KR20110064000A - Plating method for aluminum alloy wheels - Google Patents

Abstract

PURPOSE: A plating method of an aluminium wheel is provided to greatly reduce the contact failure of a plating layer after copper, nickel, chrome plating since nickel strike electroplating is done before the plating. CONSTITUTION: A plating method of an aluminium wheel comprises next steps. The aluminium wheel is pre-processed(200,210,220,230,240,250,260). Nickel strike plating is done on the pre-processed aluminium wheel(265). Copper, nickel and chromium plating are successively done on the nickel strike plating layer(280,290,300). The pre-processing step of the aluminium wheel comprises the polishing, degreasing, etching, desmut, and zincate-treating steps of the aluminium wheel. The desmut step uses mixture including oxygenated water, ammonium fluoride, sulfuric acid and Fe-series compound. The zincate treating consists of first zincate treating, zincate peeling and second zincate treating.

Description

Plating method of aluminum wheel {PLATING METHOD FOR ALUMINUM ALLOY WHEELS}

The present invention relates to a plating method for performing chromium plating on an aluminum wheel through electroplating, and more particularly, to improve the pretreatment method of aluminum wheel electroplating and to introduce a nickel strike plating process to generate the chrome plating of an aluminum wheel. The present invention relates to a method for implementing an electroplating having excellent adhesion and surface conductivity by improving a decrease in adhesion.

Aluminum has a face centered cubic structure (FCC.), Which is excellent in ductility and malleability, so it is suitable for light weight of parts. Recently, it is used for almost all structural parts. Demand is also surging.

By the way, aluminum is a metal more inferior to zinc, and as a positive metal, the surface is easily oxidized, and electroplating of aluminum cannot be directly performed in an aqueous solution, so a series of pretreatment steps are required.

FIG. 1 illustrates a process of electroplating chromium on a general aluminum product, and as shown, a pretreatment process (100 to 160), a copper plating process (170 to 180), a nickel plating process 190, and chromium plating. The process is divided into 200, and the water washing process is essentially included between each process. The specific process of these processes takes place as follows.

The pretreatment process (100 to 160) is again a polishing process 100, degreasing process 110, etching process 120, dismert process 130, jinkate primary process 140, jinkate peeling process (150 ) And the jinkate secondary process 160.

The polishing process 100 is a process of automatically or manually polishing an aluminum material for uniform plating, and the degreasing process 110 is a process of removing foreign substances and oil components remaining on the surface after polishing, and the etching process Reference numeral 120 is a step of removing the aluminum oxide film on the surface generated by alkaline cleaning. The smut process 130 is a process for removing smut, which is a reducing metal salt formed on the surface of aluminum after the etching process 120, using a solution such as rich nitric acid and hydrofluoric acid that does not penetrate aluminum. It is a process. In addition, the zincate primary step 140 is zinc substitution plating, and when clean aluminum is deposited in an alkali solution in which zinc oxide is dissolved in rich sodium hydroxide, aluminum is dissolved and replaced with zinc ionized to coat a zinc film on the surface. In the process, the zincate peeling process 150 is a process of dissolving the zinc film by nitric acid erosion, and the zincate secondary process 160 is a zinc-substituted plating to perform the same plating process as the zincate primary 140. It is a process of coating a dense zinc film through.

The copper plating process (170 ~ 180) is carried out after the activation process to obtain a leveling and smoothness, the nickel plating process 190 is a plating process for improving the corrosion resistance of the plating to form a multi-nickel plating layer In addition, the chromium plating 195 is a plating process performed to maintain corrosion resistance and glossiness.

However, unlike general aluminum products, an aluminum wheel made of an aluminum alloy such as AC4CH, which is mainly composed of Al-Si-Mg, for example, when plated through the above-described general aluminum plating method, adheres closely after plating. There are many problems such as poor or poor adhesion after shipment.

Meanwhile, the pretreatment process such as smoothing and cleaning the surface of the product to be treated before the plating process is a major factor that has a decisive influence on the quality of the final surface treatment product such as beauty, stability and durability. Though it may be considered, it is actually the largest cause of defects in surface treatment products, and the effect on the overall processing cost is considerable.

In addition, in the case of the dismute treatment process in the pretreatment process, nitric acid is generally used, which not only generates nitrate gas that is harmful to the human body during the process, but also the emission limit standards for total nitrogen and total phosphorus are being strengthened by the water environment conservation law. There is a need for a new method of processing smut.

In addition, according to the conventional method, the dispersing treatment is excessively performed, and thus, many damages are generated on the aluminum surface, thereby affecting the subsequent process of jingcating.

In addition, the customer's greatest concern for automobiles is reliable quality. The initial aluminum wheels were electroless nickel plated to prevent corrosion in the external environment, but the production cost was high. Kate electroless plating method is widely used and used in many situations.

However, when the existing Jinkate chemicals are applied to a product having a different shape and complex shape, such as an aluminum wheel and having a complex shape, adhesion is poor and adhesion problems after plating or product shipment problems have occurred. Therefore, it is difficult to perform good electroplating, and a new method of pretreatment and plating is required.

