Effect Of Chloride And Sulfate On Zinc Corrosion Investigated By A Scanning Flow Cell System With Dynamic Electrolyte Change

摘要

Zinc based coatings are of tremendous importance for corrosion protection and are object of research since decades. Besides others, salt spray tests have been used extensively for this purpose by applied researchers, providing however only a partial picture of corrosion processes under actual environmental conditions. Therefore, the predominant knowledge about this system is only of descriptive nature and illuminates just a tiny but well defined parameter space. We present here a novel high-throughput screening approach based on an electrochemical flow cell system [1] that is able to deal with the issue of the complex interrelation between many parameters, in particular the variable ion composition of salts. Since chloride and sulfate are prominent electrolyte constituents under environmental exposure conditions, exact knowledge of the individual impact, more importantly the effect of coexistence of both on corrosion characteristics, presents the key challenge. The microelectrochemical flow cell extends the concept of the classical channel electrode which allows quick exchange of the sample and concertedly enables facile coupling with downstream online analytics [2]. A high sensitivity and selectivity is achieved by using a specialized complexing agent and a custom made UV-Vis flow cell. Time resolved zinc dissolution profiles were monitored by recording the change of absorption spectra.This is utilized first of all to increase our understanding of the impact of the electrolyte components on the fundamental corrosion mechanism and kinetics, and might finally lead to enable tailoring of corrosion protection coatings with respect to the exposure conditions.