Kinetics, mechanism and characterisation of passive film formed on hot dip galvanized coating exposed in simulated concrete pore solution

Abstract

It is established that hot dip galvanized (HDG) coatings exposed in simulated concrete pore solution (SPS) develops very stable corrosion products at the coating surface and its corrosion potential gets greatly ennobled due to the formation of a passive layer. This passive layer has been identified as hydrozincite Zn5(CO3)2(OH)6. The passive film is formed in all the constituents of SPS namely hydroxides of sodium, potassium and calcium. Electrochemical impedance spectroscopy (EIS), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), XRD studies etc. have been performed to study the kinetics and understand the mechanism of formation of hydrozincite (HZ) at the corroding interface. These studies are expected to provide technique for development of an eco-friendly protective passive layer on galvanized coatings prior to their embedding in concrete.