JP2009074147A - Method for preventing problems associated with microporous plating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent problems associated with plating, such as stains and blurs formed on a microporous plating, to improve corrosion resistance of the plating, to enable continuous filtration of a plating liquid, and to enable easy maintenance and control of the plating liquid and electric potential. <P>SOLUTION: A method for preventing problems comprises: a nickel-plating step S5 of forming a nickel-plating layer on a material to be plated, such as a resin molded product or a metal product; a microporous-plating step S7 of forming a microporous-plating layer on the nickel-plating layer; a flash-plating step S8 of forming a flash-plating layer on the microporous-plating layer; and a finish-plating step S10 of forming a finish-plating layer on the flash-plating layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a microporous plating technology in which fine holes are uniformly dispersed in a plated product, and in particular, has an effect of preventing defects such as corrosion, blemishes, and burns associated with microporous plating, and further controls the potential of flash plating. The present invention relates to a defect prevention method related to microporous plating, which can obtain an appearance with good corrosion resistance and can easily maintain and manage the plating solution.

  As shown in the process diagram of FIG. 4 and the cross-sectional view of FIG. 5, the plating generally referred to as high corrosion resistance chromium plating is a double-layer nickel plating (base plating such as copper plating) or a metal material (st plating) ( Plating solution in which semi-bright nickel plating + bright nickel plating) or three-layer nickel plating (semi-bright nickel plating + trinickel plating + bright nickel plating) is performed, and further non-conductive powder such as insoluble silicate fine particles is dispersed. Is a plating method in which non-conductive powder is co-deposited and chromium plating is applied to the uppermost layer to obtain microporous plating (microporous chromium plating).

  This microporous plating is a technique that delays the progress of local corrosion by distributing corrosion current by intentionally creating a fine hole defect in an unplated state on the very rust-resistant plating on the outermost surface. For example, it is virtually impossible to apply a completely defect-free chrome plating and remain defect-free for a long time under various usage conditions. There will always be disordered defects. This disordered defect is surrounded by chrome plating which is very difficult to rust, so that corrosion is concentrated. Therefore, as in the case of microporous plating, small micropore defects that are controlled cover the entire surface, so that corrosion proceeds from all defects, and the corrosion of each defect is extremely small. It can be. That is, the corrosion resistance of the plated product can be improved.

  From the viewpoint of corrosion resistance of the plating film, the potential of the microporous plating is desirably more noble than the potential of the underlying bright nickel plating.

Various techniques for improving the corrosion resistance of bright nickel plating have been proposed. For example, as disclosed in Japanese Patent Application Laid-Open No. 5-230699 of Patent Document 1, “additional current density is changed by bright nickel plating and the potential difference is changed by one bright nickel plating layer” A method for obtaining a potential difference has been proposed.
Japanese Patent Application Laid-Open No. 5-230699

  However, since the nickel plating solution for performing the microporous plating contains non-conductive fine particles (powder), the plating solution cannot be continuously filtered. Since continuous filtration is not possible in this way, activated carbon precoat or activated carbon filter was used in the filter like other plating solutions, and this plating solution could not be purified continuously. In addition, it is necessary to add an additive for dispersing the non-conductive fine particles in the plating solution and an additive for imparting a positive charge to the fine particles in addition to the brightener. Had the problem of increasing the factor.

  If the plating solution contains a large amount of fine particles, the gloss of the plated product tends to decrease. A part or the whole of the plated product became semi-glossy, and gloss spots were easily generated on the whole. Non-conductive fine particles also accumulate brightener decomposition products or cause aggregation to increase plating defects. Therefore, it is necessary to periodically remove and replace the fine particles.

  When maintaining the plating solution, if the plating solution contains fine particles, it tends to be an obstacle to the regular purification treatment (activated carbon treatment) of the plating solution. That is, the nonconductive particles may clog the filtration filter. Since the plating solution cannot be purified at all times, the brightener decomposition products in the plating solution accumulate, and it is necessary to increase the periodic cleaning frequency (number of times) over other plating solution tanks in order to maintain a more noble potential than bright nickel plating. Had the problem of being.

