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Historical Articles

MONTHLY REVIEW

Published by the American Electroplaters Society
Publication and Editorial Office
3040 Diversy Ave., Chicago

Vol. XIV FEBRUARY, 1927 No. 2


EDITORIAL
After reading the November and January issues of our Monthly Review, I would feel remiss in my duty to the Society, as a Past President and Associate Editor, if I did not comment upon the many suggestions of our research and publishing committees.

The report of the efforts and the results of the recent Research Fund Campaign, and the contemplated action of the Bureau of Standards, in conjunction with our Research Committee, is commendable; but the support of the committee by bur membership is to be deplored, and I feel that while this effort upon the part of the American Electroplaters Society may be putting their star of destiny to a severe test, we as members of this great institution of progressive electroplating industry should at least give our support to efforts of these committees whole heartedly, that the world may know these unselfish workers are not laborers in a barren vineyard, but are the direct representatives of the most progressive body of foreman executive electroplaters in the world.

Summarizing: We have never failed in anything that was for progress, education, and good of our craft. Are we members willing to back slide, the greatest progress we have known, by neglecting to even answer the research post cards sent to each of us, and also neglect to give material for publishing committee’s needs, to give us the best publication on our craft known. Let’s awaken from our holiday depression and assume our responsibilities and turn our minds and exuberance into work that these committees may succeed, that we may be successful.

O. E. SERVIS,
Associate Editor


A NEW RUST PROOF BLACK FINISH FOR IRON AND STEEL

By Charles H. Proctor

The slogan of a nationally known paint manufacturer “protect the surface and you protect all,” is truly applicable to the metal fabricating industry whose product must of necessity be exposed to atmospheric influences, which produce-corrosion and the resulting rust—the great destroyer of ferrous metal.

We have been advised by metallurgists and investigators of atmospheric corrosion of iron and steel, that if it were possible to produce an absolutely pure iron, its surface would not rust. They cite as an example an iron pillar located near one of the great gates of the City of Delhi, India, that has stood for 1600 years, exposed to the ravages of atmospheric influence and destruction and still stands as a remarkable example of the rust resisting qualities of pure iron. We can wander over the civilized world and find examples of architectural iron fabricated hundreds of years ago by master blacksmiths at the village forges that have resisted the action of atmospheric influence for generations. What is the reason? Is it possible that in those long years ago, the workers in iron, for steel was unknown, did produce a better iron or incorporate some factors that did produce a better iron? It is not for me to discuss this phase of the subject. Metallurgists and research chemists still have a world field in which to exploit their ideas. My work is to produce commercial results, as the plater states when theory is discussed; he remarks theory is splendid, but I must produce the goods. We all know the ravages of rust when we consider for a moment that five million tons of coal, our greatest natural asset, were used in 1916 and at this date possibly more, in making one million tons of steel to replace that which was lost by rust. The importance of the saving of these products and the labor entering into them can be readily appreciated. One railroad alone reported several years ago a daily loss covering its entire system of eighteen tons per day of metal due to corrosion.

There must come a day when more attention must be paid to the protection of iron and steel from atmospheric corrosion and the resultant rust, the great destroyer, if future ages are to enjoy and benefit from the wonderful metals, iron and steel, we so lightly cast aside. Nature has been bountiful to America in natural resources but as a nation we are wasteful and profligate of these natural resources. Never again in the history of man will nature’s laboratory place below the surface of the earth and in the hills and mountains, the natural resources we have been blessed with throughout the world. Evolution of men and material only occur upon the surface of the earth, not down in its depths beyond the reach of the life-giving sun.

It is not for me to elaborate upon scientific truths; they are always with us but some day humanity of the future must do so to conserve the natural resources that is left from the iron age of today.

In the electroplating industry nearly every first-class plater that has made a thorough study of his art understands the methods in vogue for the deposition of metals upon iron and steel to protect the surface against corrosion and rust, and incidentally heat, and chemical applications which in a great measure protects steel and iron from rust when correctly applied to their surfaces.