The present invention has been made in order to solve the problems of the prior art as described above, to solve the problem to provide an electroplating method that can form a plating layer having excellent plating adhesion to the aluminum wheel.

As a means for solving the above problems, the present invention provides an electroplating method of an aluminum wheel, the method comprising: pretreating the aluminum wheel, performing nickel strike plating on the pretreated aluminum wheel, and copper plating and nickel sequentially on the nickel strike plating layer. It provides a method comprising the step of plating and chromium plating.

Conventionally, nickel strike plating has not been performed on the plating of aluminum wheels, but in the present invention, nickel strike plating is performed before copper plating, so that adhesiveness distinguished from conventional aluminum wheel plating is obtained.

In addition, in the present invention, the pre-treatment step of the aluminum wheel, characterized in that it comprises a polishing step, a degreasing step, an etching step, a smut step, and a jincate treatment step of the aluminum wheel.

In addition, in the present invention, the zinc gating treatment is composed of zinc gating primary treatment, zinc gypsum peeling and zinc gating secondary treatment, and the zinc gating primary and secondary treatments are zinc-substituted plating. Characterized in that the mixed solution containing 15g / l, 5 ~ 10g / l nickel at 20 ~ 30 ℃ 30 ~ 90 seconds, if out of the plating conditions, the galvanized layer is easily peeled off the above conditions It is preferable to perform the gating process.

In addition, in the present invention, the nickel strike plating is performed for 2 to 5 minutes at a current density of 3 to 5 A / dm 2, and when the plating conditions are out of these conditions, the galvanized layer is made of aluminum due to the stress of the plating layer. It is preferable to perform nickel strike plating under the above conditions because it is separated from the layer.

In addition, the electroplating method according to the present invention can be used for various kinds of aluminum alloys, but is particularly suitable for plating of casting alloys containing Si and Mg.

The electroplating method of the aluminum wheel according to the present invention has the following effects.

First, by performing nickel strike electroplating before copper plating, the poor adhesion of the plating layer after subsequent copper plating, nickel plating, and chromium plating is greatly reduced as compared with conventional aluminum wheels.

Secondly, the jingate treatment condition according to the present invention provides excellent adhesion and surface conductivity to a product having a complex shape with a main component different from a general aluminum material such as an aluminum wheel.

The singular forms used to describe the embodiments of the present invention are intended to include the plural forms as well, unless the phrases clearly indicate the opposite. And including means embodies a particular property, region, integer, step, operation, element, and / or component, and excludes the presence or addition of other specific characteristics, region, integer, step, operation, element, component, and / or group. It is not.

Unless defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, commonly used terms defined in advance are not to be interpreted in an ideal or very formal sense unless further interpreted and defined as having a meaning consistent with the related technical literature and the presently disclosed contents.

Hereinafter, a plating process of an aluminum wheel according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to the following embodiments. Therefore, it will be apparent to those skilled in the art that the present invention may be variously modified without departing from the technical spirit of the present invention.

2 is a process chart for the aluminum plating process according to an embodiment of the present invention. As shown, the overall process is a nickel strike plating process 265 added between the pretreatment process (200 ~ 260) and the copper plating process (270 ~ 280), compared to the general aluminum plating process, and also pretreatment of aluminum The in-situ dismudge process and the jincate process have also been changed from the conventional methods. Hereinafter, each step will be described in detail.

Pretreatment process

The pretreatment process (200 ~ 260) is a polishing process 200, degreasing process 210, etching process 220, dismuting process 230, jinkate primary process 240, jinkate peeling process 250 And a jinkate secondary process 260, each process being performed as follows.

The polishing process 200 is the first operation to make the aluminum wheel uniform plating, and in the embodiment of the present invention, an automatic polishing machine capable of simultaneously polishing four wheels after the first polishing is generally manufactured. Heavy polishing was performed, and finishing polishing was performed by hand using an orbital sander.

The degreasing process 210 is a process for removing foreign substances and oil components attached to the aluminum wheel. In an embodiment of the present invention, first, using a trade name Metex SU-486, about 2 to 5 minutes, about 60 ° C. or more. After removing the foreign matter on the surface by polishing at high temperature, the foreign matter and oil components were completely removed by ultrasonic degreasing for about 3 to 7 minutes using the trade name Metex S-1640.

The etching process 220 is a process for removing the oxide film formed on the surface of the aluminum wheel, in the embodiment of the present invention by using a trade name Uniclean (152) using a method for about 30 to 60 seconds at room temperature Was removed.

The smut process 230 is a process for removing the reducing metal salt (ie, smut) generated on the surface of the aluminum wheel after the etching process 120, in the embodiment of the present invention, Smut was removed by treatment for 1 minute at room temperature using Metex Etch Salts. Such a good result of the smut treatment contributes to the smoothing of the subsequent scouring treatment, further improving the adhesion and surface conductivity of the plating layer.

The zincate primary process 240 is zinc substitution plating, in the embodiment of the present invention, a mixed solution of zinc 6 ~ 15g / l, nickel 5 ~ 10g / l in about 30 seconds to 90 seconds at 20 ~ 30 ℃ It was.

