JPH0754192A - Method for chromium plating - Google Patents

Abstract

PURPOSE:To omit a pre-plating process, improve the plating rate and prevent microcracking in the plating layer by directly executing plating with chromium on iron-base and copper-base metals which are considered not suitable for direct chromium plating under vibrating and stirring conditions. CONSTITUTION:A process of copper plating and nickel plating on surfaces of iron-base metal, zinc-base metal or electroless copper-plated metal formed on plastics, a process of nickel plating on the surface of copper-base metal, and a process of base plating on the surface of aluminum-base metal can be omitted. Chromium plating is directly applied on surfaces of these metals under stirring and vibrating conditions by a vibrator motor with 15-60Hz frequency.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a chrome plating method for performing chrome plating directly on a metal surface which is said to be impossible to chrome plating directly on the metal surface while vibrating and stirring.

[0002]

2. Description of the Related Art In hard chrome plating, it is unavoidable that fine cracks are generated in the plating film, and in a corrosive environment, these cracks become points of corrosion, and multiple cracks occur along the cracks. Corrosion progresses. In order to suppress these corrosions as much as possible, a conventional undercoating process of copper, nickel or the like has been indispensable in hard chrome plating. For example, chrome plating on iron-based metal is often used for the purpose of rust prevention and decoration, but if chrome plating is applied directly on the iron-based metal, cracks will occur and the rust-preventive effect will be small, so it will not be applied on the iron-based metal. First, copper plating was applied, followed by nickel plating, and then chromium plating. Degreasing of ferrous metal surface → Washing with water →
Pickling → water washing → copper strike → copper plating → water washing → nickel plating → water washing → chrome plating. Even so, the generation of cracks could not be completely avoided, and satisfactory plating could not be obtained, and the fact is that each company is doing their secret technique. Plating for plastics is mainly done for decorative purposes. After chemical plating (usually chemical copper plating or chemical nickel plating), copper plating, then nickel plating, and then chromium plating are performed. It is being appreciated. Degreasing of plastics surface → Pre-etching → Etching → Catalyzing → Accelerating → Electroless copper plating → Washing → Copper plating → Washing → Nickel plating → Washing → Chrome plating. In this case as well, when the chromium plating is suddenly performed on the chemical plating layer, cracks occur. Also, in the case of plating on zinc-based metal, after copper-plating on the zinc-based metal, then nickel plating,
Chrome plating is performed. Degreasing of zinc-based metal surface → Washing → Pickling → Washing → Copper strike → Copper plating → Washing → Nickel plating → Washing → Chrome plating. Al, Al alloy, C
The same applies to u and Cu alloys. In this way, it is possible to perform direct chrome plating on metal surfaces such as iron-based metals, plastics and zinc-based metals, copper-based metals, and aluminum-based metals, which are said to be incapable of direct chrome plating on the metal surface. If possible, the step of copper plating or nickel plating as a pre-stage of chrome plating is not necessary, and its industrial significance is extremely large. It would be even better if the chrome plating process itself could be made faster than ever.

[0003]

[Objective] The present invention uses conventional methods to perform chrome plating on metal surfaces, such as iron-based metals, plastics, zinc-based metals, copper-based metals, and aluminum-based metals, which were considered impossible to perform direct chrome plating. It is to provide a novel chrome plating method which omits a certain pre-plating step, speeds up the chrome plating rate, and is free from the occurrence of microcracks in the obtained chrome plating layer.

[0004]

[First Structure] A first aspect of the present invention relates to a chrome plating method characterized in that a chrome plating is performed directly on a metal surface which is said to be impossible to be directly chrome plated on the metal surface under vibration and stirring. A second aspect of the present invention relates to a chrome plating method characterized in that, when chrome plating is performed on an iron-based metal surface, the chrome plating is performed directly under vibration and stirring without going through a copper plating step-nickel plating step.
The third aspect of the present invention is to perform chrome plating on the surface of plastics, on the electroless copper plating layer, in the copper plating step-
The present invention relates to a chrome plating method characterized in that chrome plating is performed directly under vibration and stirring without going through a nickel plating step. A fourth aspect of the present invention is characterized in that, in performing chromium plating on a zinc-based metal surface, direct chromium plating is performed on a copper plating layer under vibrating stirring without undergoing nickel plating after a copper plating step. Regarding plating method. A fifth aspect of the present invention relates to a chrome plating method characterized in that when chrome-plating a copper-based metal surface, the chrome-plating is performed directly under vibration and stirring without undergoing nickel plating. A sixth aspect of the present invention relates to a chrome plating method characterized in that, when chrome plating is performed on the surface of an aluminum-based metal, the chrome plating is performed directly under vibrating and stirring without undergoing undercoating. The present invention has discovered that, in any case, it is possible to perform chrome plating directly on the object to be plated while vibrating and stirring the metal surface, which has been considered to be impossible to perform chrome plating directly on the metal surface. This is based on what has been done, and has a great feature in that the pre-plating step for chromium plating which has been required up to now is omitted and the speed of chromium plating is greatly improved.