Zinc and cadmium are pre-eminent as metal factors. Aluminum is used to some extent by the calorizing method; a sister method to sherardizing.

In the production of rust proof black finishes upon iron and steel by heat methods, the Bower Barff, Bradley, Bon Tempi and Gesner methods are used to a more or less extent. They are all based upon the patents of Bower and Barff, granted in 1857, and consist essentially of heating iron and steel in a closed retort to cherry red at about 1200 deg. F., then superheated steam is injected into the retort, which finally results in the formation of an adhering and penetrating coating of black magnetic oxide of iron, when the surface is finally protected with an oil such as linseed oil and dried thoroughly a rust resisting black finish results.

The Bradley, Bon Tempi and Gesner patents are essentially a modification of the Bower-Barff process, a hydrocarbon such as benzine or gasoline being injected with the steam. The patentees claimed much superior results to that obtained by the Bower and Barff method. This decision is still an open question, and debatable.

In the great hotels of American, the Bower-Barff finish plus later modifications, is used extensively upon builders’ hardware and results in a very lasting finish, unaffected by oxidation and atmospheric rust. There are only three or four nationally known builders’ hardware manufacturers who produce this finish in American.

The Parker process is quite extensively used as a black rust proof finish, and without the final protective oil coating; as a basis for better rust resisting enameled surfaces applied to steel, etc. The Parker process is based upon the original patents of, Coslett and Richards of England. One of the original patents of Coslett expired last year, so is now public property.

Zinc is still the great factor in the protection of steel from corrosion, rust and whether applied by the molten or electrodepositing method, it will possibly never be replaced, due to the low cost of the metal.

Cadmium, due to its much higher cost, will be used for specific purposes. Its resistance to chlorine laden atmospheres of the sea coast makes it applicable to iron and steel surfaces when the cost of the metal is not prohibitive.

Electro zinc plating is constantly increasing in volume. The automotive industries use zinc electro-plated products extensively and the zinc mercury cyanide solutions are gradually eliminating the acid zinc type of solutions, due to its greater throwing power and greater hardness of the zinc mercury deposit which increases its resistance to friction and wear, and atmospheric corrosion.

I learned the other day in the Middle West that one of the greatest manufacturing industries in the world, whose product is found over the entire civilized world, will discard all acid zinc solutions in favor of the cyanide type this year, due to reasons heretofore stated. The firm in question has been experimenting with zinc deposits for several years in its research engineering departments, in New York and Chicago. I have developed a rust proof black finish for steel that is very simple of application. The method can be installed in any plating department that must produce rust-resisting finishes upon steel or iron. The basic idea is not new because three years ago I presented a paper at an educational session of New York Branch entitled, “The Production of Imitation Silver Deposits by the Aid of Zinc Cyanide Deposits and Antimony Oxide.” This original paper, then, was the basis for what I am pleased to term a new rust proof black finish. The details of the production of the finish are as follows:

Process for Producing a Rustproof Black Finish Upon Zinc Plated Steel Surfaces

Part No. 1—
The steel articles to be zinc plated must be clean from grease, oils, etc., and free from rust and scale. The usual procedure in cleansing steel goods for plating can and should be adhered to.

Part No. 2—
The articles should then be immediately plated in the Duozinc Cyanide solution.
Water . . . . . . . . . . . .1 gallon
Cyanegg . . . . . . . . .4 ounces
Zinc Cyanide . . . . . 4 ounces
Caustic Soda . . . . .4 ounces
Cyanobrite . . . . . .1/8 ounce
E. M. F. 5 to 6 volts. Amperage 25 S. F.
Minimum Temperature 110/120° F.
Anodes Duozinc Electrolytic Spelter 2% Mercury.
Time of Plating, 10 minutes minimum.

