JPH0741987A - Partial plating method for resin product - Google Patents

Abstract

PURPOSE:To prevent the contamination of electroplating solns. as far as possible and to surely prevent the formation of electroplating layer in a part where plating is not required. CONSTITUTION:An electroless plating layer 15 is formed in the entire part on the front surface of a grill body 2 exclusive of bottom 11a of line groove 11 having an approximately V-shaped section. The grill body 2 is then subjected to electrolytic peeling. The electroless plating layer 15 of the part where the plating is not required is completely dissolved. In the electroplating stage, at first, strike nickel plating layer is formed on the front surface of the electroless plating layer 15 of the part where the plating is required. The electroplating layer 16 is thereafter formed by subjecting the grill body to the respective plating stages of a copper plating stage, etc. The electroless plating layer 15 of the part where the plating is not required is not exposed after the strike nickel plating stage and, therefore, the dissolution of the layer in various kinds of the plating solns. does not arise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for partial plating of a resin product in which a plating layer is formed only on a portion of the surface of a resin base material which requires plating.

[0002]

2. Description of the Related Art Conventionally, as this type of technology, there is one proposed in Japanese Patent Application No. 5-83603 filed by the present applicant. In this technique, as shown in FIG. 15, for example, first, a groove 5 having a substantially V-shaped cross section is formed in the step portion 51 by molding.
2 is formed into a ring-shaped grill body 53, and the grill body 53 is electroless plated. At this time, the groove 5
In the bottom portion 52a of No. 2, since the gap distance is narrow, plating is not performed, and the electroless plating layer 54 is formed in all the portions except these. Next, the grill body 53 on which the electroless plating layer 54 is formed is subjected to electroplating. For details of this electroplating process, strike nickel plating process,
It consists of multi-step processes such as copper plating process, nickel plating process and chromium plating process. Then, in the series of electroplating steps, the electroless plating layer 54 formed in the portion not requiring plating is gradually dissolved by the electroplating solution in each step. On the other hand, in a portion requiring plating, the electroplating layer 55 including a strike nickel plating layer, a copper plating layer, a nickel plating layer and a chromium plating layer is formed on the surface of the electroless plating layer 54 by energization.
Are sequentially formed. In this way, the portion where the plating layer 56 including the electroless plating layer 54 and the electroplating layer 55 is formed is covered with the electroforming mask 57, and coating is applied toward the exposed portion to form the coating layer 58.

Therefore, by going through the above steps, a front grill can be obtained in which the plating layer 56 is formed only in the necessary portions and the coating layer 58 is formed directly on the grill body 53 in the other portions.

[0004]

However, in the above-mentioned prior art, in the above series of electroplating steps, the electroless plating layer 54 formed in the portion not requiring plating is formed by the electroplating solution in each step. It was gradually being dissolved. For this reason, all the plating solutions in each electroplating process are contaminated with the metal ions forming the electroless plating layer 54. As a result, it is necessary to frequently replace the contaminated plating solution, resulting in an increase in cost.

Further, in the electroplating process, for example, when the electroless plating layer 54 still remains in a place where plating is not required at the stage when the copper plating layer or the like is formed thick, the groove groove is carefully formed. 52 by electroless plating layer 5
Despite dividing No. 4, the copper plating layer and the groove 5
There is a possibility that the electroless plating layer 54 separated by 2 may be connected. In such a case, the electroplated layer 55 was formed on the remaining electroless plated layer 54, and as a result, the desired partially plated product could not be obtained.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a resin product in which a plating layer is formed only on a portion of the surface of a resin base material which requires plating. In the partial plating method, it is possible to prevent the electroplating solution from being contaminated as much as possible, and it is possible to reliably prevent the electroplating from being formed in an unnecessary portion of the plating. To provide.

[0007]

In order to achieve the above object, the present invention provides a partial plating method for a resin product in which a plating layer is formed only on a portion of the surface of a resin base material which requires plating. In the surface of the base material, a groove having a substantially V-shaped cross section is formed in an annular shape or a part of an annular shape in a boundary line portion between a portion requiring plating and a portion not requiring plating. Formed on the base material that has undergone the electroless plating step, and an electroless plating step of forming an electroless plating layer on a portion of the surface of the base material other than the bottom portion of the groove. An electroplating step of electrically conducting a necessary portion of the electroless plated layer to form an electroplated layer made of a plurality of metal platings on the required portion of the electroless plated layer. And in the electroplating process Kicking, or the front and rear stages thereof when subjected to the first metal plating, and the gist thereof to the electrolytic stripping the electroless plating layer in a portion that does not require plating.

