NMFRC
 

NCMSCompliance Assistance Centers

Funded by EPA
through a Cooperative Agreement

EPA

Disclaimer
The information contained in this site is provided for your review and convenience. It is not intended to provide legal advice with respect to any federal, state, or local regulation. You should consult with legal counsel and appropriate authorities before interpreting any regulations or undertaking any specific course of action.

MONTHLY REVIEW

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

VOL. XVII    AUGUST, 1930    No. 8


EDITORIAL

That the year which we have just entered may be the best in the history of the Electroplaters Society is the aim and object of the recently elected officers. President Gehling has several new men in his cabinet, whose records in the Branch Societies to which they belong, fully justify their elevation to the higher and more important offices of the Executive Board. These with the other members of the Board who have had the privilege of close association with the duties involved in an organization such as ours, have pledged their loyalty and service to the President as he endeavors to shape the destinies of the Platers’ Society for the coming year.

There are aside from the officials elected at the annual convention men who for various reasons do not aspire to holding office, but who by their experience and practical knowledge of the science of Electro-plating cannot be overlooked. Without such as these, the organization would cease to exist as a progressive educational body.

We hope through the pages of the Review every month to renew our acquaintance with one or more of the men, who because of the qualifications just mentioned, are holding positions of trust and responsibility. It is our earnest desire that they speak to us through this medium out of their great fund of knowledge.

The Branch Secretaries are a very important part of making this publication a success. We are asking your whole-hearted co-operation to this end and promise kindly courteous service in return. If it is possible have your reports typewritten as it helps the printer a lot. However desirable this may be, it is not essential the editor is not dictating, just suggesting.

Now as we enter the serious business of the year just ahead of us, we welcome any suggestions the membership may have to offer for the common good; criticism we expect, constructive criticism we covet; sometimes it is hard to differentiate between the two, but rest assured that we are striving for the best interests of everybody concerned and for the society as a whole.

In conclusion, we wish to thank Past Editor Frank Hanlon for the many courtesies extended, for the information so cheerfully given, and for the many hints from his own experience of four years’ service, all of which makes it easier to take up the duties which he has seen fit to relinquish after valued and faithful service as Editor of the ”Review.”


THE DEPOSITION OF SILVER-CADMIUM ALLOYS

By Colin G. Fink and Basil G. Gerapostolou
Read at the A. E. S. Convention, Washington, D. C.

A commercial process for electrodeposition of cadmium-silver alloys was first developed and used on a commercial scale by S. O. Cowper-Cowles in England in 1890. An English patent was obtained in 1892 (English patent No. 1,391 (1892)). In this patent it is claimed electrodeposition of silver-cadmium, silver-zinc, and silver-zinc-cadmium alloys from cyanide solutions. The solution used contained oz. per gal. silver (0.039-M or 4.1 g/L) cadmium 1134 oz/gal. (90 g/L or 0.8-M), and free cyanide (potassium cyanide) equal to 25% of that used to dissolve the cyanides of silver and cadmium (0.44-M or 28.6 g/L or 3.55 oz/gal.) They also claimed that the alloys produced were more resistant to atmospheric corrosion than pure silver plate. The patent covers the whole range of alloys from 5% to over 90% cadmium (or zinc). No current densities are given.

Philip (Philip, revision of Watt’s Electrochemistry (1911).) mentions this process and states that the alloys were plated from the cyanide solutions at 50° C and that they were brittle. He adds that these alloys cost less than pure silver and he gives a list of prices charged by the plating- company for spoons, knives, etc., but no current densities are given.
Professor Fink and I investigated the electrodeposition of the silver-cadmium alloys from cyanide solutions in order to determine the various factors affecting the composition of the deposits the appearance of the plates, and the relative resistance of these alloys to atmospheric corrosion and H2S fumes as compared to pure silver.

The cadmium cyanide we prepared from chemically pure cadmium rods dissolved in sulphuric acid and precipitated as cyanide. This precipitate filtered, washed with water, dissolved in sodium cyanide (C. P.) and analyzed served as stock solution.

