OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 Studies have shown that grain size also affects corrosion [1, 13–14]. This is usually due to the fact that grain boundaries attract crystal structure defects and inclusion atoms [6–7, 15–16]. Pitting corrosion of steel can be observed when impurity elements are present in the structure [7, 17– 19]. The impurities can form chemical compounds that increase the activity of the material in the corrosive environment [7, 20–21] due to their electrochemical heterogeneity [6]. It has been demonstrated in studies [22, 25–26] that there is a direct correlation between the magnitude of internal residual stresses and the corrosion rate of structural steel. Internal stresses can reach values that exceed the yield strength of the material. This leads to plastic deformation and an increase in the number of linear defects in the form of dislocations [22, 25–29]. Residual deformation of the material under the influence of external loads increases the anisotropy of grains, which affects the rate of the corrosion process [3, 22]. The presented data from scientific studies confirm the existence of a multiparametric dependence of corrosion processes on exogenous and endogenous factors, including the crystal structure of the material, the degree of phase homogeneity, the morphology of the surface layer, the presence of foreign chemical elements in the alloy matrix, as well as dislocation and boundary-defect formations. Numerous experimental works [23–24] have contributed to the systematization of key aspects of the kinetics and thermodynamics of corrosion phenomena, which creates a theoretical basis for identifying factors determining material degradation under conditions of a specific operating environment. The purpose of this work is to develop a multi-criteria model linking the depth of corrosion damage (integral index of aggressiveness of the environment) with microstructural, mechanical and topographic characteristics of low-carbon steel St3. The subject of the study are samples cut from rolled steel sheets with varying degrees of residual plastic deformation (ε = 0–7 %). It is possible to use such an approach by relying on mathematical methods that allow taking into account the influence of various factors, for example, by using a group method of data handling (GMDH). The objectives of the study are: – to study quantitative relationships between the depth of corrosion damage to steel, the magnitude of residual internal stresses, grain size anisotropy, and their number in an aggressive environment; – to investigate the influence of plastic deformation (not exceeding 7 %) on the kinetics of corrosion processes, with emphasis on the change in the depth of damage and the role of residual stresses; – to analyze possible crystallographic mechanisms determining the correlation between corrosion depth and residual stresses; – to develop a physical and mathematical model describing the dependence of corrosion kinetics on structural and morphological parameters, taking into account strain anisotropy and dislocation dynamics using a group method of data handling (GMDH). Methods In this study, samples were taken from St3 steel sheet stock, which was used in its initial state. The samples (4.0 × 70.0 × 25.0 mm) were prepared with their longitudinal axis perpendicular to the rolling direction of the steel. The paper [22] presents data on the magnitude of internal stresses, degree of grain anisotropy, corrosion rate of the studied samples in a 5 % hydrochloric acid solution, and also reflects the methodology for determining these parameters. The investigated samples had different values of residual strain (Table). The microstructure of the investigated samples obtained on an optical microscope is shown in Fig. 1. Sample number and corresponding residual strain value Sample No. 1 2 3 4 5 ε, % 0 1.5 3.0 4.5 6.6
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