**1. Introduction**

Erosion-corrosion is a comprehensive type of the failure process including the mechanical and electrochemical action [1]. The erosion–corrosion phenomena exist in many industries; however, especially in the chemical industry, serious accidents and economic losses occur easily because of the harsh working environments, corrosion, and other reasons. In 2016, an explosion caused by the leakage of the oil pipeline in the southern Gulf of Mexico's National Oil Company caused serious casualties and economic losses. Most pipelines of the coal chemical industry are made of carbon steel, which are seriously corroded by the working and environmental medium during operation [2]. For the erosion–corrosion problems, many researchers have conducted simulation studies. However, researchers performed only CFD simulation analysis, and the velocity vector of the flow filed is used to characterize the serious position of erosion [3]. In these researches, there were no comprehensive simulated erosion failure processes, such as electrochemical corrosion through current density or mass loss per unit area. Based on CFD model, the researchers have further simulated the failure process of particle erosion without electrochemical corrosion and obtained the trajectory of the particles hitting the wall [4]. Mass loss per unit area and the quantities of particles hitting the wall of elbow have not yet been obtained. Zeng et al. [5] have simulated the corrosion current density distribution of electrochemistry without the erosion and chemical reaction and acquired the galvanic current density. An erosion–corrosion simulation model involving the erosion, electrochemical corrosion, and chemical

reaction under the turbulent flow condition has been rarely reported. The reason may be that the CFD analysis involves a difficult process and CFD coupling erosion or electrochemical corrosion is also difficult to develop. The corrosion module in COMSOL Multiphysics features built-in interfaces, features, and examples for modeling and analyzing these different types of corrosion. The chemical reaction of steel and fluid is simulated by chemical corrosion module, which allows us to simulate all electrochemical corrosion processes. A large amount of information can be obtained, including electrochemical reactions, potentials in electrolytes and metal structures, homogeneous chemical reactions, and unique phenomena in the corrosion process. The output of such an analysis is the localized current density, which is used to calculate the average corrosion rate of any component over a given period of time. It is also possible to observe the impact of environmental variables. Simulation analysis can assist in the identification of corrosion-related problems.

The aim is to simulate the erosion-corrosion behaviors of elbow involving the erosion of particles, electrochemical corrosions of the dissolved iron and hydrogen evolution, turbulence and chemical reactions of carbonic acid ionization simultaneously in the present paper. The complex situations in tube are simplified to gas-solid two-phase flow with the chemical reactions and electrochemical reactions, and the gas is a mixture of syngas and carbon dioxide. The Finnie's erosion model is proposed to analyze the erosion of sulfur particles eroding wall through the probability of the quantities of particles and mass loss per unit area. It is expected to obtain the turbulence characteristics, substance concentration distribution, electrochemical corrosion current density, the quantities of particles striking the wall and mass loss per unit area. The turbulent characteristics of gas in elbow and the erosion failure process of particles hitting the elbow wall are simulated under turbulence condition. The effect of turbulence on the substance concentration distribution and the substance concentration distribution on the electrochemical corrosion process of hydrogen evolution reaction and iron dissolution reaction are investigated systemically. Finally, the mechanism of different physical and chemical fields on the key parts of high temperature and pressure pipeline during operation is investigated, and the simulation model of the corrosion under the multi-field coupling actions is built. The stress, temperature, and corrosion cracks of the key parts of the pipeline between corrosion development and status are achieved, and the corrosion leakage prediction model is established and the corrosion development trend and prediction method of leakage occurrence location is predicted.
