JP2004124202A - Galvanizing method and galvanized product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a galvanizing method which can prevent, at a low cost, whiskers from growing on the surfaces of galvanized products by a temporal change after galvanizing and to provide galvanized products. <P>SOLUTION: In the galvanizing method comprising a process for electrically depositing electrolyzed zinc M on the surface of a product W1 to be galvanized by immersing the product W1 as a cathode and the zinc as an anode into a plating bath and by passing an electric current between the cathode of the product and the anode of the zinc, the flowing direction of the electric current passed between the cathode of the product W1 and the anode of the zinc is periodically changed. The whiskers can be thus prevented from being produced on the surface of the galvanized product by the temporal change after the galvanizing. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a galvanizing method and a galvanized product plated by the galvanizing method.
[0002]
[Prior art]
There are innumerable types of conventional galvanized products.For example, members such as support legs constituting a free access floor adopted for a floor in a room where a computer or the like is installed are also included. One.
[0003]
[Problems to be solved by the invention]
However, the components constituting such a galvanized free access floor and all other galvanized products have a whisker, that is, a whisker-like zinc single crystal is generated on the surface thereof due to aging after plating. There is.
[0004]
Whisker, which is a single crystal of zinc, generally has a diameter of several μm and a maximum length of about 1 to 2 cm. Therefore, for example, the whisker falls off a member constituting the free access floor due to some cause. Then, floating in the indoor air, together with the air from the cooling fan, whiskers enter the circuit of the computer or the like, causing a short circuit or poor insulation, or cause noise when the computer or the like is later operated and become erroneous. Or may cause operation.
[0005]
Several galvanizing methods for preventing the generation of such whiskers have already been filed (Japanese Patent Publication No. 55-12192, Japanese Patent Publication No. 56-518, Japanese Patent Publication No. 58-2595, Japanese Patent Application Laid-open No. Hei 2-5995). 217488), these galvanizing methods are not only significantly different in configuration and method from the present invention, but also lower the productivity, increase the cost, and lose the gloss of the plating surface. Had problems.
[0006]
On the other hand, it is conceivable to perform plating of nickel or the like other than zinc, which does not generate whiskers on the surface of the plated product, but these plating methods have other problems such as significantly increasing the cost as compared with the zinc plating method. Was.
[0007]
Accordingly, the present invention has been made in view of the above problems, and while preventing whiskers from being generated on the surface of a galvanized product due to a change with time after galvanization, a galvanized method and a galvanized product capable of realizing a glossy surface. The task is to provide.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention
These are immersed in a plating bath with the zinc-coated product as the cathode and zinc as the anode, and the zinc electrolyzed by passing a current between the cathode of the product and the anode of the zinc is electrically applied to the surface of the product. In the galvanizing method to adhere,
The flow direction of the current flowing between the cathode of the product and the anode of zinc is periodically changed.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, one embodiment of the galvanizing method according to the present invention will be specifically described.
First, an iron plate (5 cm × 5 cm) having a thickness of 3 mm is sufficiently degreased on the surface with an alkaline degreasing agent, an oxide film is removed in a 10% hydrochloric acid solution, washed sufficiently with water, and washed with a 5% sodium cyanide solution. Sum up.
[0010]
Thereafter, a zinc cyanide plating bath of about 30 L (liter) containing no brightener (metal zinc concentration 30 g / L, sodium cyanide 90 g / L, sodium hydroxide 60 g / L, sodium sulfate 2 g / L, The plating operation is performed by immersing the iron plate of the cathode and the zinc plate (15 cm × 30 cm) of about 1.5 cm in thickness in the M ratio 3).
[0011]
At this time, the liquid temperature of the zinc cyanide plating bath was set to 20 to 25 ° C., and the current to both electrodes was determined by the positive current flowing in the positive direction when plating was applied and the reverse current flowing in the opposite direction to the positive current. Flow repeatedly and alternately.
