JP3276501B2 - Chromate treated metal plate with high corrosion resistance and excellent lubricity and conductivity - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chromate-treated metal plate suitable for use in bare parts such as parts for home appliances, for example, audio and video chassis.

[0002]

2. Description of the Related Art In the manufacturing process of home appliances, OA equipment, etc., steel sheets, Al or Al-based alloy plated steel sheets, Al or Al
Various metal plates such as alloy plates are pressed.

[0003] Generally, at the time of these press workings,
Processing is performed by applying lubricating oil to a metal plate, and has the following problems. (1) Lubricating oil is often applied by spraying, and the lubricating oil is scattered around and the working environment is deteriorated. (2) After pressing, it is necessary to remove the lubricating oil, and in this degreasing step, a solvent (such as Freon, 1-1-1 trichloroethane, etc.) or an alkaline cleaning agent is used. For this reason, pollution prevention measures are required, which leads to an increase in cost and a deterioration in the working environment. As described above, from the viewpoint of environmental protection, there has been an increasing demand for a metal plate that can be molded without oil and used without degreasing after molding for the purpose of omitting the degreasing step. Until now, various composite coated steel sheets have been proposed in which a chromate film is coated with an organic resin containing a solid lubricant. Representative examples are shown below.

JP-A-60-103185 discloses that a first layer has a normal chromate layer and a second layer has a complex phosphoric acid A.
1, chromic acid, rust preventive pigment, polyolefin wax, M
oS bilayer steel sheet made of urethane-modified epoxy resin layer containing ₂ or silicon resin or the like is disclosed.

Japanese Patent Application Laid-Open No. Sho 61-227178 discloses a surface-treated steel sheet comprising a chromate layer as a first layer and an acrylic resin layer having a solid lubricant as a second layer.

Japanese Patent Application Laid-Open No. 61-227179 discloses a chromate layer as a first layer, a chromate, a silica sol, a mixture of a solid lubricant and a lubricating oil, a silane and / or titanate coupling agent as a second layer. A surface-treated steel sheet comprising an acrylic resin layer containing a colored pigment is disclosed.

JP-A-1-110140 discloses that a first layer is a chromate layer, and a second layer is colloidal silica 5-40.
An acrylic resin composite coated steel sheet containing a weight percent, a solid lubricant surface-treated with a titanate coupling agent, and an epoxy resin is disclosed.

However, the related art described above has a serious drawback in that since the resin layer is formed on the metal plate, the conductivity inherent in the metal plate is impaired.

In order to improve the conductivity,
JP-A-63-83172 containing conductive particles in resin
However, with the development of information devices in recent years, the required level of conductivity and grounding of the metal surface has increased, and these related technologies cannot satisfy these requirements.

In a computer chassis or the like, conductivity of surface electric resistance of 1Ω or less is required for electromagnetic wave shielding properties such as prevention of leakage of high-frequency electromagnetic waves and prevention of noise generation due to electromagnetic induction.

A disadvantage of the related art described above is that a resin layer is uniformly formed on a chromate layer in order to improve workability. Normally, the resin has a very high volume resistivity of about 10 ¹⁵ Ω · cm. Even when applied as a very thin film of about 1 μm, the resin is present on the surface of the metal plate as a layer having an interlayer resistance of 10 ¹⁰ Ω or more, This impaired the conductivity and grounding properties of the product.

Further, in the method of improving conductivity by adding conductive particles to these resin layers, it is necessary to add a large amount of particles in order to obtain sufficient conductivity with respect to recently required levels. There were problems such as impairing the resin coating operation and the properties of the resin, and causing so-called electrolytic corrosion (contact corrosion of dissimilar metals) due to contact between the conductive particles and the underlying metal, thereby impairing the corrosion resistance.

[0013]

The object of the invention is to solve] Accordingly, the present invention is, long-term
Chromate liquid with excellent stability, lubricating property to withstand press forming without oil coating, high conductivity with no problem in spot welding and grounding properties, and high corrosion resistance to withstand naked use It is an object of the present invention to provide a chromate-treated metal plate having the following.

