Relationship between texture and corrosion resistance in hot-dip galvanized steel sheets

Abstract

Abstract The addition of lead or antimony to the zinc bath promotes both excessive growth of the zinc crystals and a dendritic solidification in the form of spangles. This phenomenon affects not only the zinc coating texture but also its surface appearance and corrosion resistance. Therefore, the effects of the zinc bath chemical composition (changed by the addition of lead or antimony) on the texture and corrosion behaviour of hot-dip galvanized steel sheets were evaluated. Standardized salt spray tests as well as exposure to a 0.5 M NaClO4 solution test were employed. The surface texture was analyzed using X-ray diffraction (XRD). In order to study the corrosion performance, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) techniques were employed. From the experimental results it was concluded that the characteristic texture of zinc coatings was not modified by an increase in the antimony content, but an increment in the lead content produced a crystallographic preferential orientation with the pyramidal family planes parallel to the coating surface. This last effect deteriorates not only the surface appearance but also the corrosion resistance of the galvanized steel sheets.