JP7303978B2 - Coating member and manufacturing method of coating member - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to covering members and methods of manufacturing covering members.

The corrosion resistance, weldability, and solderability of a metal substrate are improved by plating the surface of the substrate with nickel (Ni). Since nickel forms a passive state (Ni oxide film) on its surface, it is often used particularly to improve the corrosion resistance of substrates. For example, in an electric wire with a terminal that connects a conductor containing aluminum (Al) and a terminal containing copper (Cu), the terminal side is plated with nickel in order to suppress galvanic corrosion. Moreover, in view of the corrosion resistance of nickel, the substrate may be formed of Ni or a Ni alloy. For example, tab leads of lithium-ion batteries are sometimes made of Ni or Ni alloys.

Patent Literature 1 discloses a technique of forming a resin coating film on a nickel-plated steel sheet. This coating suppresses abrasion of the die due to the nickel plating layer when the nickel-plated steel sheet is deep-drawn. When a film is formed on the metal surface in this way, it is preferable to remove deposits such as oil on the metal surface by degreasing. In Patent Document 1, electrolytic degreasing is applied to a nickel-plated steel sheet to remove carbon-containing compounds on the plated surface.

JP 2013-249513 A

Further improvement of the corrosion resistance of the substrate may be required depending on the use of the substrate. However, since nickel having a Ni oxide film is originally excellent in corrosion resistance, almost no technology has been studied to form a film that further improves the corrosion resistance on the surface of the Ni oxide film.

One object of the present disclosure is to provide a coated member having a substrate having a Ni oxide film and having excellent corrosion resistance. Another object of the present disclosure is to provide a method for manufacturing a coated member that improves the corrosion resistance of a substrate having a Ni oxide film.

The covering member of the present disclosure is
comprising a base material and a chemical conversion coating,
The base material is
a surface layer composed of Ni or a Ni alloy;
and a Ni oxide film formed on the outside of the surface layer,
The chemical conversion coating is provided directly on the Ni oxide coating,
In the Ni oxide film, Ni(OH) ₂ /NiO, which is the ratio of the atomic concentration of Ni(OH) ₂ to the atomic concentration of NiO measured by HAXPES, is 0.25 or more.

The manufacturing method of the coated member of the present disclosure includes:
preparing a substrate having a surface layer composed of Ni or a Ni alloy and a Ni oxide film formed on the outside of the surface layer;
a step of subjecting the Ni oxide film to anodic electrolytic degreasing;
and performing a chemical conversion treatment on the Ni oxide film that has undergone the anodic electrolytic degreasing,
The anodic electrolytic degreasing is performed at a current density of 0.5 A/dm ² or more and 8.0 A/dm ² or less.

The coated member of the present disclosure has excellent corrosion resistance. In addition, the method of manufacturing a coated member according to the present disclosure can produce a coated member with excellent corrosion resistance.

FIG. 1 is a schematic cross-sectional view of a covering member exemplified in Embodiment 1. FIG. FIG. 2 is a schematic configuration diagram of a terminal exemplified in Embodiment 2. FIG. FIG. 3 is a schematic configuration diagram of a heat radiating member exemplified in Embodiment 3. FIG. FIG. 4 is a schematic configuration diagram of a tab lead exemplified in Embodiment 4. FIG. FIG. 5 is a graph showing the relationship between the depth from the surface and the element content at each depth in the coated member subjected to anodic electrolytic degreasing under the conditions according to the embodiment. FIG. 6 is a graph showing the relationship between the depth from the surface of the coated member shown in FIG. 5 and the ratio of NiO/Ni at each depth. FIG. 7 is a graph showing the relationship between the depth from the surface of the coated member subjected to cathodic electrolytic degreasing and the element content at each depth. FIG. 8 is a graph showing the relationship between the depth from the surface of the coated member shown in FIG. 7 and the ratio of NiO/Ni at each depth.

The present inventors studied forming a chemical conversion film on the Ni oxide film on the base material. At that time, the inventors examined what kind of pretreatment is most suitable for the Ni oxide film. As a result, by applying anodic electrolytic degreasing to the Ni oxide film under predetermined conditions, the Ni oxide film grows thicker than the natural oxide film, and the chemical conversion film formed on the Ni oxide film is the Ni oxide film. was found to adhere strongly to It was also found that the ratio of the Ni compound contained in the Ni oxide film showed a characteristic numerical value. Based on these findings, the covering member of the present disclosure is defined below.

[Description of Embodiments of the Present Disclosure]
Embodiments of the present disclosure are listed and described below.