Part No. 3—
Immediately after Duozinc plating, wash thoroughly in cold water, then immerse in the following solution for a moment:
Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 gallon
Caustic Soda . . . . . . . . . . . . . . . . . . . . . . 4 ounces
White Powdered Antimony Oxide . . . .1/2 ounce
Temperature 120/140° F.

A dead black adherent coating will result, remove from the solution quickly, then wash in cold and boiling water and dry with heat.

The black coating should be protected with a thin coat of lacquer (air drying).

Black Nubelac N. L. L.—2050 B. and Nubelac Thinner N. 331 in proportion of 3 parts to 1 part lacquer is an excellent protective coating. The Nubelac products are manufactured by the Nubian Paint & Varnish Co., Chicago, Ill.

We have found that Benzole colored with Nigrosine Black (Benzole Soluble) and a small amount of a cheap furniture varnish to obtain an adherent mixture will answer the purpose. This mixture should not cost more than 40 cents per gallon.

Any cheap air drying black mixture can be used or any form of black lacquer commercially advertised.
If a dipping process is used to give the articles the final black protective coating, then it is possible that an air blast can be used to an advantage in blowing off excess and drips.

The use of antimony solutions in the coloring of metals is nothing new. I have advocated them in one form or the other for years. Hiorns, in his splendid work entitled, “Metal Coloring and Bronzing,” published in London in 1892, gives considerable detail covering bronzing and coloring of various metals with antimony chloride and hydrochloric acid and antimony sulphide, and sodium hydrate. See pages 213 and 234. In the same work a formula is mentioned on page 212, due to Botteger an authority on electro-plating and metal coloring covering sodium hydroxide, mercury and antimony chloride. “Duillo,” on page 234 of Hiorns’ work, mentions an antimony solution for producing a black color upon zinc which requires an oil or varnish to protect the black, or it will rub off. There exists a U. S. patent, No. 1,436,729, dated November 28, 1922, for black coatings upon zinc prepared from water 150 gallons; sodium hydroxide 76% 2 pounds, butter of antimony 1 pint. The solution must be heated to 212 deg. F. Prior art was established by Hiorns in 1892 for coloring zinc black with antimony salts and sodium hydroxide solution. Therefore, in my opinion the patent referred to is invalidated and the writer does not consider in presenting this paper that he infringes upon any existing patent.

The solution I have advocated to produce the black finish upon the zinc plated surface, acts instantly and is adherent. Tests made with steel automobile rims finished by the process and without the final coat of protective black lacquer or other medium in the testing department of one of the largest automobile rim manufacturing plants in the United States, have found that the rust-resisting qualities of a regular zinc plated steel rim, plated in the Duozine cyanide solution has been increased from the normal 48 to 60 hours salt spray test, using the regular 20 per cent salt spray test, to 120 hours or more, or an increase in resistance to corrosion and rust of more than 100 per cent. With the application of the final coating of black lacquer or similar protective coating for the black finish, the corrosion resistance would be further increased.

It is the author’s opinion that the process being simple in application can be used extensively in the metal fabricating industry, when of necessity a rust proof black finish is desirable and should prove to be a valuable addition to present known methods in the electro-plating industry.


RESEARCH ON “SPOTTING OUT” AT THE BUREAU OF STANDARDS

As you all know, during the past two years the American Electroplaters Society has been engaged in collecting from manufacturers funds to be used for co-operative researches on electroplating at the Bureau of Standards. The goal is a fund of $10,000 per year for three years, based on contributions of $50 or more per year from each subscribing firm. To date about $4,000 per year has been raised, and the campaign is being continued by their Research Committee. All of the branches have learned from Mr. R. J. O’Connor, Chairman of the Research Committee, just what each member can do to help the committee.

Mr. W. P. Barrows, who has been working in the electroplating section of the Bureau, has been appointed as a Research Associate on this fund, and is just starting an investigation of the causes and prevention of “spotting out.” While this difficulty is especially experienced with the so called “oxidized” finishes on such articles as builders’ hardware and lighting fixtures, which consist of iron or steel, plated with copper or brass, treated with a sulphide solution, and finally lacquered; it is also occasionally observed on silver or gold plated articles, and even on solid brass that has not been plated. The information gained will undoubtedly be useful to every plater.

