## 3 Results
### Corrosion Investigations
#### 3.2.2 Immersion Tests  
Figure 4 shows the results of immersion tests without polarization plotted with the specific hydrogen volume V\({}_{\rm H_{2},spec}\) over the immersion time t. It shows the individual data points, as well as two regression lines for each test. Since the data are measured manually, there are gaps in the data shown by dotted lines. The curves exhibit an almost linear behavior at the beginning of the immersion, after 5-11 h, it turns into another linear region of the lower slope.  
\begin{table}
\begin{tabular}{c c} \hline
**Corrosion Current Density i\({}_{\rm corr}\)** & **Estimated Corrosion Rate \(\hat{\bf m}_{\rm corr,e}\)** \\ **(\(\mu\)A cm\({}^{-2}\))** & **(mg cm\({}^{-2}\) a\({}^{-1}\))** \\ \hline
8.29 & \(3.29\cdot 10^{1}\) \\ \hline
23.84 & \(9.47\cdot 10^{1}\) \\ \hline
17.32 & \(6.88\cdot 10^{1}\) \\ \hline
16.48 \(\pm\) 6.38 * & \((6.55\pm 2.53)\cdot 10^{1}\) * \\ \hline \end{tabular}
\end{table}
Table 2: Summarized results of potentiodynamic polarization measurements on Mg WE43 in a modified minimum essential medium at 36.5 \({}^{\circ}\)C; * mean value \(\pm\) SD.  
Figure 4: Results of immersion tests without galvanostatic polarization on Mg WE43 in a modified minimum essential medium at 36.5 \({}^{\circ}\)C (immersion time of 48 h).  
Figure 3: Results of potentiodynamic polarization measurements on Mg WE43 in a modified minimum essential medium at 36.5 \({}^{\circ}\)C.  
Since no data points are available for the transition, it must be understood mathematically as the intersection of both straight lines. It can be presumed that the hydrogen evolution, in reality, assumes a degressive course. For the method to be developed, the transition between both regions and the data gaps are of minor importance since a constant corrosion rate was set as a criterion. Nevertheless, the curves show a qualitatively similar behavior, exhibiting passivation. The corrosion rate of the respective tests is determined by the slope of the straight line (after the transition). This choice is justified by the larger proportion of the test duration. The mean value is \(\dot{\text{m}}_{\text{corr,mean}}=3.44\cdot 10^{1}\) mg cm\({}^{-2}\) a\({}^{-1}\) (Table 3) with a standard deviation of \(1.60\cdot 10^{1}\) mg cm\({}^{-2}\) a\({}^{-1}\). The results of the immersion tests with galvanostatic polarization are shown in the same way in Figure 5.  
Due to the different immersion times, the scaling of the abscissa is changed, and the results are shown without the unaccelerated tests. Compared to the tests without polarization, no change in the slope of the regression line is observed. After reaching a constant OCP, the curves first assume a progressive course before changing into a linear one. The dissolution rate \(\dot{\text{m}}_{\text{diss}}\) is calculated analogously to the unaccelerated immersion tests (Table 3). Through anodic polarization, the dissolution rate can be increased by up to three decades in several steps. The coefficient of determination (COD, Table 3) R\({}^{2}\) increases with increasing polarization up to a maximum of R\({}^{2}\) = 99.932% (for i\({}_{\text{a}}\) = 20 mA cm\({}^{-2}\)).