The vibrating and stirring means used in the present invention is 15 to 6
It is a new stirring means developed by the present inventor based on transmitting vibration by a vibration motor to a diaphragm in liquid and generating the vibration at 0 Hz, preferably 20 to 40 Hz. Thinking is Japanese Patent Laid-Open No. 3-
As disclosed in Japanese Patent Application No. 275130, the deformation stirring means is applied for on September 14, 1992 as Japanese Patent Application No. 4-286544. Furthermore, the technology related to vibration stirring is disclosed in Japanese Patent Application No. 5-116566 and 5-1390.
No. 28 has been filed. It is surprising that this vibration agitation, when vibration by the vibrating plate is transmitted to the entire system, makes the entire system more uniform than the agitation by the screw. The amplitude of the diaphragm is not particularly limited, but is usually 2 to 30 mm, preferably 10 to 15 mm.

1 and 2 show a plating apparatus provided with a vibration stirring means used in the present invention. 3 and 4, the plating electrode is omitted. The vibration stirring means is
The vibration generated by the vibration motor 26 is transmitted to the vibrating blade groups 22, 22 ... Through the vibrating frame 23 and the vibrating rod 21. As shown in FIGS. 2 and 3, the vibrating blade group is a plating bath 29.
Install on both sides of. The vibration from the vibration motor 26 causes the tank 2
The vibration frame 23 is attached to the mount via a spring 24 and a pedestal 25 so as not to affect the main body. Further, 27 is an electrode, and 28 is a heater for maintaining the liquid temperature. The vibrating blade may be horizontal, but is preferably attached with a slight inclination. The degree of inclination is preferably 0 to 45 ° with respect to the horizontal direction, preferably 10 to 20 °. In this example, the setting was made at 15 °. The width of the vibrating blade is not particularly limited, but if it is about 30 mm or more, its effect is sufficiently exhibited. Usually 30 to 100 mm, preferably 50 to 80 mm
It is a degree. The spacing between the stirring blades is not particularly limited, but is usually 10 to 80 mm, preferably 30 to 40 mm, and in this embodiment, the spacing was 35 mm. The positions of the left and right vibrating blades 22 may be at the same height, but they may be provided at slightly displaced positions. The uppermost vibrating blade is preferably located about 100 mm below the liquid surface. If it is provided above this, the liquid will be scattered, although it is somewhat different depending on the amplitude, which is not preferable. The lowest vibrating blade is preferably located about 50 mm above the bottom. The vibrating blade of the present invention has a width of 80 mm, a length of 400 mm, and an interval of 35 mm.

The vibrating plate in the vibrating stirring means is
It can be roughly divided into three types. (1) 2 to 10 cm wide along the periphery of the plating tank
A type in which a large number of vibration plates are provided above and below (Fig.
(Refer to 3) (Vertical vibration) (2) Type in which one or two diaphragms are provided on the bottom of the plating tank almost all over the tank, (see Fig. 4) (Vertical vibration) (3) Horizontally at the bottom of the plating tank Type with a vibrating plate that vibrates in any direction (see Figures 5 to 9) (4) Instead of the propeller stirring blades in the center of the plating tank, a vibration of an arbitrary shape with a length equal to or less than the propeller length There is a type in which a large number of plates are provided above and below (see Japanese Patent Application No. 4-286544), but the type (1) is particularly preferable. The position of the plating electrode can be above the vibrating plate or inside or outside the vibrating plate.