According to the present invention, in a chromate-treated metal plate having a chromate layer on at least one surface of a metal substrate selected from an aluminum-plated steel plate, an aluminum alloy-plated steel plate, an aluminum plate, and an aluminum alloy plate, chromium adhered to the chromate layer The amount is 10 to ²⁰⁰ mg / m ² per one side in terms of metallic Cr, and silica is contained in the chromate layer in a weight ratio of SiO ₂ / Cr of 0.1 to 200 mg / m ^2.
6.0, and further containing graphite, Mo
Lubricity-imparting particles, which are particles having a surface layer having a nonionic surfactant on the surface of at least one type of lubricating particles selected from the group consisting of S ₂ , BN, calcium stearate, and an organic lubricating substance, are contained in the chromate layer. The lubricating particles contained in the chromate layer have a weight ratio of 0.1 to 100 in the range of 0.1 to 100, and 1% to 70% of the weight of the lubricity-imparting particles is a surface layer having a nonionic surfactant. A chromated metal sheet having high corrosion resistance, excellent lubricity, and excellent conductivity is provided.

In the present invention, the organic lubricating substance is preferably at least one type of lubricating particles selected from the group consisting of natural wax, polyolefin wax, modified polyolefin wax, and fluorocarbon.

Further, the chromate layer is mainly composed of trivalent chromium, and preferably contains at least 70% by weight or more of Cr insoluble in an aqueous alkali solution in the total Cr, based on the total amount of Cr. It is preferable that the coverage of the applied particles on the metal substrate surface is 50% or less.

The chromate-treated metal plate of the present invention has a chromate layer on at least one surface of a metal substrate selected from an aluminum-plated steel plate, an aluminum alloy-plated steel plate, an aluminum plate and an aluminum alloy plate, and the amount of chromium deposited on the chromate layer. Is 10 to 10
200 mg / m ² , and the silica in the chromate layer contains SiO ₂ / Cr in a weight ratio of 0.1 to 6.0, and further contains graphite, MoS ₂ , BN, calcium stearate and organic lubricity. Lubricity-imparting particles, which are particles having a surface layer having a nonionic surfactant on the surface of one or more lubricating particles of a substance, are contained in the chromate layer, and the lubricating particles / Cr have a weight ratio of 0.1. The surface layer has a nonionic surfactant activity in the range of 1 to 100, and 1% to 70% of the weight of the lubricity-imparting particles.

In the present invention, a chromate treatment solution containing silica and lubricity-imparting particles is applied onto the metal substrate with a bar coater, a roll coater, or the like, and the resulting solution is applied to a metal substrate.
Dried at about 0 to 300 ° C. to form a chromate layer,
Ensure corrosion resistance, conductivity, etc. The chromate treatment is desirably performed on both surfaces of the metal substrate, but may be performed on only one surface. Further, lubricating particles and lubricity-imparting particles may be mixed and used.

As described above, in the present invention, since the organic resin which inhibits the conductivity is not applied, sufficient conductivity can be easily secured in an appropriate range of the silica and the lubricity-imparting particles. Therefore, the present invention can be applied not only to the spot weldability but also to a part where the earth property is a problem.

According to the present invention, if the amount of chromium adhering to the chromate layer is less than 10 mg / m ^{2 in} terms of metallic Cr on one side, high performance in corrosion resistance after press working cannot be expected. On the other hand, if the adhesion amount of chromium exceeds 200 mg / m ^{2 in} terms of metallic Cr on one side, the film thickness becomes excessively large, so that the possibility of peeling of the film at the time of press working increases, and mold seizure easily occurs. For the above reasons, the amount of chromium deposited was 10 to ²⁰⁰ mg / m ² per one side in terms of metal Cr. If the amount of chromium insoluble in alkali in the chromate layer is less than 70% by weight based on the total amount of Cr, elution of chromium in the coating process or the like becomes a problem, and the amount of chromium insoluble in aqueous alkaline solution is 70% by weight or more of the total amount of chromium. Is preferred. The chromate treatment of the present invention is desirably performed on both surfaces of the metal plate, but may be performed on only one surface.

The chromate solution used here uses chromic anhydride, dichromic acid, chromate or the like as a chromium source, and mixes silica and lubricity-imparting particles. Further, an aqueous solution obtained by partially reducing chromic acid may be used. In addition to these, phosphoric acid may be contained.

Silica is mainly added to ensure corrosion resistance, and the addition is made when the weight ratio of SiO ₂ / Cr is 0.1%.
If the weight ratio of SiO ₂ / Cr is more than 6.0, the conductivity may be impaired.
The weight ratio of ₂ / Cr was set in the range of 0.1 to 6.0. The silica used in the present invention may be aqueous silica (colloidal silica or water-dispersible silica) or gas-phase silica produced by subjecting an organosilicon compound to thermal decomposition in a gas phase, but the average particle diameter is 100 μm or less. Is desirable.