The term "first metal plating" is intended to include both the case where the first electroplating is performed and the case where the first electroplating is performed immediately after the first electroplating.

[0009]

According to the above structure, in the groove forming step,
A groove having a substantially V-shaped cross section is formed in a boundary line portion between a portion requiring plating and a portion not requiring plating on the surface of the base material so as to form an annular portion or an annular portion. Next, in the electroless plating step, an electroless plating layer is formed on the surface of the base material. At this time, the electroless plating layer is not formed because the plating solution does not reach the bottom of the groove. Therefore, the electroless plating layer is formed on the surface of the base material other than the bottom of the groove. Further, in the electroplating process, a portion of the electroless plating layer formed on the base material that needs plating is electrically conducted, and a portion of the electroless plating layer that requires plating has a plurality of metal plating layers. An electroplated layer of is formed.

According to the present invention, in the electroplating step, the electroless plating layer of the portion which does not require plating is electrolytically peeled at the time of performing the first metal plating or before and after the first metal plating. Therefore, the electroless plating layer is not dissolved in the metal plating solution in the subsequent electroplating process. Also, in the subsequent electroplating process, the electroless plating layer is not exposed in the part that does not require plating, so an electroplating layer is formed on the part that does not require plating. It will not be done.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a vehicle front grill 1 as a resin product will be described with reference to FIGS.

A front grill 1 as shown in FIG. 2 is mounted on the front surface of the vehicle. Figures 2, 3,
As shown in FIG. 7, the front grill 1 includes a front grill main body (hereinafter referred to as a grill main body) 2 as a base material made of ABS resin, and a part of its design surface, that is, a part of the front surface. The formed plating layer 3 (Fig. 3
Has a mesh-like portion) and a coating layer 4 applied and formed on a portion other than the plating layer 3 (excluding a part on the back side). More specifically, the front grill 1
Is a frame 5 having a substantially rectangular front shape, a plurality of sub-partition plates 6 extending in the horizontal direction within the frame 5, a plurality of connecting plates 7 extending in the vertical direction within the frame 5, and a mark plate (not shown) in the central portion. Mounting plate 8 and frame 5 for mounting
It has a main partition plate 9 extending from to the mounting plate 8. The plating layer 3 is formed mainly on the front side portion of the frame 5 and on the front side portion of the main partition plate 9. The coating layer 4 is formed mainly on the front side portions of the sub partition plate 6, the mounting plate 8 and the connecting plate 7.

FIG. 4 is an enlarged front view showing a part (α portion in FIG. 3) of the main partition plate 9, and FIG. 5 is an AA line in FIG.
It is a line sectional view. As shown in these figures and FIG. 7, in the front side portion of the grill body 2, at the boundary portion between the plating layer 3 and the coating layer 4, a front surface protruding vertically from the frame 5 and the main partition plate 9. The side step portion 10 is formed in an annular shape. A groove 11 having a substantially V-shaped cross section is formed in an annular shape (closed curve shape) in the front step portion 10 (see FIG. 3). Further, FIG. 6 shows a part of the back side of the frame 5 (β in FIG. 3).
It is a back view which expands and shows a (part). As shown in the figure, in the rear surface side portion of the grill body 2, a groove 13 having a substantially V-shaped cross section is formed in an annular shape at a boundary portion between the plating layer 3 and a portion where the plating layer 3 is not formed. (See FIG. 3). Further, on the rear surface side portion of the grill body 2, an electrode projection 14 is formed so as to project in the rear surface direction (vehicle rear direction) (see FIG. 3).

As shown in FIG. 7, the plating layer 3 comprises an electroless plating layer 15 and an electroplating layer 16. In this embodiment, the electroless plating layer 15 is made of nickel and has a thickness of about 0.3 to 0.4 μm. Further, the electroplating layer 16 is formed of a metal such as copper, nickel and chromium to a thickness of about 20 to 50 μm and has a multi-layer structure. More specifically, the electroplating layer 16 includes various metals in the order of a strike nickel plating layer, a copper plating layer, a semi-bright nickel plating layer, a bright nickel plating layer, and a chromium plating layer (all not shown) from the lower layer. It is formed by plating.

