JPH0372059A - Hot dip galvanizing bath composition - Google Patents

Abstract

PURPOSE:To obtain a hot dip galvanizing bath compsn. not causing ungalvanizing even by a single galvanizing work by incorporating a specified amt. of In into a hot dip galvanizing bath contg. a specified amt. of Al added so as to ensure corrosion resistance. CONSTITUTION:This hot dip galvanizing bath compsn. consists of 3-10wt.% Al, 0.1-4wt.% In and the balance Zn. In improves the adhesion of a Zn layer to a body to be treated, does not cause ungalvanizing and forms a uniform Zn layer but <0.1wt.% In is not well effective in improving the adhesion. Even when the amt. of In exceeds 4wt.%, the above-mentioned effects are not necessarily enhanced and galvanizing cost is increased because in is expensive.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a plating bath composition used when hot-dip galvanizing a steel material or 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, plating baths are known in which approximately 3 to 10% by weight of A/ is added in order to ensure corrosion resistance of the plating layer.

However, with this plating bath, the plating layer does not adhere, resulting in non-plating.

Therefore, after performing primary plating in a Zn plating bath that does not contain Al and performing Franks treatment, the Zn-A1
Secondary plating is performed in an 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.
Molten Zn-Al that does not cause unplated surfaces on objects such as steel parts even after a single plating operation! An object of the present invention is to provide an alloy plating bath composition.

[Means to solve the problem]

In order to achieve the above object, the present inventors have conducted various studies and found that by performing hot-dip galvanizing using an alloy plating bath in which appropriate amounts of Al and In are added to Zn, the workpiece can be coated with It has been discovered that the adhesion of Zn can be improved, and the details thereof will be described below.

That is, in the present invention, Al is contained in an amount of 3 to 10% by weight, and In is contained in an amount of 0.1 to 10% by weight.
The above problem was solved by using a hot-dip galvanizing bath composition containing 4% by weight of Zn and the remainder consisting of Zn and unavoidable impurities.

[For production]

The effects of each component constituting the hot-dip galvanizing bath composition according to the present invention and the reason for setting the content as described above will be described below.

The reason why AI is included in the above zinc plating bath composition is to maintain the corrosion resistance of the plating layer. The reason why the Al amount is set to 3 to 10% by weight is because if it is less than 3% by weight, there is little effect in maintaining the above-mentioned corrosion resistance, and Aj? 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 composition increases, resulting in poor workability.

Furthermore, the reason why In is included in the plating bath composition is to improve the adhesion between the plating layer and the object to be treated, thereby preventing unplated plating and forming a uniform plating layer. The reason why the In content is set to 0.1 to 4% by weight is that if the In content is less than 0.1% by weight, the effect of improving the above-mentioned adhesion will be small, and if the In content exceeds 4% by weight, the above-mentioned effect will not be achieved. This is because not only is it not necessarily possible to increase In, but also because In is expensive, the cost of plating becomes high.

In addition, when preparing the hot dip galvanizing bath composition of the present invention,
The zinc ingot used contains unavoidable impurities such as 1.5% by weight or less of lead, 0.1% by weight or less of iron, 0.3% by weight or less of cadmium, and 0.1% by weight or less of tin. Even if the present invention is used, the object of the present invention can be fully achieved.

〔Example〕

Example 1 Distilled zinc class 1 ingot according to JIS H2107, aluminum ingot with purity of 99.9% by weight or more and purity 9
Using 8% by weight or more of indium metal, a hot-dip galvanizing bath composition having the composition shown in Table 1 was melted in a No. 30 graphite crucible at 520° C. using an electric furnace.

On the other hand, a test piece with a width of 75 m and a length of 150 m was cut out from a general structural rolled steel plate with a thickness of 3 nm, and the surface of the test piece was degreased with a heated 10 wt % aqueous solution of sodium orthosilicate. The surface of the specimen was pickled by immersing it in a 25% sulfuric acid solution for 10 minutes, and then subjected to Franks treatment by immersing it in a 25% aqueous ZnClIz solution for 3 minutes and pulling it up, and finally heated to 80°C. 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.

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 hot-dip galvanizing bath composition of the present invention, a hot-dip galvanized product with ensured corrosion resistance can be obtained in a single plating operation.

Claims (1)

[Claims] (1) 3 to 10% by weight of Al, 0.1 to 4% by weight of In
1. A hot-dip galvanizing bath composition characterized in that the composition contains zinc and the remainder consists of zinc and unavoidable impurities.