Research On Corrosion Behavior Of Static Gas-liquid Interface

The corrosion behavior at the gas-liquid interface is often more complex and serious than that in the single phase.When the gas-liquid phase contains corrosive particles,it is easy to cause corrosion and cause equipment damage or even stop production.In the process of corrosion,different electrochemical reactions and different electron transfer on both sides of the gas-liquid interface produce a large potential difference in the two sides,and the difference of gas concentration on both sides of the interface can easily induce the corrosion of the primary cell.Therefore,the corrosion at the interface is particularly serious.However,there is a lack of research on the corrosion behavior at the gas-liquid interface.It is necessary to carry out a comprehensive,systematic and in-depth study on the complex corrosion mechanism of the interface.In this paper,the gas phase is injected into the surface of copper metal inverted in liquid phase.Therefore the interface area size is accurately determined.The interfacial corrosion mechanism of gas phase with or without gas,pure nitrogen and pure carbon dioxide under different concentration conditions was measured by immersion corrosion method and electrochemical method.The interface corrosion area is subdivided into thin liquid film area and gas-liquid interface area.The variation of corrosion current density with concentration in the two interface areas is obtained by theoretical calculation.According to the experimental data,the evolution process of corrosion pit in the transition area of gas-liquid interface is simulated by cellular automata method under the condition of stable particle distribution.After introducing the interface,the gas interface leads to the positive shift of open circuit potential,the increase of polarization corrosion current density,the decrease of capacitive reactance arc radius and the decrease of diffusion straight slope.The nitrogen interface leads to the negative shift of open circuit potential,the decrease of polarization corrosion current density,the increase of capacitive reactance arc radius and the increase of diffusion straight slope.The carbon dioxide interface leads to the positive shift of open circuit potential,the increase of polarization corrosion current density,the increase of arc radius in impedance spectrum,and the decrease of slope of diffusion line.The gas-phase area of the gas-soaked corrosion sample is covered with a dense CuO layer.The gas-liquid interface area is CuO with small particle size and Cu2O corrosion products stacked in layers.The liquid-phase area contains a small amount of corrosion products Cu2O;the oxygen,nitrogen and carbon dioxide samples of electrochemical accelerated corrosion experiments.The gas-phase area and the liquid-phase area are Cu2O,and the Cu2O content increases gradually with the increase from the gas-phase area to the liquid-phase area.A small amount of CuCl and CuCl2 are found on the surface of the immersed and electrochemical corrosion samples.The results show that the corrosion current at the gas-liquid interface with gas and carbon dioxide is positive and increases with the increase of Cl-concentration,in which the corrosion current at the gas-liquid interface decreases at high concentration.And the corrosion current at the gas-liquid interface with nitrogen is negative,which hinders the corrosion and increases with the increase of Cl-concentration.The existence of gas interface causes macroscopic concentration difference battery corrosion and microscopic interface energy difference corrosion,that is,the corrosion current of thin film area is higher than that of micro interface at low concentration,but the corrosion current in high concentration decreases with the increase of Cl-concentration,and the corrosion current in micro interface area increases with the increase of Cl-concentration.The evolution process of corrosion pit in the transition area of gas-liquid interface under the condition of stable particle distribution are obtained by cellular automata simulation.Gas-side metals in the interface area are oxidized to form a dense oxide layer.The liquid-side of the interface area forms pitting pits due to Cl-characteristics.Oxides and chlorides of copper coexist at the junction of the gas-liquid interface.And the depth of corrosion pit near the junction of transition area is much lower than that of liquid phase area.