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Historical Articles

May, 1953 issue of Plating

 


In some respects the stale of development of Japanese electroplating practice is ten to twenty years behind United States practice; in other respects it parallels United States practice closely. Japanese employ the same general plating procedures used in the United States. Their needs include better cleaners, bright plating solutions, and better plating equipment. The Japanese employ certain processes not used in the United States. These include: chromium plating at room temperature; Daniell cell copper plating; oxalic acid anodizing. Electropolishing of low carbon steel, chromium steel, and brass is carried out commercially.


JAPANESE ELECTROPLATING PRACTICE
— a report—

EZRA A. BLOUNT, Editor, Products Finishing Magazine.

 

INTRODUCTION
The development of Japan’s electroplating industry has not been spurred, as has the electroplating industry in the United States, by the demands of the automotive and home appliance industries. These industries are not important factors in the Japanese economy. Understandably, progress of a scientific and engineering nature in electroplating has been slow during the past fifteen to twenty years, and this fact, added to metal shortages and lack of consumer demand for the products of the electroplating industry, has been a determining factor in establishing the present position of electroplating in Japan.

There has been the further disadvantage that the industry has had to depend on private or individual research for new developments in electroplating. There has not been the concentrated effort on development of new methods by supplier companies that has been the blessing of the American electroplater. Japan’s suppliers seem to confine their efforts to the importation of such products as can be used, the manufacture of generators, rectifiers, and electrical equipment, the manufacture of buffs and buffing compounds, buffing and polishing equipment, tanks, and the basic chemicals without which the plating shop cannot operate. It has remained to the few universities, research organizations, and societies to conduct such research as was possible.

Notwithstanding the handicaps under which it has operated in recent years, the Japanese electroplating industry is substantial. It is estimated that there are about 3,000 plating shops, or plants with plating facilities, in Japan, and about 1,000 of these are in the Tokyo area. In 1949 approximately 25,000 persons were engaged in the industry, including platers, polishers, chemists and technical men, shop owners, and managers, and it is estimated that a great many more individuals are involved today.

Plating shops range in size from one- or two-room shops, employing two or three persons to fairly large plants occupying one or more buildings. Manufacturing plants in Japan are not the large, multi-story structures that are common in the United States, but are generally made up of several one- or two-story buildings grouped together in one area or “compound” surrounded by a wall or strong fence. In the smaller shops one of the buildings serves as the business office and the owner’s home. In the larger plants, the owners do not live on the factory premises.

Fig. 1. In the polishing and buffing room of the Miyata Works, Ltd., steel bicycle parts are polished, employing the following cycle: 120 emery set-up wheel (dry) 220 emery set-up wheel with tripoli as lubricant, 320 emery set-up wheel using tripoli. Polishing wheels are made by gluing buff sections together. A cold cement is used to set up the wheels. Polishing speed is 8,000 sfm. (Photo courtesy Products Finishing) Fig. 2. Cleaning lead antimony slush castings in the plant of Yamato-Gumi. The operator in the foreground has just removed a basket load of parts from the hot alkali soak cleaning tank. The tank, which is kept covered except when loading and unloading, is heated with charcoal

SUMMARY OF POLISHING AND PLATING OPERATIONS
A brief review of some of the electroplating operations carried on in Japan will indicate that some of the methods used are quite similar to those in use in the United States; others are quite different. Another factor is that the Japanese electroplating industry, like the entire Japanese economy, is geared fundamentally to hand operation.

Metal polishing is accomplished with polishing lathes and set-up wheels, followed by buffing where such an operation is required (see Fig. 1). Backstands and coated abrasive belts are not used. Emery cake is used for lubrication and cutting during the polishing operation. For buffing, tripoli and lime buffing compounds are employed. Greaseless buffing compounds used to produce a satin finish, are rarely employed.

Fig. 3. Lead antimony castings, alkali cleaned, are rinsed and scrubbed in wood tubs filled with water, using a fine abrasive powder resembling pumice. They are then racked for copper plating Fig. 4. A view of the well-arranged generator room at the Iwasaki Communications Manufacturing Company, Ltd.