[0012]
The energization conditions at this time are as follows: after the positive current is passed for 10 to 20 seconds, the reverse current is passed for 1 to 5 seconds, and the current flows so that the positive current and the reverse current alternately and repeatedly flow in such a cycle. The direction is changed alternately, and about 5 μm of plating is deposited on the surface of the iron plate.
[0013]
The current density of the positive current is 5 to 10 A / dm ² , and the current density of the reverse current is 1 to ^{2 A} / dm ² . In addition, the sodium cyanide concentration in the zinc cyanide solution is maintained so that the M ratio (sodium cyanide / zinc metal) becomes an appropriate value of 2-3.
[0014]
After sufficiently washing the plated product of the iron plate thus obtained, the alkali film on the surface is removed with a 5% nitric acid solution, and the surface is immersed in a commercially available chromate chemical for 20 seconds to form a chromate film on the surface. After the coating, it is sufficiently washed with water and dried with hot air of 60 ° C. for 20 minutes.
[0015]
Even if the plated product of the iron plate treated in this way is left in a constant temperature bath at 100 ° C. for 500 hours and placed in an environment for promoting whisker generation, and then the presence or absence of whisker generation is observed with a scanning electron microscope, No whisker of zinc single crystal is observed. In addition, the surface of the iron plate is a plated surface having luster even though no brightener is added at all.
[0016]
As described above, the present invention periodically changes the flowing direction of the current flowing between the cathode of the product and the anode of zinc, so that whiskers are generated on the surface of the plated product of the iron plate due to the temporal change after the plating. Can be prevented. Further, since the present invention does not require any special new expensive device, the generation of the whiskers can be prevented at low cost.
[0017]
Therefore, when a member constituting the free access floor is galvanized by the galvanizing method of the present invention, whiskers are generated on the surface of the member constituting the free access floor due to a change with time after the plating. The whisker that has fallen off from the members that make up the free access floor enters the circuit of the computer, etc., together with the air from the cooling fan, causing short-circuiting and poor insulation, or when the computer is operating. It is possible to prevent a malfunction due to noise.
[0018]
In contrast to such a zinc plating method of the present invention, when a brightener is added to a zinc cyanide plating bath, it is recognized that whiskers are generated on the surface of a plated product due to a change with time after plating.
[0019]
Such brighteners include double-rings, high-molecular organic compounds, aromatics, and metal salts, and are characterized by high carbon content or large molecules.
[0020]
When such a brightener is added to a zinc cyanide plating bath, the above whiskers are generated because the added brightener operates as an impurity, and somewhat hinders the electrolysis process, which is the principle of electroplating. It is considered that whiskers are generated on the surface of the plated product by doing.
[0021]
Further, in the conventional case in which plating is performed by continuously flowing the above positive current without changing the direction of current flow between the electrodes as in the present invention, the gloss of the surface of the plated product is lost and the product of the plated product is lost. Conventionally, brighteners have always been added to prevent this since the value is significantly lost.
[0022]
When plating is performed by alternately changing the direction of current flow between the cathode and the anode as in the present invention, the gloss of the surface of the plated product is not lost without adding a brightener to the plating bath. , For the following reasons:
[0023]
That is, when the above positive current flows, the adhesion of the plating to the surface of the plated product proceeds, and the surface of the plated product has a surface roughness due to the plating M attached to the plated product W1, as shown in FIG. Becomes very large.
[0024]
However, when the reverse current flows, the plating M adhered to the surface of the plated product W1 is subjected to the electropolishing action, and the peaks of the adhered plating M are dissolved. Therefore, the surface of the plating M becomes smooth as shown in FIG. 1B, and the surface roughness of the plated product becomes very small.
[0025]
Therefore, when the plating is performed by alternately passing the positive current and the reverse current, the surface roughness is significantly reduced as compared with the conventional case where only the positive current is continuously applied. It is thought that the gloss of the surface of the plated product will not be lost even if no brightener is added.
