Characterization of zinc-rich powder coatings by EIS and Raman spectroscopy

In this work, the protective mechanisms of a single coat zinc-rich powder coating are examined. Powder coating panels were applied on phosphatized steel and were studied when immersed in artificial sea water with flowing conditions. Open circuit potential and electrochemical impedance spectroscopy measurements were recorded to study changes in the coating properties with the exposure time. Moreover, Raman spectroscopy was used to analyze zinc corrosion products. This study reveals that the behavior of powder coating systems is different from solvent-based zinc-rich paints (ZRP). This is mainly attributed to the low porosity of powder coatings, due to their high wetting ability, which insulates some of the zinc particles. However, cathodic protection is active and provides the sealing of the coating pores. Finally, it is found that the barrier effect is higher than the one usually observed with solvent-based ZRP.