JPS59190385A - Production of one-side zinc-nickel alloy electroplated steel plate - Google Patents

Abstract

PURPOSE:To obtain a titled electroplated steel plate of which the non-plated surface has excellent chemical convertibility by forming an extra thin plating layer of a Zn-Ni alloy on the opposite side of the steel plate where plating is not required then dissolving preferentially the Zn on the plated layer and subjecting the steel plate to Zn-Ni alloy electroplating on the one side. CONSTITUTION:A Zn-Zi alloy contg., for example, about 13% Ni content is plated on a steel strip at a prescribed coating weight by using a sulfuric acid bath kept at 1.8pH and 55 deg.C and thereafter the strip is dipped in the plating bath without conducting electricity thereto. An extrathin plating layer of the Zn-Ni alloy is also formed on the opposite side where plating is not required, then the strip is passed through the succeeding bath. The Zn on the side requiring no plating is preferentially dissolved during the passage and an Ni-rich layer having finally 30-2,000mg/m<2> coating weight is formed thereon upon completion of the passage. As a result, the contamination during the plating treatment of the non-plated surface is prevented and the one side Nn-Ni alloy electroplated steel plate having improved chemical convertibility is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a single-sided zinc-nickel alloy electroplated steel sheet, and particularly to a manufacturing method that provides excellent chemical conversion treatment properties on the non-plated surface.

In recent years, the use of galvanized steel sheets and steel sheets coated with alloys such as zinc, nickel, zinc, and iron has been increasing in order to prevent corrosion of automobile bodies caused by antifreeze agents sprayed on roads. The part of the car body that is most severely corroded is the box structure on the inside of the car. These parts are said to be susceptible to corrosion due to the chemical treatment and heavy packaging that are likely to be incomplete, and the structure is susceptible to salt, water, dust, etc.

Galvanized or other surface-treated steel sheets are used in place of cold-rolled steel sheets to strengthen the rust prevention ability of these parts, but steel sheets treated on both sides have problems with appearance and weldability after painting. Therefore, steel plates with surface treatment on only one side are often used. It is desirable that the non-plated surface of a single-sided plated steel sheet has the same performance as a cold-rolled steel sheet, and is required to have excellent chemical conversion treatment properties and paintability.

Under these circumstances, zinc-nickel alloy electroplated steel sheets are single-phase gamma with a nickel content of 10 to 16 inches in the plating film, and have superior corrosion resistance compared to galvanized steel sheets with the same coating weight. Because it exhibits twice the corrosion resistance, it is attracting attention as a face-treated copper plate for automatic automobiles with excellent weldability and workability.

Zinc-nickel alloy plating on steel sheet strips is usually performed using an acidic bath or a chloride bath because it can be operated at high current density and the bath composition can be controlled relatively easily. When manufacturing single-sided plated steel sheets, the non-plated surface often suffers from acid corrosion, swelling due to the accumulation of melted materials over several years, and staining due to the precipitation of impurities, which deteriorates the chemical conversion properties. Ru. In addition, recently, high-tensile steel sheets, steel sheets for ultra-deep drawing, hardening hardening grade steel sheets, etc. are often used as steel sheets for automobiles. Some materials have inherently poor chemical conversion treatment properties due to the components in the steel and the elements on the second side.If you make a single-sided zinc/nickel pot 1L kimetsusa drawing board using such materials, it is natural that the chemical conversion treatment properties of the non-plated side will be poor. Generally speaking, poor chemical conversion treatment property is [-
Phosphorus can cause localized areas where clay rupture film is not formed, called ``suke'', or uneven thick dry crystals, which can cause deterioration of paternity resistance and adhesion after painting, or worse. This is an important problem in terms of quality because it gives rise to age in appearance.

The object of the present invention is to solve the problems of the above-mentioned prior art and to provide a method for manufacturing a single-sided zinc-nickel alloy dull-plated steel sheet with excellent chemical conversion treatment properties on the unplated cold-rolled surface (there are two methods).

