The microstructure of annealed galfan coating on steel substrate

Abstract

The commercially available Galfan coating containing 5-7wt.% of Al deposited on the low carbon steel substrate by hot dipping has been examined with respect to the microstructure of the coating/substrate interface area. The application of several experimental techniques (SEM/EDS, XRD, TEM/AEM/EDS/ED) allowed demonstrating the two-phase structure of the alloy coating in non-treated, commercially available Galfan samples: Zn-rich pre-eutectoid phase grains are surrounded by lamellar eutectics of -Al and -Zn. The transition layer between the alloy coating and steel substrate with the considerably higher Al content (SEM/EDS, TEM/EDS) has been found in both non-treated and annealed samples (600oC/5 minutes). Only the monoclinic FeAl3Znx phase however was revealed in the annealed sample (TEM/electron diffraction) remaining uncertain the presence of the orthorhombic Fe2Al5Znx phase, reported by several authors.