In company with Dr. Blum, Mr. Barrows recently visited a number of plants, mostly in Connecticut, and received much valuable information, and samples of both satisfactory and defective products. All the manufacturers visited expressed their willingness to co-operate in this investigation.
The exact course of the researches will depend upon the information derived from the preliminary study now in progress. The indications are that numerous factors may be involved, such as porosity of the cast or rolled metal, or variations in the methods of cleaning, plating, rinsing, “oxidizing” and lacquering the articles, or in the nature of the materials used in wrapping, or in the conditions of storage, exposure or use. A considerable period will undoubtedly be required to determine the relative effects of each of these possible factors. Whenever the results warrant, progress reports will be published in the Review.

In order that this investigation may be made as comprehensive as possible, the Bureau will be glad to receive from platers or manufacturers, typical samples of spotted products, with full information regarding their origin and history.

As above indicated, this is just the beginning of the research work on these funds collected or subscribed by the Electroplaters’ Society. All of you no doubt think of other objects that should be studied.

When more funds are available, additional researches on electroplating will be started at the Bureau. The progress made will depend largely on the interest and support of the electroplaters and their employers.


SILVER PLATING OF TABLEWARE

By Mr. Elmer Roy Unruh, Dayton Branch

The electro-plating with silver was the first of all the electro-metallurgical processes to be carried out on a large scale, silver plating having been carried on practically for more than 75 years.

All silver plating is conducted in cyanide solutions, not because it is impossible to deposit silver from other types of solutions, but because the metals to be plated would precipitate silver from the solution of its ordinary salts, and silver deposited from solutions of such salts as the nitrate or acetate is usually in very coarse crystals.

Silver deposited from regular cyanide baths is rather coarsely crystalline and frosted in appearance. To remedy this, carbon disulphide dissolved in sodium cyanide solution or in an old silver solution is added to the bath in small quantities to produce a bright deposit.

The fact that most of the metals are above silver in the electrochemical series and therefore tend to precipitate it from its solutions makes difficult the plating of such metals with adherent coatings of silver. The treatment required for any metal depends upon the potential of that metal in the silver solution, which in turn depends upon the composition and silver ion concentration of the solution. It has been found that the potential of silver, and therefore the silver ion concentration, is decreased in a silver solution by the addition of free cyanide. This is the explanation for the use of a silver strike high in free cyanide content for the initial plating upon many metals. From a cyanide silver solution containing no free cyanide, iron or steel can readily deposit silver by immersion, but from solutions with much free cyanide no such deposition occurs. This is confirmed by the fact that in silver solutions containing no free cyanide the potential of iron was found to be negative to silver (able to throw silver out of solution), while in those containing free cyanide the potential of iron is positive to silver (not able to displace it.)

It is the usual practice, especially in the east, either to silver plate direct on the metal, or immerse in a mercury dip and then silver plate. Steel articles are given a double silver strike, first in a solution containing 1/4 oz./gal. of silver, 1/4 oz./gal. copper and 12 oz./gal. sodium cyanide, then in a second solution containing 1/2 oz./gal. silver and 16 oz./gal. sodium cyanide. Brass and nickel silver articles are immersed in a mercury dip, an adherent deposit of mercury being precipitated upon the surface, and struck in a silver strike solution containing 1/2 oz./gal. of silver and 16 oz./gal. sodium cyanide.

It is the usual practice in the west to give brass, nickel silver and steel articles a light nickel plate, then silver strike and silver plate. This is the method we have found most satisfactory for silver plating tableware.

In the plating of tableware we have three distinct types of work or three distinct types of metals to prepare for the plating operation, each one of which requires a slightly different method of preparation.