The widths W and the depth D of the both groove grooves 11 and 13 are formed to be "0.5 mm" and "0.5 mm", respectively. However, the width W is not particularly limited, but is preferably "0.2 mm" or more due to processing restrictions, and is preferably "1.0 mm" or less in order to improve the designability. The depth D is also not particularly limited, but is preferably "0.2 mm" or more due to the processing limitation and "0.
6 mm "or less is preferable. Further, the ratio of the depth D to the width W (D / W) is not particularly limited, either.
"1.0" or more is preferable.

Next, the mold 21 for molding the grill body 2 will be described. As shown in FIG. 9, the mold 21 includes a fixed mold 22 and a movable mold 23. A cavity 24 for molding the grill body 2 is formed by these two molds 22 and 23. However, in the movable die 23 (or the fixed die 22),
The projections 26 and the like for forming the are integrally formed.

Further, various plating solutions for forming each metal plating constituting the electroplating layer 16 will be described. First, the plating solution for forming the strike nickel plating layer that is the lowermost layer of the electroplating layer 16 contains 250 g / L of nickel sulfate, 30 g / L of nickel chloride, and 30 g / L of boric acid.

The plating solution used to form the copper plating layer is copper sulfate 200 g / L, sulfuric acid 50 g / L, hydrochloric acid 0.
It contains 01 g / L and a slight amount of brightener. further,
The plating solution for forming the semi-bright nickel plating layer is
Nickel sulfate 280 g / L, nickel chloride 45 g / L,
It contains 40 g / L of boric acid and a slight amount of brightening agent. In addition, the plating solution for forming the bright nickel plating layer is nickel sulfate 240 g / L, nickel chloride 45 g /
L, boric acid 30 g / L and a slight amount of brightening agent and additives. In addition, the plating solution for forming the chromium plating layer contains chromic anhydride 250 g / L, sodium silicofluoride 10 g / L, and sulfuric acid 1 g / L.

When moving the grill body 2 between the plating solutions, an apparatus as shown in FIG. 8 is used. That is, in the same apparatus, a pair of carriers 31, 32 straddling each plating solution are stretched so as to be movable in the direction of the arrow in the figure. These carriers 31, 32
Are respectively connected to power supply electrodes (not shown) so that currents can flow through the carriers 31 and 32, respectively, and the currents can be alternately switched on and off. In addition, in each carrier 31, 32,
Hangers 33 and 34 made of a conductive material are suspended. When plating is performed, one hanger 33 is hooked on a portion of the grill body 2 that does not require plating, and the other hanger 34 is hooked on a portion that requires plating. .

Further, in this embodiment, a solution for electrolyzing the electroless plating layer 15 in a portion where plating is unnecessary is prepared before the formation of the strike nickel plating layer. This solution contains 50 g of sodium chloride /
L, nickel chloride hexahydrate (NiCl ₂ 6H ₂ O)
It contains 300 g / L and 25 g / L boric acid.

Next, the operation and effect of manufacturing the front grill 1 will be described. First,
The melted ABS resin is injected and filled in the cavity 24 by a known die molding method (see FIG. 9). When the resin is cooled and solidified, both molds 22 and 23 are opened and the grill body 2 is taken out. At this time, both molds 22, 2
3 is opened in parallel with the mold opening direction, that is, in the direction in which the protrusions 26 and the like come out. Therefore, the mold opening is not hindered by the protrusions 26 and the like, and the grill body 2 can be easily taken out. In this way, the grill main body 2 in which the grooved grooves 11 and 13 are annularly formed at predetermined locations is obtained.

