JP2011184776A - Inorganic rust-preventive coating film, plating method for forming inorganic rust preventive coating film and plating liquid used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inorganic rust-preventive coating film which can prevent the white rust in zinc plating to which an iron product or an iron-based alloy product is subjected from occurring, is safe to a human body and has no concern of an environmental problem, to provide a plating method for the iron product or the iron-based alloy product, and to provide a plating liquid used for the plating method. <P>SOLUTION: The inorganic rust-preventive coating film N includes a zinc coating film K formed on a base material J and a manganese coating film M formed on the zinc coating film K. The zinc coating film K has a film thickness of 5 to 20 μm and the manganese coating film M has a film thickness of 0.5 to 10 μm. The plating method for forming inorganic rust-preventive coating film N includes: a zinc plating process of immersing iron raw material of the iron product or the iron-based alloy product as material to be plated in a galvarizing solution and, thereby, obtaining a plated product having the zinc coating film formed on the surface of the iron raw material; and a manganese plating process of immersing the material to be plated into a prescribed manganese plating liquid and, thereby, obtaining a plated product having the manganese coating film formed on the surface of the iron raw material. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an inorganic rust preventive film, a plating method for forming an inorganic rust preventive film, and a plating solution used therefor, and more specifically, zinc plating applied to iron products or iron-based alloy products. Further, the present invention relates to a technique for applying manganese plating to prevent white rust.

As one of the iron anticorrosion methods, galvanization is known. However, since the zinc surface is more active than iron or steel, it is likely to change, and so-called white rust may be generated. Therefore, in the past, a technique of performing chromate treatment to prevent this white rust and forming Cr (OH) ₃ , Cr ₂ O ₃ , CrO ₃ , ZnCrO _4, etc. on the zinc surface is frequently used. In addition, the zinc surface is coated with a dense coating (epoxy resin with excellent durability as an undercoat paint, and weather resistant and low water permeability paints such as chlorinated rubber, vinyl chloride, and polyurethane resins as a top coat). Techniques for doing this are also known.

In Patent Document 1, steel (iron) is degreased and pickled in advance, and then manganese plating is applied to a normal aqueous solution bath (MnSO ₄ .7H ₂ O, (NH ₄ ) ₂ SO ₄ , CS ( A technique for performing electroplating using NH ₂ ) ₂ ) is disclosed.

JP-A-5-202488

However, when white rust is prevented by chromate treatment of the surface of galvanized iron products or iron-base alloy products, hexavalent chromium is a carcinogenic substance. There is a problem in terms of the problem. Although trivalent chromium is improved in terms of toxicity, there are problems in performance such as inferior corrosion resistance compared to hexavalent chromium, and there is a concern that it is oxidized in the atmosphere and changed to hexavalent chromium. .
When direct manganese plating is applied to iron products or iron-base alloy products, there is a problem that it is necessary to apply a relatively thick manganese plating, which is costly.
Furthermore, when white rust is prevented by forming a dense coating film on the surface of the zinc plating applied to the iron product or the iron-based alloy product, there is a problem that the coating film will eventually peel off.

Therefore, a new plating film that can prevent white rust on the zinc surface applied to iron products or iron-based alloy products is being sought. Moreover, the plating solution which can aim at the improvement at the time of plating on the zinc surface is also searched. In particular, there is a search for a plating solution that has good adhesion even when the pH of the plating solution is near neutral, or even when the current density is low, and is difficult to burn even at a high current.
The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent white rust of zinc plating applied to iron products or iron-based alloy products, and to be safe for the human body and concerned about environmental problems. It is an object to provide an inorganic rust-preventing film, a plating method for iron products or iron-base alloy products, and a plating solution used therefor.
The other object of the present invention is to improve the adhesion, and the adhesion is good under plating conditions that do not invade the base (zinc). An object of the present invention is to provide a method for plating an iron-based alloy product and a plating solution used therefor.

In order to solve the above problems, the inorganic rust preventive film according to the present invention,
A zinc coating formed on an iron product or an iron-base alloy product;
It consists of a manganese film formed on the zinc film.
In this case, the film thickness of the zinc coating is 5 μm or more and 20 μm or less,
The thickness of the manganese film is preferably 0.5 μm or more and 10 μm or less.