One class consists of flatware, such as forks, spoons and similar articles made of either nickel silver or brass. The same treatment suffices for both metals, however. The articles come to the plating room direct from the buffing room and are covered with tripoli composition and buffing dirt. The articles are placed in baskets and are immersed in boiling whale oil soap solution and remain here until the tripoli and buffing dirt are removed, which usually takes from 15 to 30 minutes. The baskets are then agitated in a warm solution of a good grade of soap chips to remove all the whale oil soap solution and to brighten the articles. The baskets are then rinsed in boiling water to remove the soap solution, and the articles are ready for the plating operation. This may seem a rather lengthy operation for the removal of tripoli and buffing dirt, but it is the only satisfactory method we have found that will consistently remove the buffing dirt and tripoli and not impair the polish and lustre of the work.

After removal from the baskets, the articles are placed in plating racks and are submitted to the following plating cycle: (1) Boiling electric potash, and (2) dipped direct into 20% solution H2SO4, (3) rinsed in running water, (4) returned to boiling electric potash, (5) rinsed in water, and (6) dipped in 20% solution H2SO4. We found it advisable to use a separate acid dip for this step and not use acid dip in step (2), as a greasy scum forms on the surface of the acid due to immersion of articles covered with hot potash, (7) rinsed in water, (8) nickel plated for 5 minutes at 2-3 volts, (9) rinsed in water, (10) silver strike, and (11) silver plate.

The second class of work consists of knives made of the ordinary steel for cutlery purposes. After the knives are polished they are washed free from grease and emery in hot coal oil and dried in sawdust. The pattern is then embossed on the handles and the knives are sent direct to the plating room. The knives are covered with a slight sawdust film and some grease from the embossing operation. They are placed in baskets and agitated in a boiling potash solution for 10 minutes and then rinsed in water and placed in a small racking up tank filled with borax solution. The knives are removed from the racking up tank and as they are removed each blade is wiped with a wet rag to remove any scum left by sawdust and placed in a plating rack. When the rack is filled it is suspended in a storage tank of borax water until enough racks are ready for a complete run. This method of preparation may seem rather laborious and costly, but we have found that it pays on this class of work for each operation plates 200 dozen or more knives day after day without having a single reject. The racks of knives are now submitted to the following plating cycle: (1) Boiling electric potash, (2) rinse, (3) 20% H2SO4, (4) rinse, (5) boiling electric potash, (6) rinse, (7) 20% H2SO4, (8) rinse, (9) nickel plate 10 minutes at 2-3 volts, (10) rinse, (11) silver strike, (12) silver plate.

The third class of work consists of knives having a stainless steel blade and a low carbon steel handle. These knives are made by welding the handle stock to the blade stock and subsequently forging, rolling and grinding. When completed this weld is an irregular line located in the bolster of the knife. It is required that the handles of the knives be plated and the blade remain unplated. If the usual plating procedure is followed the plate can be stripped off the stainless steel portion, as stainless steel does not respond to the same treatment that ordinary steel does, back to the low carbon steel handle and will expose this irregular weld, presenting an undesirable appearance, so it is desired that an adherent silver plate be placed on the small section of stainless steel in the bolster of the knife.

These knives as they come to the plating room are in the same condition as the ordinary steel knives. They are placed in baskets and agitated in the boiling potash solution for 10 minutes, then rinsed and placed in a racking up tank of borax water. They are racked up from this tank and as soon as they are racked are submitted to the following plating cycle: (1) Boiling electric potash, (2) rinse, (3) electric concentrated HCl dip, the knives being cathode, anodes being carbon, (4) rinse, (5) boiling electric potash, (6) rinse, (7) electric concentrated HCI dip, (8) rinse, (9) concentrated HCl dip, (10) rinse, (11) nickel plate 10 minutes at 2-3 volts, (19) rinse, (13) silver strike, (14) silver plate.

The composition of all solutions used in silver plating tableware is kept under control by regular chemical analyses.

