JPH01147096A - Production of slightly lustrous black steel material by alternating electrolysis - Google Patents

Abstract

PURPOSE:To produce a slightly lustrous black steel material having superior workability, weldability and corrosion resistance by plating a steel material with a specified amt. of a Zn-Ni alloy having a specified compsn. and by subjecting the plated material to alternating electrolytic treatment in a treating soln. contg. nitrate ions and Ni<2+> ions under specified conditions. CONSTITUTION:A steel material is plated with 10-40g/m<2> Zn-Ni alloy contg. 5-20% Ni. The plated material is subjected to alternating electrolytic treatment in a treating soln. contg. 1-100g/l nitrate ions and <=70g/l Ni<2+> ions under the conditions of 1:(0.1-30) ratio of cathodic treatment time:anodic treatment time, <=50Hz alternating cycle, 1-30sec total treatment time, 5-100A/dm<2> current density during anodic electrolysis and (0.1-20):1 ratio of anode current density:cathode current density. The treated material is then coated with a chromate film, etc., as required. The treating soln. is hardly deteriorated and a surface treated steel material having stable high blackness, superior workability, weldability, corrosion resistance, a high blackening degree and low luster is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing surface-treated steel materials, and more particularly to a method for manufacturing surface-treated steel materials that have a high degree of blackening and a low gloss level by an alternating electrolysis method.

<Prior art and its problems> Materials widely used for home appliances, copying machines, information communication devices, automobile interiors, interior building materials, etc. are manufactured by processing steel plates at manufacturers and then applying blackening treatment such as painting or chromate treatment. It is a product. However, in recent years, there has been an increasing demand for steel manufacturers to supply blackened surface-treated steel sheets for the purpose of eliminating process steps and reducing costs.

Particularly, in optical equipment such as copying machines, there is a demand for blackened surface-treated steel sheets that have a low gloss level in addition to the above-mentioned high degree of blackening in order to prevent light reflection.

Performances required for blackened surface-treated steel sheets include workability, weldability, corrosion resistance, and blackness.
Processing time of a few seconds) ■ Does not require major modification of the existing plating line ■ No deterioration of the processing solution ■ Uniform processing ■ Good black color tone ■ Good corrosion resistance ■ Good weldability ■Good workability [Phase] The film is not easily scratched.

Conventional blackening treatment methods include (i) black painting method;
f) Black chromate method, (iii) Chemical treatment method ((a)
JP-A-50-55546, (b) JP-A-52-762
37, (c) JP-A-52-76238, (d) JP-A-60-121275, (e) JP-A-60-1812.
77), (iv) Heat treatment method (JP-A-55-919)
93, JP-A-56-293), (V) Anodic electrolytic treatment method (JP-A-58-151490, JP-A-58-151)
491), (Vi) Cathodic electrolytic treatment method (JP-A-60-1
No. 90588).

However, (i) the black coating method requires painting equipment, requires expensive equipment investment, and increases manufacturing costs.

(if) The black chromate method requires a long reaction time and cannot be processed in an electroplating line. The drug is also expensive because it uses silver salts.

(iii) Chemical treatment methods (a) to (C) are a type of displacement plating that uses copper ions, and the temperature and concentration of the treatment liquid affect the reaction rate, and Zn etc. dissolve in the treatment liquid. Therefore, uniform black processing cannot be achieved in high-speed line production. Furthermore, sufficient film strength cannot be obtained from the blackened layer. (d) and (e) are oxidation reactions carried out in an aqueous nitric acid solution, and are basically the same as (a) to (C), in which Zn is added to the treatment solution.

Ni, etc. dissolve, and the processing liquid deteriorates in a short period of time.

Furthermore, the blackening layer thus formed also has a low degree of blackness, and only a bluish tone can be obtained.

(iv) The heat treatment method requires expensive equipment, and it is difficult to control uniform heating, making it difficult to control coloration.

(V) The anodic electrolytic treatment method is described in JP-A-58-151491 and JP-A-58-151490 as having the advantage that blackening can be controlled by the amount of electricity. but,
Plating metal may dissolve in the electrolyte, causing liquid deterioration.
Moreover, the plated metal has to be melted again, which is economically disadvantageous.