  In addition, the “plating method in which seal Ni and bright Ni are applied in the same plating tank” in Patent Document 1 is a method for improving the corrosion resistance performance of bright nickel plating, but maintains the potential difference from microporous nickel plating. Had the problem of being difficult.

  The present invention has been developed to solve such problems. That is, the object of the present invention is to further prevent plating-related defects such as stains and blurring caused by microporous plating by further plating the problem of microporous plating and top layer finish plating. An object of the present invention is to provide a method for preventing a problem associated with microporous plating that can improve corrosion resistance and further allow continuous filtration of the plating solution, and can easily maintain and manage the plating solution and also can easily maintain and manage the potential.

  According to the present invention, a nickel plating layer is formed on a material to be plated such as a resin molded product or a metal product by a nickel plating step (S5), and microporous plating is performed on the nickel plating layer by a microporous plating step (S7). Forming a layer, forming a flash plating layer on the microporous plating layer by a flash plating step (S8), and forming a finish plating layer on the flash plating layer by a finish plating step (S10). A failure prevention method related to microporous plating is provided.

For example, the finish plating layer is appearance color plating such as chromium plating, tin plating, or nickel alloy plating.
In the flash plating step (S8), it is preferable to perform plating to a thickness that does not bury the fine particle portion that is co-deposited in the microporous plating step (S7).
Plating is preferably performed so that the flash plating layer has a thickness of 0.1 to 0.5 μm.
Unlike the plating solution used in the microporous plating step (S7), in the flash plating step (S8), the components of the powder component, the powder dispersant, and the positive charge imparting agent are different from those used in the microporous plating step (S7). Plating treatment is preferably performed using the removed plating solution.

The nickel plating (S) is a nickel plating of two or three layers.
When the material to be plated is a resin molded product, chemical plating, st plating (metal material plating), and copper plating are further performed on the material to be plated.

  As described above, in the method of the present invention, the fine particles are co-deposited in the plating with the plating solution containing the nonconductive fine particles in the microporous plating step (S7), and then charged into the same kind of plating solution containing no fine particles. Excessive non-conductive fine particles are brought into the plating solution in the flash plating step (S8), but since this plating solution can always be filtered (including activated carbon filtration), only a small amount of non-conductive fine particles that are brought in are filtered. Removed by. Further, a certain amount of the brightener decomposition product can be removed at any time.

  In addition, the plating solution in the flash plating step (S8) is not limited to the nickel plating composition, and a plating film having any composition for improving the corrosion resistance of the plating film can be used as a base for chromium plating. Therefore, for example, it is possible to provide a plated product that can withstand a severe corrosive environment such as an antifreezing agent (snow melting salt) in a cold region or an automobile part to which a salt component on the coast is attached.

  Since the plating solution in the flash plating step (S8) does not contain a powder additive, the plating solution can be constantly purified by activated carbon filtration, so that the occurrence of spot defects can be suppressed. Further, it is possible to suppress a flow stain defect in which a brightener or a brightener decomposition product is adsorbed to the powder component.

  The method for preventing defects related to microporous plating according to the present invention prevents the problems related to microporous nickel plating by adding another flash plating to the question of microporous nickel plating and finish plating of the uppermost layer. This is a plating method capable of improving the corrosion resistance of plating.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a process diagram showing a failure prevention method related to microporous plating in Example 1. FIG. FIG. 2 is an enlarged cross-sectional view of a plating film of a plated product obtained by the failure prevention method related to microporous plating in Example 1.
As shown in the process diagram on the left side of FIG. 1, the failure prevention method related to microporous plating according to Example 1 of the present invention is such that when the material to be plated is a resin molded product, the resin molded product is first etched. Each process of S1, etching neutralization process S2, catalyst provision process S3, and conductive process S4 is performed. So-called pretreatment is necessary.
When the material to be plated is a metal molded product, such pretreatment is not necessary.

