Effect of NiCl₂ Content in Flux without Ammonium on the Thickness and Structure of Batch Hot-dip Galvanized Coatings

The thickness and morphology of coatings and intermetallic compound layers on Q235 steel pretreated in fluxes without ammonium but with different NiCl2 contents were analyzed by OM and SEM.The study showed that with the increase of NiCl2 content,the thickness of galvanizing coatings decreased,and with the increase of NiCl2 content the thickness of coatings decreased in a certain concentration range (0-6 g/L).However,when NiCl2 content surpassed the range,the thickness of coatings wouldn′t change with the increase of NiCl2 content,the coating thickness reached minimum when NiCl2 content was 6 g/L.To get a coating with appropriate thickness,NiCl2 content should be 4-8 g/L.NiCl2 would refine the ζ intermetallic phase,make it more compact and decrease its thickness.However NiCl2 had no obvious influence on Γ and δ intermetallic phases.