JPS60200996A - Blackened rustproof steel sheet and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture stably a blackened rustproof steel sheet in a short time without aging a treating soln. or causing environmental pollution due to waste liquor by plating the surface of a steel sheet with Zn and forming a Zn- Ni alloy layer on the plated surface. CONSTITUTION:At least one side of a steel sheet is plated with Zn or a Zn alloy to form one or more layers as an inner layer. A Zn-Ni alloy layer contg. >=15wt% Ni is formed on the inner layer as a surface layer by >=0.01g/m<2> by carrying out electrolysis using the steel sheet as a cathode and an insoluble anode as a counter electrode at <=40A/dm<2> current density in an acidic aqueous soln. of <=3pH contg. Ni<2+> and Zn<2+>. Thus, a blackened rustproof steel sheet is stably obtd. in a short time such as about several - several ten sec.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a blackened steel sheet that can be continuously manufactured in a strip state and a method for manufacturing the same.

(Prior Art and Problems) A so-called blackened steel sheet, which is a Zn-plated steel sheet whose surface is blackened, has recently attracted attention as a corrosion-resistant steel sheet in the fields of home appliances, building materials, automobiles, and the like. There are two methods for blackening Zn-plated steel sheets: That is, i, i;' A smelting agent (
chlorine, nitric acid, molybdic acid, permancanic acid, etc.) and Cu
A method in which a base steel plate coated with an inner layer is immersed in a treatment solution containing ions for 1 to 15 minutes.

A method of anodic electrolyzing a composite Zn-plated steel sheet containing Go or Ni in an ammonium monosulfate solution.

However, these methods (■■) have the following problems (a) to (e).

(b) Method ■ has a long processing time of 1 to 15 minutes, so
It cannot be applied to a continuous strip processing line and is not economical.

(b) In both methods, base (inner layer film) components dissolve and accumulate in the treatment solution, causing aging of the solution.

(c) Since the oxidizing agent and additives in the processing solution are consumed or change over time, it is difficult to control and maintain the bath concentration.

(d) Since this method performs surface oxidation at the same time as surface dissolution of the inner layer film, treatment conditions (bath components, oxidizing agent, additives, bath temperature, pH, current density, , processing time, etc.), and the degree of blackening is extremely unstable.

(e) Since the treatment liquid contains ammonium ions, treatment of the waste liquid poses a pollution problem.

(Object of the Invention) The present invention provides Zn that improves the problems (a) to (e) above.
The present invention provides a method for blackening plated steel sheets and its products.

(Structure of the Invention) The gist of the present invention is that a Zn-plated steel plate is coated with Ni'', Z
In an acidic aqueous solution (pH≦3) containing n2゛, using an insoluble anode as a counter electrode, cathode treatment was performed at a current density of 40 A/d m' or less, and the surface layer was coated with a sticking amount of 0.01 g/m' or more. , Zr1-Ni alloy (Ni215wt%) plating is applied.

The Zn-plated copper plate used as the base steel plate in the present invention may be any Zn-coated or Zn-alloy plated steel plate, but since it has particularly strong electrodeposition with the surface layer, Preferably, the steel plate is provided with a Zn plating layer, a Zn-Ni alloy plating layer, a Zn-Fe alloy plating layer, or a Zn-Al alloy plating layer.

There is no particular limit to the amount of plating, but it is usually 3 to 300g/
About m' is fine. The plating method may be any method such as electroplating, hot-dip plating, heat treatment, vacuum evaporation, thermal spraying, etc.

The reason why the pH of the acidic aqueous solution is limited to 3 or less is that if the pH exceeds 3, SCN ions and NH
This is because blackening does not occur unless 4 ions or the like are used.

In addition, in the present invention, an insoluble anode is used, and Z
In order to maintain the concentration of n2°, Ni”, Zn, Ni
1i (ZnO1ZnCO3, N1CCh, etc.) and Zn powder are replenished, but at pH > 3, the dissolution rate is too slow to be used practically. The range with the best solubility is pH≦2.0.

The current density was limited to 4 OA/d m' or less because 4
If it exceeds 0 A/drn', it will not turn black, so the preferred range is 20 A/d m' or less, and the most preferred is 5
A/d m' or less. The lower limit of the current density is not particularly limited, but the lower the current density, the more plating baths will be required, which will be uneconomical in terms of equipment costs. I A/d m'.
Two is preferable. The current waveform for cathodic treatment is direct current.

There are no particular limitations, such as direct current with a pull or pulsed current.

The Zn-Ni alloy plating layer deposited as a surface layer by cathodic treatment may contain not only metal but also a small amount of partially concentrated integrants, hydroxides, hydrates, etc. It should be said that it is a layer of a compound containing Ni as a main component. (However, in the specification, the expression "plating layer" is used.) This surface plating layer is composed of Fe, Go, C
r, Mn, Sn, Pb, In, Mo, Gu, Ti
, ca, s, p, B, C, S, etc., even if it contains one or more of them, there is no particular effect on blackening, and it is included in the scope of the present invention. It is.

The reason why the Ni-containing element Tjd in the surface layer is limited to 15 wt% or more is that blackening cannot be achieved with less than 15%.

