Effect of hydrostatic pressure on the thermodynamic and kinetic behavior of metal electrode reactions

Based on the thermodynamic and dynamic theory of physical chemistry, focusing on the problem that hydrostatic pressure affects metal corrosion reaction in deep-sea environment, this paper analyzes the influence of hydrostatic pressure on partial molar volumes and activities of metals and components in deep-sea environment, deduces the relationship between hydrostatic pressure and equilibrium potential and exchange current density of different electrode reactions, and establishes a metal corrosion model under hydrostatic pressure. The results show that under the condition of ignoring the temperature change, hydrostatic pressure can change the partial molar volume and activity of metal and environmental components, and then affect the equilibrium potential and exchange current density of each electrode reaction in the corrosion process. With the increase of hydrostatic pressure, the equilibrium potential of anodic dissolution reaction of Fe, Al and Zn decreases, and the exchange current density decreases. Furthermore, it increases the equilibrium potential and decreases the exchange current density of cathodic reduction of dissolved oxygen, while it decreases equilibrium potential and increases the exchange current density of cathode hydrogen evolution reaction. Correspondingly, the corrosion potential and corrosion current density of different corrosion cells also change under the effect of hydrostatic pressure. In addition, hydrostatic pressure will amplify the activity difference of different phases in metal, which will correspondingly lead to the increase of the difference of electrode reaction equilibrium potential and exchange current density of different phases in metal, and then affect the micro galvanic corrosion between different phases.