The vibrating plate may be vibrated uniformly as described in the above publications and specifications, but one or two parts of the vibrating plate are connected to the vibrating shaft to vibrate. You can also In this case, when the liquid tank has a quadrangular shape, two vibration shafts may be provided at both ends of one side of the diaphragm, but one vibration axis may be provided at the center of the side. Further, one vibration shaft may be provided at one corner of the diaphragm. The diagonal side of the side to which the vibration axis is attached or the corners other than the corner to which the vibration axis is attached are supported by the fixed shaft. An elastic body on the fixed shaft,
For example, it is preferable to fix the diaphragm via rubber, spring, air spring or the like, but it is also possible to rely on the elasticity of the diaphragm itself. FIG. 5 shows a specific example thereof. The vibrating rods 1 and 2 are provided via a vibration transmitting rod 5 connected to a vibrating motor by any means, and the vibrating plate 6 is fixed to the vibrating rods 1 and 9 by using rubber pieces 8 and 9, while the fixed rod is fixed. 3,4
The supporting rubber pieces 10, 1 for supporting the vibration of the diaphragm 6.
1 is fixed, and the diaphragm 6 is connected thereto. The diaphragm 6 is
Vibration transmission rods 1, 2 with the supporting rubber pieces 10, 11 as fulcrums
Since the fan vibrates like a vertical axis in line with the vertical axis, it is possible to mix and stir liquids, powders, granules, etc. by holding this in a tank.

The outline of the plating apparatus provided with the horizontal vibration stirring means used in the present invention is shown in FIGS. FIG. 6 shows a top view of a horizontal vibration stirring device used in the present invention, and FIG. 7 shows a cross-sectional view thereof. Reference numeral 31 is a vibration motor that horizontally generates vibration, and 32 is a U-shaped vibration transmitter for transmitting the vibration, which is directly or via a slide bearing 13 or the like in a tank or an arbitrary support. Installed.
33 is a support for preventing the vibration generated by the vibration motor 31 from being attenuated, and 34 is a vibrating blade 36.
It is a vertical vibration transmitter that suspends the vibrator 35 attached with and plays a role of transmitting the vibration of the U-shaped vibration transmitter to the vibrator 35. The vibrating blade 36 has a function of giving a vibrating and stirring action to liquid or powder in the tank by vibrating the vibrating motor 31. Elastic bodies 38, 38 such as springs are provided on both sides of the support body 33 to prevent the vibration of the U-shaped vibration transmitter 32 from being attenuated and to have a weight substantially equal to that of the vibration motor 31 side. Use the weight to minimize the noise generated by unnecessary vibration. The vibration motor installed on one side of the tank via the U-shaped vibration transmitter, the elastic body installed on the opposite side of the vibration motor, and the holding mechanism thereof are substantially balanced in weight. Is preferably adjusted so that

Any number of vibrating blades may be attached to the vibrator. The vibrating blades are vertically or obliquely mounted on the vibrator [see (a) to (d) of FIG. 10]. The vibrating blades can be attached to the vibrator by welding or detachably. In particular, it is preferable to adopt a method in which the blades are press-fitted to the vibrator because the size of the vibrating blades can be changed and the number of the vibrating blades can be changed according to the required stirring conditions. It is also possible to change the mounting angle of the blades. When the size of the tank is 800 mm in width, 1000 mm in length and 1100 mm in depth, for example, the width is 80 mm and the length is 50 at intervals of 50 mm.
By installing a vibrating blade having a thickness of 0 mm and a thickness of 0.15 mm, a sufficient stirring effect can be achieved.

The presence of the support body which receives both ends of the U-shaped vibration transmitter through the elastic body prevents the lateral vibration generated by the vibration motor from being attenuated. It is preferred that it be of a similarly solid structure. For example, it is possible to use an H-shaped steel material in which a foundation is struck on the ground and rises vertically to it, or a reinforcing bar, a concrete wall containing steel frames, or the like. If the wall of the tank is sufficiently solid, the wall of the tank can serve as the support.

The elastic body plays a role of receiving the vibration of the vibration transmitter and repelling the vibration from the support, and preferably has a strong spring force. For example,
As shown in FIG. 8, a spring 38 having a diameter of 3 to 10 mm made of spring steel and fitted around a round bar 37 can be used as the elastic body. It is preferable that the elastic body is symmetrically installed on the vibration motor side and the opposite side of the support. The structure of FIG. 8 has such a structure, and the spring is fixed by the stopper plate 39.

In the present invention, aeration means can be additionally provided in addition to the vibration stirring means.