<1> The covering member according to the embodiment is
comprising a base material and a chemical conversion coating,
The base material is
a surface layer composed of Ni or a Ni alloy;
and a Ni oxide film formed on the outside of the surface layer,
The chemical conversion coating is provided directly on the Ni oxide coating,
In the Ni oxide film, Ni(OH) ₂ /NiO, which is the ratio of the atomic concentration of Ni(OH) ₂ to the atomic concentration of NiO measured by HAXPES, is 0.25 or more.

The coated member according to the embodiment has, for example, superior corrosion resistance as compared with a conventional coated member having only a Ni plating layer. The reason why the coated member according to the embodiment exhibits excellent corrosion resistance is that the chemical conversion film is formed directly on the Ni oxide film, and the chemical conversion film is firmly adhered to the Ni oxide film. Here, the chemical conversion film is a film obtained by chemical conversion treatment. Chemical conversion treatment is a surface treatment method in which a stable compound is formed on a metal surface by chemical treatment (from JIS Z 0103: rust prevention and corrosion prevention terms).

The reason why the above chemical conversion coating firmly adheres to the Ni oxide coating of the base material is that the Ni oxide coating grows thicker than the natural oxide coating by anodic electrolytic degreasing at a predetermined current density, and the Ni oxide coating contributes to the formation of the chemical conversion coating. It is presumed that this is because it is in a suitable state. Normally, the Ni native oxide film is about 1 nm, but the Ni oxide film of the coated member according to the embodiment is about 2 nm to 3 nm.

Further, it can be confirmed by HAXPES (Hard X-ray Photoelectron Spectroscopy) that the Ni oxide film is obtained through anodic electrolytic degreasing. When anodic electrolytic degreasing is performed using the base material as an anode, a large amount of Ni(OH) ₂ is formed on the Ni oxide film. Therefore, by HAXPES, if Ni(OH) ₂ /NiO is 0.25 or more, it is found that the Ni oxide film was obtained through anodic electrolytic degreasing.

Here, HAXPES can perform non-destructive elemental analysis of a sample using hard X-rays, which are high-energy X-rays. Since the detection depth of HAXPES is generally 10 nm or more from the surface of the sample, it is sufficiently large compared to the thickness of the Ni oxide film of the coated member. Therefore, the information on Ni(OH) ₂ /NiO obtained by HAXPES can be considered to be information on the entire Ni oxide film in the thickness direction.

<2> As one form of the covering member according to the embodiment,
In the surface side of the Ni oxide film, NiO/Ni, which is the ratio of the atomic concentration of NiO to the atomic concentration of Ni measured by XPS, is 0.20 or more.

It can also be confirmed by XPS (X-ray Photoelectron Spectroscopy) that the Ni oxide film is obtained through anodic electrolytic degreasing. Specifically, when the NiO/Ni ratio on the surface side of the Ni oxide film is 0.20 or more, it is found that the Ni oxide film is obtained through anodic electrolytic degreasing. XPS is also called ESCA (Electron Spectroscopy for Chemical Analysis).

Here, XPS analyzes a sample using soft X-rays with lower energy than hard X-rays. Therefore, when analyzing the covering member of the embodiment, a concave portion is formed on the surface of the covering member by sputtering or the like, and information in the concave portion is obtained.

<3> As one form of the covering member according to the embodiment,
A form in which the entire base material is Ni or a Ni alloy is exemplified.

A substrate made of Ni or a Ni alloy has high corrosion resistance. A coated member of an embodiment in which a chemical conversion coating is further formed on such a substrate has superior corrosion resistance.

<4> As one form of the covering member according to the embodiment,
The surface layer may be plated with Ni or a Ni alloy.

According to the above configuration, the material of the base material can be selected according to the application. For example, when conductivity is required for the covering member, the base material is made of copper or a copper alloy. In that case, a surface layer made of Ni plating or Ni alloy plating is formed on the surface of the substrate in order to enhance the corrosion resistance of the substrate.

<5> As one form of the covering member according to the embodiment,
Examples of the chemical conversion film include a form containing trivalent Cr or Zr.

As the chemical conversion treatment, chromate treatment using hexavalent chromium is generally used. However, in recent years, non-chromate treatment has become mainstream in consideration of environmental problems. Examples of such non-chromate treatment include trivalent chromium chemical conversion treatment and zirconium chemical conversion treatment. According to these chemical conversion treatments, the chemical conversion film contains trivalent chromium (Cr) or zirconium (Zr).

<6> A method for manufacturing a coated member according to an embodiment includes:
preparing a substrate having a surface layer composed of Ni or a Ni alloy and a Ni oxide film formed on the outside of the surface layer;
a step of subjecting the Ni oxide film to anodic electrolytic degreasing;
and performing a chemical conversion treatment on the Ni oxide film that has undergone the anodic electrolytic degreasing,
The anodic electrolytic degreasing is performed at a current density of 0.5 A/dm ² or more and 8.0 A/dm ² or less.

