Results of a Round Robin Test for the Determination of Polarization Resistances on Differently Weathered Zinc Samples Using Gel Electrolytes

This article presents the results of a round robin test throughout Germany with 19 participating institutions. Corrosion product layer resistances (R_L) were determined on two differently weathered pure zinc samples and a sample activated with NaOH by means of electrochemical measurement of the linear polarization resistance (LPR) using agar-based gel electrolytes. The round robin test was organized by the Bundesanstalt für Materialforschung und -prüfung (BAM) in Berlin. The measurements were carried out by the participants in the period from May to July 2021. The results are summarized in this article comprising an assessment of the reproducibility and repeatability of the measurements. The methodology is suitable for distinguishing zinc surfaces after exposure to different atmospheres based on the corrosion product layer resistances (R_L). In addition, possible problems in the application of the method were identified, and solutions for improving reproducibility and repeatability are discussed. The results and knowledge from the round robin test are incorporated into a new test standard (DIN 50023:2024-07) for this measurement method.