Low melting point flux for hot dip plating

Abstract

The invention provides a low melting point flux for hot dip plating. The flux is characterized by comprising the following components: 80-140g / L of zinc chloride, 0-30g / L of sodium chloride, 5-20g / L of sodium fluoride, 10-40g / L of aluminium chloride, 5-15g / L of sodium bicarbonate, 0.2-3g / L of composite surfactant and the balance water. The melting point of the flux can be lowered, the time of slag floating is controlled in 90 seconds, the efficiency of the interface reaction between flux salt film and liquid zinc is increased, the wettability between a metal part matrix to be plated and liquid zinc is improved, and the rate of skip-plating is reduced. The rate and degree of the reaction between aluminium in zinc-aluminium alloy liquid and the other chlorides in the flux can be reduced, wherein aluminium chloride is prepared by the reaction; the flux can help the aluminium content of the alloy liquid to be stabilized to a certain extent; and the application range of the low melting point ammonia-free complex salt flux can be expanded in the hot dip plating technological process of the zinc-aluminium alloy liquid, and the stability of the flux can be increased.

Description

technical field [0001] The invention relates to a plating flux, in particular to a low melting point flux for hot-dip plating and a method for using the same, belonging to the technical field of surface plating of metal materials. Background technique [0002] At present, the zinc chloride-ammonium system flux, which is recognized and widely used in the hot-dip galvanizing industry, is mainly based on zinc chloride (ZnCl 2 ) and ammonium chloride (NH 4 Cl) based and mixed in a certain proportion to form an aqueous solution. The basic mechanism of action of the fluxing agent in the zinc chloride-ammonium system is to use the HCl and NH produced by the decomposition of ammonium chloride at 337.8°C 3 , to purify the surface of the metal parts to be plated and the oxides of liquid zinc, plus the stability and isolation of zinc chloride to ammonium chloride in the double salt system, it can clean the hot-dip zinc-iron reaction interface Carry out effective purification and suf...

AI Technical Summary

Problems solved by technology

This kind of plating flux is mainly composed of chloride salt as the main salt, and the melting point of the double salt is above 240°C, which is about 10°C to 60°C higher than the melting point of the above-mentioned zinc chloride-ammonium fluxing agent. In application, if the process parameters are controlled or the operation method is improper, it is easy to cause the double salt of the fluxing agent to melt and react during immersion plating, and the time for forming scum to float to the surface of the zinc liquid is prolonged, and the solid state between the steel substrate of the workpiece to be plated and the liquid zinc will be prolonged. Delayed reaction at the / liquid interface may easily cause surface defects such as missed plating and black spots on the workpiece, which will affect the production efficiency of galvanizing and the quality of the coating