The zincate peeling process 250 is a process of dissolving the produced zinc film, in the embodiment of the present invention by using a trade name Metex CA 3107 for about 1 second to 10 seconds at room temperature to dissolve the zinc film It was.

The second gating step 260 was performed under the same conditions as the first gating step 240 by zinc substitution plating, and as a result, it was possible to obtain a dense film compared to the film after the existing gating process.

Evaluation of film characteristics formed after pretreatment

The film produced through the pretreatment process was confirmed by the cross hatch test (Cross Hatch Test) method using the 3M610 tape specified in the GM9071P standard and the results are shown in FIG.

As can be seen in FIG. 3A, the marks attached to the tape are clearly observed, which means that the zinc layer is slightly peeled off after the existing jincate treatment. On the other hand, as shown in Figure 3b, unlike the comparative example in the case of the film produced according to the present invention, the marks attached to the tape is not observed at all, which means no peeling of the zinc layer at all. That is, it can be seen that a sound pretreatment coating can be obtained through pretreatment according to an embodiment of the present invention.

In addition, the surface conductivity of the film obtained through the pre-treatment process was confirmed by using a 4 Point Probe equipment, the results of the surface conductivity after the jingate treatment was as shown in Table 1 below.

Surface conductivity measurement result division unit
(/ Ωcm) After conventional jinkate treatment 0.051 After jinkate treatment according to the present invention 0.054

As can be seen from Table 1, the surface conductivity (0.054) of the zinc coated film according to the embodiment of the present invention was somewhat better than the surface conductivity (0.051) of the zinc coated film according to the conventional method.

Plating process

After the pretreatment 200 to 260 described above, nickel strike plating 265 was performed. The nickel strike plating 265 was plated for 2 to 5 minutes at a current density of 3 to 5 A / dm 2 on the quenched surface to have excellent adhesion and surface conductivity as described above, and the nickel strike plating solution was semi-gloss nickel. It was maintained at the same level as the plating solution.

The copper plating process (270 ~ 280) is a process for obtaining the leveling and smoothness, in the embodiment of the present invention by using a copper plating solution of copper sulfate 190 ~ 250g / l plating at 50 ~ 100 minutes at room temperature plating thickness A plating layer of 30 to 40 µm was formed.

The nickel plating process 290 is a process for imparting corrosion resistance to the plating layer, in the embodiment of the present invention using a nickel plating solution of nickel sulfate 250 ~ 400g / l, nickel chloride 30 ~ 50g / l 50 ~ 65 ℃ Plated under plating conditions of 10 to 30 minutes to form a plating layer having a thickness of 20 to 30 μm.

The chromium plating process 300 is a process for imparting corrosion resistance and glossiness to an aluminum wheel. In an embodiment of the present invention, plating is performed under plating conditions of 2 to 3 minutes at room temperature using a plating solution of chromic acid 200 to 350 g / l. To form a plating layer having a thickness of 0.3 μm or more.

Coating characteristic evaluation

The plating adhesion between the aluminum wheel plated in this manner and the aluminum wheel plated by the conventional method was evaluated by a band saw method.

As can be seen in Figure 4, it can be seen that the adhesion and appearance of the plated plating layer is significantly improved compared to the conventional method through the plating method according to an embodiment of the present invention. In FIG. 4, the cutting layer was cut several times with a band saw to show the result. In the case of the plating layer according to the existing method, as a result of the adhesion test by the band saw, it was found that the plating layer was partially peeled off from the cut portion, as shown in the display portion. I could confirm it.

1 is a plating process diagram of a conventional aluminum wheel.

2 is a plating process diagram of an aluminum wheel according to an embodiment of the present invention.

3A and 3B are photographs showing a state after a cross hatch test on a film formed through a conventional pretreatment process and a pretreatment process according to an embodiment of the present invention, respectively.

4A and 4B are photographs showing the state after the evaluation of plating adhesion using a band saw for the aluminum wheel plated according to the embodiment of the present invention and the conventional method, respectively.

Claims (5)

As the electroplating method of aluminum wheel, Pretreating the aluminum wheel, Performing nickel strike plating on the pretreated aluminum wheel, And copper plating, nickel plating and chromium plating sequentially on the nickel strike plating layer. The method of claim 1, wherein the pretreatment of the aluminum wheel, A polishing step, a degreasing step, an etching step, a smut step, a jinating treatment step of the aluminum wheel, The dismuting step is characterized in that using a mixture comprising hydrogen peroxide, ammonium fluoride, sulfuric acid and iron compounds. The method of claim 2, wherein the ginkgo processing, It consists of the jinkate primary treatment, jinkate peeling and jinkate secondary treatment, In the first and second treatments of zinc quenching, the mixed solution containing zinc 6-15 g / l and nickel 5-10 g / l by zinc substitution plating is treated in a range of 30 to 90 seconds at 20 to 30 ° C. Way. The method of claim 1, The nickel strike plating is performed for 2 to 5 minutes at a current density of 3 to 5 A / dm 2. The method according to any one of claims 1 to 4, wherein the aluminum wheel is made of an alloy containing Si and Mg.

Images