JPH0375349A - Flux for hot dip zn-al alloy coating - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plating flux used when hot-dip Zn-A1 alloy plating is applied to steel materials and the like.

[Conventional technology]

Traditionally, for the purpose of preventing corrosion of steel materials,
It is known to apply hot-dip galvanizing and electrogalvanizing to the surface.

Recently, many new products with high added value have entered the market by using zinc plating as a base and adding surface treatments such as painting and finishing. Users' choices regarding products such as these are becoming increasingly diverse.

In order to satisfy these demands, considerable efforts have been made to improve the properties of the galvanized layer by selecting the additive elements and amounts added in the plating bath composition for hot-dip galvanized products.

In particular, a plating bath is known in which about 3 to 10% by weight of ^l is added in order to ensure the corrosion resistance of the plating layer.

This plating bath is usually used after subjecting objects to be treated, such as steel parts, to flux treatment by immersing them in a ZnCjl aqueous solution.

However, the plated product manufactured in this way does not have a plating layer and is likely to be unplated.

Therefore, primary plating is performed in a Zn plating bath that does not contain Af, and after the above-described flux treatment, secondary plating is performed in the Zn--Aj2 alloy plating bath.

[Problem to be solved by the invention]

However, the above method has the disadvantage that it is complicated because it requires two plating steps, and the manufacturing cost is also high.

The present invention has been made in view of the above-mentioned conventional problems.
The purpose of the present invention is to provide a flux for hot-dip Zn-A1 alloy plating that does not cause unplated surfaces on objects to be treated such as steel parts even in a single plating operation.

[Means to solve the problem]

In order to achieve the above object, the present inventors conducted various studies, and as a result, they conducted a flux treatment on the object to be treated using an InCf3 aqueous solution as a flux, and injected InCf into the object.
Zn-A1 to the workpiece by adhering Cf.
It was discovered that the adhesion of the alloy can be improved, and the details thereof will be described below.

That is, the present invention uses InCj! as a flux for hot-dip Zn-Al alloy plating. The above problem was solved by using an aqueous solution containing 0.3 to 30% by weight of z.

A small amount of acid such as hydrochloric acid or sulfuric acid may be added to this aqueous solution.

[For production]

The flux of the present invention is used for molten Zn-Al alloy plating, and the reason why the zinc plating bath contains Af is to maintain the corrosion resistance of the plating layer.

The AIIJ is preferably 3 to 10% by weight. If it is less than 3% by weight, the effect of maintaining the above-mentioned corrosion resistance is small, and
This is because even if the content exceeds 10% by weight, further improvement in corrosion resistance is difficult to obtain, and the melting point of the plating bath increases, resulting in poor workability.

Furthermore, the reason why InCf is included in the aqueous solution flux of the present invention is to improve the adhesion between the Zn-A1 alloy plating layer and the object to be treated, and to form a uniform plating layer without causing unplated areas. This is to make it happen. The amount of InC1 is 0.
The reason why it is set at 3 to 30% by weight is that if it is less than 0.3% by weight, the effect of improving the above-mentioned adhesion will be small, and if the 1ncli content exceeds 30% by weight, it will not necessarily be possible to increase the above-mentioned effect. , InCl3 is expensive, which increases the cost of flux treatment.

The flux of the present invention may be used by dipping the object to be treated therein or by applying it to the surface of the object.

〔Example〕

EXAMPLES, COMPARATIVE EXAMPLES, CONVENTIONAL EXAMPLES Using a distilled zinc ingot according to the regulations of JIS H2107 and an aluminum ingot with a purity of 99.9% by weight or more, a precipitate containing 15% by weight of A, the balance Zn and unavoidable impurities was prepared. A hot-dip galvanizing bath was melted in a No. 30 graphite crucible at 520° C. using an electric furnace.

On the other hand, the plate width is 75 m from a general structural rolled steel plate with a plate thickness of 3fi.
, cut out a test piece with a plate length of 150 fl, degrease the surface of the test piece with a heated 10% by weight aqueous solution of sodium orthosilicate, and then immerse it in a 15% by weight sulfuric acid solution for 10 minutes to clean the surface of the test piece. After pickling, a flux treatment was performed by immersing the sample in an aqueous solution heated to 70°C and having the composition shown in Table 1 for 3 minutes and pulling it up.
A test piece was prepared for evaluating the degree of non-plating on a hot-dip galvanized product by drying it in a constant temperature bath maintained at ℃.

Next, the temperature of the hot-dip galvanizing bath prepared in advance as described above was adjusted to 440°C, and after stirring the plating bath sufficiently, the dross on the surface of the plating bath was removed, and the test prepared as described above was carried out. By immersing the piece in the plating bath for 60 seconds, removing the dross on the surface of the plating bath again, lifting the test piece from the plating bath, holding it in the air for 60 seconds, putting it into water, and pulling it up, A test piece that had been subjected to plating treatment was taken.

The degree of non-plating of these test pieces was visually observed. The results are shown in Table 1.

Table 1 [Effects of the Invention] As is clear from the above, according to the flux for hot-dip Zn-1 alloy plating of the present invention, hot-dip Zn-Al1 alloy plated products with guaranteed corrosion resistance can be coated in one plating operation. You can get it at

Claims (1)

[Claims] 1. A flux for hot-dip Zn-Al alloy plating consisting of an aqueous solution containing 0.3 to 30% by weight of InCl_3.