Q235 steel are 0.68, 0.48 and 0.42 mm·a^-1, respectively. With the increase of soil pH values, the rust becomes more compact and the etch pits change from narrow and deep to wide and shallow. All the corrosion products are mainly composed of SiO₂, α-FeOOH, γ-FeOOH, Fe₂O₃ and Fe₃O₄, and the mass ratio of α-FeOOH/γ-FeOOH in the corrosion products is higher with increasing pH values. Additionally, polarization curve analysis shows that when the soil pH value rises, the corrosion potential of Q235 steel increases, the corrosion current density decreases, and the corrosion rate becomes lower.