(vi) The cathodic electrolytic treatment method is an excellent treatment method in that it eliminates the dissolution of the plating layer, which is the drawback of (V), but the blackness cannot be obtained unless the blackening layer is relatively thick. The disadvantage is that the thicker the layer, the worse the strength and adhesion.

In order to solve the various problems in the prior art, the applicant has proposed a method for manufacturing surface-treated steel sheets with a high degree of blackening by employing an alternating electrolysis method.
It is disclosed as No. 125356. According to this method, a surface-treated steel material with a satisfactory degree of blackening can be obtained.

However, as mentioned above, especially in the field of optical equipment, there is a demand for blackened surface-treated steel materials with a low gloss level in order to prevent light reflection in addition to a high degree of blackening.

<Problems to be Solved by the Invention> As mentioned above, the drawback of the prior art is that the treatment with a strong black layer causes severe deterioration of the treatment solution, making it difficult to manufacture on an actual line. On the other hand, although the technique of forming a black layer by cathodic treatment causes little deterioration of the treatment solution, it has the disadvantage that the formed black layer has insufficient adhesive strength and peels off during bending or the like.

Therefore, in order to establish a processing method that has excellent adhesion and processability and provides a stable black color without deterioration of the processing solution, and furthermore, in order to establish a processing method that obtains the low gloss required depending on the application field, As a result of a detailed study of the above-mentioned conventional techniques, the present inventors have determined that the alternating electrolytic treatment method is a method that eliminates the drawbacks of (V) the anodic electrolytic treatment method and (vi) the cathodic electrolytic treatment method and obtains only the advantages. We have discovered a surface treatment method that provides a high degree of blackening and low gloss.

According to this alternating electrolytic treatment method, since anodic electrolytic treatment and cathodic electrolytic treatment are performed alternately, dissolution of metal into the electrolytic solution is reduced, and deterioration of the electrolytic solution is significantly suppressed.

<Objective of the Invention> The object of the present invention is to provide a low-gloss, high-blackening process using an alternating electrolytic method that has excellent workability, weldability, and corrosion resistance, with little deterioration of the processing solution, and a stable high blackness. An object of the present invention is to provide a method for manufacturing surface-treated steel.

<Configuration of the Invention> According to the first aspect of the present invention, after applying 10 to 40 g/m2 of Zn-Ni alloy plating containing 5 to 20% Ni to a steel material, the Zn-n-gold alloy plated material is 1~t o g/l
In a treatment solution containing nitrate ions of The cycle is 50Hz or less, the total processing time is 1
~30 seconds, the anodic electrolytic current density of the 1n-Ni alloy plated material is 5 to 100 A/dm2, and the ratio of the anodic current density to the negative 8i current density is 0.1 to 20:1. Provided is a method for producing a low-gloss black steel material by an alternating electrolytic method, which is characterized by subjecting the steel material to a low-gloss black steel material.

According to the second aspect of the present invention, after applying 10 to 40 g/rrl' of Zn-Ni alloy plating containing 5 to 20% Ni to the steel material, the Zn-N1 alloy plating material is applied at 1 to 100 g/rrl'.
In a treatment solution containing nitrate ions of Alternating cycle is 50Hz or less, total processing time is 1~
30 seconds, the anodic electrolytic current density of the Zn-Ni alloy plated material is 5 to 1008/dm2, and the ratio of the anode current density to the cathode current density is 0.1 to 20:1. A low-gloss black steel material produced by an alternating electrolytic method, characterized in that a chromate treatment is carried out with a chromate solution containing chromic anhydride as a main component to deposit a chromate film of 5 to 1 o mg/m2 in terms of Cr. A manufacturing method is provided.

According to the third aspect of the present invention, after applying 10 to 40 g/m2 of Zn-Ni alloy plating containing 5 to 20% Ni to a steel material, the Zn-Ni alloy plated material is coated with 1 to 100 g/l of nitric acid. In a treatment solution containing Ni2+ ions and 70 g71 or less of Ni2+ ions, the holding time at the anode and cathode is in the range of an anode treatment time ratio of 0.1 to 30 with respect to a cathode treatment time of 1, and the alternating period is 50 Hz. Below, the total processing time is 1~
30 seconds, the anodic electrolysis current density of the Zn-Ni alloy plated material was 5 to 1008/dm', and the ratio of the anode current density to the cathode current density was 0.1 to 20:1. After the treatment, water-dispersible or water-soluble resin or silicic acid sol is added in a dry weight of 0.3 to 3 g/rr? Provided is a method for producing a low-gloss black steel material by an alternating electrolytic method characterized by coating.

