The role of Cr in surface oxidation of hot-dip galvanized steel sheet based on molecular dynamics simulation

This study investigates the influence mechanism of Cr on the formation of uncoated defects on the surface of steel sheets during the hot-dip galvanizing process. The uncoated defects in actual are caused by unreduced alloy element oxides and iron oxides on the steel surface. By molecular dynamics simulation methods, the study analyzes the micro-effects of Cr content, O content, and temperature on the surface oxides of the substrate. The results demonstrate that an increase in Cr content enhances the interaction between Cr and O atoms, promoting the formation of a Cr oxide layer. When the Cr content is 0.156 at.%, the oxide layer is the thinnest, indicating that Cr forms dense protective film that effectively blocks further oxygen penetration. Additionally, an increase in oxygen partial pressure promotes the linear thickening of the oxide layer, affecting the atomic diffusion coefficient. This research provides significant guidance for understanding substrate surface oxidation and improving coating performance.