Next, in order to perform electroplating on the resin molded product, as shown in the process diagram on the right side of FIG. 1, double-layer nickel plating (semi-gloss) on a base plating such as copper plating or a metal material (st plating) Nickel plating S5 of nickel plating + bright nickel plating) or three-layer nickel plating (semi-bright nickel plating + trinickel plating + bright nickel plating) is performed. After the washing step S6, the non-conductive powder is eutectoidally plated by using a plating solution in which non-conductive powder such as silicate fine particles are dispersed mainly in the microporous plating step S7, and finishing the top layer. Chrome plating can be performed by applying chromium plating to the plating layer.
The potential of the nickel plating S5 is desirably nobler than the potential of the underlying bright nickel plating S5 from the viewpoint of the corrosion resistance of the plating film.

  In the present invention, the flash plating layer is formed on the microporous plating layer by the flash plating step S8 before the conventional finish plating step S10 for forming the uppermost finish plating layer. In the illustrated example, a flash nickel plating layer is formed. After this flash plating step S8, the water washing treatment S9 is followed by the finish plating step S10. Then, after washing process S11 and drying process S12, plating is completed.

  As the uppermost finish plating layer, chrome plating, so-called appearance color plating treatment is performed. Instead of the chromium plating, tin plating or nickel alloy plating can be applied.

  In the flash plating step S8, the plating is performed to a thickness that does not fill the fine particles that have been eutectoid in the microporous plating step S7. As shown in Table 3 to be described later, it is preferable to perform plating so that the thickness of the flash plating layer is 0.1 to 1.0 μm. In particular, 0.1 to 0.5 μm was suitable. This is because if the film thickness is greater than, for example, 1.5 μm or more, the number of micropores is extremely reduced, and the function as microporous plating cannot be exhibited.

  Unlike the plating solution used in the microporous plating step S7, in the flash plating step S8, a plating solution from which the components of the powder, the powder dispersant, and the positive charge imparting agent are removed is used. It is preferable to apply plating.

  Next, a specific plating method of the defect prevention method of the present invention will be described. An example of the plating solution used for the plating bath of this defect prevention method is shown in Table 1. In this case, of course, potential management is necessary.

  The basic composition of the plating solution used in the plating treatment of the present invention conforms to the Watt bath composition mainly composed of nickel sulfate, nickel chloride, and boric acid. Other nickel plating baths also basically have Watt bath composition, but the control concentration was slightly changed in consideration of the penetration of the plating bath in the previous step and the characteristics of the plating bath.

  Semi-bright nickel plating (SB-Ni) is a plating having the highest potential and good corrosion resistance in a nickel plating bath. That is, it is plating with a low sulfur component that is eutectoid on the plating film. On the other hand, since the tensile stress is the highest, excessive addition of brighteners and accumulation of brightener decomposition products cause plating cracks, so careful management is required.

  As the name suggests, the semi-bright nickel plating did not give a gloss to the high electric part, and a plating having a glossy feeling only on half of the low electric part was obtained. The leveling action, that is, the ability of the plating bath to smooth the microscopic unevenness of the substrate and the polishing strip, is the best among the nickel plating baths, but it did not reach that of bright copper sulfate.

  Since the leveler ratio is high and an intense leveler is used, the activity of the plated film is high, which causes nickel stain defects (spots like haze). In other words, spots or smudges appear on the surface after plating or after plating after the time image has elapsed. In order to prevent the product from drying when the aerial product was moved after plating, it was necessary to quickly submerge it in the next process. It also depends on the bath temperature, air temperature, and washing water temperature. It was also effective to improve drainage and drying with a pit inhibitor.

  Intense levelers are prone to filamentous white mold, so it is necessary to take measures against mold, including washing with water. A filamentous mold was likely to occur in the Butine-diol type derivative.