The plating method of the iron product or iron-based alloy product according to the present invention,
A galvanizing step of obtaining an iron-based material B having a zinc film formed on its surface by immersing an iron-based material A, which is an iron product or an iron-based alloy product, in a zinc plating solution;
A manganese plating step of obtaining an iron-based material C having a manganese film formed on its surface by immersing the iron-based material B in a manganese plating solution,
The manganese plating solution is
Manganese sulfate is 100 g / L or more and 150 g / L or less,
50 g / L or more and 150 g / L or less of ammonium sulfate or ammonium citrate,
Rhodanammon is 25 g / L or more and 80 g / L or less,
Any one selected from the group consisting of ammonium citrate, ammonium tartrate, and ammonium malate, 10 g / L or more and 30 g / L or less,
Any one selected from the group consisting of sodium hypophosphite, hydrazine sulfate and other reducing agents, 10 g / L or more and 30 g / L or less,
One selected from the group consisting of ethylenediaminetetraacetic acid disodium, amines and other chelating agents or brighteners, greater than 0 and 5 g / L or less,
The gist is to contain 1 to 50 ml / L of ammonium hydroxide and other pH adjusters.

  In this case, the manganese plating solution may include at least one of the group consisting of a cobalt salt, a nickel salt, a zinc salt, a tin salt, and an indium salt.

The plating solution of the iron product or iron-based alloy product according to the present invention is:
Manganese sulfate is 100 g / L or more and 150 g / L or less,
50 g / L or more and 150 g / L or less of ammonium sulfate or ammonium citrate,
Rhodanammon is 25 g / L or more and 80 g / L or less,
Any one selected from the group consisting of ammonium citrate, ammonium tartrate, and ammonium malate, 10 g / L or more and 30 g / L or less,
Any one selected from the group consisting of sodium hypophosphite, hydrazine sulfate and other reducing agents, 10 g / L or more and 30 g / L or less,
One selected from the group consisting of ethylenediaminetetraacetic acid disodium, amines and other chelating agents or brighteners, greater than 0 and 5 g / L or less,
The gist is to contain 1 to 50 ml / L of ammonium hydroxide and other pH adjusters.

The inorganic rust preventive film according to the present invention is composed of a zinc film formed on an iron product or an iron-based alloy product, and a manganese film formed on the zinc film. In addition to being able to prevent, there is an effect that the human body is safe and there is no concern about environmental problems.
According to the iron product or iron-base alloy product plating method according to the present invention, since it includes a galvanizing step and a manganese plating step, the iron product or iron-base alloy product is used as a material to be plated. In addition to preventing white rust from galvanization, there is an effect that an inorganic rust preventive film that is safe for the human body and free from environmental problems can be obtained.
According to the plating method and the plating solution of the iron product or the iron-based alloy product according to the present invention, since the plating solution has a predetermined composition, it is possible to perform plating with good coverage without damaging the base (zinc). effective. In addition, there is an effect that burns, pits (gas pools) and the like are not easily generated. Furthermore, even if the tank load (the size of the tank with respect to the object to be plated), the current density, the current value, and the like are various values, there is an effect that plating can be performed with good coverage.

It is a figure which shows an example of the inorganic rust preventive film which concerns on this embodiment, The figure (a) shows the example which used the planar thing as a base material, The figure (b) is the surface, such as a screw, as a base material The example using what is uneven | corrugated is shown.

  Hereinafter, a plating method for iron products or iron-base alloy products, a plating solution for iron products or iron-base alloy products, and an inorganic rust preventive film for iron products or iron-base alloy products according to an embodiment of the present invention with reference to the drawings. explain.

(Plating process of iron products or iron-base alloy products, and plating solution used therefor)
Examples of iron products or iron-base alloy products to be plated in this embodiment include screws, bolts, nuts, shafts, bearings, gears, pins, springs, other mechanical parts, and precision machine parts. It is not limited.
The plating process in the present embodiment includes (1) a degreasing process, (2) an acid dipping process, (3) a zinc plating process, (4) a nitric acid dipping process, (5) a manganese plating process, and (6) a drying process. Each of these steps will be described below.

