The Effect of Erosion on Corrosion Protection Properties of Coal Tar Epoxy Coating

In this work, the effect of erosion on corrosion behavior of coal tar epoxy coating was evaluated using electrochemical impedance spectroscopy (EIS) measurements. The surface morphology of the coating was examined by scanning electron microscope (SEM) after ۱۰, ۲۰, ۳۰, ۴۵ and ۶۰ min of erosion process at an impact angle of ۹۰º. After ۱۰ min of erosion process, the Nyquist plots showed just a single large capacitive semicircle and the phase Bode plots exhibited a line close to −۸۰o in the middle-frequency region, thereby indicating high corrosion resistance (about ۱۰۹ Ωcm۲). After ۲۰ and ۳۰ min of erosion process, the diameter of the Nyquist semicircle was decreased with time and two semicircles appeared after ۴۵ min. Furthermore, SEM observations revealed that the protection performance of coating was decreased by an increase in time of erosion due to the formation of holes and electrolyte penetration into the coating. Finally, after ۶۰ min of erosion process, the coating was partially removed and the substrate appeared.

Keywords:

erosion , Electrochemistry , Coal tar coatings , Surface morphology , EIS