Corrosion Testing

High temperature corrosion of metallic interconnects is one of the main degradation phenomena in high temperature solid oxide based devices. DTU Energy is experienced in evaluation of materials and fabrication of tailored protective coatings from small experimental batches to post-mortem analysis of full stacks.

Due to the growth of poorly conductive oxide on the surface of metallic interconnects, their electrical resistance becomes higher with time and they can react with other components of the system. Choosing suitable alloys and protective coatings can greatly reduce degradation and ensure longer life time.

FCH Test Center offers testing and analysis of metallic interconnects, metal supported solid oxide cells as well as coatings and protective layers.

Oxidation Test

DTU Energy and FCH Test Center have equipment to perform oxidation tests under carefully controlled and realistic conditions. Oxidation tests can be performed on porous as well as dense samples.Characterization of the corrosion behavior of a sample can be performed in multiple ways:

• Cyclic and continuous thermo-gravimetry for assessment of corrosion rates by controlling weight gain [1] [2].
• Measurement of area specic resistance in controlled exposure conditions.

Corrosion_graphs

Figure 1: Left: Measured mass gain versus time for a 0.3 mm thick Crofer 22 APU alloys. Measurement performed at 800 °C in air. Right: Calculation of degradation rate.

Thermodynamic Modelling

Corrosion phenomena, such as phase stabilities and reactivity, can be modelled using thermodynamic data and models. Especially issues of coatings stability, reactivity as well as sigma phase and Laves phase formation in the alloy are evaluated theoretically and experimentally.

Development of protective coatings 

Protective layers can hinder corrosion, such layers can be developed, deposited onto interconnect materials and tested at FCH Test Center. It is often relevant to use different coating materials on the hydrogen/oxygen side of interconnects as the corrosion behavior is largely dependent on the surrounding atmosphere [3].

Figure 2: SEM micrographs of sample from Figure 1 after the test: Crofer 22 APU sample exposed to 3000 hours oxidation in air. Left: surface view, Right: cross-section view with visible ~5 μm thick oxide layer.

References

[1] Molin, S., Chen, M., Hendriksen, P.V. J. of Power Sources, (2014) 251, p. 488-495.
[2] Persson, Å. H., Mikkelsen, L., Hendriksen, P. V., Somers, M.A.J. J. of Alloys and Compounds, (2012) 521, p. 16–29.
[3] Palcut, M., Mikkelsen, L., Neufeld, K., Chen, M., Knibbe, R., Hendriksen, P.V. Corrosion Science, (2010) 52(10), p. 3309-3320.

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High Temperature Corrosion Testing Brochure
Test operating conditions
Temperature Up to 1000 °C
Gas options H2, O2, Air, CO2, CO, CH4
Samples Porous / dense
Table: Test conditions
http://www.fch.dk/services/corrosion-testing
20 JANUARY 2019