The composition of the chromium plating bath used in the present invention is
Conventional chromium plating baths having various compositions can be used. As a typical formulation, (a) chromic acid (CrO ₃ ) 100 to 500 g / l sulfuric acid 0.5 to 7.7 g / l (b) chromic acid (CrO ₃ ) 200 to 300 g / l sulfuric acid 0.25 to ₃ g / L sodium silicofluoride (Na ₂ SiF ₆ ) 0.5 to 20
g / l

The iron-based metal in the present invention is iron or an alloy containing iron as a main component, the zinc-based metal is zinc or an alloy containing zinc as a main component, and the copper-based metal is mainly copper or copper. It is an alloy containing a component, and the aluminum-based metal is aluminum or an alloy containing aluminum as a main component. As the plastics, any of plastics such as ABS, polyethylene and polypropylene can be used as a control.

[0016]

【Example】

Example 1 (Plating on iron-based metal) (Suspension type) Basic process: Degreasing → Washing → Pickling → Washing → Chromium plating Equipment: FRP plating tank (vibration 200 liters) with vibration stirring means shown in the figure The frequency was 27 Hz. Anode: Titanium coated with indium oxide Liquid temperature: 60 ° C. Plated object: Steel disk (diameter 55 mm) (thickness 5 mm) Plating bath composition: CrO ₃ 300 g / l H ₂ SO ₄ 3 g / l or more When chromium was directly plated on steel under the conditions, a current density of 80 A / dm ^{2 was obtained,} and plating was performed for 20 minutes in this state. As a result, it was possible to obtain a crack-free chromium plating layer having a thickness of 7 μm at the center and a thickness of 20 μm at the outer periphery. Plating could be done at a higher speed than that without vibration stirring. JIS
The salt spray test of was still acceptable after 96 hours. In addition, the current density was reduced to 40 A / dm ² without vibration stirring, and the time required for the chrome plating step to obtain the same film thickness was half that in the case without vibration stirring.

Comparative Example 1 Example 1 was repeated except that no vibrating stirring was performed. As a result, a chromium plating film having a current density of 40 A / dm ² and a film thickness of 11 μm was obtained, but there were many cracks and the JIS salt spray test completely failed after 96 hours.

Example 2 (Plating on iron-based metal) (suspended type) The frequency was 28 Hz, the current density was 60 A / dm ^2, and the object to be plated was an iron shaft (diameter 10 mm, length 135 m).
m) was plated with chrome. The thickness of chrome plating is 2
The occurrence of cracks was not observed at 0 to 22 μm.
The JIS salt spray test passed even after 96 hours.

Comparative Example 2 Example 2 was repeated except that no vibrating stirring was performed. As a result, a chromium plating film having a current density of 40 A / dm ² and a film thickness of 11 μm was obtained, but there were many cracks and the JIS salt spray test completely failed after 96 hours.

Comparative Example 3 (Plating on iron-based metal) (suspended type) Basic process: Degreasing → washing → pickling → washing → copper strike → copper plating → washing → nickel plating → washing → chromium plating Using an object to be plated, copper plating-nickel plating was applied as usual to chromium plating (without vibration stirring). Copper sulphate plating bath Copper sulphate 230g / l Sulfuric acid 50g / l Brightener small amount Liquid temperature 25 ° C Cathode current density 3A / dm ² hours Nickel plating bath Nickel sulphate 240g / l Nickel chloride 45g / l Boric acid 30g / l Brightener small amount liquid Temperature 50 ° C. Current density 5 A / dm ² Chromium plating bath CrO ₃ 300 g / l H ₂ SO ₄ 3 g / l A Sargent bath was used. Liquid temperature: 60 ° C. Current density: 50 A / dm ² Plating time: 30 minutes As a result, a 25 μm thick chromium plating layer was obtained.
Many microcracks were observed. The JIS salt spray test failed after 96 hours.

