## 1 Introduction  
In light of the continuous development of global industry, substantial quantities of greenhouse gases, primarily CO\({}_{2}\), are being released into the atmosphere, leading to a profound climate warming phenomenon on Earth. According to the annual report of the United Nations Intergovernmental Panel on Climate Change (IPCC) in 2021 [1], the annual average CO\({}_{2}\) concentration surged to 410 ppm in 2019. This concentration level of atmospheric CO\({}_{2}\) represents the highest point observed in the past 2 million years [1], thereby posing a significant threat to both the natural ecosystem and human habitation. At the moment, storing CO\({}_{2}\) underground in geological formations is one of the most promising methods for lowering CO\({}_{2}\) emissions and slowing down global warming [2]. This approach, known as CO\({}_{2}\) capture, utilization, and storage (CCUS) technology, has garnered widespread acknowledgment and support from numerous national and regional entities as a response to global climate change [3]. Consequently, CCUS stands indisputably as a pivotal technological direction for curbing the repercussions of global warming [4, 5]. The CCUS process encompasses several key stages, namely CO\({}_{2}\) capture from power plants or industrial operations, the utilization of CO\({}_{2}\) for energy production or resource extraction enhancement, CO\({}_{2}\) transportation, and storage in geological reservoirs. Among the various options for CO\({}_{2}\) transportation, the use of metal pipes emerges as the most economically viable choice. The CO\({}_{2}\) that is carried via the pipeline is compressed to a supercritical state (with a pressure exceeding 7.38 MPa and a temperature above 31.1 \({}^{\circ}\)C) in order to maximize the CO\({}_{2}\) density and reduce the likelihood of two-phase flow. From a corrosion perspective, pure and dry supercritical CO\({}_{2}\) (Sc-CO\({}_{2}\))does not pose a corrosion threat to metal pipes [6, 7]. Unfortunately, Sc-CO\({}_{2}\) fluids naturally contain impurities like O\({}_{2}\), H\({}_{2}\)O, H\({}_{2}\)S, SO\({}_{2}\) and NOx [8, 9, 10, 11]. In the event that the metal pipes include free water, Sc-CO\({}_{2}\) and other contaminants can dissolve into the water phase, changing its chemical composition and potentially escalating the environment's corrosiveness [12]. CO\({}_{2}\) acts as an acid gas and dissolves in water as H\({}_{2}\)CO\({}_{3}\), undergoing ionization into H\({}^{+}\). This process can be represented by the following reactions [13, 14, 15, 16]:  
\[\mathrm{H_{2}CO_{3}\to H^{+}+HCO_{3}^{-}} \tag{1}\]  
\[\mathrm{HCO_{3}^{-}\to H^{+}+CO_{3}^{2-}} \tag{2}\]  
Subsequently, a cathodic corrosion process and an anodic corrosion process take place on the metal surface,  
\[\mathrm{Fe\to Fe^{2+}+2e^{-}} \tag{3}\]  
\[2\mathrm{H^{+}+2e^{-}\to H_{2}} \tag{4}\]  
and overall,  
\[\mathrm{CO_{2}+H_{2}O+Fe\to FeCO_{3}+H_{2}} \tag{5}\]  
The presence of H can cause cracking in the metal matrix, and the formation of FeCO\({}_{3}\) can result in scale formation on metal surfaces. This leads to a complex corrosion process when CO\({}_{2}\) is present. Crucially, at the same temperatures, the rate of metal corrosion in the Sc-CO\({}_{2}\) environment may be significantly greater than in a low-pressure gaseous environment. This can be attributed to two main factors. The first factor results in enhanced amounts of H\({}_{2}\)CO\({}_{3}\), HCO\({}_{3}\)\({}^{-}\), and CO\({}_{3}\)\({}^{2-}\) in the aqueous solution due to the high solubility of CO\({}_{2}\) in water at supercritical conditions. Consequently, the corresponding cathodic reaction rate increases, ultimately elevating the overall corrosion rate and substantially increasing the risk of damage to metal pipelines and casings [17, 18, 19]. The second factor stems from the ability of water to evaporate into Sc-CO\({}_{2}\), leading the Sc-CO\({}_{2}\) phase to contain trace amounts of water, making it highly corrosive to metals.