The results of several round-robin exercises on electrochemical impedance spectroscopy are published now:

S. Ritter, R.-W. Bosch, F. Huet, et al., Results of an international round-robin exercise on electrochemical impedance spectroscopy, Corrosion Engineering, Science and Technology, 2020, DOI: 10.1080/1478422X.2020.1850070
The accepted manuscript will be published “green open access” after the embargo period has ended (Nov 26, 2021) here:  https://www.dora.lib4ri.ch/psi/islandora/object/psi:35138