Cleaning is done by means of trichlorethylene degreasers, with lot caustic solutions (see Fig. 2), or by means of soap solutions and hand scrubbing with a type of pumice (see Fig. 3). These operations may be combined to produce the desired results, or may be used in connection with various pickling operations either before or after the cleaning operation proper, One great need of the Japanese electroplater is a counterpart of the modern, American well formulated cleaner, which has been designed for a specific purpose,
Pickling, acid dipping, or bright dipping operations are carried out with hydrochloric, sulfuric, phosphoric, and nitric acids. In bright dips for brass and aluminum, phosphoric acid is favored over sulfuric as one of the ingredients.

Metals deposited include: copper, brass, nickel, zinc, cadmium, chromium, silver, tin, gold, black-nickel, iron, and lead. Although automatic plating machines are quite rare, barrel-copper, cadmium, zinc, nickel, and chromium plating is carried out, as well as periodic reverse-copper plating, indicating that some of the more recent developments are being adopted. Aluminum anodizing is performed by the sulfuric acid process or by an oxalic acid process1. Electropolishing of brass, carbon steel, chromium steel, and aluminum also chemical polishing of aluminum—is done. Metal coloring to obtain many interesting effects on electroplated products is an ancient art in Japan and is still carried on extensively.

A review of some of the applications for electroplating in Japan will furnish a better background from which to examine the industry in general and detailed processes in particular. Copper-nickel-chromium, brass-nickel-chromium, or copper-chromium bright finishes are used on automobile, truck and bus parts, sewing machines, bicycles, electric irons, umbrella stems, clock parts, and similar products for export or domestic use. Zinc and cadmium are applied to steel for corrosion resistance, and in a few installations, a chromic acid type bright dip is used after zinc plating to produce a bright finish resembling chromium. Copper and chromium are deposited on printing rolls for color printing; iron and copper are deposited in electroforming printing plates. Hard-chromium plating on dies, journals, shafts, either to obtain increased service life or as a repair procedure, is carried on in about the same way it is in the United States. Anodized aluminum, with or without dyed or lacquer finishes of various kinds, is used extensively in the production of aluminum kitchen utensils, trays, and aluminum communication equipment. Silver and gold plating of jewelry products, brass cosmetic cases; and other luxury items for export are carried out. Electropolishing of brass followed by gold plating is used on some of the elements of telephone receivers. Electropolishing of carbon steel clock pins and straight chromium steel turbine blades is being accomplished2. Aluminum reflectors are being produced by electropolishing and anodizing.

Generally, bright plating solutions are not in use in Japan. Conventional cyanide solutions for plating brass, copper, zinc, cadmium, silver, and gold are employed. Copper is also plated from acid solutions, and in the Daniell cell, in which no outside source of electric current is used. The Watt nickel solution is used generally, and either the 21 Baumé chromium solution containing sulfate in the ratio of 100/1, or a room temperature chromium solution employing ammonium fluoride is used for depositing chromium. A fluoborate copper solution in an electrotyping plant, and both lead fluoborate and lead sulfamate solutions in a refining plant are examples of other solution types that were observed being employed.

There are burnishing barrels in use, but barrel finishing is not well developed. Electricity is more readily available than any other form of power and that fact dictates the choice and design of equipment. Equipment for electroplating is adequate to handle the solutions and the methods employed. Generally, steel or wood tanks are used. Some steel tanks are lined with lead where such is necessary. Nickel plating tanks are usually made of wood and lined with pitch. Concrete tanks; lined with lead or pitch, are used in the larger anodizing shops. Rubber or plastic tank linings are not available; neither are plastic rack coating materials. Solutions are heated by electric immersion heaters, steam coils, coal, or charcoal. Since heat in factories is not general, tank heating becomes a difficult matter. Power for plating is supplied by motor generator sets (see Fig. 4), selenium rectifiers, or mechanical rectifiers. It is quite common for each plating shop to install its own private transformer station. This is an added expense to the electroplater. Solution maintenance is not a strong point with Japanese electroplaters partly by reason of the slow speeds of plating, and the kinds of solutions used. There are some solution filters and a few resin demineralizers to purify the water for precious metal plating. A few centrifugal dryers, electrically heated, are in use.