Subsequently, the grill body 2 is immersed in an electroless plating solution to perform electroless plating. At this time, the grill main body 2 is hooked on the hangers 33 and 34 of the above-mentioned apparatus, moved along with the movement of the carriers 31 and 32, and is first immersed in the electroless plating solution. Here, as shown in FIG. 10, the bottom parts 11a, 1 of the two groove parts 11, 13 are formed.
In 3a, the plating solution does not reach because the gap is narrow (however, in FIGS. 7 and 10 to 13,
For convenience of explanation, only the front side groove 11 will be described,
The same can be said for the groove 13 on the back side). Therefore, the bottoms 11a and 13a are not plated. In other words, the bottom portions 11a, 1 on the surface of the grill body 2
The electroless plating layer 15 is formed on all parts except 3a.

Next, as shown in FIG. 1, the grill body 2 on which the electroless plating layer 15 is formed is dipped in a solution for electrolytic stripping. At this time, a current from the power supply electrode flows through one carrier 31, and the current flows through the hanger 33 to an unnecessary portion of the electroless plating layer 15 on the surface of the grill body 2. Then, the electroless plating layer 15 formed on the unnecessary portion of the plating is electrolytically peeled by the current and dissolved in the solution. Further, the other carrier 34 is cut off from the current from the power electrode. For this reason, the electroless plating layer 15 formed on the portion where plating is required with the grooves 11 and 13 as boundaries is maintained as it is without being electrolytically peeled. Therefore, by subjecting to the above-mentioned electrolytic peeling, as shown in FIG. 11, the electroless plating layer 15 is formed only on the portion of the surface of the grill body 2 where plating is required.

Subsequently, as described above, the grill main body 2 having the electroless plating layer 15 formed only on the portions where plating is required.
Is subjected to an electroplating process including a strike nickel plating process, a copper plating process, a semi-bright nickel plating process, a bright nickel plating process and a chrome plating process. That is, by moving the carriers 31 and 32, the grill main body 2 is dipped in a plurality of types of electroplating solutions for each of the above-mentioned steps, and a portion requiring plating (mainly the front side portion of the frame 5 and the main portion). The front side portion of the partition plate 9) is electrically connected. That is, the current of the opposite sign flows through the other carrier 32 different from the electrolytic peeling, and the current of the one carrier 31 is cut off. Therefore, the current from the power supply electrode flows through the carrier 32 and the hanger 34 to the portion of the electrode projection 14 that is formed to project on the rear surface side portion of the grill body 2.

Here, first, in the strike nickel plating step, the grill main body 2 on which the electroless plating layer 15 is formed is dipped in the plating solution for forming the strike nickel plating layer for a predetermined time, and
The portion requiring plating is electrically connected. Then, the electroless plating layer 15 is formed on the portion that does not require plating.
No plating is formed because there is no.
On the other hand, the strike nickel plating layer is formed relatively thin on the surface of the electroless plating layer 15 in the portion requiring plating.

Then, in the copper plating step, the semi-bright nickel plating step, the bright nickel plating step and the chromium plating step, the same operations as above are performed (see FIG. 1). At this time, the electroless plating layer 1 of the portion that does not require plating
5 is already dissolved in the electrolytic stripping solution,
It does not exist at these points. Therefore, in various electroplating processes after the strike nickel plating process, the electroless plating layer 15 is not dissolved in each plating solution. As a result, it is possible to prevent each plating solution from being contaminated.

Further, since the electroless plating layer 15 is not exposed at a portion where plating is unnecessary, the electroplating layer 16 is naturally formed on the portion of the electroless plating layer 15 where plating is not required. Nothing. Therefore, it is possible to prevent the plating layer 3 from being formed in a portion that does not require plating and short-circuiting between the grooves 11 and 13.

Then, as shown in FIG. 12, the electroplating step consisting of the various steps described above is performed to form the electroplating layer 16 having the above-mentioned multilayer structure (lower side of the figure). In this way, the grill body 2 in which the electroless plating layer 15 and the electroplating layer 16 (plating layer 3) are formed is formed only in the portion that requires plating.

Thereafter, as shown in FIG. 13, the plating layer 3
The portion on which is formed is covered with the electroforming mask 27.
That is, the electroformed mask 27 is a metal plate having a thickness of “several mm” and has a shape conforming to the shape of the front grill 1. Further, the electroforming mask 27 is appropriately formed with an opening 28 that is opened only in a portion necessary for forming the coating layer 4. By covering the electroformed mask 27, a portion necessary for forming the coating layer 4 is exposed from the opening 28.

