JPS59170289A - Ferrous electroplating method - Google Patents

Abstract

PURPOSE:To maintain a uniform concn. of Sn in a plating bath without depending on the case of a plating vessel in an electroplating method of Fe contg. Sn by adding Sn in the form of metallic Sn to the plating bath and limiting the content of Sn in a supply source for metallic Sn to a specific content. CONSTITUTION:This invention relates to an electroplating method of Fe contg. Sn, more particularly an electroplating method of Fe which electroplates discontinuously the surface layer of Fe-Zn-Sn on the underlying electroplating layer of Zn-Ni or Zn-Fe. Sn is added in the form of metallic Sn to a plating layer and the content of Sn in a supply source for metallic Sn is limited to 0.1-20wt%. For example, a soluble anode alloyed with 0.1-20wt% Sn with a steel or pure iron is used. The same supply source for metallic Fe is used for the supply source of metallic Sn and 0.1-20wt% Sn is compounded with the supply source in the stage of using the insoluble anode.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an iron-based electroplating method containing Sn, in particular a Zn-N
1 type or Zn-Fe type lower electrical metal layer
This invention relates to an iron-based electroplating method for discontinuous Zn-5n surface layer electroplating.

Conventionally, when carrying out Fe-based electroplating containing Sn, the method of supplying Sn into the plating bath is to add Sn soluble salts (e.g., stannous chloride, stannous sulfate, etc.) into the plating bath. It was customary to introduce it directly. However, when added in this way, the Sn salt may float in the plating bath, resulting in insufficient dissolution or
In addition, it is difficult to control the amount of Sn salt added to the plating bath in order to keep the amount of Sn in the plating film constant as it often changes during plating operations. There were drawbacks such as the ion concentration being high only near the input port and becoming non-uniform depending on the location of the plating tank.

In particular, it has recently been reported that the corrosion resistance of plated layers with the addition of a small amount of Sn is significantly improved. It is requested.

Therefore, one object of the present invention is to
An object of the present invention is to provide a method for making the amount of Sn in a bath uniform regardless of the location of the plating bath in an Fe-based electroplating method including the above.

Broadly speaking, it is an object of the present invention to provide a method that does not require special supply equipment for adding Sn and can be easily implemented using existing equipment.

Furthermore, another object of the present invention is to provide a method that does not require automatic control of the Snn deposition amount in response to variations in the plating deposition amount.

Here, the gist of the present invention is to add Sn in the form of metal Sn to a plating bath, and to adjust the Sn content of the source of the metal Sn from 0.1 to 20.0. ii) This is an iron-based electroplating method containing Sn, which is characterized by a limited weight %.

The present invention generally includes iron-based electroplating methods containing Sn, such as Fe-based or Fe-Zn-based alloy plating, composite plating, dispersion plating, etc. Small amount of Nj, Cr+Co+Cu+M
o+Mn+ν+Cd, In, TI, Pb, Sb+Ti
, P and the like are also within the scope of the present invention. In a preferred embodiment, the present invention is particularly advantageously applied to a method of performing discontinuous surface electroplating of Fe-Zn-5n on a Zn-Ni or Zn-Fe lower electroplating layer. "Surface discontinuous electroplating" here means electroplating that forms a discontinuous plating layer on the surface to be plated.
Representative examples of n-3n surface discontinuous electroplating include Japanese Patent Application No. 57-201427 and Japanese Patent Application No. 57-20348.
There is a method related to item 8.

When performing electroplating and using a soluble electrode, the source of the metal Sn is steel or pure iron with 0.1
A soluble anode alloyed with ~20.0% by weight may also be used. In addition, when using an insoluble anode, the above metal S
The source of n may be the same as the source of metallic iron, and 0.1 to 20.0% by weight of Sn may be added to the source.

In such a case, the source of metallic iron is steel or pure iron powder, particles, lumps, plates, or linear bodies, and the metallic Sn to be mixed therewith is as follows:
Even if alloyed with them, or metal Sn
It may also be a mixture of powders (particles). From a practical point of view, scraps of Sn-plated steel sheets (tinplate sheets) or defective products generated on the manufacturing line are advantageously used as a source of such metal Sn (which is also a source of metal iron). used.

In addition, in the present invention, the Sn content of the metal Sn supply source is limited within a predetermined value range, but this is limited to one 5ni
Regarding the Sn supply source, if a plurality of Sn supply sources are provided, each of them is adjusted to fall within the above-mentioned predetermined value range. Therefore, there is no direct correlation between the Sn content and the amount of Sn ions in the plating bath.
Adjustment of the plating bath can be made as appropriate by increasing or decreasing the number of Sn supply sources or by increasing or decreasing the number of metal iron supply sources that do not contain Sn. Furthermore, in the present invention, since Sn is supplied in the form of metal Sn, Sn ions are quickly and uniformly supplied to the plating bath throughout the bath, and therefore the Sn ion concentration in the plating bath is Adjustment 4; I:, Sn
This can be done easily and accurately by increasing or decreasing the number of supply sources, and even changes in the amount of plating deposited can be quickly responded to without any special control, as Sn ions are quickly supplied. can.