The lubricity- imparting particles are added to ensure the lubricity of the metal plate. In the present invention, the graph
Aite, MoS ₂ , BN, calcium stearate, yes
Has surface-active properties on lubricating particles composed of mechanical lubricating substances
The particles on which the surface layer is formed are referred to as lubricity-imparting particles. Black
When manufacturing a mate treated metal plate
Stability is also an important factor in industry, use the same liquid for a long time
Nonionic boundaries lubricating particles instead of the lubricating particles in the case of
Using lubricity-imparting particles with surface active surface
You.

As the lubricating particles, graphite, MoS
₂ , one or more of BN, calcium stearate and an organic lubricating substance can be used in combination. However, if the average particle diameter exceeds 20 μm, the particles are liable to fall off from the coating, and these particles are added to a mold during processing. It is preferable that the average particle diameter is as fine as 20 μm or less, since the sediment easily accumulates due to particles and film fragments. Here, the average particle diameter refers to the Stokes average diameter determined by an optical method.

As the organic lubricating substance, natural wax,
Lubricated particles composed of one or more of polyolefin wax, modified polyolefin wax, and fluorocarbon can be used. The lubricating particles in the present invention are more preferably polyolefin wax (including polyethylene wax), oxidized polyolefin wax (including polyethylene oxide), and modified polyolefin wax (including modified polyethylene) such as halogen-modified and acid-modified from the viewpoint of press moldability. Wax) and fluorocarbons such as polytetrafluorocarbon.

[0026] The addition amount of the lubricity providing particles has no lubricity improving effect is less than 0.1 in a weight ratio of the lubricating particles / Cr, whereas when it exceeds 100 adhesion of the film is deteriorated, type in press Since it causes galling, the amount of the lubricity- imparting particles is limited to the range of 0.1 to 100 in terms of the weight ratio of lubricating particles / Cr.

In order to disperse the lubricating particles in the aqueous solution, the surface of the particles can be charged and electric repulsion can be used, or nonionic steric hindrance can be used. However, in general, the chromate solution has a high electrolyte concentration, and in a method utilizing electric repulsion, ions are adsorbed in a direction to neutralize the surface charge, whereby the repulsion between the particles is reduced, and as a result, the particles are aggregated. Resulting in. The aggregated particles precipitate or float and separate, and the function of the chromate solution containing the lubricating particles to impart lubricity gradually decreases.

Therefore, a layer having a nonionic surfactant is formed on the surface of the lubricating particles. The nonionic surfactant layer can be formed by adsorbing a nonionic surfactant or a water-soluble polymer to lubricating particles.

As nonionic surfactants, alkylphenol surfactants (R-φ-O- (CH ₂ CH ₂ O) nH, (R = C ₉ H)
₁₉ or C ₈ H ₁₇ , n = 2 to 50, R represents an alkyl group having a straight or simple side chain), a higher alcohol surfactant (RO (R′O) n (R ″ O) mH, (HLB value = 7-1)
6, R is an alkyl group having a straight or simple side chain (C _x H _{2x + 1} , X = 1 to 20), and R ′ and R ″ are an alkylene group having a straight or simple side chain (C _x H _2x ,
X = 1-20), n = 1-30, m = 1-30), polyalkylene glycol-based surfactant (RO (EO / P
O) nH, (R is an alkyl group having a straight or simple side chain (C _x H _{2x + 1} , X = 1 to 20), E = CH ₂ CH ₂ ,
P represents a propylene group, and n = 1 to 50). Examples of the water-soluble polymer include polyethylene glycol and polyvinyl alcohol.

If the nonionic surface layer is less than 1% by weight of the lubricity-imparting particles, the ability to disperse the particles is small, and the particles will aggregate and precipitate in the chromate solution. When the lubricating component (i.e., the lubricating particles) in the lubricating particles is less than 30% by weight, the contribution of lubricity is reduced. A lubricating substance (i.e., lubricating particles) inside the particles, and a range of 1% or more and 70% or less by weight of the lubricating particles is a surface layer having a nonionic surfactant.