Example 3 (Barrel plating on iron products) The barrel plating apparatus used in this example is shown in FIG. 11 (top view) and FIG. 12 (cross-sectional view). The vibrating agitating means applies the vibration generated by the vibrating motor 56 to the vibrating frame 53,
This is transmitted to the vibrating blade groups 52, 52 ... Through the vibrating rod 51. The vibrating blade groups are installed on both sides of the circulation tank 59 as clearly shown in FIGS. The vibration frame 53 is attached to the main body via a spring 54 and a pedestal 55 so that the vibration from the vibration motor 56 does not affect the main body of the circulation tank 59. The inclination of the vibrating blade was set at 15 ° with respect to the horizontal direction. The width of the vibrating blade was 80 mm, and the distance between the stirring blades was 35 mm. As shown in FIG. 12, the vibrating blade portion is provided between the barrel 63 and the electrode 57. The barrel 63 is an octagonal cylindrical body having a large number of holes with a diameter of 3 mm and is made of a hard vinyl chloride resin having a capacity of about 3 liters. As the article to be plated, an iron columnar body having a diameter of 20 mm and a length of 20 mm was used. This product is not plated with copper or nickel. The composition of the chrome plating bath was as follows. Chromic anhydride (CrO ₃ ) 250 g / l Sulfuric acid (H ₂ SO ₄ ) 2.5 g / l Cathode current density 25 A / dm ² , plating temperature 60 ° C., barrel rotation speed 6 r. p. m. Then, it plated for 1 hour. In addition,
The article to be plated was filled to 1/3 of the barrel volume. After completion of plating, washing with water, neutralization with acid, washing with water and drying were performed. As a result, the current density does not increase and the chrome plating film can hardly be formed when the vibration stirring is not performed, whereas in the third embodiment, the chrome film having a thickness of 10 μm is formed uniformly, This film thickness was almost the same as in the case of plating using a suspender.

Example 4 (Barrel plating on iron products) Example 1 was repeated except that a chromium plating bath having the following composition was used, the cathode current density was 50 A / dm ² , and the plating temperature was 55 ° C. Chromic anhydride (CrO ₃ ) 260 g / l Potassium silicofluoride (K ₂ SiF ₆ ) 4 g / l Potassium dichromate (K ₂ Cr ₂ O ₇ ) 25 g / l Sulfuric acid (H ₂ SO ₄ ) 1 g / l As a result, The chromium plating layer was formed about 1.3 times faster than in Example 1.

Example 5 (Plating on plastics) Basic process: Degreasing → pre-etching → etching → catalyzing → accelerating → electroless copper plating → chrome plating Polyacetal disk (diameter 20 mm, thickness 20 m)
m) was subjected to chemical plating (chemical copper plating) to activate the surface, and then subjected to chromium plating directly under vibration and stirring. The plating conditions were the same as in Example 1, and the plating time was 20 minutes. The thickness of the chromium plating layer was 20 μm, and no microcracks were observed. JI
The result of the salt spray test with S was acceptable even after 96 hours.

Comparative Example 4 (Plating on Plastics) Basic Process: Degreasing → Pre-etching → Etching → Catalyzing → Accelerating → Electroless Copper Plating → Copper Plating → Nickel Plating → Chrome Plating The same polyacetal disk as in Example 2 Comparative Example 1
After copper plating and nickel plating were performed in the same manner as above, chromium plating was performed (without vibration stirring). After plating for 20 minutes,
The thickness of the chromium plating layer was 11 μm, and the presence of microcracks was recognized. The result of the salt spray test according to JIS was unsuccessful after 96 hours.

Example 6 (plating on zinc-based metal) (suspending method) Basic process: degreasing → washing → pickling → washing → copper strike → copper plating → washing → chrome plating zinc-plated copper-based metal disk ( Chromium plating was performed for 20 minutes in the same manner as in Example 1 except that the diameter was 20 mm and the thickness was 20 mm and the frequency was 28 Hz. As a result, the occurrence of microcracks was not observed,
In the salt spray test of No. 1, it passed even after 96 hours.

Comparative Example 5 (plating on zinc-based metal) (suspension method) Basic process: degreasing → washing → pickling → washing → copper strike → copper plating → washing → nickel plating → washing → chrome plating Copper strike treatment Zinc-based metal disc (diameter 20
mm, thickness 20 mm) was subjected to copper plating → nickel plating → chromium plating by the usual basic process with the same formulation as in Comparative Example 1. The chromium plating time was 20 minutes. As a result, microcracks were generated in the chromium plating layer.

Example 7 (plating on aluminum metal) (suspension system) CrO ₃ 300 g / l H ₂ SO ₄ 1 g / l was used as a chromium plating bath, and an aluminum die cast product (diameter 55 mm, thickness 5 mm) was used. The sample was subjected to plating at a frequency of 27 Hz, a liquid temperature of 60 ° C. and a current density of 80 A / dm ² for 20 minutes in the same manner as in Example 1. It was possible to obtain a chromium plating layer having an average film thickness of 15 μm and having no crack. Usually, it is not necessary to provide a treatment layer such as a zinc substitution method or a zinc alloy substitution method that has been conventionally used as an intermediate treatment, and a corrosion-resistant plating layer without generation of microcracks can be obtained at high speed. In addition,
Normal degreasing, washing with water, and activation treatment are carried out by conventional methods.

