###### Abstract  
This study explores the potential corrosion inhibition mechanisms of alkanolammonium salts, exemplified by ethylethanolammonium 4-nitrobenzoate (EEA4 NB), for carbon steel, utilizing experimental and theoretical methods. The interactions between metal and inhibitor, focusing on adsorption behavior in saline solutions, will be thoroughly investigated. Analysis of potentiodynamic polarization curves and electrochemical impedance spectroscopy reveals that the inhibition efficiency (IE) increases with the rising concentration of EEA4 NB, reaching 96% at 5 \(\times\) 10\({}^{-3}\) M. Negative adsorption free energy and a high adsorption equilibrium constant suggest the spontaneous formation of a protective inhibitor layer on the metal surface, effectively blocking reaction sites and reducing the corrosion rate, according to the Langmuir isotherms model. As confirmed by scanning electron microscopy, physical and chemical interactions contribute to the adsorption mechanisms. Quantum chemical calculations explore the relationship between EEA4 NB molecular configuration and inhibition efficiencies. The study emphasizes the potential efficacy of alkanolammonium salts, exemplified by EEA4 NB, as effective corrosion inhibitors for carbon steel in aggressive environments. While the mechanism of corrosion inhibition is not fully elucidated, it is generally attributed to a physical/chemical adsorption process or a combination thereof. The strength of the interaction formed between the substrate and organic CI plays a pivotal role in this process [6]. In essence, organic inhibitors safeguard the metal substrate by forming an adsorbed layer--a departure from inorganic compounds that passivate the metal by creating an oxide film on its surface [7]. The adsorption of organic inhibitor molecules notably enhances the mechanical and physical properties of the metal when subjected to aggressive attacks, resulting in the formation of a hydrophobic film on the metal surface [8]. Within the extensive range of organic CIs, amines/alkanolamines, and carboxylic acids have emerged as notably active compounds for passivating various metals in aqueous solutions [9; 10]. Alkanolamines (e.g., ethylethanolamine, N,N\({}^{\prime}\)-dimethylaminoethanol) function as dual-role mixed corrosion inhibitors, impeding both anodic and cathodic reactions, while diminishing chloride ion migration within the concrete matrix [11; 12; 13; 14] The research highlights that the presence of a hydrogen atom on the nitrogen atom enhances hydrogen bond formation, promoting increased inhibition in surface-chelated molecules [11]. To enhance the performance of alkanolamine-based inhibitors, a strategy involves utilizing various formulations by combining two or more types of inhibitors for improved corrosion protection efficiency [15]. Recently, carboxylic acids and their salts have demonstrated effectiveness in preventing corrosion in alkaline media, despite differing perspectives on their interactions with metal surfaces. Studies suggest that carboxylates form chelates with iron ions on the surface, hindering the migration of chloride ions to the reinforcing steel [16; 17]. Contradictory opinions still persist regarding the nature of interactions with metal surfaces. The inhibitory effectiveness is significantly influenced by factors such as chemical structure, steric considerations, \(\pi\)-orbital character of donating electrons, aromaticity, and electron density at the donor atoms of the corrosion inhibitors [18; 19; 20; 21; 22]. This paper aims to explore the potential mechanisms of a mixed corrosion inhibitor through a comprehensive approach, combining both experimental and theoretical methods. Specifically, our focus is on unraveling the intricate metal-inhibitor interactions and adsorption behavior in saline solutions.