Plating assistant and plating assisting solution for hot dip galvanizing and zinc alloy coating

Abstract

The invention relates to a plating assistant and plating assisting solution for hot dip galvanizing and zinc alloy coating. The invention is characterized in that the plating assistant is composed of the following salts in parts by weight: 25-40 parts of zinc chloride, 5-10 parts of ammonium chloride, 5-10 parts of potassium chloride and 0.1-1 part of bismuth chloride. The plating assisting solution is a solution prepared from any plating assistant, water and hydrochloric acid. The zinc chloride concentration of the plating assisting solution is 250-400 g / L.

Description

technical field [0001] The invention relates to the technical field of coating technology on the surface of iron and steel materials, in particular to a new type of fluxing agent for hot-dip galvanized aluminum-magnesium alloy coating. Background technique [0002] Hot-dip plating is one of the effective methods to prevent corrosion of steel materials at present. The traditional plating solution used for hot-dip plating is generally zinc. After the iron and steel parts are immersed in the flux for a period of time, a layer of salt film will be formed on the surface after the flux, which can prevent the surface oxidation of the steel parts and further clean the surface of the workpiece. Most of the existing fluxes are A mixed solution of zinc chloride and ammonium chloride. With the development of technology, new alloys suitable for hot-dip plating have emerged including zinc-aluminum-magnesium alloy (Zn-6Al-3Mg) and Galfan alloy (zinc-5% aluminum-rare earth), but for these ...

AI Technical Summary

Problems solved by technology

With the development of technology, new alloys suitable for hot-dip plating have emerged including zinc-aluminum-magnesium alloy (Zn-6Al-3Mg) and Galfan alloy (zinc-5% aluminum-rare earth), but for these new alloys due to The addition of aluminum, the surface of the bath due to oxidation, including Al 2 o 3 The oxides contained in it will make the wettability of the plating solution and the steel substrate worse, making it difficult to control the quality of the coating, and there will be a phenomenon of missed plating, especially when the plate is hot-dipped, because its specific surface area is small, and due to the plating The Al content in the liquid is relatively high. When using the traditional ammonium zinc chloride flux, ammonium chloride and zinc chloride will react with aluminum to form a cyan AlCl 3 (AlCl 3 The boiling point is 182°C, and the sublimation temperature is 179°C) smoke, resulting in a large number of bubbles and pinholes on the surface of the coating or even missing plating, and it is impossible to obtain a coating with qualified surface quality

At the same time, a large amount of acid fumes produced will also cause environmental pollution and corrosion of production equipment

[0003] Chinese patent document CN1476487A discloses a kind of improvement and is used for hot-dip plating fluxing agent, points out adding alkali metal or alkaline earth metal salt, and NiCl in traditional ammonium zinc chloride fluxing agent 2 、CoCl 2 , MnCl 2 One of the and PbCl 2 , SnCl 2 , SbCl 3 、BiCl 3 One of them, and pointed out that the flux is suitable for galvanizing, zinc-aluminum-magnesium alloys and Galfan alloys (Zn-5%-Re, that is, Zn-5%-rare earth), but we found in the study that the use of this document After the flux treatment, only the hot-dip plating method of nitrogen bubbling in the galvanizing bath and longer dipping time mentioned in this document can be used to achieve a better galvanizing effect, but the obtained The thick coating of the specimen will cause excessive consumption of coating metal. If the conventional hot-dip coating method is used, the quality of the coating obtained is poor

And in this document, preferred plating flux has adopted the salts such as nickel chloride, plumbous chloride that are difficult for hydrolysis in water, and the aqueous solution of plating flux is weakly acidic (pH about 4), and through we find, chloride Nickel will cause blistering on the surface of the coating and affect the quality of the coating

[0004] Chinese patent document CN 103510031A also discloses an aqueous solution of plating flux that can be used for zinc-aluminum-magnesium alloys, which consists of ZnCl 2 35%-45%; NaF 2%-10%; CeCl 2 0.5-3.5%; SnCl 2 4.5%-8.5%;H 2 o 2 0.5-2%; surfactant 0.1%-0.5%, the balance is water; although the flux does not use ammonium chloride, it avoids the generation of smoke during hot-dip plating, but the added fluoride is harmful to the environment The pollution and the toxicity of operators are more serious than ammonium chloride, and we found in the experiment that the flux is only suitable for zinc-aluminum-magnesium alloys, not for Galfan alloys, and we also found that the flux is actually It is only suitable for thinner steel wires. When the workpiece is plate-shaped, the processing effect is not satisfactory.

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