Examples of electrolytic degreasing include cathodic electrolytic degreasing, in which the object to be degreased is the cathode, and anodic electrolytic degreasing, in which the object to be degreased is the anode. In cathodic electrolytic degreasing, hydrogen gas is generated in the vicinity of the object to be degreased, and the hydrogen gas removes deposits on the surface of the object to be degreased. On the other hand, in anodic electrolytic degreasing, oxygen gas is generated in the vicinity of the object to be degreased, and the oxygen gas removes deposits on the surface of the object to be degreased. Oxygen gas is generated in the vicinity of the object to be degreased by decomposing H ₂ O into oxygen (O ₂ ) and protons (H ⁺ ). In anodic electrolytic degreasing, an oxide film is formed on the surface of the object to be degreased. Therefore, the oxidized film is usually removed from the surface of the object to be degreased after anodic electrolytic degreasing by pickling.

The inventors investigated the optimum electrolytic degreasing for further forming a chemical conversion film on the Ni oxide film which is excellent in corrosion resistance. As a result, in anodic electrolytic degreasing of the Ni oxide film, by setting the current density of the anodic electrolytic degreasing to 0.5 A/dm ² or more and 8.0 A/dm ² or less, the surface of the Ni oxide film was improved for the formation of the chemical conversion film. It was found to be in a suitable state. NiO, Ni(OH) ₂ , NiOOH and the like are formed on the surface of the Ni oxide film subjected to anodic electrolytic degreasing as shown in the following chemical reaction formulas. These Ni compounds are presumed to improve the adhesion of the chemical conversion film to the Ni oxide film.
Chemical reaction formula: Ni+2OH ⁻ →NiO+H ₂ O+2e ⁻
Ni+2OH ⁻ →Ni(OH) ₂ +2e ⁻
Ni(OH) ₂ +OH ⁻ →NiOOH+H ₂ O+e ⁻

By treating the Ni oxide film by anodic electrolytic degreasing at the above current density, the Ni oxide film grows thick and the surface of the Ni oxide film is modified to a state suitable for forming a chemical conversion film. If the current density for anodic electrolytic degreasing is less than 0.5 A/dm ² , the Ni oxide film will hardly grow and the surface of the Ni oxide film will not be in a state suitable for forming a chemical conversion film. On the other hand, if the current density for anodic electrolytic degreasing exceeds 8.0 A/dm ² , a large amount of protons are generated in the vicinity of the Ni oxide film, and the pH drops extremely, so that the grown Ni oxide film dissolves. put away. As a result, the thickness of the Ni oxide film is not thickened, and the surface of the Ni oxide film is not in a state suitable for forming a chemical conversion film.

<7> As one form of the manufacturing method of the coated member according to the embodiment,
A step of washing with water after the anodic electrolytic degreasing,
An example is a form in which the chemical conversion treatment is performed without pickling.

As already mentioned, the object to be degreased that has undergone anodic electrolytic degreasing is usually pickled. However, in the manufacturing method of the coated member according to the embodiment, the Ni oxide film is grown and the Ni oxide film is reformed by anodic electrolytic degreasing. Therefore, when the Ni oxide film is pickled, the modified Ni oxide film may be removed. Therefore, by performing chemical conversion treatment without pickling after anodic electrolytic degreasing, the adhesion of the chemical conversion coating to the Ni oxide coating can be improved.

[Details of the embodiment of the present disclosure]
A specific example of a covering member according to an embodiment of the present disclosure and a method of manufacturing the covering member will be described with reference to the drawings. The same reference numerals in the drawings indicate the same or corresponding parts. The present invention is not limited to these examples, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

<Embodiment 1>
≪Covering material≫
FIG. 1 schematically shows a cross section of a covering member 1 according to an embodiment. As shown in FIG. 1 , the coated member 1 according to the embodiment includes a base material 10 , a Ni coating (surface layer) 11 , a Ni oxide coating 12 and a chemical conversion coating 13 . FIG. 1 is a schematic diagram, and the thickness ratio of each layer in FIG. 1 differs from the actual one. Each configuration of the covering member 1 will be described in detail below.

[Base material]
The base material 10 is made of metal. The material of the base material 10 is not particularly limited. Examples of materials for the base material 10 include Al, Al alloys, Mg (magnesium), Mg alloys, Cu, and Cu alloys. Substrate 10 may be Ni or a Ni alloy. If the substrate 10 is Ni or a Ni alloy, the Ni coating 11 is not present. In that case, the portion on the surface side of the substrate 10 is the surface layer.

Here, the X alloy (X is a metal element) is an alloy containing the largest amount of X among the elements constituting the X alloy. For example, a Ni alloy is an alloy with the highest Ni content.

