Effect of Environmental Medium on Corrosion Behavior of X80 Steel under Dynamic DC Interference

The corrosion behavior of X80 steel in soil, quartz sand + soil simulation solution, soil simulation solution and soil extract under dynamic DC interference was studied by weight loss method and electrochemical impedance spectroscopy. The results showed that the corrosion morphology of X80 steel was localized corrosion in solid environment medium and general corrosion in liquid environmental medium under symmetric dynamic DC interference. When the interference current density in the negative half cycle was greater than that in the positive half cycle, the corrosion morphology of X80 steel in solid and liquid environmental mediums was general corrosion and localized corrosion respectively, and the corrosion rate and current corrosion efficiency of X80 steel in different environmental mediums were reduced. Among the four environmental mediums, the order from low to high corrosion rate and current corrosion efficiency of X80 steel was in soil, quartz sand + soil simulation solution, soil simulation solution and soil extract. The main reason for the low current corrosion efficiency of X80 steel in environmental mediums was the charge-discharge effect on capacitance elements of corrosion product film and electric double layer, and the participation of cathodic process. The participation of cathodic process promoted the reduction of more Fe²⁺ to Fe and the formation of Fe₃O₄, Fe₂O₃ and Fe(OH)₃ with Fe³⁺, which might be an important reason for the reduction of weight loss of X80 steel in solid medium compared with that in liquid medium under the same interference condition.