Enhancing Corrosion Resistance of Galvanized Steel by Phosphating and Silicate Post – Sealing

Soha A. Abdel-Gawad
2018 International Journal of Electrochemical Science  
Hot dip galvanized (HDG) coatings are widely used in various industrial fields for better corrosion protection of steels. Comparative study of the corrosion behavior of the phosphated hot-dip galvanized steel conversion coatings and post-sealing in sodium silicate solution were characterized in 3.5 % NaCl solution by different techniques, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The surface morphology and elemental composition of hot-dip galvanized steel
more » ... post treated were characterized by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). The results showed that after phosphating the porous phosphate crystals formed on the surface of HDG steel and the phosphating followed by post-sealing samples in sodium silicate solution filled into the phosphate pores. The optimum silicate concentration ranged from (3-5 g/l), its morphology has fine crystal, compacted and dense uniform coating (zinc-silicate complex). Low silicate concentration (3-5 g/l) have better protection property and best corrosion performance than other high concentration (7-10 g/l) due to cracks formation in coating and bad protection.
doi:10.20964/2018.03.18 fatcat:yla3hgnv5vav5dwut2hmw2cnsy