[Ni coating]
The Ni coating 11 is made of Ni or a Ni alloy. The Ni coating 11 is formed by plating, for example. In the example shown in FIG. 1, the Ni coating 11 is formed only on one surface of the substrate 10, but the Ni coating 11 may be formed on the entire surface of the substrate 10. FIG.

The thickness of the Ni coating 11 is not particularly limited. In order to increase the corrosion resistance of the base material 10, it is preferable to increase the thickness of the Ni coating 11. FIG. Considering the time and effort required to form the Ni coating 11, it is preferable to make the Ni coating 11 thin. Considering the balance between corrosion resistance and productivity, the thickness of the Ni coating 11 is preferably 0.5 μm or more and 10 μm or less, for example. A more preferable thickness of the Ni coating 11 is, for example, 1 μm or more and 6 μm or less.

[Ni oxide film]
The Ni oxide film 12 is a passive state formed on the outside of the Ni coating 11 . The Ni oxide film 12 is formed by oxidizing Ni contained in the Ni coating 11 .

The Ni oxide film 12 of this example is obtained by subjecting a natural Ni oxide film to anodic electrolytic degreasing, which will be described later. A natural oxide film of Ni is about 1 nm. On the other hand, the Ni oxide film 12 of this example is about 2 nm to 3 nm. The reason why the Ni oxide film 12 is thicker than the Ni natural oxide film is that the Ni oxide film 12 is obtained through anodic electrolytic degreasing at a predetermined current density.

It can be confirmed by HAXPES that the Ni oxide film 12 is obtained through anodic electrolytic degreasing. When anodic electrolytic degreasing is performed using the base material 10 as an anode, a large amount of Ni(OH) ₂ is formed on the Ni oxide film 12 . Therefore, if the ratio of the atomic concentration of Ni(OH) ₂ to the atomic concentration of NiO, Ni(OH) ₂ /NiO, is 0.25 or more by HAXPES, the Ni oxide film 12 can be obtained through anodic electrolytic degreasing. It can be seen that it is a thing that was taken. HAXPES measurement conditions are shown in Test Example 1 described later.

Here, HAXPES can perform non-destructive elemental analysis of a sample using hard X-rays, which are high-energy X-rays. Since the detection depth of HAXPES is generally 10 nm or more from the surface of the sample, it is sufficiently large compared to the thickness of the Ni oxide film of the coated member. Therefore, the information on Ni(OH) ₂ /NiO obtained by HAXPES can be considered to be information on the entire Ni oxide film in the thickness direction.

It can also be confirmed by XPS that the Ni oxide film 12 is obtained through anodic electrolytic degreasing. Specifically, when NiO/Ni, which is the ratio of the atomic concentration of NiO to the atomic concentration of Ni on the surface side of the Ni oxide film 12, is 0.20 or more, the Ni oxide film 12 is obtained through anodic electrolytic degreasing. It can be seen that the XPS measurement conditions are shown in Test Example 2 described later.

Here, XPS analyzes a sample using soft X-rays with lower energy than hard X-rays. Therefore, when analyzing the covering member 1 of the embodiment, a concave portion is formed in the surface of the covering member 1 by sputtering or the like, and measurement data at the bottom of the concave portion is obtained. In practice, the depth of the concave portion is gradually increased, and measurement data is acquired each time. In the present embodiment, when the atomic concentration (atomic %) of the main elements of the chemical conversion coating detected by XPS and the atomic concentration of Ni are equal, it is considered that the concave portions have reached the surface of the Ni oxide coating. For example, in the case of a Zr-based chemical conversion film, when the atomic concentration of Zr detected by XPS becomes equal to the atomic concentration of Ni, it is considered that the concave portions have reached the surface of the Ni oxide film. Therefore, NiO/Ni in this embodiment is obtained from measurement data in which the atomic concentrations of the main elements and Ni are equal.

[Chemical film]
Conversion coating 13 is a stable compound formed on the metal surface by chemical treatment. Examples of the chemical conversion coating 13 include a chemical conversion coating 13 containing chromate of trivalent chromium, a chemical conversion coating 13 containing zirconium salt, and the like. In addition, a chemical conversion film 13 containing phosphate is included.

The thickness of the chemical conversion film 13 is not particularly limited. For example, the thickness of the chemical conversion coating is 1 nm or more and 100 nm or less. A preferable thickness of the chemical conversion film 13 is 5 nm or more and 50 nm or less.

The coating member 1 described above has excellent corrosion resistance. This is because the chemical conversion film 13 is formed directly above the Ni oxide film 12 . Further, since the surface of the Ni oxide film 12 is modified to a state suitable for forming the chemical conversion film 13, the adhesion of the chemical conversion film 13 to the Ni oxide film 12 is high. The adhesion of this chemical conversion film 13 also contributes to the improvement of the corrosion resistance of the coated member 1 .

