CORROSION OF ELECTROGALVANIZED STEEL

Abstract

The surface morphology, composition and corrosion products of zinc coated surface deposited in acidic and basic electrolytic bath at two different current densities of 25 mA/cm2 and 50 mA/cm2 were studied. The techniques used to achieve this include scanning electron microscope (SEM), polarization curves, X-ray Diffraction and Tafel- Extraplotation method. The corrosion rate decreases in case of basic electrolyte and at lower deposition current density of 25mA/cm2. Corrosion product analysis using Energy Dispersive X-ray Spectroscopy (EDXS) disclosed that the formation of white rust, that is formation of zinc oxide and zinc hydroxide was a corrosion product found in both types of coatings. Formation of passive oxide-hydroxide layer slows down the dissolution rate which results in the decrease in corrosion rate.