The gist of the present invention is as follows.

In other words, in the manufacturing method of single-sided zinc/nickel alloy type A-plated steel sheet, in which a steel sheet strip is passed through multiple acid bath plating baths and one side is continuously electroplated with zinc/nickel alloy, (2) Forming an extremely thin layer of zinc-nickel alloy on the opposite side of the JA temporary strip that does not require plating; of a single-sided zinc-nickel base electroplated steel sheet comprising the step of bath-dissolving the steel sheet to form a nickel-enriched layer χ with a final adhesion amount of 30 to 2000 my/n! This is the manufacturing method.

Japanese Unexamined Patent Publication No. 56-296 previously disclosed in the related art of the present invention
There are 61. This is coated with an extremely thin layer of galvanized steel to prevent unplated stains on the single-sided galvanized steel sheet.
A technique has been disclosed in which the plating layer is completely eliminated by redissolving it in a bath upon completion of threading, but the present invention does not completely eliminate the plating layer, but rather actively allows the nickel-enriched layer to remain. It improves chemical conversion treatment properties,
This point is essentially different.

Next, details of the present invention will be explained based on basic practice.

Steel plate (zinc-nickel alloy plating with a Ni content of about 13%) using a sulfuric acid bath with a pH of 1.8 and a bath temperature of 55°C.
After plating with a coating amount of F/&, it was immersed in the plating bath without electricity to investigate its dissolution state.

Figure 1 shows the electroprope microanalyzer (EP)
This figure shows the relationship between the X-ray detection intensity of Zn and Ni using MA) and the immersion time. It can be seen from FIG. 1 that by immersing the zinc-nickel alloy plating layer in the plating solution, the zinc is preferentially decomposed and a nickel-enriched layer is formed. The present invention does not require plating of a single-sided zinc-nickel alloy electroplated steel sheet, but it forms an extremely thin zinc-nickel alloy plating layer only at the initial stage of passing the strip through the bath.
In addition, the thinned layer is created by dissolving the zinc preferentially during the subsequent bath passing of the strip, as described above, and forming a nickel-enriched layer upon completion of the strip passing. It is used to improve chemical conversion treatment properties.

The zinc in the extremely thin plated layer of the strip is preferentially bath-dissolved, and the amount of the nickel-enriched layer that is finally formed is limited. The effect of preventing stains on non-plated surfaces is insufficient, and the effect of improving chemical conversion treatment properties is small. 2000■/rr again? Even if it exceeds 30 to 20%, the chemical conversion treatment effect will be saturated and the economic loss will be large.
The type and dimensions of the steel used in the present invention are not limited, and are limited to the range of 00η/-.
After pretreatment such as degreasing, pickling, and water washing according to conventional methods, zinc-nickel alloy plating is performed.

As the plating bath, an acidic plating bath is used, and sulfate baths, chloride baths, and mixtures thereof can be used. The conditions for the salt bath and chloride bath are shown in Table 1, but a mixed bath of sulfate and chloride can also be plated under the same conditions as shown in Table 1.

In addition, when performing single-sided plating on a steel plate in a plating apparatus having a plurality of plating baths, the present invention also provides an anode on the non-plated side at the beginning of passing through the bath, and adjusts the current flowing through this anode. The ultra-thin plating layer on the non-plated surface, which controls the amount of extra-thin plating on the non-plated surface, causes preferential dissolution of zinc during subsequent passing through the bath, resulting in nickel concentration. The dissolution behavior varies depending on the pH of the bath, bath temperature, plate passing time, etc. That is, low pH, Ei bath temperature,
When immersed for a long time, the dissolution of the plating layer is large, and vice versa. In the present invention, it is necessary to control the final amount of the nickel-enriched layer to be in the range of 30 to 20,007 n9/i, but the specific method for doing so varies depending on the plating equipment and plating conditions, as in the case of He. So the bath p
It is necessary to decide by taking H1 bath temperature, line speed, etc. into consideration.