≪Method for producing coated member≫
The covering member 1 of the embodiment shown in FIG. 1 is obtained by a manufacturing method comprising the following steps.
Preparing step: The substrate 10 having the Ni oxide film 12 is prepared.
• Degreasing step: anodic electrolytic degreasing is performed on the Ni oxide film 12 to promote the growth of the Ni oxide film 12 .
Water washing step: The substrate 10 is washed with pure water.
- Chemical conversion treatment step: the Ni oxide film 12 is subjected to a chemical conversion treatment to form the chemical conversion film 13 right above the Ni oxide film 12 .

[Preparation process]
The substrate 10 is not particularly limited as long as it has a surface layer made of Ni or a Ni alloy. For example, the substrate 10 made of Ni or a Ni alloy can be used. A base material 10 having a Ni coating 11 made of Ni or a Ni alloy is also included. In this case, the portion other than the Ni coating 11 is composed of a metal element or alloy other than Ni or Ni alloy.

[Degreasing process]
The anodic electrolytic degreasing is electrolytic degreasing in which the base material 10 is immersed in a degreasing treatment liquid and an electric current is applied using the base material 10 as an anode. Due to this anodic electrolytic degreasing, the Ni oxide film 12 grows thick, and the surface of the Ni oxide film 12 becomes suitable for forming the chemical conversion film 13 .

The degreasing liquid is an alkaline solution. Examples of the degreasing liquid include a NaOH (sodium hydroxide) solution. The pH of the alkaline solution is preferably 11 or more and 13 or less.

Anodic electrolytic degreasing is performed at a current density of 0.5 A/dm ² or more and 8.0 A/dm ² or less. If the current density is 0.5 A/dm ² or more and 8.0 A/dm ² or less, the Ni oxide film 12 grows thick and the surface of the Ni oxide film 12 is reformed to a state suitable for forming the chemical conversion film 13. be done. On the other hand, when the current density is less than 0.5 A/dm ² , the Ni oxide film 12 does not grow thick. Also, when the current density exceeds 8.0 A/dm ² , the Ni oxide film 12 does not grow thick. It is speculated that if the current density is too high, the grown Ni oxide film 12 will dissolve. A preferable current density is 0.5 A/dm ² or more and 5.0 A/dm ² or less. A more preferable current density is 1.0 A/dm ² or more and 3.0 A/dm ² or less.

The degreasing time can be selected as appropriate. For example, the degreasing time may be 1 second or more and 60 seconds or less. If the degreasing time is short, the Ni oxide film 12 is difficult to grow thick. When the thickness of the Ni oxide film 12 becomes thick to some extent, the Ni oxide film 12 hardly becomes thick. Therefore, even if the degreasing time is too long, the time is just wasted. A more preferable degreasing time is 3 seconds or more and 10 seconds or less.

[Washing process]
In order to remove the degreasing solution from the surface of the substrate 10, the substrate 10 is washed with water. For example, the degreasing liquid may be removed from the surface of the substrate 10 by showering with pure water.

Here, generally, the degreased object subjected to anodic electrolytic degreasing is washed with water after being pickled. This is to remove the oxide film formed on the surface of the object to be degreased by the anodic electrolytic degreasing. However, in this embodiment, the Ni oxide film 12 is grown by anodic electrolytic degreasing. Therefore, in this embodiment, pickling, which may remove the surface of the Ni oxide film 12, is not performed.

[Chemical treatment]
The chemical conversion treatment is performed, for example, by applying a chemical conversion treatment solution to the surface of the Ni oxide film 12 subjected to anodic electrolytic degreasing. A commercial item can be used for the chemical conversion treatment liquid. In consideration of the environment, the chemical conversion treatment liquid is preferably a non-chromate chemical conversion treatment liquid. For example, a trivalent chromium chemical conversion treatment solution or a Zr-based chemical conversion treatment solution is suitable.

After applying the chemical conversion treatment liquid, it is preferable to dry the chemical conversion treatment liquid. The drying time is preferably a time according to the specifications of the chemical conversion treatment solution.

<Embodiment 2>
The covering member 1 of Embodiment 1 can be used for the terminal 2 electrically connected to the conductor 50 of the electric wire 5, as shown in FIG.

The terminal 2 of this example comprises a wire barrel 20 crimped onto a conductor 50 . From the viewpoint of weight reduction, the conductor 50 is preferably an Al alloy. Moreover, from the viewpoint of conductivity, the terminal 2 is preferably made of a Cu alloy. For example, in a combination in which the conductor 50 is an Al alloy and the terminal 2 is a Cu alloy, galvanic corrosion can be suppressed by applying the configuration of the covering member 1 of the first embodiment to the terminal 2 .

