Atmospheric Corrosion Monitoring of Electrolytic Zinc Coatings by Electrical Resistance Measurements in Cyclic Salt Spray Test

摘要

Results of a recently developed refined, high-sensitive electrical resistance (ER) measurement method for corrosion monitoring are presented. Steel probes plated with semi-bright zinc coatings without passivation, with blue chromate, blue chromate and silicate-based sealer and with yellow chromate were tested by the ER method in combination with cyclic corrosion test (CCT) in a salt spray chamber. The ER method is shown to provide fast quantitative corrosion measurements in chamber tests. In most cases an instant corrosion rate can be calculated after a few hours exposure in CCT, whereas visual inspections will require exposure for several days to reveal corrosion. To test the reliability of the ER-measurements as compared to well-known methods, additional corrosion experiments on zinc-plated steel immersed in NaCl-solution were performed. Results from electrochemical impedance spectroscopy (EIS), weight-loss measurements and ER-measurements were in quite good agreement, confirming the reliability of the new ER-method.