Molecular dynamics study on corrosion mechanism of Ni-Co composite cladding layer at different corrosion stages

Abstract

Preparation of Ni-Co composite cladding layer on the surface of ductile iron can result in a more wear-resistant and corrosion-resistant cladding layer. However, when the Ni-Co composite cladding layer is used in the residual seawater environment, seawater corrosion still occurs. Quantitative analysis reveals the microscopic corrosion process of the surface layer of the Ni-Co composite cladding layer under different corrosion stages in the marine environment, which can provide important theoretical basis for improving the service life of the cladding layer. This paper combines experimental methods with numerical simulation. The wear and corrosion resistance of the Ni-Co composite cladding layer were verified by the experimental method. The results show that the main elements on the upper part of the Ni-Co composite cladding layer are Co, and the crystal structure is mainly FCC structure. It is mainly composed of dendrites and has fine grains. Based on the experiments, the reaction position molecular dynamics simulation was carried out using the LAMMPS software to establish the molecular dynamics models of the surface layer of the Ni-Co composite cladding layer at different corrosion stages in the seawater environment, and the movement laws of molecules and atoms during the corrosion process of the cladding layer surface in the seawater environment were calculated and revealed. The calculation shows that in the initial corrosion stage, the model corrosion trend is weak and the corrosion degree is light. In the corrosion development stage, the model corrosion trend increases, and the migration rate of OH⁻ to the Co layer increases. In the rapid corrosion stage, the concentration of OH⁻ near the Co layer gradually saturates, and the corrosion of the Co layer accelerates. And with the increase of time, the change speed of each parameter of the corrosion model also gradually increases.