[High corrosion resistance nickel plating and chromium plating]
For the purpose of improving the corrosion resistance of the plated product, semi-bright nickel plating was first applied on the copper plating, and then the nickel plating was further performed thereon (WNi plating method). A plating film that takes advantage of the fact that the corrosion potential and corrosion resistance of the nickel plating film change depending on the sulfur component, oxygen, carbon, etc. mixed in the nickel plating film, and that the progress of corrosion does not reach the deep part of the plating film by sacrificial protection It has a configuration.

  Currently, the above two-layer nickel plating and three-layer nickel plating are performed, and MPNi (joule nickel, seal nickel) and post nickel strike plating (PNS) described later are plated on 1.0 to 2.0 μm and chromium. A method of applying microporous chrome plating or microcrack chrome plating obtained by plating 0.15-0.5 μm to improve the corrosion resistance of the decorative chrome plating can be used.

  Conventional three-layer nickel plating has the highest S content of three-layer nickel plating between the semi-bright nickel plating and the bright nickel plating, and further corrosion resistance by plating the lowest potential plating about 1.0-2.0 μm Can be improved.

FIG. 3 is an explanatory view of the progress of corrosion of nickel plating. (A) is single-layer nickel plating, (b) is double-layer nickel plating, and (c) is triple-layer nickel plating.
Single layer nickel plating (single nickel plating) (see FIG. 3A), double layer nickel plating (double nickel plating) (see FIG. 3B), and three layer nickel plating (triple nickel plating) ( The difference in the progress of corrosion from that shown in FIG. 3C is as shown below if the potential difference is normal. All the plated products shown in FIG. 3 have a microporous chrome finish.

  In any case, when the corrosion starts from the exposed part of the nickel plating such as micro-holes or micro cracks opened in the chrome, and the corrosion progresses to the copper and the blue rust of the copper comes out, it is determined as rust (blue rust determination). Decline of chromium due to nickel corrosion is determined as a surfi pit (white rust determination). There are some automobile manufacturers in which the two types of corrosion determination methods of blue rust determination and white rust determination are not clearly divided, and there is a difference in determination for each manufacturer, so care must be taken.

  In the case of single layer nickel, nickel corrosion reaches copper at once. In the case of double-layer nickel, when the corrosion reaches the semi-bright nickel layer, the semi-bright nickel layer is electro-corrosive due to the potential difference between the bright nickel layer and the semi-bright nickel layer, until the bright nickel layer corrodes to some extent. Corrosion of is suppressed. As a result, the time until the occurrence of copper rust extends from the single-layer nickel-plated product. That is, the corrosion resistance is improved.

  Further, in the case of the three-layer nickel, when the corrosion of the bright nickel layer reaches the three-layer nickel layer, the bright nickel layer is electrically protected by the potential difference between the bright nickel layer and the three-layer nickel layer, and the three-layer nickel layer is corroded first. . When the corrosion of the three-layer nickel layer reaches the semi-bright nickel layer, a potential difference occurs between the three-layer nickel layer and the semi-bright nickel layer, but the potential difference between the bright nickel layer and the semi-bright nickel layer (two-layer nickel layer) In this case, since the potential difference is larger, the anticorrosion effect of the semi-bright nickel layer is superior to that of the double-layer nickel.

  Since the three-layer nickel is integrated with the bright nickel and exhibits an anodic behavior, only the three-layer nickel corrodes in a tunnel shape and does not escape. Recently, the potential difference between the three-layer nickel and the bright nickel plating is 10 to 20 mV, so that the potential difference is not excessively controlled. In addition, since it is easy to raise | generate adhesion failure between three-layer nickel / bright nickel, it puts into a bright nickel plating tank without washing with water.

