Title:	First-principles calculations of the corrosion behavior of NiCrMo and FeCrNi alloys
DNr:	NAISS 2023/5-218
Project Type:	NAISS Medium Compute
Principal Investigator:	Jinshan Pan <jinshanp@kth.se>
Affiliation:	Kungliga Tekniska högskolan
Duration:	2023-06-01 – 2024-03-01
Classification:	10407 10403 20506
Homepage:	https://www.kth.se/profile/jinshanp/
Keywords:

Abstract

Corrosion of metal materials, either pure metals or alloys, causes degradation of the materials, which not only results in huge economic cost and environmental impact, but also may lead to catastrophes with loss of human lives. Corrosion initiates at metal surface due to chemical and electrochemical reactions with corrosive substances in the service environment. Oxidation of metals by O2 and H2O leads to degradation of the material or formation of passive film on its surface. Halide ions, especially Cl-, may cause breakdown of protective passive film on metal surface and thus initiation of dangerous pitting corrosion. Moreover, H atoms can easily enter into metals and cause degradation of the microstructure leading to hydrogen embrittlement. S interacts with metal to form sulfides, or enters into metals, causing or promoting hydrogen ingress and corrosion cracking. Traditionally, corrosion experiments are carried out by using different techniques to explore the kinetics and mechanism of the corrosion processes. The development of corrosion resistant alloys for different applications, i.e., advanced high-performance alloys, requires fundamental knowledge of the corrosion mechanism at molecule and atomic scale. Nowadays, state-of-the-art experimental techniques allow analysis of the surface and bulk microstructure of metal materials down to nano and atomic scale. Some of synchrotron and neutron techniques enable in-situ or operando analysis of the corrosion processes at atomic level. The combination of in-situ or operando analysis of the corrosion processes at atomic level with first-principles calculations could provide fundamental understanding of the corrosion initiation and mechanisms, which is of great significance in scientific research and engineering. In recent years, we have employed density functional theory (DFT) calculations to study the energetics of surface adsorption and dissociation of corrosive species, the work function, the hydrogen traps in precipitates, and the role of defects in properties of passive film on pure metal. Reactive force fields molecular dynamic (ReaxFF MD) simulation also has been used to investigate corrosion processes of pure metals, e.g., Al, Fe and Cu. In this proposed project, we will perform DFT calculations to explore the effect of defects in the surface layer on the lattice parameters of NiCrMo and FeCrNi industrial alloys, and to study the impact of aggressive ions on the growth of passive film (nanometer thick oxides) and dissolution behaviors of the alloys. Furthermore, the degradation of the passive film covered alloy will be simulated in the presence of aggressive species, e.g., H and Cl, to investigate the breakdown of passive film on NiCrMo and FeCrNi alloys. We aim to perform ReaxFF MD calculations to identify the interfacial reactions at atomic scale during corrosion of NiCrMo and FeCrNi alloys in aqueous solution containing NaCl. The DFT studies of these behaviors will be done in parallel to our experimental studies using synchrotron techniques.