JPS589998A - Manufacture of steel plate plated with zinc-nickel alloy - Google Patents

Abstract

PURPOSE:To manufacture a plated steel plate with superior corrosion resistance and a fine appearance by specifying the concns. of Fe and Pb, Cd or Cu in a Zn-Ni alloy electroplating bath. CONSTITUTION:When a steel plate is electroplated with a Zn-Ni alloy in an acidic plating bath contg. Zn and Ni, the concn. of Fe in the plating bath is adjusted to <=1.0g/l, or the total concn. of 1 or >=2 kinds of metals selected from a group consisting of Pb, Cd and Cu is specified to <=20mg/l. By plating a steel plate using the resulting bath, Zn-Ni alloy plating with superior corrosion resistance and a fine appearance can be manufactured stably.

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing zinc-nickel alloy coated steel sheets that improves corrosion resistance by lowering the S degree of impurity elements. Conventionally, metal plating has been used to improve the corrosion resistance of steel sheets. teeth,
Zinc plating is widely used (commonly used C plating mainly prevents corrosion of steel sheets by sacrificial corrosion of zinc, and corrosion resistance depends on the amount of zinc deposited. In other words, high corrosion resistance can be achieved. If this is to be done, the amount of zinc deposited must be increased, and in this case, it is unavoidable that some problems will arise, such as increased bust or a decrease in weldability due to the increased amount of zinc required.

In recent years, with the expansion of the application of anti-rust plated steel sheets to automobile bodies to extend their corrosion-resistant lifespan, various types of corrosion-resistant plating with a small amount of coating have been reconsidered, and one of them is 6FC zinc- Nickel alloy plating is available. This zinc-nickel alloy plating has a coating content of approximately 1
It is known that it has excellent corrosion resistance in the range of 0 to 20X, and shows several times the corrosion resistance compared to zinc plating with the same basis weight.
Because electrolytic zinc-nickel alloy plating can be plated at high current density and the bath has good electrical conductivity, tatami-dori is usually plated in an acidic bath mainly containing chloride or sulfate. 〇When producing industrial zinc-nickel alloy plating using this method, what are the conventional zinc and nickel concentrations, bath temperature, bath current density, and bath temperature? Even if the plating conditions, such as the relative speed of the blobs, are the same (and even if the plating conditions are the same), the quality characteristics of the product often vary, resulting in products with poor corrosion resistance, gloss, and uniform appearance. Therefore, it is an object of the present invention to solve this problem and to industrially and stably produce a zinc-erata alloy plated steel sheet that always has good corrosion resistance and appearance.

According to the present invention, when performing electrolytic zinc-nickel alloy plating on a steel plate in an acidic plating bath containing zinc and nickel, the F@lightness in the bath is set to 1.0 f/L or less or pb%c.
d, the total concentration of one or more metals selected from the group of Cu, j! The above objective can be achieved by setting it to Oq/A or less.

In addition, the FIe1m degree in Rakuchu is 1.0 f/ or less,
Furthermore, it goes without saying that further effects can be obtained by setting the total concentration of one or more metals selected from the group of Pb3O4%Cm to 20q/4 or less.

According to research conducted by the present inventors, the corrosion resistance or deterioration of the appearance of zinc-nickel alloy plating has a strong correlation with the concentration of impurity elements in the plating bath, especially F@sPb% (1:d, (:u). The present invention was developed based on the discovery that the important factor causing variations in the quality characteristics of zinc-nickel alloy coated steel sheets for industrial purposes is due to changes in the concentration of these elements. The specific effects and appropriate range of the method will be explained in detail. ・Figure 1 shows the degree of iron ion and the basis weight in an acidic bath mainly containing zinc sulfate and nickel sulfate.
This figure shows the relationship between the corrosion resistance and appearance of Metsu Kinha Metal when it is incubated at 0 f /ml. From this figure, it can be seen that when the iron ion content exceeds 1 f/, the corrosion resistance deteriorates.
It can also be seen that the appearance becomes dull. Although the effect was greater for ferrous ions than for ferrous ions, the trend was the same. Figure 2 shows the same acidic plating bath as in Figure 1 and #C.

This figure shows the relationship between the individual or total concentrations of lead, oxide, and steel, and the corrosion resistance and appearance of the plating film when plated with a basis weight of 20 t/d. , all have a proportional relationship with III,
It can be seen that when the temperature exceeds 20''F/, both corrosion resistance and appearance deteriorate.

From the above, it is extremely important to control the concentration of impurities in the bath for zinc-nickel alloy plating, and in order to industrially stably obtain products with excellent corrosion resistance and appearance, it is necessary to control the concentration of impurities in the bath. 1.0f/A or less and or lead, cadmium,
It is clear that it is effective to keep the total concentration of one or more types of copper at 20/1 or less.
Below f/L, the amount of nickel in the plating layer does not change at all, so it is difficult to think that this is due to an essential change in the plating film.Probably, the electrodeposition of iron into the plating layer causes the change in the gold wave film. Lead, cadmium, and copper have an adverse effect at much lower concentrations than iron, which is thought to promote the slow battery action and accelerate the progress of corrosion.
A common feature of all of them was that they increased the amount of nickel in the plating layer. Therefore, the deterioration of corrosion resistance due to these elements is caused by the electrodeposition of lead, cadmium, and copper in the plating layer. The increase in corrosion current due to the formation of a nickel-enriched layer is considered to be the cause.The contamination of iron into the bath is mainly due to the dissolution of S)17. Lead increases in concentration by dissolution of the lead or lead-based electrode when insoluble anodes are used, from impurities in the electrode when soluble zinc anodes are used, or by being supplied from the lead electrode bed. do. Cadmium mainly comes from impurities in electrodes.
Copper also gets mixed into the plating bath due to impurities in the electrodes and dissolution of the electrical wiring system around the plating bath. In the case of iron, these harmful components can be removed by using a chelate resin that has selective adsorption ability. This is carried out by a precipitation method or a method of dumping a part of the metsusha bath. Also,
In addition to dumping out part of the lead, cadmium, and copper plating solution, zinc powder or zinc particles can be added to the bath to remove these metals by displacement precipitation, or in the case of a sulfate bath, the removal of nutrontium and padacum can be done. There is a method in which a metal compound is added to a bath and removed by co-precipitation with the generated strontium sulfate and barium sulfate. Usually, F, Pb, CI, and C1l coexist as impurities in the plating process, but the effect of their coexistence is almost at an additive level of the effect of each individual concentration. Therefore,
Taking this point into consideration, the management of the Metsusha bath near the back is to keep the F concentration below 1t7 and the total concentration of one or more types of pb%Cd%Cu below 20q/j. It is essential to obtain a good product.

