THE X-RAY DIFFRACTION ANALYSIS OF PHASE EVOLUTION IN ZN-AL-MG COATING LAYER

Variety of zinc-based coatings has been investigated in the last 35 years to improve their properties. The zinc-based coating on hot-dip galvanized steel provides excellent sacrificial protection over the steel substrate. The corrosion resistance of zinc coatings is determined primarily by the thickness of the coating but varies with the severity of environmental conditions. In case of zinc-based alloys for steel coating the phase type and its quantity developed upon solidification determine corrosion resistance as well. In this study the phase quality and evolution along thickness of the Zn-Al-Mg coating layer was studied by x-ray diffraction analysis. During investigation the coating was removed in a controlled manner in several steps. Each individual step of removal was followed with x-ray diffraction measurement and subsequent analysis of x-ray diffraction patterns. Inhibition layer composed of Al3Fe was identified using scanning electron microscopy as well as x-ray diffraction.