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 withsemi-bright zinc coatings without passivation, with blue chromate, blue chromate andsilicate-based sealer and with yellow chromate were tested by the ER method incombination with cyclic corrosion test (CCT) in a salt spray chamber. The ER method isshown to provide fast quantitative corrosion measurements in chamber tests. In mostcases 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 wereperformed. Results from electrochemical impedance spectroscopy (EIS), weight-lossmeasurements and ER-measurements were in quite good agreement, confirming thereliability of the new ER-method.