JPH07100877B2 - Amorphous iron-tungsten alloy coating electrodeposition method - Google Patents

Description

The present invention relates to a method for depositing an amorphous iron-tungsten alloy coating.

[Problems to be Solved by Prior Art and Invention]

Tungsten cannot be electrodeposited alone from an aqueous solution, but it is known that it is an induced eutectoid metal that can be co-deposited with an iron group metal, and various iron-tungsten alloy plating methods have been conventionally used. Proposed.

However, many of the plating films obtained by the conventional iron-tungsten alloy plating method have a crystalline structure, and an amorphous iron-tungsten alloy plating film is desired from the viewpoint of corrosion resistance and the like. There are few proposals for a method capable of industrially electrodepositing the iron-tungsten alloy coating.

Further, in particular, many of the iron-tungsten alloy platings that have been conventionally reported have a bath temperature of about 80 ° C., which is problematic in terms of workability and the like.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for reliably and industrially electrodepositing an amorphous iron-tungsten alloy coating.

[Means and Actions for Solving the Problem] As a result of various studies to achieve the above-mentioned object, the present inventors have found that a water-soluble tartrate salt of a water-soluble ferrous salt and a water-soluble tungstate salt is obtained. Contained, and using a weak alkaline plating bath containing 20 mol% or more of tungsten relative to the total amount of tungsten and iron, the object to be plated is electroplated at a bath temperature of 50 ° C or less, and the tungsten content is 40% by weight. % Of the iron-tungsten alloy plating film achieves amorphization, the amorphous iron-tungsten alloy plating film has high corrosion resistance, and the above method has a low plating temperature. It was found that the cost merit is large and the practicability is high.

Hereinafter, the present invention will be described in more detail.

As described above, the plating bath used in the method of the present invention contains the water-soluble ferrous salt, the water-soluble tungstate and the water-soluble tartrate as a complexing agent, and the total amount of tungsten and iron is A weak alkaline plating bath containing 20 mol% or more of tungsten is used to obtain an iron-tungsten alloy plating film having a tungsten content of 40% by weight or more.

Here, as the water-soluble ferrous iron salt, ferrous sulfate conventionally used for iron-tungsten alloy plating is used,
As the water-soluble tungstate, an alkali metal tungstate such as sodium tungstate is used,
As the water-soluble tartrate salt, aluminum tartrate, sodium tartrate, potassium tartrate and sodium potassium tartrate are used.

The concentrations of the above components are selected according to the intended plating film composition, and in this case, as the amount of tungsten in the plating bath increases, the amount of tungsten in the plating film increases, but in the present invention, From the viewpoint of amorphization, the composition of the plating bath is selected so that the amount of tungsten in the plating film is 40% or more. Therefore, from such a point, the plating bath of the present invention, the amount of tungsten in the bath is 20 mol% or more, more preferably 26 mol% with respect to the total amount of iron and tungsten.
As described above, the content is more preferably 30 mol% or more. Therefore, the concentrations of the water-soluble ferrous salt and the water-soluble tungstate are selected so that W / W + Fe has the above-mentioned molar concentration. In this case, the concentration of the water-soluble ferrous salt is 1.8 g / l to 36 g / l (0.13 mol / l
l), the concentration of water-soluble tungstate is 4g / l ~ 43g / l (0.
13 mol% / l) is preferable, but 9 g / l or more of the water-soluble ferrous salt is more preferable from the viewpoint of current efficiency. Also,
The relationship between the total metal salt in the solution and the complexing agent is that the water-soluble tartrate is generally the sum of the water-soluble ferrous salt and the water-soluble tungstate in view of the metal complex structure and the properties of the electrodeposited alloy. It is preferable to be equivalent to the molar amount, usually 48 g /
l (0.26 mol% / l) or less.

Further, the plating bath of the present invention is adjusted to be weakly alkaline with a pH of 7-9.

When electroplating an appropriate object to be plated using the plating bath, the plating temperature is 50 ° C or lower, more preferably 40 ° C.
In the present invention, sufficient plating can be performed at room temperature of 30 ° C or lower. The cathode current density can be obtained as an amorphous film at any cathode current density of ² to 20 A / dm ² if the plating temperature is 40 ° C. or lower, but at a plating temperature higher than that, 3 A / dm ² or more, In particular, a current density of 5 A / dm ² or more is preferably adopted from the viewpoint of amorphization.

The stirring may be unstirred, but it is preferable to stir with a stirrer or the like, and an insoluble anode such as a platinum-plated titanium mesh is usually used as the anode, but an iron anode can also be used.

Next, the present invention will be described more specifically by way of examples.

〔Example〕

FeSO ₄ · 7H ₂ O as a plating _{bath, Na 2 WO 4 · 2H 2} O, (NH 4) 2 C 4
Using H ₄ O ₆ at the following concentrations, pH 3 to 8, plating temperature 28 to 80
Plating was performed at a temperature of ² ° C. and a cathode current density of ² to 20 A / dm ² .

In addition, a 500 ml glass cylindrical container was used as the electrolytic cell, a platinum plated titanium mesh (95 x 65 mm) was used as the anode, and a circular copper plate (6 cm ² x 0.3 ^t ) was degreased and pickled as the cathode (plating object). Used.

