JPS61110798A - Manufacture of steel sheet blackening treatment - Google Patents

Abstract

PURPOSE:To obtain a satisfactory blackened steel sheet by applying an anodic treatment to the steel sheet having an Ni alloy plated layer contg. Ni of a specified quantity or more as the uppermost layer, under a specified condition in a bath contg. the specified quantity of NO<->3 ion. CONSTITUTION:The steel sheet as a material to be treated, has the Ni alloy plated layer contg. >=5wt% Ni (especially >=8wt%) as the uppermost layer. The steel sheet is treated electrolytically by using the plated sheet as an anode under the condition of 10-800coulomb/cm<2> electrical quantity, in the bath contg. 3-500g/L No3<-> ion. If >= one kind amond SO4<2->, Cl<->, Br<->, F<->, CN<->, PO4<3->, as anion are further added into the bath by 5-300g/L in total, blackened degree is further increased. It is further desirable to form a chromate film having 5-200mg/m<2> expressed in terms of Cr quantity and an organic resin film having 0.2-4mu thickness on the plated layer surface blackening treated.

Description

[Detailed description of the invention] (Rental technology and problems) The present invention relates to a method of manufacturing a black plated steel sheet.

Conventionally, Zn, Zn alloy, Sn, and N were used for corrosion prevention purposes.
Plating such as i, Cr, etc. is applied to the steel plate, but since these platings have a white or gray-white appearance,
There are restrictions on its use for collecting stool. on the other hand,
There is a growing need for steel sheets with a black appearance for the purpose of collection in fields such as office supplies, optical equipment, electrical products, and automobile parts.

Therefore, a steel plate with a blackened surface has recently been developed, and has been used in a wide range of fields because it has a high-quality appearance even for use in collecting stools. That is, known blackening methods include the following methods.

(a) A method of forming a black resin film containing carbon black or the like as a main component on the surface of a steel plate or a plated steel plate (JP-A-56-82998) (b) A method of forming a film containing A on the surface of a steel plate.

(c) A method of treating a steel plate with a treatment solution prepared by adding an inorganic nitrate to an aqueous solution of iron tannin (Japanese Patent Application Laid-open No. 56-829F1
8) (d) Method of anodizing Zn-plated steel sheet containing C:o and additives (JP-A-58-151490, JP-A-58-
151491).

However, these known methods (1) use noble metals such as silver, so they are disadvantageous in terms of cost;

(2) Films containing carbon black or the like as a main component have poor adhesion. (3) There are problems in that the appearance changes not only depending on the anodizing treatment but also on the plating conditions.

For the purpose of improving the above-mentioned problems, the present inventor previously proposed Japanese Patent Application No. 58-228471 and Japanese Patent Application No. 511-3434.
2 was submitted, but as a result of intensive research to expand the operating conditions and make it easier to control one color tone, Ni
By anodizing the alloyed Zn-plated steel sheet containing
The present invention has been made based on the idea that the object can be achieved.

(Structure of the Invention) The gist of the present invention is that a blackened layer is formed on the surface of the steel plate by anodizing the alloyed Zn plating layer containing Ni in a bath containing NO; ions. be.

To explain the present invention with reference to the drawings, 5w of Ni is added to the top layer.
A steel plate (2) having a Zn-based alloy makeup (1) containing t
3) Inside, the plated plate is used as an anode to generate an electric quantity of lO~600.
Electrolytic treatment with Coulomb/drn' (hereinafter referred to as anodization)
As a result, a black lower layer (4) is formed in the form of a plating layer.

In the present invention, the treated material to be subjected to the blackening treatment must contain at least 5wt$ of Ni as a component in its top layer, and preferably contains at least 8wH of Ni. If the old content is less than 5wt1, not only will it take a long time to process, but also sufficient color development will not be obtained, and uniform color development will also not be obtained.

The treatment liquid used for blackening contains NO;
．． It is necessary to contain 7 x to 5 oox/l. If it is less than 35 g/l, the blue color will be strong and the black color will not be sufficient. If it is more than 500 g/u, it will not be economical, and the blackness will decrease because the bath temperature must be raised to further dissolve it. .