<Embodiment 3>
The covering member 1 of Embodiment 1 can be used for the heat radiating member 3 attached to the heating element 6, as shown in FIG.

The heat dissipating member 3 of this example includes a main body portion 30 that contacts the heating element 6 and fins 31 that are provided on the opposite side of the main body portion 30 from the heating element 6 . As the material of the base material of the heat radiating member 3, for example, AlSiC, which is a combination of Al and SiC (silicon carbide), or MgSiC, which is a combination of Mg and SiC, is suitable. When the heat radiating member 3 is welded to the heating element 6, it is preferable that the surface of the heat radiating member 3 that contacts the heating element 6 is coated with Ni. In such a configuration, the corrosion resistance of the heat radiating member 3 can be improved by forming a chemical conversion film on the Ni oxide film formed on the surface of the Ni coating.

<Embodiment 4>
The covering member 1 of Embodiment 1 can be used for a tab lead 4 provided in a lithium ion battery 7, as shown in FIG.

The lithium ion battery 7 of this example includes an enclosure 70 that seals the electrolyte. A portion of the tab lead 4 is connected to an electrode plate (not shown) located inside the enclosure 70 . That is, part of the tab lead 4 is immersed in the electrolytic solution. In such a configuration, by applying the configuration of the covering member 1 of the first embodiment to the tab lead 4, the corrosion resistance of the tab lead 4 can be improved.

<Test Example 1>
In Test Example 1, a plurality of coated members (Samples 1-1 to 1-3 8 ) were produced by subjecting a substrate to chemical conversion treatment. Then, Ni(OH) ₂ /NiO in the Ni oxide film of each sample was measured, and various corrosion resistance tests were conducted.

[Preparation process]
The substrate was either a Ni plate, a MgSiC plate with Ni plating, a Cu plate with Ni plating, or an Al (JIS A1050) plate with Ni plating. All substrate dimensions were 60 mm long, 30 mm wide and 1 mm thick.

[Degreasing process]
Substrates were degreased either by anodic electrolytic degreasing, cathodic electrolytic degreasing, or immersion degreasing. The conditions for each degreasing are as follows.

The anodic electrolytic degreasing was performed by immersing the substrate in a 2.5% by mass NaOH aqueous solution. The current density for anodic electrolytic degreasing was either 0.3 A/dm ² , 0.5 A/dm ² , 2.0 A/dm ² or 9.0 A/dm ² . All processing times were 5 seconds.

Cathodic electrolytic degreasing was performed by immersing the substrate in a 2.5% by mass NaOH aqueous solution. The current density of the cathodic electrolytic degreasing was 2 A/dm ² and the processing time was 5 seconds.

Immersion degreasing was performed by immersing the substrate in a 2.5% by mass NaOH aqueous solution. Bubbling was performed during immersion. The immersion time was 5 seconds.

[Chemical treatment process]
The degreased base material was washed with water and subjected to chemical conversion treatment. In the chemical conversion treatment, the substrate was coated with a chemical conversion treatment liquid and dried at 100° C. for 5 minutes. The chemical conversion treatment liquid was Top Tripassive (manufactured by Okuno Chemical Industry Co., Ltd.) or Surfcoat EC1000 (manufactured by Nippon Paint Co., Ltd.). Top Tripassive is a conversion treatment solution that forms a conversion coating with trivalent chromate. Surfcoat EC1000, on the other hand, is a chemical conversion treatment liquid that forms a chemical conversion film having a Zr salt.

[Measurement of Ni oxidation state]
For each sample, the oxidation state of Ni in the Ni oxide film was evaluated by HAXPES. The conditions of HAXPES are as follows.
・Measured at Spring-8 BL16XU line ・X-ray energy: 8 keV
・Energy calibration: Ni metal of Ni2p ・Photoelectron extraction angle: 50°
・BL conditions: Si (111) double crystal spectroscope and Si (111) channel cut crystal spectroscope ・Front mirror Rh: 3.5 mrad
・Back mirror: None ・Detector: Photoelectron analyzer (R4000 manufactured by Scienta Omicron)

Analysis of data obtained by HAXPES was performed using analysis software (trade name: multipack) manufactured by ULVAC-Phi, Inc. The atomic concentration (%) of Ni(OH) ₂ and the atomic concentration (%) of NiO were determined by analysis software, and Ni(OH) ₂ /NiO was determined by calculation. The results are shown in Tables 1 and 2.

