## 1 Introduction  
Addressing global warming, one of society's significant challenges, involves mitigating the emission of the greenhouse gas CO\({}_{2}\), primarily originating from power plants. A proposed solution is Carbon Capture and Storage (CCS), a process comprising three key stages: the capture and compression of CO\({}_{2}\) and emission gases directly from combustion processes at the source (such as coal power plants), the transmission through pipelines, and the injection into suitable geological formations [1; 2]. During this process, CO\({}_{2}\) is pressurized to a supercritical (or liquid) state [3; 4]. Hence, a key area of research focuses on understanding the corrosion behavior of steels in supercritical CO\({}_{2}\)[5] or CO\({}_{2}\)-saturated saline aquifer waters [6]. In the process of injecting CO\({}_{2}\) into deep geological saline aquifer reservoirs, as observed in the Northern German Basin [7; 8; 9], the dissolved CO\({}_{2}\) in the aquifer water creates a highly corrosive environment that can lead to the failure of pipe steels [10; 11]. The general corrosion process is explained as follows: An FeCO\({}_{3}\) corrosion layer (siderite) forms on the alloy surface due to the anodic dissolution of iron from the pipe steel [10; 12]. In a CO\({}_{2}\)-rich environment, simultaneous anodic and cathodic reactions result in the formation of corrosion products that precipitate on the steel surface. These products mainly consist of FeCO\({}_{3}\) (siderite), Fe(HCO\({}_{3}\))\({}_{2}\) (iron bicarbonate), and FeOOH (goethite) [10; 13]. Corrosion processes in Carbon Capture and Storage (CCS) environments are significantly influenced various environmental factors, including the composition of the surround ing media and alloy, temperature, CO\({}_{2}\) partial pressure, flow conditions, contaminations, dissolved salts and the formation of protective scales [10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22] Although high-alloyed steel generally exhibits good corrosion resistance, corrosion in the injection pipe can occur in CO\({}_{2}\)-rich aquifer water, particularly if phase boundaries form during intermissions of the injection process when the aquifer water flows back into the pipe [13; 14; 15]. 1.4021 is a widely used martensitic stainless steel in industry, featuring 13% Cr and 0.20% C. Another notable stainless steel, 1.4542 (AISI 630, X5 CrNiCuNb16-4), is a precipitation hardening martensitic variant with approximately 3% small copper particles distributed in the matrix for enhanced precipitation hardening [23; 24]. Research indicates a direct correlation between the mechanical and corrosion properties of various steel types and their surface conditions resulting from machining processes [25; 26; 27; 28; 29]. Generally, corrosion resistance improves with reduced surface depth on carbon steel [26], austenitic stainless steel [28] after shot peening [29], and ferritic stainless steel when Ra exceeds 0.5 \(\upmu\)m [28]. Interestingly, the impact of relative humidity on internal pipeline corrosion is more significant than that of initial surface roughness; reducing humidity proves more effective than altering initial surface conditions [27]. Smooth surfaces and compressive surface stress have a positive correlation with improved fatigue behavior in air under corrosive environments. This relationship extends to enhanced corrosion resistance, leading to improved corrosion fatigue behavior as well [30; 31; 32; 33]. To ensure the required longevity of pipes utilized in Carbon Capture and Storage (CCS) technology, employing protective coatings composed of heat-resistant ceramics is a viable technical solution [34; 35]. Alumina coatings emerge as promising choices owing to their high inertness and stability at elevated temperatures [36; 37]. Various methods, such as plasma spraying, chemical vapor deposition, and ceramic slurry application, are employed to produce thick alumina coatings, while the sol-gel technique allows for the application of thin alumina coatings [34; 35; 38; 39].