Fig. 5. Steel bicycle parts, previously brass and nickel plated, are chromium plated at room temperature in the Tokyo plant of Miyata Works, Ltd. Lead anodes containing 4 per cent antimony are used; the tank is steel unlined. A 300 ampere, 10 volt rectifier (right background) furnishes power for the operation. (Photo Courtesy Products Finishing) Fig. 6. One of the room temperature chromium plating tanks in the plant of Toyo Dento K.K. The tank is steel, unlined and lead antimony anodes are used. Racks used for chromium plating are insulated with a solution of celluloid in amyl alcohol, and with vinyl chloride tape

ROOM TEMPERATURE CHROMIUM PLATING
During the course of the author’s term of service in Japan, it was his privilege to visit a number of electroplating plants and factories with electroplating departments. The practices and equipment noted in a few of these will be outlined to serve as illustrations of general conditions existing in the Japanese electroplating industry.

One solution not used in the United States, which is used to a considerable extent in Japan, is the room temperature chromium plating solution. This bath was observed in operation at both the Tokyo and Matsumoto plants of the Miyata Works, Ltd.3 (see Fig. 5) and at the Toyo Dento K.K. (The Oriental Electroplating Company). At the Miyata plant steel bicycle parts are polished, brass and nickel plated, and’ then chromium plated for two to three minutes in the following solution under the operating conditions noted:

Chromic acid 33. 5 oz/gal
Chromium sulfate 0.2 ozlgal
Ammonium fluoborate 0.8 oz/gal
Temperature 77° F
Voltage 4.5 volts
Current density 50 to 70 asf
Anodes lead, 4 per cent antimony
Anode to cathode ratio 3.5

A thickness of 0.00002 to 0.00005 inches is obtained. Parts to be plated in this solution are nickel buffed with a white lime composition, wiped with dry chalk, racked or wired, dipped in 10 per cent sulfuric acid, water rinsed, and then chromium plated. Following plating, work is rinsed in a concentration or dragout rinse, and then in clear water.

The development of the room temperature chromium plating solution is attributed to the late Yostio; Koshino4, and has been described also by Dr. Saliae Tajima5, 6. Two general types of solution are recommended, with variations of each being employed by various shops to suit their own conditions. The two types of solution are:

Chromic acid 33.5 to 10.0 oz/gal 48 oz/gal
Ammonium fluoride 0.4 to 0.8 oz/gal 0.8 oz/gal
Chromium sulfate none 0.2 oz/gal

The solution containing ammonium fluoride only is said to produce a deposit with a dark luster suitable for some special purposes, while the solution containing both ammonium fluoride and chromium sulfate produces the bluish chromium deposit suited to general use. A solution with a higher chromic acid concentration exhibits less tendency toward burning and produces a brighter deposit.

In the plant of the Toyo Dento K.K. such items as gasoline tank caps, umbrella stems, builders’ hardware, and automobile bumpers are chromium plated by this method. The solution used at Toyo Dento is as follows:

Chromic acid 32 oz/gal
Sulfuric acid 0.33 oz/gal
Ammonium fluoride 0.54 oz/gal
Current density 50 asf
Voltage 4.5 volts
Temperature 80° F

Plating is carried out in a plain steel tank (see Fig. 6) and lead anodes containing 11) per cent antimony are used. Advantages of the low temperature plating process, as outlined by Toyo Dento officials, include the fact that the low current density favors plating shop operation during periods when electric power is restricted. Since nickel is so limited, very little nickel is applied and the lower current density in chromium plating prevents peeling of the nickel plate, which might otherwise be experienced under such conditions. Job plating shops with varied production also find the improved throwing power of the low temperature solution advantageous, since auxiliary anodes are required less frequently.

