KR20030091468A - Composition for flux in fused zinc galvanizing-coating - Google Patents

Abstract

PURPOSE: A flux composition for hot dip galvanizing is provided, which substantially reduces scattering and visible plume generated when the flux composition is dipped into hot dip galvanizing pot, and which is less influenced by inflow of acid so that the composition obtains superior performance compared to an existing flux composition. CONSTITUTION: The flux composition for hot dip galvanizing comprises 5 to 30 wt.% of zinc chloride (ZnCl2); 5 to 25 wt.% of potassium chloride; 1 to 3 wt.% of non-aromatic amine; and 50 to 70 wt.% of water, wherein the flux composition further comprises 4 to 6 wt.% of sodium chloride or a mixture in which sodium chloride is mixed with calcium chloride in a ratio of 1:1, and wherein the non-aromatic amine is one or more compounds selected from the group consisting of tricaprylyl methyl ammonium chloride, alkyl dimethyl ammonium chloride (where alkyl group is an alkyl group having 8 or less of carbon atoms) and trimethyl ammonium chloride.

Description

Hot dip galvanized flux composition {COMPOSITION FOR FLUX IN FUSED ZINC GALVANIZING-COATING}

The present invention relates to a flux composition for hot dip galvanizing steel structures, which is used for flux treatment prior to depositing the steel structures in a molten zinc bath.

In the zinc plating process, the following steps are usually performed before the plating step.

1: degreasing step to remove oil, dust and the like on the surface of the plated body;

2: a first washing step of washing the surface of the degreased plated body with water to prevent the introduction of impurities into the pickling solution, which is a subsequent process;

3: pickling step of removing an oxide layer on the surface of the plated body by using an aqueous solution of sulfuric acid or hydrochloric acid;

4: a second washing step of washing the plated body from which the oxide layer has been removed with water in order to suppress the introduction of impurities such as acid and iron salt into the flux solution after the pickling step;

5: Flux solution is used to improve the zinc plating performance, and after the flux step to prevent iron oxide removal and reoxidation of the surface of the plated body, it is deposited in a molten zinc bath to be plated, followed by zinc in the cooling step. The plating process takes place.

The flux solution used for the flux treatment performed before the deposition in the molten zinc bath is also called double salt of ammonium chloride, and three kinds are mainly used as follows.

ZnCl ₂ : NH ₄ Cl (molar ratio) ZnCl ₂ : NH ₄ Cl (weight ratio)

1: ZnCl ₂ NH ₄ Cl 1: 11: 0.39

2: ZnCl ₂ · 2NH ₄ Cl 1: 11: 0.78

3: ZnCl ₂ · 3NH ₄ Cl 1: 11: 1.17

Among them, ammonium chloride emits Nox, Cl ^−, and NH ₃ gas upon pyrolysis, and is the main substance generating white lead. Problems with such flux solutions include the problem of fugitives generated during deposition in molten zinc baths and the generation of toxic gases and white lead, especially in the plating industry due to the occurrence of white lead. It is becoming a factor to increase the environmental costs such as installing an air pollution prevention facility separately or operating a vacuum pump for suctioning white smoke.

Therefore, it is urgent to develop a hot-dip galvanized flux composition that can suppress the generation of white lead and scattering to solve this problem.

In order to solve the above problems, an object of the present invention is to provide a flux solution of a new composition which can suppress the generation of scattering and white smoke.

1 is a graph showing the film formation state according to the acid inflow in the flux solution of the composition according to the present invention and the existing flux solution.

As a result of intensive studies to achieve the above technical problem, the present inventors can suppress the generation of smoke when potassium chloride is used instead of ammonium chloride, and also by adding a non-aromatic amine-based surfactant, The present invention has been completed by focusing on being able to suppress the occurrence of.