The plating bath used in the present invention contains zinc and nickel mainly composed of sulfur salt or chloride and has a pH of about 1.
These are acidic baths with a temperature of 5 to 15 degrees Celsius, and are commonly used because they provide a high current density and the plating bath has good electrical conductivity. In the case of zinc-nickel alloy plating, the composition of the deposited metal layer varies depending on the plating conditions such as the bath composition of 1PH, the current density with respect to the tube and the relative speed of the bath. By reducing the content of certain iron, lead, aluminum, and copper to below a certain level as mentioned above, zinc can be produced with excellent corrosion resistance and appearance.
The main purpose is to stably produce nickel alloy plating, and there is no need to particularly limit other bath compositions and plating conditions.The present invention will be described below with reference to preferred examples and comparative examples.

〔Example! ]

Zinc-nickel alloy plating was applied to cold-rolled steel strip under the following conditions using a horizontal type continuous plating equipment.
%0150, FlI O, 1f/l, Pb 2 Cape/j, Cdl Cape/'s Cvs i ''F/ t s
pH 10, bath temperature 50°C ■ Current density 60 Aldd ■ Nut η tube speed 15 B/lIk ■ Plating deposition amount 20 f/d After target plating, corrosion resistance test by salt spray test and eye l
The surface appearance was observed using Ik.The results are shown in the first part along with other examples! Ii (show.

[Example ■]

Zinc-nickel alloy plating was applied to the same Reijima Koki using the same plating equipment as in the summer under the following conditions.

α) Plating bath N15O,-6&03GOf/j, Za80m-
7H, 0150f/l, Fe 0.6f/l%
Pb 6Q/l % Cd2mF/j s Cu
2q/L %$10, bath temperature 50℃ ■ Current density, slip speed, plating coating weight - Example! Same as [Example] Plating bath NiC4 81% 0240t/j The same cold-rolled steel strip number was used in the same shed equipment as in Example ■, and zinc-nickel alloy was applied under the following conditions. ! s Zn fake 14
01/1.

F・031/”s Pb 6*z'ts Cd 8
"l/L sCu 1n/l s pH 3, Os Bath temperature 50℃ ■ Current density, S) 9 tube speed, plating amount... Same as Example [Comparative Example ■] Same plating equipment as Example I The same cold rolled steel strip was subjected to zinc-nickel alloy plating under the following conditions. Plating bath N15O, -6H, 0300t/l, ZnSO4
-7&0150f/j, F・1.6f/l s
Pb gay/z sCd 3q/l % Cu
2wt/l % pH 2.0, bath temperature 50℃ ■ Current density, stripping speed, coating weight...same as Example Summer [Comparative Example ■] On the same cold rolled steel strip using the same plating equipment as Example X, Zinc-nickel alloy plating was performed under the following conditions. 〇ω Plating bath Ni fake 6 Karasu 0 2401/l, Mu fake 1401/l
l.

Fe 0.7f/1% pb 26q/'s Cd
5q/1sCu 2wg/l s pH3, O1 bath temperature 50℃■ Current density, U-tube speed, plating coating weight...Example! Table 4 summarizes these results and shows that iron, iron,
It can be seen that the Sou Example, which has a low degree of chaining of impurities such as lead, has superior corrosion resistance and appearance compared to the Comparative Example, which has a high concentration of iron, lead, etc. ・The impurity concentration listed in the comparative example is zinc - It is at a level that can be easily procured during industrial mass production of nickel alloy metal fittings.

From these results, it is clear that the method of the present invention is extremely important for industrially stably obtaining zinc-nickel alloy plating that is excellent in both corrosion resistance and appearance.

Table 1

[Brief explanation of the drawing]

Figure 1 shows the relationship between the iron concentration in an acidic plating bath containing zinc and nickel and the corrosion resistance and appearance of the plating film. 1 is a graph showing the relationship between the total corrosion resistance of one or more metals of lead, copper, and copper, and the corrosion resistance and appearance of a plating film. Patent Applicant: Kawasaki Steel Co., Ltd., Benefactor, Attorney: Nozomi Minoru Liquid Figure 1 Fe Freezing Level 9ha Figure 2 Concentration m9/1

Claims (1)

[Claims] Electrolytic zinc-nickel alloy plating is performed on the copper plate in an acidic plating bath containing zinc and nickel, and the F concentration in the bath is set to below LOf/ or one or more selected from the group of h1Cds. A method for manufacturing a zinc-nickel alloy steel sheet, characterized in that the total concentration of metals is 20q/or less.