Fig. 7. Small parts for clocks are barrel nickel plated and then barrel chromium plated 10 minutes in the Seikosha Works. The drive motor for rotating the barrel at 2 rpm can be seen in the center background, and, in the right foreground, can be seen the down-draft exhaust Fig. 8. A view of one of the eight Daniell Cell acid copper plating tanks in the Yamdto-Gumi plant. Castings are cyanide copper flashed and then plated 5 to 20 hours in this solution. Electrical energy is generated in the tank and no external powers employed. The plating tank is wood, insulated inside and out with asphalt

BARREL CHROMIUM PLATING
Barrel chromium plating is being accomplished in one plant of the Seikosha Works, largest clock manufacturer in Japan. Small steel clock parts of various kinds are first barrel nickel plated and then chromium plated in the barrel shown in Fig. 7. The solution used is chromic acid, 50 oz/gal, and sulfuric acid in the ratio of 100/1. Plating is carried out at 35000 amperes for a seven-pound load, ten volts, and a temperature of 115° F. The barrel, which rotates at two rpm, is made of nickel chromium steel. The plating tank is steel, glass lined, and is jacketed with a water jacket fitted with steam coils.

As a matter of information, a barrel chromium plating process to be operated at 80 to 90° was developed by Yoshio Koshino, and has been reported in the literature. This solution contains chromic acid, boric acid, and ammonium fluoborate.

HARD CHROMIUM PLATING
Hard chromium plating on camera parts, steel molds for the plastics industry, steel rolls for rubber mills, wire drawing dies, paper drying rolls, diesel engine crankshafts, pipe forming mandrels, dies for steel extrusions, and similar applications, is accomplished in the plant of Koka Chrom a leading hard chromium plater in the Tokyo area. The solution used is the conventional bath containing 33 oz/gal chromic acid and 0.33 oz/gal sulfate, operated at 130° F. Articles to be plated are cleaned by vapor degreasing, immersed in the solution and treated anodically for five to fifteen minutes. Plating is then accomplished in the normal manner at 250 to 500 asf for a sufficient length of time to produce the desired thickness. Koka Chrom officials stated that in some cases plating thicknesses of 0.01 inch were being deposited. Although the plate is fairly bright, it is buffed with green chrome rouge, in some cases, to produce a smooth surface.

Lead lined, steel plating tanks are used, and these tanks are insulated to minimize heat loss. Electric immersion heaters maintain operating temperatures. Plain steel anodes, shaped as required, are employed. The iron content is controlled by electrolyzing the solutions, employing a cathode in a porous cup, when the plant is not in operation. Ferric hydroxide is formed at the cathode and retained in the cup. Some idea of the size of the plant may be gained from the fact that there are eight large chromium plating tanks installed, and the generator capacity is over 8,000 amperes.

DANIELL CELL COPPER PLATING
Daniell Cell acid copper plating seems to be well suited for copper plating lead antimony alloy slush castings which, when complete, form cigarette cases, ash trays, jewel boxes, powder boxes, candy dishes and similar items. Advantages cited for the process include the claim that the copper is deposited uniformly all over articles of intricate shape, and that as much as four times the quantity of work can be plated in a tank at one time as could be plated in a conventional acid copper solution.

In the Yamato-Gumi plant, the lead antimony castings are buffed, soak cleaned in a hot solution containing 10 per cent sodium hydroxide and 1 per cent of a mixture of sodium silicate, soda ash and rosin (see Fig. 2). They are then rinsed and hand brushed with a fine powder resembling pumice (see Fig. 3). Racked on simple contact racks insulated with celluloid tubing, the castings are flashed in cyanide copper and hung in the Daniell cell copper plating tank (see Fig. 8).

As can be noted, the “cathode” rods are located along both sides of the tank, and the “anode” rods located in the center. Cross bars connect the anode bar with the cathodes. The plating solution is an acid solution of copper sulfate of about 20° Baumé density. The skin membrane bags in the center of the tank contain a dilute solution of sulfuric acid. Zinc metal is hung inside the skin bags and connected electrically to the “anode” rod. As the zinc dissolves in the sulfuric acid, electrical energy is generated which causes the copper to be deposited on the articles hung on the “cathode” bars. A plating time of from five to twenty hours is employed. In twenty hours a plate thickness of approximately 0.0005 inch can be produced.