The above treatment solution further contains SO4 and CI as anions.

By adding at least one of B;, F, I, C1, or PO4 in a total amount of 5 to 300 g/i, the degree of blackness can be increased. Further, by adding these, the conductivity of the bath can be greatly improved, and there is also the advantage that the electric power required for treatment can be reduced. If the concentration of these anions is less than 5g/l, the additive has no effect, and
g/! L or more is not economical.

Regarding the amount of electricity, below 10 coulombs/drn',
After treatment, the appearance has a strong bluish tinge and the degree of blackness is insufficient, and the degree of blackness is also large, and if the treatment is over 600 coron/drrl', the plating film will be leached to a large extent, which is not economical, and conversely, the degree of blackness will decrease. It becomes grayish. In addition, processing unevenness also occurs. Therefore, the appropriate amount of electricity is 10 to SOO coulombs.

Although the blackened steel sheet obtained by the above-described treatment has fairly good corrosion resistance in a dry atmosphere, white rust occurs relatively early in a humid atmosphere. In addition, the above treatment alone produces a slight interference color, and the appearance changes slightly depending on the anodizing conditions. In order to solve these problems, a chromate layer H (5) and/or an organic resin layer M (8) is formed on the blackened plating layer. The chromate film preferably has a chromium content of 5 to 200 mg/rn'; less than 5g/m' is ineffective;
On the contrary, black color is deteriorated above rf. Examples of organic resins include acrylic resin, polyester resin, alkyd resin, polyvinyl alcohol, and phenol resin.

There are fluororesins, hydroxyethyl cellulose, etc.
As long as the film to be formed is transparent, its type is not particularly limited, and the film thickness is suitably 0.2 to 4 mm;
If it is less than 4%, interference color will appear due to the resin coating, which is undesirable, and if it is more than 4%, the adhesion of the resin film will deteriorate.

Next, the effects of the present invention will be explained with reference to Examples and Comparative Examples collectively shown in Table 1 below.

The Niwt$ in the plating calendar is 5wt$ or more, and the composition of the anodizing bath is NO; ions are 3 to 500g/l, S
In Examples 1 to 4, which contain o Hei ions in the range of 5 to 300 g/drrl and the electrical quantity is in the range of 10 to B00 coulombs/drrl, the appearance of the blackened steel sheet is excellent or good and can be used naked. The product was obtained.

Comparative example 1 where plating wt$ is 5wt$ or less. No: In the case of Comparative Example 2 which does not contain ions, Comparative Examples 3 and 4 where the amount of electricity is out of range, and Comparative Example 8 where sony ions are out of range, the appearance of the blackened steel sheet is suitable for collection. I couldn't get anything.

Table 2 shows the results of forming only a chromate film, and a chromate film and an organic resin film on the blackened steel sheet obtained under the conditions of Example 1.

(Effects of the Invention) According to the present invention, it is easy to control the blackening process,
Moreover, a good blackened steel sheet can be obtained.

[Brief explanation of drawings]

The accompanying drawings are explanatory diagrams showing an uninvented manufacturing method. 1 Metsuki calendar 2 steel plate 3 treatment baths 4 Black film 5 chromate film 6 Organic resin film

Claims (3)

[Claims] (1) As the top layer, a steel plate having a Zn-based alloy plating layer containing 5 wt% or more of Ni is coated with 3 to 3 NO^-_3 ions.
A method for producing a blackened steel sheet, characterized in that it is anodized with an electrical quantity of 10 to 600 coulombs/dm^2 in a bath containing 500 g/l. (2) The treatment bath contains SO^-^1_4 as anions,
Cl^-, Br^-, F^-, I^-, CN^- or P
At least one type of O^3^-_4, 5 to 30 in total
The method according to claim 1, wherein the bath contains 0 g/l. (3) A chromate film with a Cr content of 5 to 200 mg/m^2 and/or an organic resin film with a film thickness of 0.2 to 4 μm is formed on the surface of the blackened plating layer. Manufacturing method described in section.