Corrosion resistance of steel components validated

The contact resistance between the steel and protective coating was evaluated by measuring the area specific resistance (ASR) on coated steel plates. Details about the sample preparation and measurement set-up can be found in Deliverable 3.6. In D3.6, it was shown that Mn-GCO coated Crofer 22 APU achieved an ASR of ca. 10 mΩcm2 in reducing conditions (wet H2-N2) at 750 °C. The ASR set-up was not suitable for studying the development of resistance with time. Therefore, to evaluate the degradation rate, CGO-coated Crofer 22 APU was pre-aged in 50H2O-50H2 atmosphere at 600 °C for 500 h before measuring the ASR with the same set-up. The ASR as function of temperature in air and wet H2-N2 is plotted in the figure below. The ASR of bare Crofer 22 AU, pre-aged under the same conditions, is shown as a reference.

The results shows that the ASR of CGO-coated Crofer 223 APU after pre-aging remains below 10 mΩcm2 in the whole temperature range (600-750 °C) and in both air and wet H2-N2 atmospheres. Compared to the as-prepared sample, the ASR after pre-aging is slightly improved (lower). This could be due to increased conductivity of the thermally grown oxide scale due to incorporation of dopant elements from the coating, although experimental variations cannot be ruled out. The reference sample (pre-aged, bare Crofer 22 APU) has a higher ASR than the coated sample in air (exceeding 25 mΩcm2 at 600C), while the ASR in wet H2-N2 is much lower and comparable to the coated sample.