Fig. 9. In the plant of the Seikosha Works carbon steel clock pivots and small screws are electropolished for 90 seconds in a mixture of perchloric and acetic acids. Exhaust hoods are mounted over the small tanks. A 40-volt rectifier furnishes power for the installation Fig. 10. A view of the electropolishing installation in the Nikko Kinzoku-Kagaku K.K., one of the two electropolishing Job shops in Japan. Chromium steel turbine blades, bobbins for the textile industry, and similar products are electropolished in a phosphoric-sulfuric-chromic acid solution

ELECTROPOLISHING
The electropolishing installations visited in Japan were comparatively small and specialized in their work. In the Seikosha Works, previously mentioned, carbon steel clock pivots and small screws are electropolished in a perchloric-acetic acid solution developed by Jacquet. The laboratory scale setup (see Fig. 9) consists of three one-gallon glass tanks fitted with exhaust hoods. Glass cooling coils around the inside of each tank hold temperatures below 86° F.

Pivots and screws are cleaned by tumbling in wood powder, racked on small spring-type racks, and electropolished for ninety seconds. They are then rinsed in hot water containing 3 per cent oxalic acid and dipped in a petroleum base corrosion inhibitor.

One of the two job shops in Japan organized to perform electropolishing exclusively is Nikko Kinzoku Kagaku K.K. Here, 13 per cent chromium steel turbine blades, bobbins for the textile industry, and similar products are processed. The articles are given a preliminary polishing with 200 emery, and then racked on stainless steel racks fitted with brass hooks for electropolishing.

Parts are electropolished lor one to seven minutes in a solution of:

Phosphoric acid (1.95 sp. gr.) 5 parts
Sulfuric acid (1.80 sp. gr.) parts
Chromic acid 1 part
Water—less than 5 per cent by volume

The solution is operated at 210 to 250° F in heat resistant, acid proof crocks, as shown in Fig. 10. A current density of 150 to 400 asf at 20 volts is employed. The president of Nikko Kinzoku-Kagaku reported that the electropolishing solutions had been used for three years. Additions of sulfuric, phosphoric, or chromic acids are made periodically as each solution requires.

Fig. 11. In the communications industry the oxalic acid anodizing process is employed to impart electrical resistance to aluminum surfaces. These telephone parts are being anodized in oxalic acid in the Iwasaki Communications Manufacturing Company, Ltd. plant. The parts are anodized and sealed—not dyed Fig. 12. A view of one portion of the anodizing department of Nasu Aluminium Industry Company, Ltd. The tanks are concrete, lead lined. When large kettles (right foreground) are anodized, separate cathodes must be used. The regular graphite cathodes are fitted with shields and a baffle arrangement to catch drops of sulfuric acid which rise from the solution on hydrogen gas bubbles

ANODIZING
The anodizing of aluminum kitchen utensils and similar products forms a substantial section of the finishing industry in Japan. In Japan very thin metal is used for kitchenware, and anodizing is used to minimize corrosion and abrasion of the article, and is also used as a strong sales point. The yellow color is used to identify good quality ware. Dr. Sakae Tajima has reported that there are about 100 job anodizing shops in the country in addition to some 200 manufacturers of aluminum ware who have large anodizing installations in their plants. Anodizing solutions of sulfuric acid or oxalic acid are employed. The film formed by the sulfuric acid process is preferred for articles which are to be dyed, and the oxalic acid process is used for articles to be finished in the clear anodic coating (see Fig. 11).

Generally, in the oxalic acid process, the electrolyte is 2-6 per cent oxalic acid, and anodizing is carried out in an asphalt-lined tank. The solution is circulated through another tank for cooling. Aluminum parts are anodized at about 10 asf current density and from 60 to 100 volts a.c. for forty minutes. The a.c. is superimposed on 15 to 30 volts d.c. in many eases.

In the operation of the sulfuric acid process, 15 per cent sulfuric acid at a temperature of 77° F is used. The tank is usually constructed of concrete, asphalt or lead lined. Cooling water is circulated through lead coils in the tank for cooling. Current density is 10 asf at 15 volts d.c.; anodizing time is forty minutes. Parts anodized by either process are steam sealed at 70 to 75 psi for twenty to thirty minutes.

