JPS58144495A - Electroplating method - Google Patents

Abstract

PURPOSE:To certainly prevent the passivation of an Fe anode, in Fe or Fe-alloy plating, by imparting a flow speed satisfying a specific formula to a plating liquid on the surface of the Fe anode. CONSTITUTION:In Fe plating or the plating of an Fe containing alloy such as Fe-Zn or Fe-Ni, as an anode, a ferrous type such as pure iron or usual carbon steel is used. To a plating liquid on the surface of the Fe type anode, a flow speed satisfying relative formula V>=(I-25)X0.66 is imparted to carry out electroplating. In the formula,Iis current density (A/dm<2>) and V is the flow speed (m/mm.) of the plating liquid. By this method, the passivation of the Fe anode can be prevented and, while the increase of Fe<3+> in the bath and the generation of an O2 gas are suppressed, uniform plating quality is obtained under a stable condition.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electroplating Fe or an alloy containing Fe, and more particularly to an electroplating method in which a flow rate is applied to a plating solution on the surface of an Fe-based anode with a specific relationship between the current density and the current density. It is about the method. .

It is known that increasing the current density during electroplating increases the plating efficiency. However, in plating Fe or an alloy containing Fe, when electroplating is performed at a high current density, the Fe anode becomes passive, and Fe2+ ions are oxidized to Fe3+ at the Fe anode (electrical reaction Fe2+→Fe3++e). As a result, the plating quality is adversely affected, such as a decrease in plating efficiency and an increase in plating stress, and there is also a shortage of Fe2+ supply, and the anode becomes insoluble, resulting in a decrease in pH due to the generation of O2 gas, which causes problems in bath management. Therefore, in order to deal with such problems, it is known to take measures such as improving the bath composition (such as a chloride bath), lowering the bath pH, or increasing the bath temperature. In practice, Fe-based plating has no choice but to be carried out at a low current density, since this adversely affects quality and the like.

By the way, in electrolytic galvanizing, rather than Fe-based plating, which is the object of the present invention, Japanese Patent Laid-Open No. 49-123
As described in No. 131, in order to prevent anodic polarization,
A method for fluidizing a plating solution at a high flow rate is disclosed.

In such electroplating of Zn, the problem is a matter of academic purity, and attention needs to be paid only to prevention of polarization. However, problems with F'e-based plating are complex and diverse.

In other words, if electroplating is continued at a high current density, not only will the voltage increase, but also the anode potential will increase due to the accumulation of dissolved substances on the anode surface, forming an oxide film on the surface, and F
eProduces anodic passivation. In the case of Zn plating, there is no oxidation. In Fe-based plating, when passivation occurs, the amount of adhesion decreases in the passive region, resulting in an uneven distribution of the amount of adhesion. In addition, as mentioned above, Fe3+ increases more rapidly than Fe30 of Fe2+. Therefore, in the past, especially in a sulfuric acid bath, the current density was at most 20 AAm.

The present invention solves the above-mentioned conventional problems at once, and its purpose is to reliably prevent the passivation of the Fe anode, suppress the increase in Fe3+ in the bath and the generation of O2 gas, and thereby maintain stable bath conditions. An object of the present invention is to provide an electroplating method that can obtain uniform and desired plating quality.

To achieve this objective, the present invention provides Fe'f or alloy plating containing Fe, in which the plating solution on the surface of the Fe-based anode has ■≧(1-25) Xo, 66 [where I: current density (A/dmj)■Two plating solution flow rate (m/mil+)), so as to satisfy the following relational expression:
O has a configuration in which electroplating is performed by applying a flow rate.
The plating targeted by the present invention is Fe plating or F plating.
e Zn or Fe-containing alloy plating such as Fe N'i.

In such Fe-based plating, as described above, the Fe anode becomes passivated under a unique high current density condition that is not found in Zn plating or the like. This passivation is influenced by the electrolytic cell structure and current distribution, but in order to eliminate this influence 5 and achieve uniform anode dissolution, the plating solution can be fluidized on the surface of the Fe anode. The person who paid attention to Oko (
To explain qualitatively the technical meaning of 3), passivation of the Fe anode occurs under conditions of high current density because Fe2+ salt dissolved from the anode accumulates at the interface and this is absorbed by the current. One reason is thought to be that n1 acts as a barrier and causes current concentration, and as the n1 current density increases, the amount accumulated per time increases. Therefore, by applying a flow rate to the plating solution on the surface of the Fe anode, significant accumulation can be prevented.

