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This document specifies a method for the electrochemical measurement of ion transfer resistance of the rust layer formed on weathering steel alloys in order to assess their protective properties against corrosion thereafter^[3]. This method uses an electrochemical AC impedance measurement^{[4][5][6] [7][8]} , together with harmonic analysis, to identify the ion transfer resistance, and a rust thickness measurement to characterize the stability of the protective rust layer in terms of corrosion protection under used environments.

[3] Kihira H., Ito S., Murata T. Quantitative classification of patina conditions for weathering steel using a recently developed instruments. Corrosion. 1989, 45(4) p. 347

[4] Feliu S., Galvan J.C., Feliu Jr S., Bastidas M., Simankas J., Morcillo M., Almeida E.M. An electrochemical impedance study on the behaviour of some pretreatments applied to rusted steel surfaces. Corrosion Science. 1993, 35(5) p. 1351

[5] Tsuru T. Application of AC impedance method to corrosion and protection field. Bosei Kanri. 1986, 30(11), pp. 351

[6] Itagaki M. (Ed.) Electrochemical Impedance Method. Maruzen, Japan, 2013

[7] Kawai N. An instrument to evaluate coating deterioration by AC impedance method. Bosei Kanri. 2016, 371

[8] Orazem M.E., Tribollet B. (Eds.) Electrochemical Impedance Spectroscopy. John Wiley & Sons, Inc., 2008