*Article* **The Role of Grain Boundaries in the Corrosion Process of Fe Surface: Insights from ReaxFF Molecular Dynamic Simulations**

**Zigen Xiao 1, Yun Huang 2, Zhixiao Liu 1,\*, Wangyu Hu 1, Qingtian Wang <sup>3</sup> and Chaowei Hu 3,\***


**Abstract:** Intergranular corrosion is the most common corrosion phenomenon in Fe-based alloys. To better understand the mechanism of intergranular corrosion, the influence of grain boundaries on Fe-H2O interfacial corrosion was studied using molecular dynamics simulation based on a new Fe-H2O reaction force field potential. It is found that the corrosion rate at the polycrystalline grain boundary is significantly faster than that of twin crystals and single crystals. By the analysis of stress, it can be found that the stress at the polycrystalline grain boundary and the sigma5 twin grain boundary decreases sharply during the corrosion process. We believe that the extreme stress released at the grain boundary will promote the dissolution of Fe atoms. The formation of vacancies on the Fe matrix surface will accelerate the diffusion of oxygen atoms. This leads to the occurrence of intergranular corrosion.

**Keywords:** ReaxFF; corrosion; Fe-H2O interface; grain boundary