Although it is the behavior at the time of corrosion of multilayer nickel plating, the electric potential produced here is influenced by S content and impurities contained in nickel. The pre-process of semi-bright nickel plating is copper plating, and accumulation of copper ions can be considered. There is also an accumulation of brightener decomposition products.
The management of the plating bath, especially the management of the brightener, is important. A potential difference that is too large also accelerates corrosion. Pay particular attention to the bright Ni / semi-gloss Ni potential. Macroscopic holes generated on the plated surface of the surface, so-called surface pits, are likely to occur.
The potential sequence is SBNi>MPNi>BrNi> TrNi.

When the Ni potential difference is measured with a plated product, only the relative potential difference of the plating solution state used in the line can be measured. Moreover, since the film thickness of microporous nickel plating is too thin, an accurate numerical value is difficult to grasp. Based on the new plating solution, semi-bright nickel plating solution, comparatively controlled by plating each nickel plating on a hull cell plate, a special type electrolytic cell that observes the state of the electrode surface at various current densities It is desirable to do.
Semi-bright nickel plating is required to have leveling properties and internal stress (plating stress) as small as possible, not containing S, that is, high potential.

[Confirmation of appropriate film thickness of plating by the method of the present invention]
In carrying out the defect prevention method of the present invention, it is necessary to secure the number of micropores that can be obtained by microporous plating (microporous nickel) plating. Therefore, it is necessary to confirm the appropriate film thickness of the microporous plating by the defect prevention method of the present invention, that is, the film thickness that can suppress the decrease in the number of micropores to the minimum, and the confirmation test was performed.

[Test method]
Flash using a plated product obtained by changing the film thickness of the flash plating from 0 μm to 2 μm in 0.5 μm increments on the plated product from copper plating to microporous nickel plating by 0.3 μm. The relationship between the increase in the plating film thickness and the decrease in the number of pores (number of micropores) was measured.
For the flash plating, a plating solution in which a standard amount of a brightening agent for microporous nickel was added to a watt bath was used. The bath temperature was 50 ° C. 3 A / dIm ² and the plating time was changed from 0 sec to 3 min 40 sec.
Microporous nickel plating was performed using a standard concentration plating solution under the conditions of 50 ° C./2 min 3 A / dm ² . Table 3 shows the relationship between the plating film thickness and the number of micropores.

[Examples and evaluation]
Electro-copper plating is 20 μm, semi-bright nickel plating is 12 μm, bright nickel is 7 μm, and microporous nickel plating is plated on the condition of 50 ° C./2 min 3 A / dm ² with flash plating of 0.5 μm, A product plated with 0.3 μm of chrome plating was prepared, and it was evaluated how the corrosion resistance of the plated product was different depending on the presence or absence of microporous nickel plating.

  In the plated product not subjected to the flash plating treatment of the present invention, the microporous plating time was extended by the flash plating, and the plating film thickness was adjusted to be the same as that of the product of microporous plating + flash plating.

  For flash plating, a solution obtained by adding a standard amount of a brightening agent for microporous nickel plating to a Watt bath-based nickel plating solution was used.

  Corrosion resistance evaluation was conducted after a cast test (CASStest (Copper Accelerated Acid Salt Spray Test)) for 80 hours, and then with Rating No. And surface pit no. Was evaluated for corrosion. That is, acetic acid salt water whose corrosion action was accelerated by addition of copper salt was sprayed to examine the corrosion resistance of the film.

  For defects related to microporous nickel plating (mainly stain defects), the amount of secondary brightener in the microporous nickel plating solution is greater than the chemical control range (primary brightener standard amount 10ml / L test product 15ml) / L + secondary brightener standard 3 ml / L test product 5 ml / L), and verified whether there is a difference in the defect rate under the condition that stain defects are likely to occur. The results of comparing the corrosion resistance evaluations are shown in Table 2, and the failure rate change confirmation test is shown in Table 3.

