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The damage to materials caused by CO2 dissolving in water is known as CO2 corrosion. In low-alloy steels, CO2 not only causes general corrosion but also leads to local corrosion, which appears in three basic forms: pitting, planar erosion, and flow-induced corrosion. Furthermore, carbon steel also undergoes corrosive cracking in the CO2-H2O system (which is generally considered to be due to anodic dissolution). The currently widely accepted mechanism for CO2 corrosion is that CO2 dissolves in water to form carbonic acid, which then undergoes electrochemical reactions on the metal surface. The factors affecting CO2 corrosion can be mainly divided into two categories: environment and material. Among these, environmental factors include: 1. The influence of CO2 partial pressure – when the CO2 partial pressure is below 0.021 MPa, the corrosion is mild ； Pitting may occur at 0.021~0.2 MPa ； Above 0.2 MPa, severe localized corrosion occurs. 2. Influence of temperature: Temperature affects the corrosion behavior of steel through chemical reactions and the properties of corrosion product films. The ionization constant of carbonic acid increases as temperature rises; therefore, an increase in temperature enhances the acidity of the medium, leading to the dissolution and loosening of the corrosion product film, and thus promoting both general corrosion and local corrosion. Below 90°C, the corrosion rate increases as the temperature rises ； At around 110°C, coarse crystals appear on the FeCO3 protective film, which gradually grow and peel off, causing localized corrosion. At around 150°C, a thin and dense protective film forms on the steel in the first 20 hours in the presence of CO2. The effect of temperature and flow rate on the corrosion rate is closely related; at different temperatures, the critical flow rate in the medium also varies. At a CO2 partial pressure of 0.1 MPa and 25°C, an increase in flow rate leads to a sharp rise in the corrosion rate, with the flow rate threshold being 0.32 m/s. 3. Effect of pH value: Changes in pH value directly affect the form in which CO2 exists in water. When the pH is below 4, it exists mainly as H2CO3; in the absence of O2, carbon steel corrosion is primarily due to H+ depolarization. At pH values between 4 and 10, it exists as HCO. When pH is greater than 10, it exists mainly as CO, which facilitates the formation and stabilization of carbonate scaling.