Although there is no particular upper limit, the higher the N1 content, the higher the coating cost. At 60% or more, the surface film becomes slightly hard,
Although the rejectability is reduced, there is no problem in light bending processing and flat panel applications, which are often used in home appliances and building materials. If it is less than 30%, the film will be able to withstand strong processing such as press molding for automobile tenons. The degree of blackening is stable at 20% or more.

The reason why the surface layer pricking j11 was limited to 0.01 g/m' or less is because if it is less than 0.01 g/rri', it will be too thin and the color of the inner layer will fade. There is no upper limit, but the production cost will increase as the number of plated 4 archery states increases. In order to be suitable for heavy processing, it is desirable to have a value of 2.0 g/rrf or less. Since micropores and microcracks are likely to occur in the plating film, and discontinuous coating is likely to occur, the plating film is preferably 0.1 g/m' or more. The range where stable production is easy is 0.5 g/m' or more. Therefore, the preferred range is 0.1 to 5 g/m2, and the most preferred range is 0.5 to 2.0 g/m'
It is.

The blackened steel sheet of the present invention is further coated with a known chromate treatment or an organic resin film such as a thin 1-cycliar run force on its surface layer to improve corrosion resistance, gloss, 1ml/ml fingerprint resistance, etc. You can also do that.

The blackened steel sheet of the present invention may be blackened on both sides, but the opposite side may be a bare steel sheet surface, or may be coated with Zn coating, Zn alloy coating, other coatings, A1 coating, Cu coating, coating, Ni plating, or synchromesh coating. Any form, such as a metal-like paint treatment, may be used. Next, the present invention will be explained by examples. Note that the test materials in Examples were manufactured using steel plates with an inner layer applied only to one side.

(Example 1) As an inner layer, a steel plate plated with Zn with a coating amount of 80 g/m' was coated with a Ni concentration of 2° Bog/l and a Zn concentration of 3''.
In an acidic aqueous solution with a pH of 1.0 to 2.0 and a bath temperature of 50 to 70°C, cathodic treatment was performed with the insoluble anode as a counter electrode and the current sonicity varied to cause the surface layer to stick. The degree of blackening of the obtained test materials was compared. The number of fleas sticking to the surface layer of each test material was unified to 1 g/m' by adjusting the current application time.

FIG. 1 shows the relationship between electric current and evaluation of black color intensity. (
5 Good, 3 Fair, 1 Bad) From FIG. 1, it can be seen that blackening is good in the range of 40 A/d m' or less.

(Example 2) A steel plate was coated with a Zn-Fe alloy electroplated film (Fe20 tz) with a sticking amount of 20 g/m' as an inner layer.
2.0-3.0 bath temperature 60-80°C, plating current density 5
A/drn', cathodically treated in an acidic aqueous solution containing N12° and Zn'' with an insoluble anode as the counter electrode to reduce the adhesion amount to 0.
．． A surface layer of 5 g/m' was obtained. In addition, the Ni” concentration is 20~
The Zn2° concentration was varied in the range of 10 to 60 g/text in the range of 120 g/text to obtain test materials provided with surface plating layers of different N1 wt%.

FIG. 2 shows the relationship between N1wt% in the surface layer and evaluation of the degree of blackening. (5 Good, 3 Fair, 1 Bad) From FIG. 2, it can be seen that blackening is good when the N1 content is 15 wt% or more.

(Example 3) Various Zn-based and Zn alloy-based plating layers were applied as an inner layer to a cold-rolled quilted steel sheet, and furthermore, Zn with various N1wt% and coating amount was applied by the method of the present invention. −
The Ni-based alloy plating layer was inspected and a comparative material (No.
No. 0) and the test material of the present invention (No. 32)
I got it. The degree of blackening was evaluated for each test material. The results are summarized in the table. From the table, it can be seen that the test material of the present invention achieved excellent blackening.

Separately, it was confirmed by a salt spray test, a wet test, etc. that the blackening treatment of the present invention had no effect on the corrosion resistance performance of the inner layer.

(Effects of the Invention) The present invention is not a deception; it is a treatment method that is not limited by the substrate, does not have aging of the treatment solution, pollution problems of wastewater, etc. Due to its short length, it is an excellent method that can be applied to continuous strip processing lines. Furthermore, the obtained steel sheet has a stable black tone and is of high commercial value.

[Brief explanation of drawings]

FIGS. 1 and 2 are graphs showing test results of Examples. Agent Patent Attorney Shuntetsu Sasaki Figure 1 Moxibustion Figure 2 Ryo

Claims (2)

[Claims] (1) At least one side of the steel plate is coated with one or more layers of Zn plating or Zn alloy coating as an inner layer, and the surface layer is coated with an acidic aqueous solution (p
H≦3) with the insoluble anode as the counter electrode, 40A/dm'
(4 pieces 17 (
A blackened rust-proof steel sheet characterized by having a Z':n-Ni alloy (Ni215 wt%) plating layer of 0.01 g/m' or more. (2) Apply one or two or more layers of Zn coating or Zn alloy plating to at least one side of the steel plate, and then coat this plated surface with an acidic aqueous solution (pH
≦3) with the insoluble anode as the counter electrode, 40 A/d
Cathode-treated at a current density of m' or less to form a surface layer of 0.0
1g/m' or more c7) Zn-Ni alloy (Ni215
A method for producing a blackened anti-corrosion steel sheet characterized by adhering a metal layer (wt%).