JPH0250986B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to Which the Invention Pertains] The present invention relates to electroless plating, and particularly to a circulation type electroless plating method in which a pretreatment liquid, a plating liquid, etc. are forcibly circulated by a pump.

[Prior art]

Conventional electroless plating is a method in which the object to be plated is immersed in a plating solution, so it is possible to plate even complex shapes. Retention tends to occur, and due to this air layer, the plating solution does not touch these areas, resulting in areas that are not plated. Therefore, it was necessary to always take this point into consideration when determining the shape of the workpiece. For this reason, when plating an item that has a horizontal tubular part, such as a heat exchanger, it is necessary to divide it into two parts in advance so that there are no parts that create air pockets before plating. However, the plating of the welded parts makes welding impossible. Therefore, this plating must be removed by some method before welding, which increases the cost and requires a long time to complete the work.

[Purpose of the invention]

The present invention eliminates these drawbacks, and its purpose is to eliminate air pockets and enable plating by forcibly circulating the plating liquid, etc., even if the part to be plated has a complicated shape that tends to cause air pockets. An object of the present invention is to provide a circulating electroless plating method.

[Key points of the invention]

In the circulating electroless plating method of the present invention, when plating the internal passage of an article having a structure having an inlet and an outlet and a bent passage inside, the article is exposed to hot water or hot water in a heat-insulating case. The article is kept warm by a heater, piping is connected to the inlet and outlet of the passage of the article, and the pre-treatment liquid is forced to circulate through the piping from a tank stored with a pump. After washing with water, the plating liquid is forced from the plating liquid tank by a pump. It is characterized by being made to circulate.

[Embodiments of the invention]

To explain the target article to which the circulating electroless plating method of the present invention is applied and the parts that require plating, Figure 1 shows the article, which is a barrel (also called cylinder) used in a twin-screw extruder. This is one of the divided parts.

1 is the barrel body, and 2 is a hole into which the screw shaft of the twin-screw extruder is inserted. 3 is a cooling water flow path;
As shown in the figure, a bent passage is formed inside the barrel body 1. Since industrial water flows through this cooling water channel, it is plated to prevent rust from forming. Figure 2 is an expanded view of the A-A cross section in Figure 1, with lids 4 on both end surfaces.
are fixed by welding to prevent cooling water from leaking. 5 is the inlet of the cooling water, and 6 is the outlet, and the cooling water circulates through the bent passage to efficiently cool the barrel.

FIG. 3 is a diagram showing an example in which the barrel shown in FIG. 1 is subjected to circulation electroless plating. In FIG. A workpiece 13 that is almost filled with water 12 and has a maze-like conduit 13A in which, for example, a plurality of long horizontal pipes are connected by short vertical pipes, is immersed in the water 12, and the water 12 is heated to about 90°C by the heater 14. It has been heated. And the pipe line 13A
This is the part that should be removed. In addition to heating with hot water, a heater (not shown) may be directly attached to the workpiece 13. The pipe line 13A has two pipes 15 and 1.
6, the pipe 15 is connected to a compressed air source 18 via a shutoff valve 17, and the pipe 16 is opened to the atmosphere via a shutoff valve 19. Reference numeral 20 denotes a plating liquid tank, which stores plating liquid 22 heated to approximately 90°C by a heater 21, into which pipes 23 and 24 are inserted, and pipe 23 passes through a pump 25 and a shutoff valve 26 to pipe 15. And the pipe 24 is the shutoff valve 2
By connecting the plating liquid 22 to the pipe 16 through the pipe 7, the plating liquid 22 is circulated within the pipe 13A.

An acid solution 28 made of diluted sulfuric acid or hydrochloric acid for pretreatment is stored in an acid tank 29, and pipes 30 and 31 are inserted in the same way as in the case of the plating solution tank 20, and a pump 32. The shutoff valves 33 and 34 and the pipes 15 and 16 allow the fluid to circulate within the pipe line 13A. Similar to the acid solution 28, an alkaline solution 35 in which caustic soda or the like is dissolved for pretreatment is stored in an alkali tank 36, and the alkaline solution 35 is connected to pipes 37 and 3.
8, a pump 39, shut-off valves 40 and 41, and pipes 15 and 16 to circulate within the pipe line 13A. Water 42 is stored in a water tank 43 for cleaning the plating liquid 22, and the water 42 is circulated in the pipe line 13A through pipes 44 and 45, a pump 46, shut-off valves 47 and 48, and pipes 15 and 16. It's getting old.