The solution which charges composition most rapidly and which is the source of much defective work in silver plating is the silver strike. We have found it advisable to maintain very rigid standard conditions for striking as regards cement density and composition of solution. The composition of the strike used in our method is 3/4 Troy oz./gal. silver, and 10 oz./gal. free cyanide. Strikes are analyzed for silver and free cyanide content at least weekly and usually twice a week and additions made to maintain above composition as closely as possible.

Very little trouble is experienced with the nickel solutions as we deposit a very light nickel plate. The solutions were originally made up of 20 oz./gal. single nickel salts, 3 oz./gal. sodium chloride, 3 oz./gal. boric acid. The pH of the nickel solutions is determined weekly and maintained at 5.9 by additions of boric acid. The nickel and chloride content is determined monthly and maintained by additions of single nickel salts and nickel chloride.

Little difficulty is experienced in the operation of the silver solutions if the composition is kept in the neighborhood of 4.00-5.00 oz./gal. silver and 7-9 oz./gal. free sodium cyanide and if care is taken in the use of the carbon disulphide brightening solution. There is much discussion concerning the carbonate content of silver plating solutions. Formerly it was customary to freeze out the carbonates during the winter months, and later the use of carbonates in amounts up to 12 oz./gal. was advocated to increase the conductivity of the bath. I am of the opinion that the presence of carbonates up to 12 oz./gal. is beneficial and that the advantages gained by freezing out the silver solutions is not due to the removal of carbonates but to the removal of other inert salts. To gain further information along these lines I operated representative silver solutions for over four years and was surprised to find one morning this summer that crystals had separated out from the solution and attached themselves to the anodes and anode rods. Upon analysis I found the crystals to be sodium fenocyanide. I have not definitely determined whether they were introduced into the solution as an impurity in the sodium cyanide or whether they were formed in the solution, but I am sure that the benefits derived from freezing out silver solutions are due to the removal of sodium fenocyanide and similar inert salts, rather than due to the removal of sodium carbonates.

The alkalinity of the cleaning solutions or potashes is determined weekly and computed in terms of per cent NaOH. The alkalinity is maintained at from 4-8% sodium by dioxide by additions of one part caustic soda to two parts soda ash.

In conclusion of this article on silver plating of tableware I might say that the operations and methods I have described are those used in producing the better grades of silverware. However we also produce cheap grades and for this purpose we have found that an automatic plating machine is very satisfactory in increasing production and reducing the amount of experienced help required.

We are using a Full Automatic Plating Conveyor, which has the following cycle:

Electric cleaner . . . . . . . . 3 minutes
Cold rinse . . . . . . . . . . . .35 seconds
Cold rinse . . . . . . . . . . . .10 seconds
Sulphuric acid dip . . . . .35 seconds
Cold rinse . . . . . . . . . . . .10 seconds
Nickel plate . . . . . . . . . . . .5 minutes
Cold rinse . . . . . . . . . .2 1/2 minutes
Silver strike . . . . . . . . . . .35 seconds
Silver plate . . . . . . . . . . . . 3 minutes
Standing rinse . . . . . . . .10 seconds
Cold rinse . . . . . . . . . . . .35 seconds
Dryer . . . . . . . . . . . . . . 6 3/4 minutes

We have also found that this cycle is satisfactory for work receiving a heavier deposit than that which can be obtained in three minutes, so we have placed a variable speed moving cathode silver plating tank in conjunction with the automatic plater so that it can be used for work receiving a heavier deposit by having an operator remove the plating rocks from the work hanger of the automatic plater as they come out of the strike, place them on the variable speed plater to get the deposit and return the rocks to the work hanger (of course not the same hanger they were removed from) of the automatic as it enters the silver solution.

ELMER ROY UNRUH
Muncie, Ind.


One kind of Plating is East and another is West,
While the self-same sneezes blow.
It’s the place of the Sales and not the gales
Which bids it where to go.

Like the Hydrogen of the Cathode, are the ways of the fates. Many salesmen never realize this until they are stopped at the gates.

 


 



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