[Corrosion resistance test]
Each sample was subjected to a salt spray test, a high temperature and high humidity test, and an electrolyte immersion test. The salt spray test is a test in which 35° C. and 5 mass % NaCl water are sprayed for 96 hours (JIS Z 2371:2015). The high-temperature high-humidity test is a test in which the sample is placed in an atmosphere of 85% humidity and 85° C. for 1000 hours (JIS C 60068-2-78:2015). In addition, an electrolytic solution immersion test for examining the corrosion resistance of a lithium ion battery (LiB) to an electrolytic solution was performed by immersing a sample in a lithium ion battery electrolytic solution containing 1000 ppm by mass of water at 60° C. for two weeks. Tables 1 and 2 show the results of these corrosion resistance tests. In the salt spray test, a sample without pitting corrosion was rated as "Good" and a sample with pitting corrosion was rated as "Bad". In the high-temperature and high-humidity test, a sample without discoloration was rated as "Good", and a sample with discoloration was rated as "Bad". In the electrolytic solution immersion test (LiB electrolytic solution resistance in the table), a sample without pitting corrosion was rated as "Good" and a sample with pitting corrosion was rated as "Bad".

As shown in Table 1, sample ^{no .} 1 to sample no. In No. 18, Ni(OH) ₂ /NiO was 0.25 or more. It was also found that the higher the current density of the anodic electrolytic degreasing, the higher the Ni(OH) ₂ /NiO. These sample nos. 1 to sample no. 18 showed no corrosion in any of the corrosion resistance tests.

As shown in Table 2, sample no. 19 to sample no. No. 26, and sample No. 26 subjected to immersion degreasing. 27 to sample no. 34 had a Ni(OH) ₂ /NiO of less than 0.25. Moreover, these sample nos. 19 to sample no. 34 showed corrosion in at least one corrosion resistance test.

On the other hand, as shown in Table 2, sample No. 2 with a current density of less than 0.5 A/dm ² or more than 8.0 A/dm ² even by anodic electrolytic degreasing. 35 to sample no. 38 had a Ni(OH) ₂ /NiO of less than 0.25. Moreover, sample no. 35 to sample no. In No. 38, corrosion was observed in corrosion resistance tests other than the high temperature and high humidity test.

[Confirmation of thickness of Ni oxide film]
Each sample was cut along its thickness direction and cross-sectional observation was performed. Cross-sectional observation was performed with a scanning transmission electron microscope. As a result, sample no. 1 to sample no. The thickness of the Ni oxide film of sample No. 18 is 19 to sample no. It was clearly larger than the thickness of the Ni oxide film of No. 38. Sample no. 19 to sample no. The thickness of the Ni oxide film of 38 is considered to be about the same as the natural oxide film.

[summary]
From the above results, it was clarified that the thickness of the Ni oxide film was increased by anodic electrolytic degreasing at a current density of 0.5 A/dm ² or more and 8.0 A/dm ² or less. It was also found that the anodic electrolytic degreasing increases the concentration of Ni(OH) ₂ contained in the Ni oxide film. As a result, it is considered that the surface of the Ni oxide film is modified so as to easily adhere to the chemical conversion film.

On the other hand, in cathodic electrolytic degreasing, immersion degreasing, and anodic electrolytic degreasing with a current density of less than 0.5 A/dm ² , the Ni oxide film does not grow, and the concentration of Ni(OH) ₂ contained in the Ni oxide film also increases. didn't. Therefore, it is considered that the surface of the Ni oxide film was not improved to a state in which it is easy to adhere to the chemical conversion film.

Here, the reason why the Ni oxide film did not grow in the anodic electrolytic degreasing with a current density exceeding 8.0 A/dm ² is assumed to be that a large amount of protons were generated in the vicinity of the anode. It is believed that the Ni oxide film dissolves because the protons lower the pH in the vicinity of the anode.

<Test Example 2>
In Test Example 2, sample No. 1 of Test Example 1 was used. 1 to No. The oxidation state of Ni in the Ni oxide film of No. 34 was measured by XPS.

In the measurement by XPS, a recess was formed on the surface of the sample by sputtering, and the recess was measured by XPS. Sputtering conditions are as follows.
・Ar (argon) beam accelerated at an acceleration voltage of 1 kV ・Sputtering speed: 5.59 nm/min

The conditions for XPS are as follows.
・ Measuring device: Quantera SXM (manufactured by ULVAC-Phi, Inc.)
・X-ray conditions: beam size: 100 μm, AlKα
・Incident angle…90°
・Photoelectron extraction angle … 45°
Analysis of the XPS measurement results was performed using analysis software (trade name: multipack) manufactured by ULVAC-Phi, Inc. The atomic concentration (%) of NiO and the atomic concentration (%) of Ni were determined by analysis software, and NiO/Ni was determined by calculation.