(1) A degreasing process removes the oil and fat adhering to the metal surface of a to-be-plated object by performing electrolytic treatment for a predetermined time at predetermined temperature using a commercially available degreasing liquid. The degreasing liquid used in the degreasing step is not particularly limited, and can be arbitrarily selected depending on the type of oil and fat.

(2) The acid dipping step is a step of dipping the object to be plated that has undergone the degreasing step in a 5% to 100% hydrochloric acid solution (for example, a 25% hydrochloric acid solution or a 36% hydrochloric acid solution) for 10 seconds to 5 minutes. Thereby, the surface is activated and black rust and red rust called scale are removed.

(3) A galvanization process is a process of immersing the to-be-plated object which passed through the acid immersion process in the galvanization bath for 5 minutes-60 minutes. Thereby, the zinc film is plated with a thickness of 5 μm or more and 20 μm or less on the object to be plated that has undergone the acid dipping process. The thickness of the zinc film is more preferably 7 μm or more and 10 μm.
The zinc plating bath that can be used is not particularly limited. For example, an alkaline bath such as a cyan bath, a low cyan bath, a zincate bath, an amine bath, a neutral bath such as a zinc chloride bath, an acidic bath such as a zinc chloride bath, and zinc sulfate. A bath or the like can be used. Table 1 shows examples of a zinc cyanide plating bath, a zincate bath, and a chloride bath.

(4) The nitric acid dipping step involves immersing the object on which the zinc film is formed in a 0.1% to 1% nitric acid solution (for example, a 0.5% nitric acid solution) for 1 second to 1 minute (for example, 10 seconds). And a step of activating the surface of the object to be plated.

(5) The manganese plating step is a step of forming a manganese film having a thickness of 0.5 μm or more and 10 μm or less by immersing an object to be plated that has undergone the nitric acid dipping step in a manganese plating solution. The thickness of the manganese film to be formed is more preferably 1 μm or more and 5 μm or less. Table 2 shows an example of a manganese plating bath.

The reason why manganese sulfate is set to 100 g / L or more and 150 g / L or less is that if the amount is too small, the surroundings will be poor and scorching will easily occur in the high current portion. Because.
The reason why the amount of ammonium sulfate or ammonium citrate is set to 50 g / L or more and 150 g / L or less is that if it is too small, it tends to burn, and if it is too much, the attachment is worsened.
The reason why the amount of rhodanammon is 25 g / L or more and 80 g / L or less is that if it is too small, it will be burnt easily, and if it is too much, the attachment will be poor.
The reason why any one selected from the group consisting of ammonium citrate, ammonium tartrate and ammonium malate is 10 g / L or more and 30 g / L or less is that if it is too small, it is easy to burn, and if it is too much, it is uneconomical.
The reason why any one selected from the group consisting of sodium hypophosphite, hydrazine sulfate and other reducing agents is set to 10 g / L or more and 30 g / L or less is that if it is too small, a high current is required, and if it is too much, it is attached. This is because the surroundings tend to get worse.
The reason why any one selected from the group consisting of disodium ethylenediaminetetraacetate, amines, and other chelating agents or brightening agents is set to more than 0 and not more than 5 g / L is that if the amount is too small, the plating becomes rough and is too much. This is because the attachment is easy to get worse.
The reason why ammonium hydroxide and other pH adjusting agents are set to 1 ml / L or more and 50 ml / L or less is that if the amount is small, a high current is required so that zinc does not dissolve in the plating solution. It is.
The current density is preferably 1 A / dm ² or more and 20 A / dm ² or less, particularly preferably 10 A / dm ² . The reason for this is that if it is low, the area around it tends to be bad, and if it is high, it will burn.
The pH is preferably 5.5 to 8.0, and particularly preferably 5.5 to 6.5. It is because a to-be-plated object will not melt if it is this range.
The temperature is preferably 20 ° C. or more and 50 ° C. or less, and particularly preferably 40 ° C. This is because if it is low, it will burn, and if it is high, the attachment will tend to deteriorate.

(6) A drying process is a process of drying the to-be-plated object which passed through the manganese plating process. As a drying method, warm air drying, natural drying, or the like can be employed, and there is no particular limitation.

