Investigation of steel corrosion near the air–liquid interface in NaCl solution and soil environment

To examine the macro-galvanic corrosion of carbon steel near the air–liquid interface, a test panel of array electrodes was developed for investigating the corrosion behaviour in NaCl solution and wet soil environment. The corrosion rates were evaluated by electrochemical approaches and verified by the corrosion exposure tests. The analysis focused on the interaction between the macrocell and microcell according to the ZRA, EIS, and OCP measurements. Test results reveal that the coexisting of macrocell and microcell corrosion would change the position of maximum corrosion, and it was inferred the relationship of actual current density and microcell current density. In addition, the wet soil environment shows both microcell and macrocell corrosion near the air–liquid interface should be more severe than that in an iso-concentrated NaCl aq environment, whereas its macro-galvanic interaction of steel at the deep region should be smaller due to the low-diffusion rate in the soil environment.