Corrosion Behavior of Q235 Steel in Three Typical Soil Environments

The near-neutral yellow brown soil from Wuhan, the alkaline saline-alkali soil from Tianjin and the acid red soil from Nanchang were selected as corrosive media. The indoor simulated accelerated corrosion test of Q235 steel was carried out. The corrosion rate, corrosion morphology and corrosion product composition of the test steel were compared, and the corrosion mechanism was analyzed. The results show that the test steel in all the three soils had uneven comprehensive corrosion and local pitting. The outer layer structure of the corrosion products was loose, mainly composed of Fe₂O₃ and FeOOH. The inner layer structure was dense and mainly composed of Fe₃O₄. In the alkaline saline-alkali soil, a structurally complete corrosion product layer was formed on the surface of the test steel, which inhibited the oxygen-consuming reaction of the cathode; the corrosion rate was the lowest. The higher concentration of H⁺ in acid red soil promoted the process of the cathodic hydrogen evolution reaction and the generation of cracks; the corrosion rate of the test steel was the highest. In the later stage of corrosion, the dense inner rust layer of Fe₃O₄ was formed on the surface of the test steel; the corrosion rate of the test steel during 15 d was higher than that during 30 d.