According to the fourth aspect of the present invention, Zn-Ni alloy plating containing 5 to 20% Ni is applied to the steel material at 10 to 40 g/rr? After the treatment, the 1n-Ni alloy plated material was held on the anode and cathode in a treatment solution containing 1 to 100 g/l of nitrate ions and 70 g/l or less of Ni'' ions, during cathodic treatment. The anodizing time ratio for time 1 is in the range of 0.1 to 30, and the alternating cycle is 50 Hz or less, and the total treatment time is 1 to 30.
30 seconds, the anodic electrolytic current density of the Zn-Ni alloy plated material is 5 to 100 A/drn', and the ratio of the anode current density to the cathode current density is 0.1 to 20:1. After application, chromate treatment is performed with a chromate solution containing chromic anhydride as the main component, and a chromate film of 5 to 100 mg/rrl' in terms of Cr is deposited.
There is provided a method for producing a low-gloss black steel material by an alternating electrolysis method, characterized in that a water-dispersible or water-soluble resin or silicic acid sol is applied at a dry weight of 0.3 to 3 g/m'.

The present invention will be explained in detail below.

The Zn-Ni alloy plating material containing 5 to 20% Ni, which is the object of the present invention, may be manufactured by any plating method such as electroplating, hot-dip plating, or vapor deposition plating. The base material to be plated may be a steel plate, an aluminum plate, a stainless steel plate, or the like.

Further, various plating may be performed on the lower layer of the Zn-old alloy plating layer containing 5 to 20% Ni, and the surface layer may be coated with the Zn-old alloy plating layer.
-Ni alloy plating layer should be formed in an amount of 10 to 40 g/m2. This is because if the plating layer is less than 10 g/m2, corrosion resistance will be poor, and if it exceeds 40 g/m2, workability will be poor.

The Ni content of the zn-Ni alloy plating is preferably 5 to 20%. If the Ni content is less than 5%, black color cannot be obtained, and 20
This is because if the Ni content exceeds 7%, the plated layer becomes hard and brittle, resulting in poor workability.In order to obtain a stable and good black color, the Ni content is preferably 7 to 18%.

In the present invention, the Zn-Ni alloy plating material is coated with 1 nitrate ion.
Surface treatment with a high degree of blackening is carried out by alternating electrolysis in a treatment solution containing up to 100 g/l and Ni''' ions of up to 70 g/l.

This is because if the nitrate ion content is less than 1 g/l, the blue color will be strong and the color will not be sufficiently black, and if it exceeds 100 g/l, it will become uneconomical. In addition, Ni2″″ ion is 708/l
Although it is effective for lowering gloss when it is higher than that, it is not preferable because the amount of Ni increases on the surface, which makes the plating layer hard and brittle.

Even more preferably, the effect is large in the range of 5 to 70 g/l.

In the alternating electrolysis method, the time for holding the Zn-Ni alloy plated material on the anode and cathode is set in the range of 0.1 to 30 seconds for the anode holding time to the cathode holding time of 1, and the total processing time is 1 to 30 seconds. do it.

The anodic electrolytic current density of the Zn-Ni alloy plated material in alternating electrolysis is in the range of 5 to 100 8/drn'', and the Zn-Ni
The anodic electrolytic current density of alloy plating material is cathodic electrolytic current density 1
0.1 to 20.

The alternating period should be in the range of 501 (z or less).

The reasons for limiting each of the above conditions are described below.

In the alternating electrolysis method, positive 8! The i/cathode processing time ratio and current density ratio greatly influence the degree of blackness and glossiness, and by limiting these, the level of glossiness can be controlled.

The present invention is characterized by adding Ni2+ ions to the treatment solution in advance to reduce gloss, and by adding N12+ ions, the anode/cathode treatment time ratio and current density ratio can be widened. was completed.