When lubricating particles having a surface layer having a nonionic surfactant are used, the amount of the lubricating particles added is
The weight ratio of lubricating particles / Cr is preferably in the range of 0.1 to 100, and the average particle size of the lubricating particles is preferably 20 µm or less.

The coverage of the metal plate surface with the lubricity-imparting particles is preferably 50% or less. Coverage is 5
If it exceeds 0%, there is a possibility that a problem may occur in the conductivity and the like.

[0033]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. As a test material, a 55% Al-Zn hot-dip coated steel sheet having a coating amount of 60 g / m ² on each of the front and back surfaces of a cold-rolled steel plate (SPCC) having a thickness of 1 mm, and a coating amount of 4 on each of the front and back surfaces.
5g / m ² hot-dip aluminized steel sheet and JI
A SA5182 aluminum alloy plate was used.

The chromate solution is prepared by adding chromic anhydride to liquid phase silica having an average particle diameter of 14 nm (Snowtex O (trade name) manufactured by Nissan Chemical Industries, Ltd.) and gas phase silica having an average particle diameter of 7 nm (manufactured by Nippon Aerosil Co., Ltd.) Was adjusted arbitrarily using. In addition, the chromate solution was appropriately subjected to preliminary reduction using a reducing agent. Cr that did not dissolve in the alkaline aqueous solution was 85 to 95% by weight based on the total amount of Cr. The lubricating particles used in Table 1 are: Graphite B. MoS ₂ C.I. BN D. Calcium stearate Polyethylene wax F. PTFE (polytetrafluoroethylene wax)
It is.

The nonionic surfactants used in Table 1 are described in W.W. Lion Co., Ltd. Liponox NC-100: alkylphenol-based LEOCOL SC-90 manufactured by Lion Corporation: higher alcohol type Sanyo Kasei's PEG 1500: polyethylene glycol, but is not limited thereto.

The anionic and cationic surfactants used in Table 1 are described in Na lauryl sulfate anion Stearyl dimethylbenzylammonium chloride is a cationic system .

As a wax emulsion having a nonionic surface layer, a. Sanyo Kasei KUE-13 natural wax 29% wax in solids b. KUE-8 modified polyethylene wax manufactured by Sanyo Chemical Industries 86% wax in solid content was used.

As a wax emulsion having an anionic surface layer, c. EMUSTAR-0001 synthetic wax manufactured by Nippon Seisakuwa was used.

As a method of adsorbing a surfactant to lubricating particles such as MoS ₂ , BN, and polyolefin wax to obtain lubricity-imparting particles, first, an aqueous solution of the surfactant is prepared, and the lubricating particles are added. Aged with stirring.
Thereafter, a chromate solution was mixed to a required concentration. The lubricating particles A, B, C, D, E, and F used were particles whose particle diameters were adjusted to the values shown in Table 1 by a ball mill.

After mixing the lubricating particles or lubricity-imparting particles with the prepared chromate solution, it was immediately applied to the above-mentioned various metal substrates with a bar coater and dried at 150 ° C. Table 1 shows the conditions of the chromate film. After the liquid preparation, the liquid was stored for one week while stirring, then applied to a metal substrate with a bar coater, and dried at 150 ° C. Table 1 shows the conditions of the chromate film in this case. At this time, the amount of Cr attached to the chromate film was 50 mg / m ^{2 in} terms of metallic Cr, and
The weight ratio of iO ₂ / Cr was set to 3.0.

(Press Formability) The press formability was evaluated based on the following criteria. In the case of a plated steel sheet, a blank diameter 73
mm was determined to be able to be squeezed out without oiling and by the amount of powdering. ×: What cannot be drawn Δ: Can be drawn but the amount of powdering on the side wall is 0.5 g / m
^More than ² ○: Can be squeezed, but the amount of side wall powdering is 0.1 g / m
Exceeding ^{2 and not} more than 0.5 g / m ² ◎: No drawing, and the amount of powdering on the side wall is 0.1 g / m ²
m ² or less of those

In the case of an aluminum plate and an aluminum alloy plate, a blank diameter of 66 m was obtained in a cylindrical drawing test with a diameter of 33 mm.
m was determined to be able to be squeezed without oiling and by the amount of powdering. ×: What cannot be drawn Δ: Can be drawn but the amount of powdering on the side wall is 0.5 g / m
^More than ² ○: Can be squeezed, but the amount of side wall powdering is 0.1 g / m
Exceeding ^{2 and not} more than 0.5 g / m ² ◎: No drawing, and the amount of powdering on the side wall is 0.1 g / m ²
m ² or less of those

