JPS63153253A - Hot dipping agent for iron-base secondary worked product - Google Patents

Abstract

PURPOSE:To produce a hot dipping providing superior smoothness, fine appearance and other superior performance to iron-base secondary worked products by adding a specified percentage of Al to a hot dipping agent consisting of Zn and Sn in a specified ratio. CONSTITUTION:A hot dipping agent for iron-base secondary worked products is produced by adding 0.0005-0.004%, preferably 0.001-0.004% Al to a hot dipping agent consisting of 2-89% Zn and 98-11% Sn. When iron-base secondary worked products such as screws or pressed products are dipped in the hot dipping agent in a way similar to conventional hot dip galvanizing, films having superior smoothness, fine appearance and superior accuracy in uniform thickness of <=about 0mum or <=about 150g/m<2> can be formed. The films also have such high corrosion resistance that they are not corroded in salt water for >=500hr.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a zinc-tin based plating agent, and particularly to a plating agent that is effectively used for plating iron-based secondary processed products.

(B) Conventional techniques and their problems Various methods have been known for imparting properties such as eating properties, workability, smoothness, and appearance to steel materials by plating them.

That is, methods such as electroplating and hot-dip plating are appropriately selected depending on the use of the steel material and the performance to be imparted, and the effects of plating are obtained accordingly.

Among the conventional hot-dip plating techniques, the one closest to this invention is Japanese Patent Publication No. 52-19531. This is Z
o to a plating bath consisting of n3~91%, 3097~3%,
oos ~ 0.3% of A1 is added, and steel plates, rods,
This is a technology that applies plating to subsequent processed products such as pipes.

However, the plating bath composition disclosed in this technique can be applied to steel materials such as steel plates and steel wires that can be continuously plated in a non-oxidizing atmosphere and has a so-called -second processing amount. It is difficult to employ industrially the hot-dip plating method for secondary processed products with complicated shapes and surfaces, which is carried out using ordinary 7 lux.

According to research conducted by the inventors of this invention, due to the high amount of aluminum added, aluminum oxide is formed on the surface of the plating bath, resulting in poor wetting. It was found that this was due to non-plating, which could only occur without passing through.

As described above, although the above-mentioned conventional techniques can plate steel materials (raw materials), they are no longer able to meet the strict demands from users in recent years.

Particularly in the automobile industry, the salt damage resistance of suspension parts has become a problem, especially in exported cars, and surface treatments (plating) are required for screws, pressed products, etc. that have better salt water resistance and screw precision after plating. ing.

At present, there is a zinc-chromic acid composite film treatment called dacrotized treatment, which is a surface treatment with excellent salt water resistance and screw precision, and is being widely adopted in the automobile industry, but the film has poor adhesion strength. Furthermore, it has poor outdoor weather resistance, so it has not yet been adopted.

On the other hand, in the electroplating industry, alloy plating methods such as zinc-tin, zinc-nickel, and zinc-iron have been developed to meet these demands, and although they have received some praise in terms of performance, A fatal flaw in the electroplating method is unavoidable, which is the formation of unplated areas in the areas where the electroplating occurs, and an increase in costs is unavoidable due to the high cost of processing equipment and the difficulty of managing the plating bath. This also makes full-scale recruitment difficult.

Furthermore, in the water supply industry, as water quality has deteriorated in recent years, rust prevention of the inner surfaces of conventionally used hot-dip galvanized pipes and joints has become a problem.

One is the generation of cloudy water due to the elution of zinc, and the other is the formation of cloudy water due to the elution of zinc, and the other is the so-called "" This causes the occurrence of "red water".

Furthermore, in the case of small assemblies, such as construction scaffolding pipe clamp joints, which are plated as a whole after being assembled, it is necessary to plate them while maintaining a predetermined gap so that they do not stick to each other. These products are extremely difficult to produce by electroplating as well as by hot-dip plating.

As described above, the conventional technology has a problem in that it has excellent plating performance, maintains dimensional accuracy such as screw accuracy, and cannot meet the demand for plating into gaps such as small assembly products.

(c) Means and operation for solving the problems In order to solve these problems, the present invention, as a result of various studies, added aluminum to a plating agent consisting of normal lead and tin.
．． This was done after discovering that by hot-dip plating iron-based secondary processed products in a bath containing 0.04%, it was possible to achieve beautiful plating with excellent film thickness accuracy and corrosion resistance. Specifically, l! of a plating agent consisting of 2 to 89% zinc and 98 to 11% tin! This is a plating agent for iron-based secondary processed products, characterized in that aluminum is added in an amount of 0.004% to 0.004%.

What is important here is that the plating agent of the present invention is not intended for mere steel materials, but for secondary processed iron products.

In this invention, iron-based "secondary processed products" refer to primary molded products, molded rods, molded pipes, extruded products, etc. made from materials containing iron, which are separated and subjected to the necessary processing to produce the final product. refers to something that has a certain shape. For example, bolts, nuts, pipe joints, clamps, etc. whose surface shape is not just flat but has curved parts,
Examples include things with complex shapes and braids.

