PSI - Issue 51

Nils Wegner et al. / Procedia Structural Integrity 51 (2023) 122–128 N. Wegner et al. / Structural Integrity Procedia 00 (2022) 000–000

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change afterward. This effect can be observed for both variants so that despite the different corrosion rates, hardly any differences in residual fatigue strength are apparent. The protective effect of the PEO layer, leading to a lower corrosion rate, a more uniform corrosion morphology, and higher residual fatigue strengths at OCP, is negligible under polarization, so the test methodology does not apply to this material. For WE43, GSP intensifies the already existing pitting tendency on nobler precipitates, so that the method can be considered as a kind of worst-case estimation.

Fig. 4. Exemplary results of a MAT for a PEO modified specimen (initial condition) with visualization of fatigue strength estimation.

Fig. 5. a) Exemplary results of a MAT for a PEO modified specimen (after immersion with GSP for 48 h) with visualization of fatigue strength estimation, b) summarized results of MAT for WE43 (PEO) specimens after immersion at OCP and with GSP. 5. Conclusions In this study, the influence of galvanostatic polarization on hydrogen evolution rate, corrosion morphology, and residual fatigue strength was investigated using the magnesium alloy WE43 with and without plasma electrolytic oxidation (PEO). This application aims to reproduce the long-time immersion behavior and thus to evaluate the mechanical stability under increasing degradation of Mg-based implants in a time-efficient manner. On this basis, the following conclusions can be drawn. Due to the anisotropy of the corrosion properties between longitudinal and cross section, the degradation behavior was overestimated. As a result of the extrusion process, the arrangement of the precipitates in longitudinal section was affected, leading to an increased hydrogen evolution rate and corrosion rate. Nevertheless, through the testing method, a qualitative control of the degradation behavior was possible. For both material variants, a comparable corrosion morphology and residual fatigue strengths were present after polarization. For the PEO modified specimens, this resulted in a change of the corrosion mechanism present at open circuit potential, making the method unsuitable for predicting the degradation behavior. Regarding the PEO modification,