Then, as shown in FIG. 14, spray coating is applied to the exposed portion outside of it. By this coating, the coating film layer 4 is formed on the required portions of the coating film. On the other hand, the coating layer 4 is formed on the portion covered with the electroforming mask 27.
Are not formed.

After the coating layer 4 is formed, the coating of the electroformed mask 27 is released to obtain the front grill 1 as shown in FIG. That is, the plating layer 3 is provided mainly on the front side portion of the frame 5 and on the front side portion of the main partition plate 9, and the sub partition plate 6 and the mounting plate 8 are provided.
Further, the front grill 1 having the coating layer 4 mainly on the front side portion of the connecting plate 7 can be obtained.

As described above, according to this embodiment,
When forming the electroless plating layer 15 described above, the groove 1
The electroless plating layer 1 is formed on the bottom portions 11a and 13a of the electrodes 1 and 13.
5 is not formed. Then, when the electroplating layer 16 is formed, only the portion requiring plating is electrically conducted. Therefore, the electroplating layer 16 having a multi-layer structure can be formed on the surface of the electroless plating layer 15 in the portion where plating is required.

According to the present embodiment, the electroless plating layer 15 at a portion which does not require plating is electrolytically peeled off in a step before the strike nickel plating step which is the first step in the electroplating step. Therefore, the electroless plating layer 15 is not dissolved in the plating solution in the subsequent electroplating process. Further, in the subsequent electroplating process, the electroless plating layer 15 is not exposed in the portion that does not require plating, so the electroplating layer 16 is formed on the electroless plating layer 15 that does not require plating. Is not formed. Therefore, according to the present embodiment, the electroless plating layer 15 is not dissolved in the plating solution in various steps after the strike nickel plating step. Therefore, it is possible to prevent each plating solution from being contaminated. As a result, it is not necessary to replace each plating solution due to contamination, and thus cost can be reduced.

Further, it is possible to prevent the plating layer 3 from being formed in a portion which does not require plating, and the short-circuit between the grooves 11 and 13 from occurring.
Furthermore, in the present embodiment, the plating layer 3 can be formed only in the necessary portion. Therefore, when forming the coating layer 4, it is possible to directly form the coating layer 4 on the grill main body 2 without interposing a primer layer. As a result, the step of forming the primer layer is unnecessary, so that it is possible to reduce the number of work steps and the cost. Further, since it is not necessary to form the electroplating layer 16 on the entire surface of the grill body 2, the cost can be reduced accordingly.

At the same time, in the front grill 1, the coating layer 4 is directly formed on the grill body 2. Therefore, the thickness of the portion is reduced by the amount that the plating layer 3 and the primer layer are not interposed. As a result, the thickness of the coating film layer 4 portion can be reduced, and the appearance quality can be improved. Further, since the coating layer 4 and the grill body 2 are both made of a resin material, the coating layer 4 can be firmly bonded to the grill body 2. Therefore, the durability of the coating layer 4 of the front grill 1 can be improved.

In addition, in this embodiment, the groove 11 on the front side serves as a boundary between the coating layer 4 and the plating layer 3. For this reason, the parting portion of the boundary portion is clearly formed instead of the zigzag shape. As a result, the parting line can be made clear and clear, and further, the appearance quality can be further improved.

The present invention is not limited to the above-mentioned embodiment, but may be implemented as follows with a part of the structure appropriately changed without departing from the spirit of the invention. (1) In the above embodiment, the embodiment is embodied in the case where electrolytic stripping is performed before the strike nickel plating step, which is the first plating step in the electroplating step. However, when electrolytic stripping is performed simultaneously with the strike nickel plating step, Alternatively, it may be embodied when electrolytic stripping is performed immediately after the same step.
In these cases, the plating solution in the strike nickel plating step is contaminated, but other than that, the same effect as that of the above-described embodiment is obtained. Further, electrolytic stripping may be performed between the strike nickel plating step and the copper plating step.

(2) In the above-mentioned embodiment, the electroplating process is composed of five processes including the strike nickel plating process, and the electroplating layer 16 made of a plurality of metal platings is formed. If the plating process is composed of a plurality of processes, the order, the number of processes, the type of plating, etc. are not particularly limited. Therefore, for example, the strike nickel plating step can be omitted, the order of the plating steps can be changed, or another plating step can be introduced.