However, according to many experiments by et al., the amount of accumulation is proportional to the current density.
It was found that there is a correlation shown in the figure. Relational equation line f-(1
-25) Region Z1 bordering on XO166 is a region targeted by the present invention where Fe anode can be applied as a soluble anode without passivation, and region Z2 is a region where passivation occurs. The figure also shows that the current density is 2 s hA
It has also been shown that passivation can be avoided even if the flow rate is less than m.

(4) In the present invention, there is basically no upper limit on the flow rate, but in order to achieve a high flow rate, a large-capacity pump is required, which increases equipment costs and running varnish. Determined only by 扛.

When giving a flow rate to the plating solution on the Fe anode surface, F
eThis can also be achieved by fluidizing the entire plating solution, not just the vicinity of the anode surface. Specifically, in addition to flowing the plating solution between the electrodes, there are methods such as applying the plating solution to the anode surface using a nozzle, or vibrating the anode.

In the present invention, Fe-based materials such as pure iron and general carbon steel are used as the anode. Note that the above-mentioned passivation is noticeable in the sulfuric acid bath, and in the n1 chloride bath, the C1-
At high concentrations, the passive state is destroyed. However, using a chloride bath causes corrosion of the plating equipment. However, if this is sacrificed, a chloride bath or a sulfuric acid bath to which iron chloride is added can be used in addition to the sulfuric acid bath.

Next, the present invention will be explained in further detail with reference to Examples.

The apparatus used in the experiment is shown in Fig. 2, in which the plating solution from the tank 3 is passed between the electrodes 2 arranged in parallel in the cell 1 and the object to be plated, with a circulation pump 4 giving a flow rate. However, the flow rate and the flow rate are adjusted by a regulating pulp 5, and the flow rate is determined from the flow rate indicated by a flow meter 6. The total amount of plating solution was 41, the size of the electrodes was 70 x 100 mm for both the anode and cathode, the distance between the electrodes was 20 mm, and cold rolled steel plates were used as the electrodes.

Example 1 The plating bath composition was changed to ferrous sulfate 2001//l! , sulfuric acid 7
/Mo, =- Lamb 100g/Cpie2.5, Bath temperature 5°C
Under these conditions, continuous plating was performed for 40 minutes at a current density of 30 A/dm with various flow rates of the plating solution, and changes in the surface of the anode and Fe3+ concentration in the bath were measured. Some of the results are shown in Figure 3 [and the static bath and flow rate 57y]
At 1/mm, the potential rose after energization, Fe3+ in the bath increased, the anode surface became white and glossy, and no 02 gas was observed to be generated. In contrast, at 10w7m or higher, no increase in Fe3+ in the bath was observed, no passivation occurred, and the anode surface was black and no gas generation was observed.

Example 2 In order to perform FeZn plating, the plating bath composition was changed to ferrous sulfate 200. ! i'/V (Fe4 (Lj9/l), zinc sulfate 50g/13, sodium sulfate 50jj/l, pH 2.0, bath temperature 50°C, under these conditions,
While changing the flow rate of the plating solution, the current density was increased to 6.
Continuous plating was performed at 0 A/dm% for 2 hours. At that time, changes in Fe2+ concentration and pH in the bath were investigated, and the results shown in Figure 4 were obtained.According to the same figure and results not shown, the flow rate of the plating solution was increased by 2.
Below 0 m/mrn, the pH decreases and the F♂1 concentration decreases after energization, and Fe3+ increases.

In this case, the anode surface was white, and the voltage rose to 162 cm, indicating that passivation had occurred.

(7) In contrast, when the flow rate was increased to 307,717 m1n, no pH drop or increase in Fe2+ concentration occurred, and the voltage was 14. No passivation occurred with OV.

As described above, the present invention applies a specific flow rate to the plating solution on the Fe-based anode surface in Fe-based plating, so changes in bath composition, bath temperature, or bath pH that adversely affect plating quality, etc. It has a great advantage in that it can reliably prevent passivation while avoiding harmful effects.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the area targeted by the present invention in the relationship between current density and plating solution flow rate, Figure 2 is a schematic diagram of the experimental equipment, and Figure 3 is the correlation obtained in the case of Fe plating. Figure 4 shows the n obtained in the case of Fe-Zn plating.
FIG. 1...Metsukicell 2...Electrode 4...Circulation pump C8) Figure 1 Figure 2

Claims (1)

[Claims] (1) In Fe or alloy plating containing Fe,
For the plating solution on the surface of the Fe-based anode, ■≧(1-25) An electroplating method characterized by performing electroplating by applying a flow rate so as to achieve the desired effect.