Composition for hot dip galvanizing flux according to the present invention is zinc chloride (ZnCl ₂ ) 5 to 30% by weight; 5 to 25 weight percent potassium chloride; 1-3 weight percent of non-aromatic amine; And 50 to 70% by weight of water is characterized in that it comprises. If the amount of potassium chloride exceeds 25% by weight, the transparency of the liquid deteriorates, and a problem arises in that the stability cannot be maintained continuously. In the case of the non-aromatic amine used as the surfactant, the most suitable content was found to be 2 to 3% by weight.

In the composition for hot dip galvanizing flux according to the present invention, the composition may further comprise 4 to 6% of sodium chloride or a 1: 1 mixture of sodium chloride and calcium chloride. If sodium chloride is used alone or in combination with calcium chloride, the zinc material generated during plating on the steel surface is well separated, thereby improving plating quality.

In addition, as the non-aromatic amine, it is preferable to use at least one selected from the group consisting of tricaprylyl methyl ammonium chloride, alkyl dimethyl ammonium chloride, wherein the alkyl group is an alkyl group having 8 or less carbon atoms, and trimethyl ammonium chloride.

The fugitive acid has a surface tension of about 50-55 dyn / cm of zinc chloride ammonia double salt solution (30% standard), which is applied to the surface of steel by 50-60%. Since much water remains on the surface until it is deposited in the zinc bath (450 ° C), zinc is exploded and scattered to the outside due to rapid expansion of water. Therefore, the surface tension of the double salt solution of the inorganic salt which does not generate white lead is adjusted to 40 or less, and as a surfactant compatible with the double salt, the transparency of the double salt solution is improved under weak acidity, and the surface moisture is quickly replaced by the double salt film. Surfactants with the ability to do so were selected. Synthesis and basic experiments in the present laboratory have shown that a mixture of ammonium chloride and betaine having up to 8 carbon atoms, a mixture of cationic and amphoteric surfactants, is the best.

White lead is thinly coated with flux on the steel surface, and is formed from the flux when deposited in a molten zinc bath, especially formed by ammonium softening. In order to solve this problem, it is possible to prevent the adhesion of aluminum oxide, which does not burn at 450 ~ 470 ℃, and is a role of conventional ammonium chloride. This completes the composition according to the present invention.

Through the following examples look at the configuration of the present invention in more detail. The following examples show one example of the present invention, and the scope of the present invention is not limited by the examples.

Comparative Example 1

23.4 wt% of ammonium chloride (NH ₄ Cl) and 20.0 wt% of zinc chloride (ZnCl ₂ ) were mixed to prepare the same flux composition as the composition used conventionally. Its appearance was colorless and transparent, pH was 4.5 and specific gravity was 1.218. The alloy layer was well formed and the uniformity of the plating was also good. In order to compare the degree of smoke generation and the degree of zinc scattering with respect to the embodiment of the present invention, the degree of smoke generation and zinc scattering in the comparative example was set as 100.

Example 1

20.3 wt% zinc chloride (ZnCl ₂ ), 10.9 wt% potassium chloride (KCl), 65.8 wt% water, and 3 wt% tricaprylyl methyl ammonium were used as the flux composition. The appearance was colorless and translucent, pH was 4.5, specific gravity was 1.226, and the alloy layer formation and plating uniformity were about the same as compared with the case of the comparative example. Smoke generation was 0.1, 99.9% reduction when the comparative example was set to 100. The smoke generation is based on visual judgment, and when smoke generation is the same as Comparative Example 1, it is reduced by 0%. It can be seen that the state is not reduced by 100%, in the case of Example 1 almost no occurrence of white smoke, but was not seen to be reduced by 100%, it was determined that 99.9% decreased.

The degree of zinc scattering was reduced by 80% compared with that of the comparative example.

In the case of the comparative example, the distance from which zinc is scattered was 10 to 20 m in the comparative example, and thus, when the scattering distance was the same, it was seen to decrease by 0%, and by 50% when the scattering distance of zinc was 5 to 10 m. In the case of the example, since the operator was not feeling the risk of scattering within 1m of the zinc scattering distance, it was determined that the reduction of 80%.