(3) In the above-described embodiment, the present invention is embodied in the vehicle front grill 1. However, in addition to the above, the vehicle door mirror bracket outer cover, back panel, louver, pillar garnish, quarter vent, It may be embodied as a mark plate or the like. Further, the present invention is not limited to the above resin products, and the present invention may be embodied in other resin products partially having a plating layer.

(4) In the above embodiment, the resin material forming the base material is made of ABS resin. However, in addition to this, various resin materials such as polypropylene, polyphenylene oxide, polyamide, polysulfone, polyester, etc. May be used.

(5) In the above embodiment, the electroless plating layer 1
Although 5 is made of nickel, it may be made of copper or the like. (6) In the above embodiment, the grooves 21 and 1 are formed by the mold 21.
3 is formed, but each groove is formed by an NC cutter,
It may be formed by post-processing using an ultrasonic cutter or the like.

(7) The composition of each plating solution described in the above embodiment is not limited to the above.

[0043]

As described in detail above, according to the present invention,
In the partial plating method of the resin product in which the plating layer is formed only on the portion of the resin base material that requires plating, the contamination of the electroplating solution can be prevented as much as possible,
Moreover, there is an excellent effect that it is possible to surely prevent the electroplating from being formed on the unnecessary portion of the plating.

[Brief description of drawings]

FIG. 1 is a process chart showing the sequence of respective steps of an electroless plating process and an electroplating process in one embodiment of the present invention.

FIG. 2 is a front view showing a front grille according to an embodiment.

FIG. 3 is a view showing a plated portion of the front grille in one embodiment, and is a schematic view of the front grille developed on the front surface and the back surface.

FIG. 4 is an enlarged front view showing a part of the main partition plate of the front grille in one embodiment.

5 is a cross-sectional view taken along the line AA of FIG. 4 in one embodiment.

FIG. 6 is an enlarged back view showing a part of the frame of the front grill in one embodiment.

7 is a cross-sectional view showing an enlarged main part of FIG. 5 in one embodiment.

FIG. 8 is a perspective view showing a carrier and the like used in various plating steps in one embodiment.

FIG. 9 is a cross-sectional view showing, in an enlarged manner, a part of a mold for molding the grill body in one embodiment.

FIG. 10 is a partial cross-sectional view showing a state in which electroless plating is applied to the grill body in the embodiment.

FIG. 11 is a partial cross-sectional view of a grill body showing a state in which electroless plating of a portion where plating is unnecessary is melted by electrolytic peeling in one example.

FIG. 12 is a partial cross-sectional view showing a state in which electroplating is performed on the grill body having the electroless plating layer formed therein in one example.

FIG. 13 is a partial cross-sectional view showing a state in which an electroformed mask is coated on a portion of the grill body on which a plating layer is formed in one embodiment.

FIG. 14 is a partial cross-sectional view showing a state in which a coating layer is formed on a portion of the grill body where the plating layer is not formed, in one example.

FIG. 15 is a cross-sectional view of an essential part showing the vicinity of a groove of a front grill in a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Front grill as a resin product, 2 ... Grill main body as a base material, 3 ... Plating layer, 11, 13 ... Grooves, 11
a, 13a ... bottom part, 15 ... electroless plating layer, 16 ... electroplating layer.

Claims (1)

[Claims] 1. A partial plating method for a resin product, wherein a plating layer (3) is formed only on a portion of a surface of a resin base material (2) that requires plating, wherein the base material (2) ) In the boundary line between the portion requiring plating and the portion not requiring plating, a groove groove (11, 13) having a substantially V-shaped cross section is formed into an annular shape or a part of an annular shape. A step of forming a groove, and an electroless plating layer (1) on the surface of the base material (2) other than the bottom (11a, 13a) of the groove (11, 13).
5) and an electroless plating step of forming the electroless plating layer of the base material (2) that has been subjected to the electroless plating step. The electroless plating layer (1
5) an electroplating step of forming an electroplating layer (16) composed of a plurality of metal platings on the above-mentioned necessary plating portion, and at the time of performing the first metal plating in the electroplating step, or before and after that. A partial plating method for a resin product, characterized in that the electroless plating layer (15) in a portion not requiring plating is electrolytically peeled in the step.