(Inorganic rust preventive film of iron products or iron-base alloy products)
FIG. 1 shows the structure of an inorganic rust preventive film N according to the present embodiment. FIG. 1 (a) shows an example in which a flat substrate is used as the substrate, and FIG. 1 (b) shows a screw or the like as the substrate. The example using what the surface of this is uneven | corrugated is shown. As shown in the figure, the inorganic rust preventive coating N is made of a base material J (that is, an iron product or an iron-based alloy product such as a screw, bolt, nut, shaft, bearing, gear, pin, spring, or other mechanical parts, A zinc coating K formed on the surface of an iron product such as a precision machine part or an iron-based alloy product) and a manganese coating M formed on the surface of the zinc coating K. Instead of the manganese film M, a manganese / cobalt film, a manganese / nickel film, or a manganese / zinc film may be used. The inorganic rust preventive film N according to the present embodiment can be produced through the plating step, but is not limited thereto.
The film thickness of the zinc film K and the film thickness of the manganese film M is preferably about 2: 1 to 5: 1 as a ratio. The film thickness of the zinc coating K is preferably 6 μm to 10 μm, and particularly preferably 8 μm. The thickness of the manganese film M is preferably 0.5 μm to 2.5 μm, and particularly preferably 2 μm.

Examples of the present invention and comparative examples will be described below.
(Example 1 and Example 2)
For Examples 1 and 2, an M8 bolt made of iron (hexagonal bolt with a diameter of 13 mm) was used as an object to be plated, (1) degreasing step, (2) acid dipping step, (3) galvanizing step, (4) nitric acid dipping An inorganic rust preventive film N (see FIG. 1B) was formed by performing each step of the step, (5) manganese plating step, and (6) drying step. Each process is as follows.

(1) In the degreasing step, an electrolytic treatment was performed at 50 ° C. for 2 minutes using an Okuno Pharmaceutical Industrial Ascreen 850 as a commercially available degreasing solution.
(2) In the acid immersion step, the substrate was immersed in a 25% hydrochloric acid solution for 1 minute.
(3) In the galvanizing step, M8 bolts were immersed in the galvanizing bath shown in Table 3 for 25 minutes under the conditions shown in the same table to form an 8 μm thick zinc film on the M8 bolts.
(4) In the nitric acid immersion step, M8 bolts were immersed in a 0.5% nitric acid solution for 10 seconds.
(5) In the manganese plating step, M8 bolts are immersed in a manganese plating solution for 1 minute, 2 minutes, 3 minutes (made in three ways), and 1 μm, 2 μm, 3 μm manganese film is formed on the zinc film. Formed.
(6) In the drying step, M8 bolts were dried by hot air drying.

(Comparative Example 1)
For Comparative Example 1, each of the M1 bolt made of iron (hexagon bolt of 13 mm diameter) to be plated was subjected to (1) degreasing step, (2) acid dipping step, (3) manganese plating step, and (4) drying step. By performing the process, a manganese film was formed. Each process is as follows.

(1) In the degreasing step, an electrolytic treatment was performed at 50 ° C. for 2 minutes using an Okuno Pharmaceutical Industrial Ascreen 850 as a commercially available degreasing solution.
(2) In the acid immersion step, the substrate was immersed in a 25% hydrochloric acid solution for 1 minute.
(3) In the manganese plating process, M8 bolts were electrolyzed in the manganese plating solution for 1 minute, 2 minutes, and 3 minutes (made in three ways), and 1 μm, 2 μm, and 3 μm manganese films were formed on the surface of M8 bolts. The one formed was formed.
(4) In the drying step, M8 bolts were dried by hot air drying.

(Plating evaluation)
When the surroundings of the plating of Example 1 and Example 2 were visually confirmed, the brown coating of manganese could be observed, but the white coating of the lower layer zinc was not visible, so it was confirmed that the surroundings of plating were good did it. On the other hand, in the comparative example 1, the lower layer M8 bolt substrate was visible in some places. That is, in Example 1 and Example 2, since the plating can be performed even when the pH of the plating bath is increased, there is no concern that the dissolution of manganese plating starts from the moment when electricity is turned off even if the current density is low. Therefore, it is thought that the white coating of zinc was not visible. On the other hand, in Comparative Example 1, since the pH is low, even if the current density is increased and plating is performed, the manganese plating starts to dissolve when the power is turned off. As a result, the plating starts to dissolve in the plating solution. Therefore, it is considered that the lower layer substrate was visible.