Thus, in the present invention, the Sn content in one Sn supply source is limited to 0.1 to 20.0% by weight,
If it is less than 0.1 F%, the amount of Sn ions in the plating bath will not be sufficient, especially when performing discontinuous plating of Fe-Zn surface layer on inner layer Fe2O%-Zn 80% alloy electroplating. Chemical treatment properties (P/P+lI ratio)
, the water resistant adhesion becomes poor after painting. Here, P is the phosphoric acid-treated film phosphumeferai I (Zn2Fe (
11 represents the amount of pohide (Zn3 (PO4)2, former 120). The higher this ratio is, that is, the greater the phosphoophierite content, the better the adhesion of the coating film after painting (that is, the water-resistant adhesion after painting). In addition, iron (steel)
The level of Sn content as an impurity in the
It is about 1 to 0.005% (maximum 0.01% for converter materials, and somewhat higher for electric furnace materials).

On the other hand, if the Sn content exceeds 20% by weight, adding high Sn-containing scrap or
Addition of Sn-containing ferroalloy, Sn metal particles, etc. in an electric furnace,
It is necessary to use a large quantity in a converter, etc., which increases the cost of auxiliary materials and is not only uneconomical, but also, in the case of a soluble anode, the steel electrode tends to melt unevenly, and the electrode may not adhere to the material to be plated, which is the opposite electrode. The distance between them changes, causing unevenness in the amount and thickness of the plating. In addition, if the Sn content exceeds 20.0% by weight, granular shedding occurs due to preferential melting of the grain boundary segregation, and the shedding pieces float in the plating bath and become cloudy and adhere to the plated material, causing roughness and The rate of product defects such as indentation defects increases rapidly.

Next, the present invention will be further explained by examples.

Example E In this example, a continuous horizontal plating bath for steel plates was used, and a Fe-based horn 1-bath (plating bath composition: Fe"40g/
It, Fe”+] g/e, Na2SO41
At 50g/(1, pH 3, temperature 70”c),
A steel ingot containing 0.01% C was used as a soluble copper anode.

One of the above anodes is used, and its Sn content is varied,
A series of continuous plating operations were conducted.

If the Sn content in the steel exceeds 20%, granular flakes will occur from the soluble anode, which will fall onto the steel plate to be treated, causing frequent indentation scratches between the various rolls after plating to occur on the product. Admitted. The operational results at this time are shown graphically in Figure 1. Here, the purchase rejection rate was determined by visually inspecting the products for the presence of indentation defects, and those found to have indentation defects were rejected.

Column 2 An alloy electroplated layer of 18% Fe, 72% Zn, 0.01% Cr on a lower layer with a thickness of 40 g/m2, and 90% Fe.
Surface discontinuous electroplating of a plating layer thickness of 5 g/m 2 containing , ZnlO%, and Sn was performed using an insoluble anode under the same manufacturing conditions as in Example 1. However, in this example,
As a source of metallic iron, sintered steel grains with a diameter of 1 to 3 mm were packed in a packed tower, and a coating solution was passed therethrough to supply a solution of 1/8. At that time, the Sn content in the iron grains was varied, and the Sn content in the iron grains was varied, followed by continuous electroplating.The sample thus obtained was then carved, chemically treated with a phosphate, and then electrocoated. was applied. The chemical conversion film formed at this time (P/P+lI
) ratio and water resistant adhesion after painting. This water-resistant adhesion after painting was determined by immersing it in 50°C ion-exchange water (for 10 days), then making slits in the paint film at 2 mm intervals, pasting cellophane tape on it, and then removing it again. It was evaluated based on the coating film remaining rate when it was removed.The results are as follows:
They are summarized in graphs in Figure 3 and Figure 3, respectively. As can be seen from this, the Sn content in the metallic iron supply source is 0.
．． If it was less than 1%, good results could not be obtained.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the Sn content in the metal iron supply source and the product rejection rate; FIG. 2 is a graph showing the relationship with the (P /P+l+ ) ratio of chemical crystals; FIG. 3 is a graph showing the relationship with water resistant adhesion after painting. Applicant: Sumitomo Metal Industries Co., Ltd. Agent, Patent Attorney Akira Hirose - Ka/Zu Metal Iron Supply, SR in Hara, Shonen Year <Jyuban] 2012 50 content (weight%) tail 3
figure

Claims (4)

[Claims] (1) Adding Sn in the form of metal Sn to the plating bath, and increasing the Sn content of the metal Sn supply source from 0.1 to 20
．． An iron-based electroplating method containing Sn, which is limited to 0% by weight. (2) The iron-based electroplating method may be applied to Zn-Ni or Z
Fe-Zn-3n applied to n-Fe-based single electroplated layer
Claim No. 7, which is a surface layer discontinuous electrical system
The method described in section 1). (3) A soluble anode is used, and the source of the metal Sn is a soluble anode in which steel or pure iron is alloyed with 0.1 to 20.0% by weight of Sn. Method. (4) Using an insoluble anode, the source of gold MSn is
is the same as the metallic iron source, and the metallic iron source is SnO
, 1 to 20.0% by weight of steel or pure iron.