The behaviour of water structure on the surface under varying applied surface potentials is a key factor in understanding the corrosion and passivation processes. The average water adsorption energy as a function of applied surface potentials is reported in Figure . Figure pictures the H-down water configurations on the Fe(100) surface as a function of applied potentials at -2.26 V/-2.0e, -1.73 V/-1.0e, -0.65 V/+1.0e, and -0.36 V/+2e, respectively, which are relative to the standard hydrogen electrode. Figure shows the water-surface interactions as a function of surface potentials. The adsorption energy increases as the applied potential on the water layer increases (more negative), indicating strong adsorption of water molecules was observed just above the PZC value. It is noted, however, that the adsorption potential touched the bottom at the vicinity of -0.5 V/SHE. This is further confirmed by the decreasing watersurface distance, from 2.96 Å to 2.88 Å, as the surface becomes more positively charged (Figure ). This reduction in distance occurs alongside a change in the dipole orientation of the water layer, decreasing from 109° to 98°, causing the oxygen atoms of the water molecules to face more directly toward the iron surface and helping to counterbalance the increase in surface positive charge (Figure ). This suggests that under oxidizing conditions, water has a strong affinity for the surface, which can promote the formation of corrosion products by facilitating Fe dissolution. At a potential near -0.36 V (the final setup in Figure ), one water molecule flipped and moved away from the surface due to steric repulsion between surfaceattracting water molecules, increasing the average water-surface distance to around 2.97 Å.