PSI - Issue 83

Goran Vukelić et al. / Procedia Structural Integrity 83 (2026) 57– 62

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4. Discussion and conclusion The results presented in Figure 2 indicate a progressive reduction in specimen mass during exposure to the marine environment, reflecting ongoing material deterioration over time. This effect is more evident in the AM and hybrid CM–AM welded samples than in the CM welded specimens. A noticeable increase in mass loss occurs after three months of immersion, with the CM–AM joints exhibiting the highest level of degradation. The fitted equations shown in Figure 2 can therefore serve as a practical tool for estimating the time-dependent mass loss behaviour of AISI 316L stainless steel under marine exposure. The equations are fitted through the month 12 of the exposure time, thus giving a possible indication of how the mass loss will evolve over time. Figure 3 illustrates that the ultimate tensile strength of all tested specimens decreased as the exposure period increased. The most significant decline was observed in the CM–AM welded specimens, suggesting that the interface between conventionally manufactured and additively manufactured materials is particularly vulnerable to environmental degradation. By comparison, the AM specimens showed a more consistent and moderate reduction in tensile strength throughout the exposure period. The relationship between tensile strength and exposure duration is represented by trend curves fitted to the experimental data, which effectively describe the observed deterioration in mechanical performance. Here, the equations are also fitted through the month 12 of the exposure time, thus giving a possible indication of how the tensile strength will evolve over time. The reference sample (RA) in Figure 4 shows a relatively low and uneven oxygen signal, corresponding mainly to the naturally formed passive oxide layer typical of stainless steels exposed to atmospheric conditions. After one month of marine exposure (M1), the oxygen signal (green area) becomes more pronounced and locally concentrated, indicating the initial formation of corrosion products and surface oxidation due to seawater interaction. The specimen exposed for three months (M3) exhibits a significantly higher and more uniformly distributed oxygen signal, suggesting increased surface oxidation and the accumulation of corrosion products over time. Following six months of exposure (M6), the oxygen distribution remains extensive, confirming continued oxidation and the presence of stable corrosion products on the surface. The observed progression in oxygen intensity with increasing exposure time reflects the gradual development of corrosion-related surface layers under natural marine conditions Future investigations should include a more detailed analysis of corrosion pit formation on the material surface, since such defects frequently act as initiation points for cracks that may compromise structural reliability. To better evaluate the long-term performance of AISI 316L stainless steel in marine environments, extended exposure periods are recommended (Xia et al., 2025). In addition, comparing results obtained from natural seawater exposure with those from standardized accelerated corrosion tests performed under controlled laboratory conditions could provide valuable insights (Duarte et al., 2024). Further research could also examine the influence of different marine conditions, including wave-induced loading, splash zone exposure, and tidal variations (Pastorcic et al., 2023). Moreover, a comparative assessment of degradation occurring in the base metal, weld metal, and heat-affected zone (HAZ) would contribute to a deeper understanding of localized corrosion processes and associated mechanical deterioration. These aspects represent important directions for the continuation of the present research. Acknowledgements Funded by the European Union – NextGenerationEU, under the University of Rijeka project PU-175, uniri-iz-25 111, "Assessment of 3D-Printed Material Corrosion Using Artificial Intelligence - 3D-Cortelligence". References Bogdanovic, M., Ivosevic, S., 2025. Offshore Wind Energy Potential: Assessing Capacity Factor and Electricity Generation in Montenegro. Pomorstvo 39, 150–166. https://doi.org/10.31217/p.39.1.12 Braun, M., Schubnell, J., Sarmast, A., Subramanian, H., Reissig, L., Altenhöner, F., Sheikhi, S., Renken, F., Ehlers, S., 2023. Mechanical behavior of additively and conventionally manufactured 316L stainless steel plates joined by gas metal arc welding. Journal of Materials Research and Technology 24, 1692–1705. https://doi.org/10.1016/j.jmrt.2023.03.080 Cortis, D., Pilone, D., Campana, F., Broggiato, G., Orlandi, D., 2024. Joining Dissimilar Steels by Means of Selective Laser Melting: Material Microstructure and Interfacial Characteristics. Procedia Structural Integrity, Third European Conference on the Structural Integrity of