INFLUENCE OF FLUX MODIFICATION BASED ON ZNCL2-NH4CL ON THE FORMATION OF ZINC COATING ON STEEL

The main stage of surface preparation for hot-dip galvanizing is the fluxing operation. Immersing products in flux removes oxide films and activates the surface, providing a bond between the base metal and the zinc coating. The purpose of this work is to compare five modifications of the most popular flux composition based on ZnCl₂ and NH₄C1 produced by Promkhimperm with an imported sample produced in Spain, as well as to identify the influence of the modifying components of the compositions on the quality of galvanized products. The samples were immersed in a flux solution heated to 50 °C, kept in the solution for 15 minutes, and then dried. The study of the structure and elemental analysis of flux samples dried on a steel surface was studied on a TESCAN VEGA SB scanning electron microscope, with the uniformity of element distribution assessed by mapping carried out by energy-dispersive microanalysis using the INCA-act attachment. To determine the wetting ability of fluxes, contact angle measurements were carried out using the “seated drop” method. The wetting and spreading of zinc melt over fluxed steel was assessed by the cleanliness of the holes (zinc plating) on the samples. It has been established that all presented fluxes have good surface wetting properties. Most fluxes have a frosty crystallization pattern of zinc chloride. All modifying components of fluxes, with the exception of manganese, are distributed evenly over the surface. A visual assessment of the quality of the zinc coating formed after fluxing with various compositions showed that the best galvanization of holes with a diameter of 10 mm is provided after fluxes with the ratio of the main components: 21 % ZnCl₂ – 20 % NH₄Cl. A flux with more complete sorption of impurities made it possible to obtain a clean hanging hole with a diameter of 4 mm

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