Next, the operation of the embodiment described above will be explained. Pipe line 13A which is the part to be plated of workpiece 13 heated to about 90°C by hot water 12 in heat insulation case 11
is first pickled as a pretreatment step. In this case, shut-off valves 17 and 19 are closed and shut-off valves 33 and 34 are closed.
After opening, by driving the pump 32, the acid solution 28 is transferred from the acid tank 29 to the pipes 30, 31, 1.
5, 16, etc., to the conduit 13A for about 20 minutes for forced circulation. After the pickling, the pump 32 is stopped and the shut-off valves 33 and 34 are closed, and then the shut-off valves 47 and 48 are opened for washing with water.
6 for about 5 minutes, the water 42 in the water tank 43 circulates through the pipe 13A and washes it.

After washing with water, shutoff valves 47 and 48 are closed.

Next, as a second alkali pretreatment step, the shutoff valves 40 and 41 were opened and the pump 39 was turned on for about 20 minutes.
By driving for a minute, the alkaline liquid 35 is transferred from the alkaline tank 36 to the pipes 37, 38, 15, 16.
The liquid is forced to circulate through the pipe 13A. After the alkaline washing is completed, washing with water 42 is carried out for about 5 minutes in the same manner as in the case of the pickling described above. After this, as a plating step, the shutoff valves 26 and 27 are opened, the pump 25 is driven, and the plating liquid 22 is discharged from the plating liquid tank 20.
Pipe 13A via pipes 23, 24, 15, 16, etc.
The plating process of the pipe line 13A is performed by forcedly circulating the inside for two to three hours. After the plating is completed, rinse with water for about 5 minutes in the same way as in the case of pickling described above.Finally, by opening the shutoff valves 17 and 19, compressed air from the compressed air source 18 is sent into the pipe 13A, and the remaining water droplets are removed. If you can blow it away, the series of plating operations will be completed.

In the above explanation, the pretreatment process was performed in the order of acid and then alkali, but the order of alkali and then acid may be reversed. In addition, pumps were provided for each of the plating liquid, acid, alkali, and water, but one pump (not shown below) was used, and its discharge pipe was connected from the shutoff valve to pipe 15, and the pipe between the shutoff valve and the pipe was connected to the pipe 15. Road 15
A circuit for cleaning the pump and shut-off valve is provided from the connection part of the pump through an on-off valve. The pump has four suction pipes: plating liquid, acid, alkali, and water, which are inserted into each tank, and shutoff valves 27, 34, and 4 are connected to each tank from pipe 16.
1 and 48.

〔Effect of the invention〕

As explained above, in the circulation type electroless plating method of the present invention, if the bent shape part, which conventionally could not be plated due to air pockets inside if it was left as one piece, can be pretreated if it has a shape that allows circulation. Electroless plating has become possible because the liquid and plating solution are forced to circulate. For this reason, what used to be split into two pieces, plated, and then put back together can now be made into one piece, which has the advantage of lowering costs and significantly shortening the working time. Further, the present invention also has the advantage that electroless plating can be applied to articles having a structure that cannot be split into two.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the barrel of a twin-screw extruder to which the plating method of the present invention is applied, Fig. 2 is an expanded view of the A-A cross section of Fig. 1, and Fig. 3 is FIG. 1 is a mechanism diagram showing an embodiment of the present invention. 11... Heat insulation case, 13... Work, 13A... Part to be plated, 15, 16... Piping, 20... Plating liquid tank, 22... Plating liquid, 28... Acid liquid (pre-treatment liquid), 29... Acid tank, 35... Alkaline liquid (pretreatment liquid), 36...tank, 42...water, 43...water tank.

Claims (1)

[Claims] 1. When plating the internal passage of an article that has an inlet/outlet and a bent-shaped passage, the article is kept warm with hot water or a heater in a heat-insulating case, and the passage of the article is Circulating type electroless plating in which piping is connected to the inlet and outlet, and through these piping, the pre-treatment liquid is forced to circulate from a tank using a pump.After washing with water, the plating liquid is forcibly circulated from the plating liquid tank by a pump. Method.