Regarding the treatment time, the ratio of the anode treatment time to the cathode treatment time of 1 is in the range of 0.1 to 30, and the anode current density is in the range of 0.1 to 20 to the current density of 1 to achieve low gloss and A product with a good degree of blackening can be obtained.

If the anodic treatment time is less than 0.1 with respect to the cathode treatment time of 1, the L value will be extremely high, and if it exceeds 30, high gloss will result and the deterioration of the treatment solution will also increase. In addition, cathode current density 1
On the other hand, when the anode current density exceeds 20, the gloss is no longer low, and when it is less than 0.1, the L value becomes extremely high.

If the alternating period exceeds 50 Hz, the polarity changes before electrolytic equilibrium is reached, so the rate of black layer formation slows down and black color cannot be obtained.

Next, the anodic electrolysis current density is 5 ^/drr? If it is less than 100^/dn'1'', the dissolution of the plating layer will increase and the formation of the black layer will be delayed, and if it exceeds 100^/dn'1'', the efficiency of the formation of the black layer will similarly deteriorate.

After alternating electrolytic treatment under the above conditions, to improve corrosion resistance,
Chromate treatment is performed, and the chromate film has a Cr count of 5.
It is preferable to deposit ~100mg/m2.

The chromate treatment method does not need to be particularly limited, and known reactive chromates, coating chromates, electrolytic chromates, etc. can be used. Is the amount of Cr attached 5mg/rr? If it is less than that, there will be no chromate treatment effect and no improvement in corrosion resistance. 1
00 mg/rr? Even if it exceeds the above, the corrosion resistance will be saturated, and the adhesion of the coating film will deteriorate when resin coating, painting, etc. are performed.

By applying a water-dispersible or water-soluble resin or silicic acid sol after the alternating electrolytic treatment or after performing the chromate treatment after the alternating electrolytic treatment, it is possible to increase the depth of the black color and significantly improve corrosion resistance. can. The coating amount of these resins and silicic acid sol is 03 to 3 g/m2
(dry weight) range is good. If it is less than 0.3 g/m2, the above-mentioned effect will not be obtained by coating. If it exceeds 3 g/m2, the appearance will be good, but weldability will be extremely poor. Examples of water-dispersible or water-soluble resins include carboxylated polyethylene resins, acrylic resins, epoxy resins, polyurethane resins, and melamine resins.

Note that the differences between the alternating electrolysis method and the simple anodic electrolysis method are as follows.

That is, in the anodic electrolysis method, there is only a reaction of dissolving the metal surface, and the dissolved metal ions accumulate in the electrolyte, causing the electrolyte to deteriorate. In the alternating electrolysis method of the present invention, metal ions dissolved during anodic electrolysis are electrodeposited onto the metal surface again during cathode electrolysis, so accumulation of metal ions in the electrolyte can be suppressed and the life of the electrolyte can be extended. It will be significantly longer and the loss of plating metal will be kept to a minimum.

In addition, in the alternating electrolysis method, since melting-electrodeposition-dissolution is repeated, depressions are created in the Zn-Ni plating layer during melting, and electrodeposition occurs on the projections during electrodeposition, resulting in the formation of fine craters. It is easy to blacken and can be blackened in a short time and with a small amount of electricity.

In the present invention, in addition to nitrate ions, Ni2'' ions are added to the treatment solution for alternating electrolysis. As a result, the Ni'' ions and Zn- By utilizing the fact that metal ions eluted from N1 plating are preferentially electrodeposited on convex parts, the surface is further roughened to maintain high blackness while reducing gloss to the required level. be able to.

In the present invention, since Ni'' ions are added in advance to the treatment solution, a correspondingly large amount of metal is deposited on the convex portions during electrodeposition. Therefore, the anode/cathode treatment time ratio and current density ratio can be varied over a wide range.

<Example> Next, the present invention will be explained in more detail based on examples.

[Examples and comparative examples]

Zn--Ni alloy plated steel sheets were treated using the treatment solution having the composition shown in Table 1 and the treatment conditions to obtain various blackened surface-treated steel sheets. Test pieces were taken from the obtained blackened surface-treated steel sheets, and performance evaluations were conducted on blackness, gloss, corrosion resistance, workability, film adhesion, black durability, film strength, and weldability tests. The results shown in 1 were obtained.

