## 4 Results and Discussion  
### Potentialodynamic Tests  
The results of the potentiodynamic tests on carbon textiles are shown in Figure 3 as a current-potential curve in logarithmic scaling. The potential labels P1 to P3 indicate the potentials for the potentiostatic tests, see Section 3.3.  
Figure 3: Current-potential curve for all materials.  
Figure 2: Specim with S4 anode, spacers and titanium electrode (**a**) and an E4 anode (**b**).  
Note, that current and not current density is plotted in Figure 3. This is due to the fact that the exact calculation of the anode surface of rovings without impregnation is complicated: the exact number of fibres in contact with the solution is undefined.  
From Figure 3 it is seen that the polarizability of carbon impregnated with SBR-based material until 1000 mV versus NHE is better and thus delivers the highest current, while E4 achieves the lowest current. From 1100 mV versus NHE UC delivers more current than carbon impregnated with SBR-based material. The curve of the test with UC_WS is similar to UC with the difference that UC_WS can deliver more current up to 900 mV versus NHE and after that potential less current than UC.  
The OCP of the non-impregnated carbon fibres amounts to about 100 mV versus NHE and is between the OCPs of E4 (60 mV versus NHE) and S4 (180 mV versus NHE). Panel area 1 is between 200 and 900 mV versus NHE for the non-impregnated carbon fibres. The transition section is small, the panel area 2 is between 950 and about 1100 mV versus NHE. For S4, panel area 1 is between about 300 and 1150 mV and panel area 2 between 1225 and 1300 mV. The transition section of E4 is not clearly defined, it could be between 950 and 1150 mV. The transition sections of all experiments are characterized by a brief reduction in the slope of current density followed by a renewed and steeper increase in current density.  
The images of carbon samples UC before and after polarization are exemplarily displayed in Figure 4. Strong deposits can be seen on the polarized sample, which will be discussed later in this paper.  
A discoloration of the calcium hydroxide solution could not be observed for the potentiodynamic experiments on all experiments.  
The SEM investigations of S4 and E4 before and after polarization in Asgharzadeh et al. (2012) showed a destruction of the impregnation material. There was not investigated, whether the sizing under the impregnation was affected or not. To this end, the UC sample is examined in the present study. Figure 5a shows the unpolarized carbon fibre. On the right the polarized carbon fibre is shown (Figure 5b). The carbon fibres are round and have slight longitudinal grooves. This shows cracks in the sizing both in the longitudinal and in the radial direction at regular distances. The carbon fibre underneath seems to be intact. Such a clear destruction of the sizing was observed at several carbon fibres. It is concluded that the sizing deteriorates and the carbon fibre remains intact.  
Figure 4: Unimpregnated carbon fibres before the test (**a**) and after (**b**).  
An energy dispersive X-ray spectroscopy (EDX) of the polarized sample probing the deposition shows the presence of calcium, carbon and oxygen (Figure 6).