The number of micropores (pieces / cm ² ) was not changed on the vertical surface of the product by flash plating at 0.5 μm. On the 10 ° receiving surface of the product, since fine particles are likely to remain on the microporous nickel plating, the flash plating increased conversely at 0.5 μm.
When 1.0 μm was plated, the number of micropores decreased to 1/3 on the vertical surface of the product. Even at the 10 ° receiving surface, it decreased to 2/3.
If the number of micropores in the ground microporous nickel is ensured to be 30,000 (pieces / cm ² ), even if the plating thickness of the flash plating is 1.0 μm (when microporous nickel plating is 1.0 μm), the final plating micro It was confirmed that the number of holes could be secured 10,000 (pieces / cm ² ) or more. As shown in Table 3, the plating film thickness usage range of flash plating is 1.0 μm or less, preferably 0.5 μm. The film thickness of the finish plating layer was suitably 0.1 to 0.5 μm. When the film thickness was 1.5 μm or more, the number of micropores was extremely reduced. This means that the function as microporous plating cannot be exhibited.

  In the corrosion resistance evaluation by the cast test, no difference was found in the corrosion resistance. However, when the plating solution in the microporous plating step S7 was an aging solution, a slight difference in corrosion resistance was observed.

  In addition, this invention is not limited to embodiment of the invention mentioned above, The trouble which concerns on plating, such as a stain and a blurring which arise in microporous plating, is prevented, corrosion resistance of plating is improved, and also continuous filtration of plating solution is possible As long as the plating method can easily maintain and manage this plating solution and can easily maintain and manage the potential, the plating solution is not limited to the illustrated method, and various modifications can be made without departing from the scope of the present invention. Of course.

  The method for preventing defects related to microporous plating of the present invention is suitable for resin molded products, but can also be used for metal molded products.

FIG. 3 is a process diagram illustrating a failure prevention method related to microporous plating in Example 1; It is an expanded sectional view of the plating film of the plating product by the malfunction prevention method regarding the microporous plating of Example 1. It is explanatory drawing of the progress state of corrosion of nickel plating, (a) is single layer nickel plating, (b) is double layer nickel plating, (c) is triple layer nickel plating. It is process drawing which shows the conventional microporous plating method. It is an expanded sectional view of the plating film of the plating product by the conventional microporous plating method.

Explanation of symbols

S5 Nickel plating process S7 Microporous plating process S8 Flash plating process S9 Finish plating process

Claims (7)

A nickel plating layer is formed by a nickel plating process (S5) on a material to be plated such as a resin molded product or a metal product,
A microporous plating layer is formed on the nickel plating layer by a microporous plating step (S7),
A flash plating layer is formed on the microporous plating layer by a flash plating step (S8),
A method for preventing a problem associated with microporous plating, wherein a finish plating layer is formed on the flash plating layer by a finish plating step (S10). 2. The method for preventing a failure associated with microporous plating according to claim 1, wherein the finish plating layer is appearance color plating such as chromium plating, tin plating or nickel alloy plating. The method for preventing a problem associated with microporous plating according to claim 1, wherein in the flash plating step (S 8), the microporous plating step (S 7) is plated to a thickness that does not bury the fine particles that have co-deposited in the microporous plating step (S 7). . 4. The method according to claim 3, wherein the plating treatment is performed so that the thickness of the flash plating layer is 0.1 to 0.5 [mu] m. Unlike the plating solution used in the microporous plating step (S7), in the flash plating step (S8), the components of the powder component, the powder dispersant, and the positive charge imparting agent are different from those used in the microporous plating step (S7). 2. The method for preventing defects associated with microporous plating according to claim 1, wherein the plating treatment is performed using the removed plating solution. 2. The method for preventing a problem associated with microporous plating according to claim 1, wherein the nickel plating (S5) is a two-layer or three-layer nickel plating. When the material to be plated is a resin molded product,
2. The method of preventing defects associated with microporous plating according to claim 1, wherein chemical plating, st plating (metal material plating), and copper plating are further performed on the material to be plated.

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