The plating agent of the present invention is intended to be used for such iron-based secondary processed products, and is different from one that was conceived on the premise that processing would be performed after plating.

Therefore, even if a predetermined plating effect is applied to the so-called "next processing amount", when the plating is processed, a kiss may be formed, and the adhesion may be impaired due to complicated bending processing, but with the plating agent of this invention, such No problems occur. In addition, by using the plating agent of the present invention, uniform and beautiful plating can be obtained to suit complex shapes, and even if the gap is narrow, it is possible to perform predetermined plating on both sides while maintaining the gap.

The plating agent according to the present invention can be applied in a so-called "dobuzuke" manner, which is carried out in the atmosphere after pretreatment using 7 lux, in the same manner as in conventional hot-dip galvanizing methods.

The composition of the plating agent of this invention is 2 to 89% of zinc.
%, and the amount of aluminum added is 0.0005-0.004% relative to the total zinc-tin amount.
, preferably 0.001 to 0.004% (% refers to shrinkage %). same as below).

The amount of aluminum added is important and is 0.000
Even if it is about 2%, it can be plated, but the appearance will be poor, and 0.
If the amount exceeds 0.04%, the bath liquid will feel sticky, and the bath liquid will not be able to flow smoothly into narrow gaps, making it easier for plated surfaces to stick together.

The temperature, time, etc. for use of the plating agent of this invention can be those of a normal hot-dip plating method. The plating thickness is also adjusted depending on the shape of the object and the environment in which it will be used, so that effective performance can be achieved with each shape and plating thickness.

Next, the present invention will be explained using Examples, but is not limited thereto.

(Margins below, continued on next page) Example 1 Using an alloy plating agent consisting of 8092% ZN 8% AI 0.003%, MloXSOllll
After immersing the bolt in 7lux (zinc chloride-ammonium chloride slack), immersing it in a bath consisting of the above plating agent at 210°C for 1 minute, dripping it, and cooling it with water. A uniform and beautiful plated product of IIf176o4 was obtained, and the fit of the nut was also good.

When we conducted a salt spray test on this product,
No red rust occurred even after 800FR.

Comparative Example 1 Using an alloy plating agent consisting of Sn 92% Zn 8% AIO, 01%, M10×5011II
When bolt I was plated in the same manner, non-plating occurred.

Comparative Example 2 When hot-dip galvanizing was applied to a similar bolt, adhesion @
255Q4 plating was obtained, and the nuts did not fit together at all.

When we conducted a salt spray test on this product,
Red rust developed after 240 hours.

Example 2 Using an alloy plating agent consisting of 60% Sn, 7040%, and 0.003% AI, a 1/2-inch Mariapul socket was immersed in 7lux (zinc chloride-ammonium chloride flux) and then heated at 380°C for 1 hour. After soaking in the bath of the above plating agent for a minute, draining and cooling with water,
A uniform and beautiful plated product with an adhesion of 1105 aJ was obtained.

When we conducted a salt spray test on this product, it was found that
No red rust appeared even after the passage of time.

Comparative Example 3 3n 60% Zn 40% AI 0.02% When a 1/2-inch malleable socket was similarly plated using the above alloy plating agent, non-plating occurred.

Comparative Example 4 When a 1/2 inch malleable socket was plated in the same manner using an alloy plating agent consisting of Sn 10% 7-n 9G% AI 0.003%, it was plated with IIm3.
A plated product weighing 80 g and weighing Q was obtained, and when a salt spray test was conducted on this product, red rust developed after 360 hours.

Example 3 Using an alloy plating agent consisting of Sn 60% Zn 40% AlG, 004%, M6 automotive screws were immersed in flux (zinc chloride-ammonium chloride flux) and then plated at 400°C for 1 minute. By performing dripping, dripping, and water cooling, a uniform and beautiful plated product with an adhesion of 185 μ4 was obtained, and the nut fit was also good.

When this product was subjected to a salt spray test, 80
Red rust did not occur even after 0 hours had passed.

Comparative Example 5 When a similar machine screw was hot-dip galvanized,
A plated product of I 450Q4 was obtained, and the screws did not fit together at all.

When we conducted a salt spray test on this product, 2
It developed red rust after 40 hours.

Example 4 Using an alloy plating agent consisting of Sn 94% Zn 6% AlO, 0005%, M6 automotive screws were immersed in 7lux (zinc chloride-ammonium chloride slack) and then heated at 300°C for 1 minute. By plating, trimming, and water cooling, a beautiful plated product with a uniform fl162Q4 adhesion was obtained, and the nut fit well.

When this product was subjected to a salt spray test, it was found that 50
Red rust did not occur even after 0:00.

(d) Effects of the Invention From these Examples and Comparative Examples, it is clear that the products plated by the method of the present invention not only have excellent smoothness and appearance, but also have resistance to contact with salt water for more than 500 hours. The film thickness and uniform film thickness (less than 20μ or less than 15004) accuracy are extremely excellent.

Claims (1)

[Claims] An iron-based secondary characterized by adding 0.0005 to 0.004% aluminum to the total amount of plating agent consisting of 1.2 to 89% zinc and 98 to 11% tin. Plating agent for processed products.