Each performance test method and its evaluation were performed using the following methods.

〔Test method〕

(1) Blackness As an index representing the blackness of the surface of the steel sheet subjected to the blackening treatment, the color tone, a and b values were measured using a 3M color computer manufactured by Suga Test Instruments Co., Ltd., and evaluated by the L value. The L value is divided into 0 to 100 levels, and - for boat fishing, high L values are white and low L values are black.

(2) Glossiness As an index representing the glossiness of the surface of the blackened steel plate, the G value (60° glossiness) was measured using an SM color computer manufactured by Suga Test Instruments ■, and evaluation was made using this. This G
The value represents the magnitude of the intensity of reflected light at an incident angle of 60°, and generally, the higher the G value, the higher the gloss, and the lower the G value, the lower the gloss.

(3) Corrosion resistance test A salt spray test was conducted on the flat plate portion and the 90° bent portion. The salt spray test was conducted in accordance with JIS-Z-2371. The test piece was evaluated by sealing the end face and measuring the time required for the amount of white rust to reach 5% in terms of area ratio.

(4) Workability test (a) DuPont impact test: diameter 12.7 mm (1/
A 2-inch) punch is used to drop a weight of I kg from a height of 50 cm, and the film is peeled off by applying Sellotape to the impact area. Evaluation was made based on the degree of peeling of the film.

(b) Erichsen extrusion test: A steel plate is extruded 61 times using an Erichsen extrusion tester, cellophane tape is adhered to the convex portion, and the film is peeled off. Evaluation was made based on the degree of peeling of the film.

Evaluation ◎: No peeling O: Several % peeling 6710 - 30% peeling ×: 31% or more peeling (5) Adhesion of the film Cut 10 squares of 2+++ m square on the film with a cutter knife.
0 incisions are made and cellophane is adhered to these 100 squares to peel off the film.

Evaluation was made based on the number of peeled eyes as follows.

Evaluation 5: No peeling evaluation 4: Peeling first, number of stitches 1 to 10 evaluation 3: Peeling first stitch number 11 to 30 pieces evaluation 2: Peeling first stitch number 31
~50 pieces evaluation 1: Number of peeling holes 51 pieces or more (
6) Black durability test: Only irradiated with ultraviolet rays using a sunshine weather meter.
Tested for 240 hours. Color tone of the specimen surface before and after the test (
L, a, b values) were measured, and the color difference ΔE was determined and evaluated.
When the ΔE value is 0.5 or less, the durability is extremely excellent.

△E= (7) Film strength test A load of 2 kg was applied to the filter paper surface of 10×20III11.
The film was reciprocated 100 times at a distance of 0 cm, and the degree of peeling of the film due to this suppression was observed and evaluated.

Evaluation ◎: No peeling ○: Slight peeling △: Slight peeling ×: Significant peeling (8) Welding machine used for weldability test Nispot welding machine (semi-synchronous type) Electrode material, shape: Cr-Cu, CF type 4.5 mmφ Rated capacity: 35 KVA Input voltage: 200V Pressure force: 150Kg Welding time: 10Hz Welding current = Vary from 5 to 12KA in 0.5KA increments.

Welding was performed under the above welding conditions and evaluated based on the welding current range from nugget formation to welding with the electrode and the degree of splintering.

Evaluation welding current range: The wider the range, the better the occurrence of splintering: Evaluated at the welding current value at which failure started to occur.A Splattering occurs at near KA or higher.B: Spatter occurs at A between 5.5 and 6.5.C: Spatter occurs at 5KA. Occurrence <Effect of the invention> In the conventional blackening treatment method, the blackness of the Zn-Ni alloy plated material is insufficient and only a black color close to gray can be obtained. It was necessary to add organic substances such as Furthermore, in the blackening treatment by anodic oxidation, the electrolyte deteriorates in a short time because dissolved metal accumulates in the electrolyte.

According to the present invention, a deep black color (L value of 13 or less) can be easily obtained even with Zn-Ni alloy plating.

Furthermore, since the plating surface is further roughened, low gloss can be obtained. Another major advantage is that deterioration of the electrolyte can be significantly suppressed. Furthermore, since Ni2+ ions are added in advance to the alternating electrolytic treatment solution, a correspondingly large amount is deposited during electrodeposition.