[0026]
Such an operation principle of the present invention also leads to the following effects. That is, when plating a square plate-shaped plated product W2 as shown in FIG. 2, the plating starts to be started from the A, B, D and E portions near the corners, and gradually the C portion in the center. Therefore, when a positive current is continued to flow as in the related art, the plating thickness is larger in the portions A, B, D, and E than in the portion C.
[0027]
On the other hand, when a positive current and a reverse current are alternately flowed as in the present invention, initially, the plating adheres to the A, B, D, and E portions earlier than the C portion due to the positive current. When a reverse current is applied, portions A, B, D, and E are more strongly electropolished as a high current portion, and dissolution of plating is promoted more than portion C. Depending on the electric current, it is difficult to dissolve without being subjected to the electropolishing action. As a result, the plating thickness of the plated product W2 can be made more uniform over the portions A to E than before.
[0028]
Further, it is needless to say that the application of the present invention is not limited to the members such as the support legs constituting the free access floor, and the present invention can be applied to any other products, and the same effects can be obtained. it can.
[0029]
As the power supply, a pulse power supply, a PR (Periodic Reverse) power supply (a power supply that periodically changes the direction of current), an AC combined power supply, an intermittent power supply, and the like are used. Considering the appearance, gloss, small number of pinholes, and uniform electrodeposition, the effect of the PR power supply is great.
[0030]
When galvanizing is performed using the present invention, the thickness of the galvanizing is not particularly limited, but 3 to 20 μm is appropriate. If the thickness is 3 μm or less, physical properties and corrosion resistance decrease, and if it is 20 μm or more, productivity may decrease and cost may increase.
[0031]
【The invention's effect】
As described above, according to the present invention, it is possible to inexpensively prevent whiskers from being generated on the surface of a galvanized product due to a change with time after galvanizing.
[0032]
Therefore, when a member such as a support leg constituting the free access floor is galvanized by the galvanizing method of the present invention, whiskers are formed on the surface of the member constituting the free access floor due to a change with time after the plating. The whisker that has fallen off from the members that make up the free access floor enters the circuit of a computer or the like together with the air from the cooling fan, causing short-circuiting or insulation failure, or causing the computer or the like to fail. It is possible to prevent a malfunction during operation due to noise.
[0033]
Such a galvanizing method according to the present invention is a high-value-added plating method that can use existing galvanizing equipment and chemicals only by periodically changing energizing conditions, and does not require the addition of a brightener. Its practical effect is great, and its utility value on an industrial mass production scale is high.
[Brief description of the drawings]
FIG. 1 is a view showing a state of plating M adhered to a plated product W1 by a zinc plating method of the present invention, and FIG. 1 (a) is a view showing an adhered state of plating M when a positive current is applied; FIG. 1B is a diagram showing a state of adhesion of the plating M when a reverse current is applied.
FIG. 2 is a plan view of a plating product W2 referred to for describing that a plating thickness attached to the plating product W2 is uniform over the entire surface.
[Explanation of symbols]
M plating W1, W2 plating

Claims (4)

These are immersed in a plating bath with the zinc-coated product as the cathode and zinc as the anode, and the zinc electrolyzed by passing a current between the cathode of the product and the anode of the zinc is electrically applied to the surface of the product. In the galvanizing method to adhere,
A galvanizing method, wherein a flowing direction of a current flowing between a cathode of the product and an anode of zinc is periodically changed. The galvanizing method according to claim 1, wherein a zinc cyanide plating bath is used as the plating bath. The galvanizing method according to claim 1, wherein addition of an additive such as a brightener to the plating bath is restricted. These are immersed in a plating bath with the zinc-coated product as the cathode and zinc as the anode, and the zinc electrolyzed by passing a current between the cathode of the product and the anode of the zinc is electrically applied to the surface of the product. In galvanized products plated by galvanizing method to adhere,
A galvanized product, which is plated by a galvanizing method in which a flowing direction of a current flowing between a cathode and a zinc anode of the product is periodically changed.

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