Effect of a thin prior-metallic coating on the morphology of hot-dip Zn coating

Abstract

Copper has been investigated as a potential alloying element in the molten Zn bath and was found to have significant effects in phase formation kinetics as well as corrosion performance. In the present work, the effect of a prior-Cu coating process on hot-dip Zn coating morphology and thickness has been investigated. A thin layer of Cu was coated on steel by a displacement reaction having a thickness of 70-90 nm. The Cu and Zn coatings were characterised using glow discharge optical emission spectroscope, scanning electron microscope and confocal laser scanning microscope. The prior-Cu coating acted as a barrier to Fe dissolution and altered the substrate surface roughness as well as the interfacial energies resulting in modification of nucleation and growth of Fe-Zn intermetallic phases.