The reason why the present invention improves the chemical conversion treatment properties of non-plated surfaces is considered to be as follows. In other words, the ultra-thin plating layer formed on the non-plated side of the strip at the beginning of the bath-threading causes the zinc to preferentially dissolve during the subsequent bath-threading, preventing acid corrosion of the base steel and reducing smut. It has the effect of preventing the occurrence of stains on non-plated surfaces due to the effects of formation and thorny surface concentration elements. Furthermore, the nickel-enriched layer formed on the surface upon completion of threading has the effect of precipitating phosphate crystals finely and uniformly when the JA temporary is subjected to chemical conversion treatment. It is thought that these two effects make it possible to obtain single-sided zinc-nickel alloy electroplated steel sheets with extremely excellent chemical conversion treatment properties on the unplated cold-rolled surface, even if the material originally has poor chemical conversion treatment properties. .

Example: A horizontal plating plate consisting of 10 pieces was used on one side of a 0.8 mm thick cold-rolled steel plate that had been pretreated by degreasing, washing, water washing, etc., and 5 pieces were tested under the conditions shown in M2ff. The material is electroplated with zinc-nickel alloy. In addition, plating was performed on non-plated surfaces that did not require plating, except for sample material A3, and only in the first plating tank under the conditions shown in Table 2. After plating,
We investigated the amount of plating and Ni content in the plating layer on the non-plated surface, observed the state of dirt with the naked eye, and then chemically treated the non-plated surface with a treatment solution containing zinc sulfate as the main component. , the amount of chemical conversion film deposited and the crystalline state were investigated, and the results are shown in Table 3. The seven reasons for each display in Table 3 are as follows.

Condition of non-plated surface stain O: No streaky stains or gray-black stains, uniform - Table 2 Δ: Slight rib-like stains or gray-black stains X: Significant streaky stains or gray-black stains Crystalline condition of the generated chemical conversion coating ○: Dense, uniform, and no "walls" ×: Coarse crystals and "walls" in some parts Non-plated surface of Koken Zaiya 1, 2 and 5 which are examples from Table 3 It can be seen that there is no staining due to passing through the bath, and the chemical conversion treatment properties are excellent. On the other hand, comparative examples such as sample material A3, in which the non-plated surface is not plated, and sample material A4, in which the coating amount is less than the limit amount of the present invention even if plated, are both plated in the bath. It causes stains and has poor chemical conversion treatment properties.

As is clear from the above examples, the present invention is a method for producing a single-sided zinc/nickel alloy electroplated copper plate, in which an extremely thin plated layer of zinc/nickel alloy is formed on the opposite side, which does not require plating, at the initial stage of sheet passing. , then the zinc in the $i thinning layer is preferentially dissolved and the final N amount is 30 to 2000#.
the law of nature/? By forming a nickel-enriched layer of F/, it was possible to prevent the non-plated surface from becoming dirty during plating treatment and to improve chemical conversion treatment properties.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the detected X-ray intensities of Zn and Ni when the plated surface was immersed in a plating bath (without energization) after zinc-nickel alloy plating and changes in the plated surface were investigated using EPM A.

Claims (1)

[Claims] (1) In the manufacturing method of single-sided zinc/nickel alloy electroplated steel sheet, in which the steel sheet strip is passed through multiple acid bath plating baths and one side is continuously coated with zinc/nickel alloy, forming an ultra-thin galvanized layer of zinc-nickel alloy on the opposite side of the steel strip that does not require plating, and carrying out the ultra-thin galvanizing by preferentially dissolving the zinc in the ultra-thin galvanizing layer on the hind leg to make it the longest. Adhesion amount is 30~
forming a nickel iridescent layer of 2000 yr9/lri.
Method for manufacturing nickel alloy electroplated steel sheet.