PSI - Issue 59

Liubomyr Poberezhnyi et al. / Procedia Structural Integrity 59 (2024) 158–166 Liubomyr Poberezhnyi et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. Scheme of specimen geometry for corrosion modeling in COMSOL: (a) welded joint (WJ), (b) WJ with isolation, (c) WJ with various isolation defects (1-4).

COMSOL corrosion simulations require following material's input parameters: tempetature, exchange current density, anodic and cathodic transfer coefficients, and equilibrium potential. Most of the electrochemical input data for the simulations are taken from the COMSOL material library for "High Strength Low Alloy Steel". The base metal (BM), heat affected zone (HAZ), and weld metal (WM) zone differed only in the value of the equilibrium potential, taken from (Borko et al, 2019). Following the completion of electrochemical tests, the obtained values of the OCP and the computed exchange current density were utilized. An insulating, nonconductive material from the COMSOL library was utilized as an anticorrosion coating in the modeling process.. To gain a deeper understanding of behavior of corrosion in the presence of defects in the anti-corrosion coating, it suggestion was to place defects inside and at the boundaries of the welded joint parts (Fig 2, c). Based on the literature data indicating the highest risk of corrosion processes directly in the heat-affected zone and at its boundaries, the positions of defects 1-3 were selected. Defect 4 was strategically placed in the base metal area to simulate the interaction between welded joint

and the main construction. 3. Results and discussion

Using nail polish to isolate specific areas of the sample’s working surface enabled us to measure the electrode potential kinetics not only for the base metal and weld metal but also for the heat affected zone. Upon analyzing the electrode potential kinetics, it is evident that after 4 hours of exposure to a 3.5% NaCl solution, it stabilizes (Fig. 3). According to the experimental results, the weld metal exhibited the lowest electrode potential. Based on the literature data, it was expected that the potential of the heat affected zone (HAZ) would be the lowest (Borko et al, 2019). The OCP for the HAZ, initially 27 mV lower than that of the base metal (BM), ended up 33 mV higher.