Here, in this test example 2, the depth at which the atomic concentration (atomic %) of Ni measured by XPS and the atomic concentration (atomic %) of Zr or Cr are equal was determined as the boundary between the Ni oxide film and the chemical conversion film. and calculated NiO/Ni. For example, sample no. The graph of FIG. 5 shows the relationship between the depth from the surface of the coating member at 16 and the atomic concentrations of Ni and Zr, and the graph of FIG. 6 shows NiO/Ni at each depth. Also, sample No. 1 subjected to cathodic electrolytic degreasing. The relationship between the depth from the surface of the coating member at 23 and the atomic concentrations of Ni and Zr is shown in the graph of FIG. 7, and the NiO/Ni at each depth is shown in the graph of FIG.

5 and 7, the horizontal axis is the depth (nm) from the surface of the coated member, and the vertical axis is the atomic concentration (atomic %) of Ni and Zr. 6 and 8, the horizontal axis is the depth (nm) from the surface of the coated member, and the vertical axis is the ratio of NiO/Ni. Tables 3 and 4 show the results of NiO/Ni. Tables 3 and 4 also show the results of the corrosion resistance test performed in Test Example 1.

As shown in Table 3, sample ^{no .} 1 to sample no. In No. 18, NiO/Ni was 0.20 or more. It was also found that the higher the current density of the anodic electrolytic degreasing, the higher the NiO/Ni ratio.

As shown in Table 4, sample no. 19 to sample no. No. 26, and sample No. 26 subjected to immersion degreasing. 27 to sample no. 34 had a NiO/Ni of less than 0.20.

As is clear from the above results, the measurement of NiO/Ni by XPS also shows that the Ni oxide film was obtained through anodic electrolytic degreasing.

Further, from the results of FIG. 6, it was found that NiO/Ni peaked near the surface of the Ni oxide film by subjecting the Ni oxide film to anodic electrolytic degreasing under predetermined conditions. On the other hand, from the results of FIG. 8, even if the Ni oxide film was treated by cathodic electrolytic degreasing, the NiO/Ni peak did not appear.

<Appendix>
In view of the results of Test Example 2, the following configuration can be mentioned as a coating member having excellent corrosion resistance.
≪Appendix 1≫
comprising a base material and a chemical conversion coating,
The base material is
a surface layer composed of Ni or a Ni alloy;
and a Ni oxide film formed on the outside of the surface layer,
The chemical conversion coating is provided directly on the Ni oxide coating,
A coated member, wherein in the Ni oxide film, NiO/Ni, which is the ratio of the atomic concentration of NiO to the atomic concentration of Ni measured by XPS, is 0.20 or more.

It can also be confirmed by XPS measurement of the Ni oxide film that the Ni oxide film is obtained through anodic electrolytic degreasing. Therefore, the coated member of appendix 1 is a coated member having excellent corrosion resistance in which the chemical conversion coating is firmly adhered to the Ni oxide coating.

REFERENCE SIGNS LIST 1 coating member 10 base material 11 Ni coating 12 Ni oxide coating 13 chemical conversion coating 2 terminal 20 wire barrel 3 heat radiation member 30 main body 31 fin 4 tab lead 5 electric wire 50 conductor 6 heating element 7 lithium ion battery 70 enclosure

Claims (6)

comprising a base material and a chemical conversion coating,
The base material is
a surface layer composed of Ni or a Ni alloy;
and a Ni oxide film formed on the outside of the surface layer,
The chemical conversion coating is provided directly on the Ni oxide coating,
In the Ni oxide film, Ni(OH) ₂ /NiO, which is the ratio of the atomic concentration of Ni(OH) ₂ and the atomic concentration of NiO measured by HAXPES, is 0.25 or more.
covering material. 2. The coated member according to claim 1, wherein NiO/Ni, which is the ratio of the atomic concentration of NiO to the atomic concentration of Ni measured by XPS, is 0.20 or more on the surface side of the Ni oxide film. 3. The coated member according to claim 1, wherein the entire base material is Ni or a Ni alloy. 3. The coated member according to claim 1, wherein the surface layer is Ni or Ni alloy plating. The coated member according to any one of claims 1 to 3, wherein the chemical conversion coating contains trivalent Cr or Zr. preparing a substrate having a surface layer composed of Ni or a Ni alloy and a Ni oxide film formed on the outside of the surface layer;
a step of subjecting the Ni oxide film to anodic electrolytic degreasing;
a step of washing with water after the anodic electrolytic degreasing;
a step of chemical conversion treatment without pickling the Ni oxide film that has undergone the anodic electrolytic degreasing,
The anodic electrolytic degreasing is performed at a current density of 0.5 A/dm ² or more and 8.0 A/dm ² or less.
A method for manufacturing a covering member.

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