Therefore, the anode/cathode treatment time ratio and current density ratio can be varied over a wide range.

Furthermore, since it has excellent properties such as weldability, corrosion resistance, blackness, and black durability, it can be widely used in home appliances, copying machines, automobile interior materials, etc. In particular, since it has a low gloss level, it is useful in fields such as optical equipment that require prevention of light reflection.

cl;1・-2 Hizuji

Claims (4)

[Claims] (1) After applying 10 to 40 g/m^2 of Zn-Ni alloy plating containing 5 to 20% Ni to steel material, the Zn-Ni alloy plating material is coated with 1 to 100 g/l of nitrate ion and 70 g
In a processing solution containing less than /l of Ni^2^+ ions,
The holding time at the anode and the cathode is in the range of an anode treatment time ratio of 0.1 to 30 with respect to the cathode treatment time 1, and the alternating period is 50 Hz or less, the total treatment time is 1 to 30 seconds, and the Zn -The anodic electrolytic current density of Ni alloy plating material is 5~
A method for producing a low-gloss black steel material by an alternating electrolytic method, characterized in that the electrolytic treatment is carried out at 100 A/dm^2 and at a ratio of anode current density to cathode current density of 0.1 to 20:1. (2) After applying 10 to 40 g/m^2 of Zn-Ni alloy plating containing 5 to 20% Ni to the steel material, the Zn-Ni alloy plating material was coated with 1 to 100 g/l of nitrate ion and 70 g
In a processing solution containing less than /l of Ni^2^+ ions,
The holding time at the anode and the cathode is in the range of an anode treatment time ratio of 0.1 to 30 with respect to the cathode treatment time 1, and the alternating period is 50 Hz or less, the total treatment time is 1 to 30 seconds, and the Zn -The anodic electrolytic current density of Ni alloy plating material is 5~
After electrolytic treatment at 100 A/dm^2 and a ratio of anode current density to cathode current density of 0.1 to 20:1, chromate treatment is performed with a chromate solution containing chromic anhydride as the main component, Chromate film is 5 to 10 in terms of Cr.
A method for producing a low-gloss black steel material by an alternating electrolysis method, characterized by depositing 0 mg/m^2. (3) After applying 10 to 40 g/m^2 of Zn-Ni alloy plating containing 5 to 20% Ni to the steel material, the Zn-Ni alloy plating material was coated with 1 to 100 g/l of nitrate ion and 70 g.
In a processing solution containing less than /l of Ni^2^+ ions,
The holding time at the anode and the cathode is in the range of an anode treatment time ratio of 0.1 to 30 with respect to the cathode treatment time 1, and the alternating period is 50 Hz or less, the total treatment time is 1 to 30 seconds, and the Zn -The anodic electrolytic current density of Ni alloy plating material is 5~
After electrolytic treatment with a current density of 100 A/dm^2 and a ratio of anode current density to cathode current density of 0.1 to 20:1, a water-dispersible or water-soluble resin or silicic acid sol is added to the dry weight of 0. A method for producing a low-gloss black steel material by an alternating electrolysis method, characterized in that the coating is applied at a rate of 3 to 3 g/m^2. (4) After applying 10 to 40 g/m^2 of Zn-Ni alloy plating containing 5 to 20% Ni to the steel material, the Zn-Ni alloy plating material was coated with 1 to 100 g/l of nitrate ions and 70 g
In a processing solution containing less than /l of Ni^2^+ ions,
The time for holding the electrode and the cathode is in the range of 0.1 to 30 as a ratio of anode treatment time to cathode treatment time 1, and the alternating period is 50 Hz or less, the total treatment time is 1 to 30 seconds, and the Zn -The anodic electrolytic current density of Ni alloy plating material is 5~
After electrolytic treatment at 100 A/dm^2 and a ratio of anode current density to cathode current density of 0.1 to 20:1, chromate treatment is performed with a chromate solution containing chromic anhydride as the main component, Chromate film is 5 to 10 in terms of Cr.
After adhering 0mg/m^2, add water-dispersible or water-soluble resin or silicic acid sol to 0.3-3g/m by dry weight.
A method for producing a low-gloss black steel material by an alternating electrolytic method characterized by applying ^2 coating.