(Conductivity) Conductivity was evaluated using Mitsubishi Yuka's surface resistance meter Loresta MCP-
The surface resistance was measured and evaluated using a tester (trade name). The measurement was performed ten times, and the average value was evaluated. ◎: less than 0.1Ω ○: 0.1Ω or more and less than 0.5Ω △: 0.5Ω or more and less than 2Ω ×: 2Ω or more

(Corrosion resistance) The corrosion resistance was 5% in a salt spray test (JIS Z 2371).
A sample having a rusting time of less than 100 hours was evaluated as x, and a sample having a rusting time of 100 hours or longer was evaluated as ○.

(Ratio of Lubricating Component) The ratio of the lubricating component in the lubricity-imparting particles was determined by the ratio of the weight of the added lubricating particles to the weight of the solid content after adsorbing the surfactant.

The coverage of the metal plate surface with the lubricating particles or lubricity-imparting particles was determined by observing the surface with a SEM (× 100
0) was obtained as an average value of arbitrary 20 visual fields. The above evaluation results are also shown in Table 1.

As is clear from the above, all of the examples of the present invention shown in Table 1 show excellent press moldability (lubricity), conductivity and corrosion resistance.

When the chromate-treated solution was stored for 7 days (when applied 7 days after bathing shown in Table 1 ),
In Nos. 1 and 23, since no surfactant was used, lubricating particles aggregated and did not enter the chromate film, resulting in poor workability. N
o. In Nos. 2 and 24, the nonionic surfactant was insufficient, and the lubricity-imparting particles were aggregated and did not enter the chromate film, resulting in poor workability. No. Since 3 , 4 , 5 , 15 , and 25 are ionic surface layers, lubricity-imparting particles are aggregated and do not enter the chromate film, resulting in poor workability. No. 6 , 7 , 16 and 17 are poor in workability due to excessive surface active layer and insufficient lubricating particles.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

[0053]

According to the present invention, one or two or more kinds of products treated with one or more nonionic surfactants of graphite, MoS ₂ , BN, calcium stearate and an organic lubricating substance are used as lubricating particles. By adding an appropriate amount to the chromate film containing SiO ₂ , a chromate solution with excellent long-term stability was obtained and applied.
Then, it is possible to obtain a metal plate which can be pressed without oil coating, has high corrosion resistance, and has a surface electric resistance of 0.5Ω or less.

Continuation of the front page (56) References JP-A-3-219086 (JP, A) JP-A-2-34792 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22 / 00-22/86

Claims (4)

(57) [Claims] 1. A chromate-treated metal plate having a chromate layer on at least one surface of a metal substrate selected from an aluminum-plated steel plate, an aluminum alloy-plated steel plate, an aluminum plate and an aluminum alloy plate, wherein the amount of chromium deposited on the chromate layer is metallic Cr. 10-2 per side in conversion
00 mg / m ² , and silica in the chromate layer in a weight ratio of SiO ₂ / Cr in the range of 0.1 to 6.0, and further containing graphite, MoS ₂ , BN, calcium stearate and organic lubricity Lubricity-imparting particles, which are particles having a surface layer having a nonionic surfactant on the surface of at least one lubricating particle selected from the group consisting of substances, are contained in the chromate layer; It has a high corrosion resistance characterized in that the weight ratio of Cr is in the range of 0.1 to 100, and the range of 1% to 70% of the weight of the lubricity-imparting particles is the surface layer having a nonionic surfactant. Chromate treated metal plate with excellent lubricity and conductivity. Wherein the organic lubricant material is natural wax, polyolefin wax, modified polyolefin wax, and lubricity have high corrosion resistance as claimed in claim 1 is at least one lubricating particles selected from the group consisting of fluorocarbons Chromate treated metal plate with excellent conductivity. Wherein said chromate layer is mainly composed of trivalent chromium, according to claim 1, Cr which is insoluble in an aqueous alkaline solution in at least all Cr is contained 70 wt% or more based on the total amount of Cr
Or a chromate-treated metal plate having high corrosion resistance and excellent lubricity and conductivity according to 2 . Wherein said lubricity chromate treated metal excellent in lubricity and conductivity has a high corrosion resistance as claimed coverage of the metal substrate surface imparting particles to any one of claims 1 to 3 is 50% or less Board.