Density functional theory (DFT) method has been widely used in studying various stages of metal corrosion such as iron and steel corrosion, especially the initial stage. For example, DFT calculations have been used to predict adsorption energies, preferred adsorption sites, and orientations of corrosive agents such as water , oxygen , hydrogen , and other aggressive chemicals . Analysing interactions between these chemicals and metal or metal alloys has enabled researchers to identify key structural components and morphologies that drive or inhibit corrosion, thereby developing effective corrosion-resistant strategies. The potential energy surface (PES) of a system as a function of atomic positions can be mapped out by performing DFT calculations. PES provides valuable information about reaction pathways and energy barriers associated with the corrosion process, as energetics of a system can be calculated to understand defects formation, chemical species migrations, stability of different phases, and likelihood of surface degradation patterns and reconstruction. Hence, DFT offers a comprehensive approach to investigate mechanisms of iron and steel corrosion at atomic and molecular levels.