JP2756318B2 - Flux for hot-dip Zn-Al alloy plating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a plating flux used for applying a hot-dip Zn-Al alloy plating process to a steel material or the like.

[Conventional technology]

BACKGROUND ART Conventionally, to prevent corrosion of steel materials and the like, it has been known to apply hot-dip galvanizing and electrogalvanizing to the surface thereof.

In recent years, a number of new, high-value-added products have been introduced to the market by using zinc plating as a base and further adding surface treatments, such as painting and processing, to the base. The choices of users for such products are becoming more and more diversified.

In order to satisfy these requirements, with respect to the hot-dip galvanized product, it has been considerably attempted to improve the characteristics of the plating layer by selecting the added element and the added amount as the plating bath composition.

Particularly, a plating bath to which Al is added in an amount of about 3 to 10% by weight in order to ensure the corrosion resistance of the plating layer is known. This plating bath usually deposits Zn on the workpiece such as steel parts.
It is used after flux treatment such as immersion in Cl ₂ aqueous solution.

However, the plated product manufactured in this manner does not have a plated layer and is apt to cause non-plating.

Therefore, once, the primary plating is performed in a Zn plating bath containing no Al, and after performing the flux treatment as described above,
Secondary plating is performed in a Zn-Al alloy plating bath.

[Problems to be solved by the invention]

However, the above method has the drawback that it is complicated to perform the plating process twice and the production cost is high.

The present invention has been made in view of the above-described conventional problems, and provides a flux for hot-dip Zn-Al alloy plating that does not cause non-plating even in a single plating operation on a workpiece such as a steel part. Aim.

[Means for solving the problem]

In order to achieve the above object, the present inventors have conducted various studies, and as a result, as a flux, ZnCl ₂ , NaCl and CH ₂ C
Flux treatment of the object to be treated is performed using an aqueous solution containing HCOOH (acrylic acid), and ZnCl ₂ , NaCl and
By attaching CH ₂ CHCOOH, Zn-Al
It has been found that the adhesion of the alloy can be improved, and details thereof will be described below.

That is, the present invention is a flux for hot-dip Zn-Al alloy plating ZnCl ₂ 150-300 g /, NaCl 20-40 g / and C
By using an aqueous solution of H ₂ CHCOOH 10~120g / include those wherein the foregoing problems are eliminated.

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

(Operation)

The reason for using the flux of the present invention as hot-dip Zn-Al alloy plating and containing Al in the zinc plating bath is to maintain the corrosion resistance of the plating layer. The Al content is preferably 3 to 10% by weight. If the content is less than 3% by weight, the effect of maintaining the above-mentioned corrosion resistance is small, and if the content of Al exceeds 10% by weight, it is difficult to further improve the corrosion resistance, and the melting point of the plating bath is increased. This is because the sex becomes worse.

Further, the inclusion of ZnCl ₂ , NaCl and CH ₂ CHCOOH in the aqueous flux of the present invention improves the adhesion between the Zn-Al alloy plating layer and the object to be treated, and does not cause non-plating.
This is to form a smooth plating surface.

If at least one of the ZnCl ₂ content, the NaCl content and the CH ₂ CHCOOH content is less than the respective lower limits, the above effect is not sufficient, and if the ZnCl ₂ content exceeds 300 g /
Not only the above effect cannot always be increased, but also the total amount becomes difficult to dissolve. In addition, NaCl acts to prevent non-plating, but when its content exceeds 40 g /, the melting point of ZnCl ₂ , NaCl and CH ₂ CHCOOH mixed salt attached to the workpiece increases, and the flux property decreases. I do. Furthermore, CH ₂ CHCOOH not only does not cause non-plating, but also acts to form a smooth plating surface, but its content is 120 g /
This effect does not necessarily increase even if the pressure exceeds.

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

〔Example〕

Examples, Comparative Examples, and Conventional Examples Using distilled zinc ingot (one kind) and aluminum ingot having a purity of 99.9% by weight or more according to JIS H2107, Al5
A hot-dip galvanizing bath having a composition of weight%, balance Zn and unavoidable impurities was placed in a graphite crucible No. 30 using an electric furnace at 520%.
Melted at ℃.

On the other hand, the width of 75mm,
A test piece with a plate length of 150 mm was cut out, the surface of the test piece was degreased with a heated 10% by weight aqueous solution of sodium orthosilicate, and then immersed in a 15% by weight sulfuric acid solution for 10 minutes to make the surface of the test piece acidic. Rinse, wash, and immerse in an aqueous solution of the composition shown in Table 1 heated to 70 ° C. for 3 minutes, pull up, and finally dry in a constant temperature bath maintained at 80 ° C. A test piece for evaluating the degree of non-plating on the hot-dip galvanized product was prepared.

Next, the temperature of the hot-dip galvanizing bath previously melted as described above was adjusted to 440 ° C., and after sufficiently stirring the plating bath, dross on the plating bath surface was removed, and the test prepared as described above was performed. The specimen was immersed in the plating bath for 60 seconds, the dross on the plating bath surface was removed again, and the test piece was pulled up from the plating bath.Then, the specimen was kept in the air for 60 seconds, then put in water, and pulled up. A test piece subjected to a plating treatment was collected.

The degree of non-plating of these test pieces was visually observed. Table 1 shows the results.

[Effects of the Invention] As is clear from the above, according to the flux for hot-dip Zn-Al alloy plating of the present invention, the hot-dip Zn in which corrosion resistance is ensured
-An Al alloy plated product can be obtained in one plating operation.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C23C 2/02 C23C 2/06 C23C 2/30

Claims (1)

(57) [Claims] (1) ZnCl ₂ is 150 to 300 g / NaCl is 20 to 40 g /
And CH ₂ CHCOOH consisting of an aqueous solution 10～120G / containing molten
Flux for plating Zn-Al alloy.