Compared to the case of Example 1 and the pH change of the flux according to the acid inflow of Example 1 and the flux film forming state is shown in Table 1 below.

Acid inflow (%) pH change Film formation state Comparative Example 1 Example 1 Comparative Example 1 Example 1 0.2 4.47 4.50 Good Good 0.4 4.41 4.49 Good Good 0.7 4.35 4.46 Good Good 1.0 4.12 4.41 Good Good 1.2 3.92 4.37 Good Good 1.5 3.76 4.32 Bad Good 2.0 3.29 4.26 Bad Good 3.0 2.87 4.13 Bad Good 5.0 2.12 3.67 Bad Bad 7.0 2.03 3.22 Bad Bad 10.0 1.00 2.31 Bad Bad

In the flux composition of Comparative Example 1 containing ammonium according to the prior art, when the acid inflow amount is 1.5% or more, whereas the film formation is poor while the pH is 3.76 or less, in the case of the flux composition according to the present invention The pH is 4.13 until the acid inflow is 3.0%, which results in good film formation. The resulting graph is attached to FIG. 1.

As a method of grasping the state of film formation, it was judged whether there was an unplated part, whether it is possible to repair, and whether it should be replated. In addition, it was determined whether the zinc material that was not dropped out was attached, the degree to which it could simply be dropped, and whether it was necessary to replat. In addition, the strength was judged by tapping with a hammer for adhesion.

This indicates that the composition according to the present invention is much less affected by the acid flowing in the pickling bath than the conventional products, and thus, the film formation sustainability of the flux is much better.

Example 2

A flux solution was prepared by mixing 15 wt% potassium chloride, 15 wt% zinc chloride, 4 wt% 1: 1 mixture of sodium chloride and calcium chloride, 64 wt% water, and 2 wt% tricaprylyl methyl ammonium. The same result as in Example 1 was obtained.

Example 3

A flux solution was prepared by mixing 20 wt% potassium chloride, 10 wt% zinc chloride, 5 wt% 1: 1 mixture of sodium chloride and calcium chloride, 62 wt% water, and 3 wt% tricaprylyl methyl ammonium. The same result as in Example 1 was obtained.

Example 4

A flux solution was prepared by mixing 25 wt% potassium chloride, 5 wt% zinc chloride, 6 wt% 1: 1 mixture of sodium chloride and calcium chloride, 62 wt% water, and 2 wt% tricaprylyl methyl ammonium. The same result as in Example 1 was obtained, but the liquid was slightly clouded. This problem occurs when the proportion of potassium chloride in the content exceeds 25%. There was no problem in use as the flux composition.

Each component composition of Examples 2-4 is shown in Table 2 below.

Example 2 Example 3 Example 4 Potassium chloride 15% 20% 25% Zinc chloride 15% 10% 5% 1: 1 mixture of sodium chloride and calcium chloride 4% 5% 6% water 64% 62% 62% Tricaprylyl Methyl Ammonium 2% 3% 2%

As described above, the composition according to the present invention significantly reduces the generation of fugitive and white smoke generated upon deposition in the molten zinc bath, and is less affected by acid inflow, and thus, its performance is superior to conventional flux compositions.

Claims (3)

Zinc chloride (ZnCl ₂ ) 5-30% by weight; 5 to 25 weight percent potassium chloride; 1-3 weight percent of non-aromatic amine; And Hot-dip galvanizing flux composition comprising 50 to 70% by weight of water. According to claim 1, Sodium chloride, or a mixture of sodium chloride and calcium chloride 1: 1 to 4 to 6% by weight further characterized in that it comprises Composition. According to claim 1, As the non-aromatic amine, it is used to use at least one selected from the group consisting of tricaprylyl methyl ammonium chloride, alkyl dimethyl ammonium chloride (where the alkyl group is an alkyl group having 8 or less carbon atoms) and trimethyl ammonium chloride Hot dip galvanized flux composition.