(Evaluation test and evaluation results)
A salt spray test (JIS Z2371) was carried out for 48 hours on the plated M8 bolts produced in Example 1, Example 2 and Comparative Example 1. That is, 5% saline solution (35 ° C.) was sprayed on the plated M8 bolt for 48 hours to confirm whether white rust or the like was generated. In Example 1 and Example 2, white rust and red rust did not occur, but in Comparative Example 1, red rust occurred. From this, it was found that when a manganese film was formed on the zinc film, an excellent corrosion resistance was obtained.

  Although the inorganic rust preventive film according to one embodiment of the present invention, the plating method for forming the inorganic rust preventive film, and the plating solution used therefor have been described, the present invention is limited to the above embodiment. Rather, various modifications are possible.

  The inorganic rust preventive film according to the present invention, the plating method for forming the inorganic rust preventive film, and the plating solution used therefor are screws, bolts, nuts, shafts, bearings, gears, pins, springs and other mechanical parts. It can be put to practical use for plating precision machine parts. Moreover, according to the plating method for forming the inorganic rust preventive film according to the present invention and the plating solution used therefor, barrel plating and cage plating are possible, so that mass production more than conventional can be put into practical use.

Claims (5)

A zinc coating formed on an iron product or an iron-base alloy product;
An inorganic rust-proof coating comprising a manganese coating formed on the zinc coating. The thickness of the zinc film is 5 μm or more and 20 μm or less,
The inorganic rust-proof coating according to claim 1, wherein the manganese coating has a thickness of 0.5 µm or more and 10 µm or less. A galvanizing step of obtaining an iron-based material B having a zinc film formed on its surface by immersing an iron-based material A, which is an iron product or an iron-based alloy product, in a zinc plating solution;
A manganese plating step of obtaining an iron-based material C having a manganese film formed on its surface by immersing the iron-based material B in a manganese plating solution,
The manganese plating solution is
Manganese sulfate is 100 g / L or more and 150 g / L or less,
50 g / L or more and 150 g / L or less of ammonium sulfate or ammonium citrate,
Rhodanammon is 25 g / L or more and 80 g / L or less,
Any one selected from the group consisting of ammonium citrate, ammonium tartrate, and ammonium malate, 10 g / L or more and 30 g / L or less,
Any one selected from the group consisting of sodium hypophosphite, hydrazine sulfate and other reducing agents, 10 g / L or more and 30 g / L or less,
One selected from the group consisting of ethylenediaminetetraacetic acid disodium, amines and other chelating agents or brighteners, greater than 0 and 5 g / L or less,
A plating method for an iron product or an iron-based alloy product, comprising ammonium hydroxide and other pH adjusters in a range of 1 ml / L to 50 ml / L.   4. The iron product or iron-based alloy product according to claim 3, wherein the manganese plating solution contains at least one member selected from the group consisting of a cobalt salt, a nickel salt, a zinc salt, a tin salt, and an indium salt. Plating method. Manganese sulfate is 100 g / L or more and 150 g / L or less,
50 g / L or more and 150 g / L or less of ammonium sulfate or ammonium citrate,
Rhodanammon is 25 g / L or more and 80 g / L or less,
Any one selected from the group consisting of ammonium citrate, ammonium tartrate, and ammonium malate, 10 g / L or more and 30 g / L or less,
Any one selected from the group consisting of sodium hypophosphite, hydrazine sulfate and other reducing agents, 10 g / L or more and 30 g / L or less,
One selected from the group consisting of ethylenediaminetetraacetic acid disodium, amines and other chelating agents or brighteners, greater than 0 and 5 g / L or less,
A plating solution for an iron product or an iron-based alloy product, comprising ammonium hydroxide and other pH adjusters in an amount of 1 ml / L to 50 ml / L.

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