Fig. 13. Anodized aluminum lunch boxes are dyed the favored light yellow color by 1-minute immersion in a hot tea solution in the Nihon Alumilite Company plant. Then the interior surfaces are dyed bright red, blue, or any desired color by mounting the boxes in pairs on a suction plate covered with soft rubber. A vacuum line holds the articles on the plate while dyeing is accomplished. The rubber prevents leakage of the dye solution to the inside of the lunch box
Fig. 14. Following anodizing and dyeing, aluminum articles are sealed in steam at 75 psi. This is a view of one of the three autoclaves in the plant of Nasu Aluminium Industry Co. Ltd.

At Nihon Alumilite Company buffed aluminum lunch boxes, canteens, trays, and kitchen utensils are prepared for anodizing by the following process:

1. Degrease in 5 per cent sulfuric acid at 175° F.
2. Water rinse.
3. Dip in 5 per cent potassium dichromate, acidified.
4. Water rinse.

Following a sulfuric acid anodizing operation (see Fig. 12), parts are rinsed in cold water, dyed for one minute in a hot solution of Japanese tea, rinsed (or dyed), dipped in 2 per cent potassium dichromate, rinsed in hot water, and steam sealed. Many interesting effects are obtained by dyeing and airbrushed lacquer designs (see Fig. 13). Following steam sealing (see Fig. 14) and final lacquering, if utilized, products are buffed lightly to impart a gloss to the surface (see Fig. 15). Open flame gas heaters are used to warm the articles slightly prior to final buffing.

Fig. 15. A view of the color buffing line in the plant of Daito Kinzoku K.K. After steam sealing and lacquering, aluminum products are buffed lightly on loose buffs, using a lime compound Fig. 16. A view of the well-arranged plating department in the plant of Iwasaki Communications Manufacturing Company, Ltd. The tanks shown are steel, asphalt lined, and are used for nickel plating

SOCIETIES AND ASSOCIATIONS
The Japanese have many groups of technical and management men interested in electroplating. Their practice appears to favor the organization of many independent groups, rather than the American method of forming many branches of a national organization. The societies, as well as the universities, sponsor classes in electroplating theory and practice. Such efforts are aiding improvements in plating shop methods and equipment, as illustrated by the well-arranged plating room shown in Fig. 16. The Japanese are quick to discover their needs, and most industrious in working to improve their methods and equipment.

ACKNOWLEDGMENT
The author gratefully acknowledges the assistance and cooperation of Dr. Sakae Tajma, in arranging tours to many electroplating plants and in acting as interpreter. A sincere expression of appreciation is due also to the following societies and companies, whose cooperation and assistance made possible the collection of information and photographs appearing in this article:

  • Japanese Electroplating Society
  • Society of Metal Finishers
  • Miyata Works, Ltd.
  • Ohsawa Plating Shops
  • Seikosha Works
  • Nippon Kogaku K.K.
  • Yamato- Gumi
  • Tohei Plating Company
  • Fukni Denka
  • Koka Chrom
  • Toppan Printing Company
  • Nasu Aluminium Industry Company, Ltd.
  • Daito Kinzoku K.K.
  • Nihon Alumilite Company
  • Toyo Dento K.K.
  • Iwasaki Communications Manufacturing Co., Ltd.
  • Furukawa Electric Company
  • Nikko Kinzoku-Kagaku K.K.

LITERATURE CITED
1. Sakee Tajima “Anodizing Aluminum with Oxalic Acid’ Products Finishing 17, No. 3, 42 (1952).
2. Sakee Tajima, “Studies on the Electrolytic Polishing”, The Japan Science Review 1, No. 4 (1950).
3. Ezra A. Blount, “Bicycle Finishing in Japan”, Products Finishing 16, No. 9, 88 (1952).
4. Yoshio Koshino “Chromium Plating at Room Temperature”, Plating (Japan), No. 90 (1949)
5. Sakne Tajima, “Recent Developments in Electrolytic Surface Treatments”, J. Electrochem. Soc., JapaD, 17, 279 (1949).
6. Sakae Tajima, Metal Finishing 48, No. 6, 95 (1950).
7. Yoshio Koshino, “Barrel Chromium Plating”, Plating (Japan), No. 114 (1951).
8. Sakae Tajima, private Communication, July, 1952.



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