The X-ray diffraction method was used for the determination of the amorphous structure, and the plasma emission analysis method and the fluorescent X-ray method were used together for Fe, Mo and W in the electrodeposited film. For the film structure, the distribution of constituents was determined using AES. For the electrochemical behavior of the electrodeposited film, an automatic polarization measuring device manufactured by Hokuto Denko was used.

(1) Fe-W amounts indicated effects following composition _{FeSO 4 · 7H 2 O 36g /} l Na 2 WO 4 · 2H 2 O first diagram W ratio in the plating film on the amorphous alloy film (NH ₄ ) ₂ C ₄ H ₄ O ₆ 48 g / l pH 8 plating bath was used, plating was performed at various cathode current densities at a plating temperature of 28 ° C, and the composition of the obtained plating film was analyzed. It was evaluated whether or not it was amorphous. The results are shown in Fig. 1.

From the results shown in FIG. 1, it was confirmed that when the W content in the Fe—W alloy coating was 40% by weight or more, an amorphous coating was obtained.

(2) the amount shown in FIG. 2 as Fe-W W ratio of impact following composition _{FeSO 4 · 7H 2 O 36g /} l Na 2 WO 4 · 2H 2 O W in the plating bath on the amorphous alloy film (NH ₄ ) ₂ C ₄ H ₄ O ₆ 48 g / l pH 8 plating bath was used, plating was performed at 8 A / dm ² at a plating temperature of 28 ° C, and the composition of the obtained plating film was analyzed and It was evaluated whether or not was amorphous. Results are shown in FIG.

From the results shown in FIG. 2, it is found that if the W content in the plating bath is 20 mol% or more of the W + Fe content, a Fe-W alloy film having a W content of 40% by weight or more can be obtained and an amorphous film can be formed. Was recognized.

The relationship between W / Fe + W in the bath and the current density is shown in FIG.

(3) Fe-W Effect of pH on the amorphous alloy film following composition _{FeSO 4 · 7H 2 O 36g /} l Na 2 WO 4 · 2H 2 O 43 〃 _{(NH 4) 2 C 4 H} 4 O 6 Use a plating bath of 48〃 and change the pH to a plating temperature of 28
Plating was performed at a temperature of ² ° C. and a cathode current density of 2 A / dm ² and 4 A / dm ² , and the composition of the obtained plating film was analyzed, and whether or not it was amorphous was evaluated. Results are shown in FIG.

From the results shown in FIG. 4, it was confirmed that an amorphous film was obtained when the pH of the plating bath was weakly alkaline from 7 to 9.

(4) Fe-W Effect of Plating Temperature on amorphous alloy film following composition _{FeSO 4 · 7H 2 O 36g /} l Na 2 WO 4 · 2H 2 O 43〃 _{(NH 4) 2 C 4 H} 4 O ₆ A plating bath of 48 〃 pH 8 was used, plating was performed while changing the plating temperature and the cathode current density, and it was evaluated whether or not the obtained plating film was amorphous. Results are shown in FIG.

From the results shown in Fig. 5, an amorphous film was obtained at any current density when the plating temperature was 40 ° C or lower, and 3 at 50 ° C.
It was confirmed that an amorphous film was obtained at ˜4 A / dm ² , especially at 5 A / dm ² or more.

(5) Corrosion resistance of Fe-W alloy coatings Fe-W alloy plating coatings with W contents of 28% by weight, 37% by weight and 49% by weight were immersed in a 1N hydrochloric acid solution at 30 ° C to determine the anode polarization curve. . Results are shown in FIG.

From the results shown in FIG. 6, it was confirmed that the amorphous Fe-W alloy plating film having a W content of 49% by weight had good corrosion resistance.

〔The invention's effect〕

According to the present invention, an iron-tungsten alloy plating film that is amorphous and has excellent corrosion resistance can be electrodeposited reliably and industrially.

[Brief description of drawings]

Fig. 1 is a graph showing the relationship between the amount of W in the Fe-W alloy coating and the amorphization of the coating, and Fig. 2 is the W in the Fe-W alloy plating bath.
Amount and the amount of W in the Fe-W alloy film and the relationship between the amorphization of the film, FIG. 3 is a graph showing the relationship between W / Fe + W in the plating bath and the current density, and FIG. 4 is Plating bath pH and Fe-
FIG. 5 is a graph showing the relationship between the amorphization of the W alloy film, FIG. 5 is a graph showing the relationship between the plating temperature and the amorphization of the Fe—W alloy film, and FIG. 6 is a graph of various Fe—W alloy plating films. The anodic polarization curve in normal hydrochloric acid is shown.

Claims (1)

[Claims] 1. A weakly alkaline plating bath containing a water-soluble ferrous salt, a water-soluble tungstate salt and a water-soluble tartrate salt, and containing 20 mol% or more of tungsten with respect to the total amount of tungsten and iron. A method for electrodepositing an amorphous iron-tungsten alloy coating, characterized in that an object to be plated is electroplated at a bath temperature of 50 ° C. or lower to obtain an iron-tungsten alloy coating with a tungsten content of 40% by weight or more. .