Zinc deposition with pack cementation on low carbon steel substrates

The structure of Zn coatings formed with pack cementation at 250, 350, 380, 400 and 450 deg. C have been studied with Scanning Electron Microscopy, X-ray diffraction and microhardness measurments. From this investigation it turned up that these coatings are composed of two layers referring to Γ-Fe11Zn40 and δ-FeZn10 phases of the Fe-Zn phase diagram, while inclusions were also detected, composed of Fe and Zn at almost equal concentrations. Furthermore it was deduced that the coating thickness at 400 and 450 deg. C is a function of t 1/2, where t is the heating time. However, the microstructure is similar in every case. Finally, it was concluded that the microhardness of the pack coatings is higher than the microhardness of the hot-dip galvanized coatings