Coupling Effects of pH and Dissolved Oxygen on the Corrosion Behavior and Mechanism of X80 Steel in Acidic Soil Simulated Solution

In an acidic red soil environment, the corrosion mechanism of X80 steel may be closely related to the pH value and oxygen content, but it has not yet formed a systematic understanding. In this paper, the coupling effects of pH and dissolved oxygen on the corrosion behavior and mechanism of X80 steel in an acidic soil simulated solution were further analyzed by electrochemical methods and three-dimensional video microscope. Results showed that the hydrogen reduction reaction was almost the only cathode process in the anoxic and low pH system, and small and dense pits were present on the electrode surface. pH value increased, the pits decreased, but the size of pits increased. In the oxygen-adequate system, oxygen-consuming (OC) corrosion preferentially occurred, and a protective corrosion product layer (including FeOOH, Fe3O4, etc.) might be formed accordingly, but the proportion of hydrogen evolution (HE) increased and the product layer had defects at a low pH environment. The specific corrosion mechanism of X80 steel in an acidic soil simulated solution is described in the relevant models.