[0028]

【effect】

(1) The present invention can simplify the preliminary plating step, which has been required until now, when chromium plating is applied to iron-based alloys, plastics or zinc-based metals by using vibration stirring. This simplification of the process leads to a great improvement in working efficiency and also eliminates the need for a preliminary plating solution, which has a great advantage in treating wastewater and is a very large effect. (2) In the present invention, by using vibration stirring, it is possible to obtain a plating rate almost twice as high as that of the chromium plating in the conventional method. This has a close relation with the fact that a high current density can be achieved by vibrating stirring. For example, in the conventional chrome plating, the current density is 40 A / dm ² , and the chrome plating thickness is 11 at 20 minutes.
Whereas in the chromium plating of the present invention, the current density is 80 A / dm ² , and the chromium plating thickness is 22 in 20 minutes.
Since the thickness is μm, it is possible to perform double-thickness chromium plating in the same time. In other words, it is clear that the plating rate has doubled. (3) The obtained chromium plating layer has no microcracks as in the conventional product, and the durability is further improved as compared with the conventional product.

[Brief description of drawings]

FIG. 1 is a top view of a vibration stirrer used in an example of the present invention.

FIG. 2 is a side view of a vibration stirrer used in an example of the present invention.

FIG. 3 is a side view of the vibration stirrer used in the example of the present invention as seen from the other side.

FIG. 4 is a perspective view of only a main part of a vibration stirrer used in an example of the present invention.

FIG. 5 is a perspective view showing a modified example of the vertical vibration stirring means that can be used in the plating method of the present invention.

FIG. 6 is a top view of a lateral vibration stirrer used in an example of the present invention.

7 is a cross-sectional view of FIG.

FIG. 8 is an enlarged sectional view of a portion A in FIG.

FIG. 9 is a schematic view of a vibration transmission mechanism and a vibrator.

10 (a) to 10 (d) show various attachment modes of the vibrating blade to the vibrator.

FIG. 11 is a top view of a barrel plating apparatus provided with a vibration stirring means.

12 is a cross-sectional view of FIG.

[Explanation of symbols]

 1 Vibration Rod 2 Vibration Rod 3 Fixed Rod 4 Fixed Rod 5 Vibration Transmission Rod 6 Vibration Plate 7 Tank Bottom 8 Supporting Rubber Piece 9 Supporting Rubber Piece 10 Supporting Rubber Piece 11 Supporting Rubber Piece 21 Vibration Rod 22 Vibrating Blade 23 Vibration Frame 24 Spring 25 Pedestal 26 Vibration motor 27 Electrode 28 Heating heater 29 Plating bath 31 Vibration motor 32 U-shaped vibration transmitter 33 Support body 34 Vertical vibration transmitter 35 Vibrator 36 Vibration blade 37 Round bar 38 Spring 39 Stop plate 40 Heater 41 Electrode 42 Tank 43 Slide Bearing 51 Vibration Rod 52 Vibration Blade 53 Vibration Frame 54 Spring 55 Pedestal 56 Vibration Motor 57 Electrode 59 Tank 62 Rotation Shaft 63 Barrel

Claims (6)

[Claims] 1. A chrome plating method characterized in that chrome plating is performed directly on a metal surface which is said not to be directly chrome plated on the metal surface under vibration stirring. 2. A chrome plating method characterized in that when chrome-plating an iron-based metal surface, the chrome-plating is performed directly under vibration and stirring without going through a copper plating step-nickel plating step. 3. Chromium plating on the surface of the plastics is performed directly on the electroless copper plating layer under vibrating stirring without performing the copper plating step-nickel plating step. Plating method. 4. A chrome plating method characterized in that when chrome-plating a surface of a zinc-based metal, the chrome-plating is performed directly on a copper-plated layer under vibrating stirring without undergoing nickel-plating after the copper-plating step. . 5. A chrome plating method characterized in that when chrome-plating a copper-based metal surface, the chrome-plating is performed directly under vibration and stirring without undergoing nickel plating. 6. A chrome plating method characterized in that when chrome-plating an aluminum-based metal surface, the chrome-plating is performed directly under vibration and stirring without passing through a base plating.