The silver cyanide solution we prepared from Merk’s silver nitrate (C. P.) in the same way as cadmium.

The sodium cyanide we used in all solutions we obtained from Eimer and Amend. This salt analyzed to 99.944 sodium cyanide and contained traces of chloride, ferrocyanide, and sulphate.

For electroplating we prepared the following solutions:

Cadmium Metal
Silver Metal
Free Cyanide
Mol. RA
Solution
Molar
g/L
oz/gal
Molar
g/L
oz/gal
Molar
g/L
oz/gal
Cd/Ag
A
0.75
84.3
11.25
0.05
5.4
0.72
0.35
17.15
2.29
15/1
B
0.75
84.3
11.55
0.15
16.2
2.16
0.35
17.15
2.29
5/1
C
0.75
84.3
11.25
0.25
27.0
3.60
0.35
17.15
2.29
3/1

In order to determine the effect of the free cyanide of the bath on the deposits we prepared three more solutions of the same composition but with free cyanide content 1.0 Molar (49 g/L or 6.53 oz/gal NaCN).

The silver anodes we used were made from pure silver crystals cast into rods and pressed by a hydraulic press into sheets about 3/32” thick. The cadmium anodes we used we prepared from pure cadmium rods made into sheets in the same way as in the case of the silver anodes.

The volumes of solutions we used for each cell were 150 c. c. (about 3 oz.) Larger volumes of solutions were not used because of the high cost of the solutions.

For analytical purposes we employed 60/40 brass cathodes 1/2 sq. in. area (or 1 sq. in. total surface). We cleaned them by a rotating wire brush and then by a cloth brush, and finally wiped out with a clean towel. This treatment introduced very probably a very thin film of dirt which made the deposits easy to remove by bending the cathodes. We did not employ chemical stripping because the copper and zinc dissolved from the brass cathode would make the analysis very long and would introduce many errors due to the loss of precipitate in the separate of the metals. I may mention here that with high cadmium content alloys we could not dissolve the deposits completely. Some grains remained on the brass plate which could not be dissolved even after considerable amount of copper would dissolve from the plate.

The cathodes we used for corrosion tests were made from rolled sheet copper cut into pieces 1/ sq. in., with a total surface of 3 sq. in. These cathodes were cleaned by a hot 10% sodium hydroxide solution, then dipped for a few seconds in a concentrated sulphuric acid solution containing a little hydrochloric and a little nitric acid, and after thorough washing we coated with mercury by dipping for a few seconds in mercury blue dip, (7.5 g/L mercuric chloride and 4 g/L ammonium chloride).

ANALYSIS OF SAMPLES
The cathodes before and after deposition were weighed in order to determine the total amount of deposit obtained. The deposits removed from the plates we dissolved in concentrated nitric acid and evaporated the solution to dryness. We dissolved the residue in distilled water and precipitated the silver with a 0.5-N hydrochloric acid solution. The silver chloride, after heat coagulation, cooling, filtration, and washing, we dissolved in a measured volume of standard, 0.4-N, sodium cyanide solution and titrated the excess of cyanide with a 0.1-N silver nitrate solution. This method of analysis gave results within lo for amounts of silver 100-300 mg. as we found out by repeated checks.

The filtrate from the silver chloride we evaporated to dryness, dissolved in water, and after adjusting the acidity we precipitated the cadmium as cadmium sulphide with hydrogen sulphide gas. The cadmium sulphide, after filtering and washing, we dissolved in hot hydrochloric acid, 1.3, and then transformed into sulphate and weighed the residue left after the evaporation of the acids. The filtrate from the cadmium sulphide precipitation we evaporated to dryness to find out if any cadmium did not precipitate. This is the reason we used hydrochloric acid instead of ammonium chloride for silver chloride precipitation, i. e., we did not want to have any non-evaporating residues in our solutions.

The sums of the cadmium and silver found from analysis in each case did not differ from the amount of deposit used by more than l%.

EXPERIMENTAL WORK AND RESULTS
In the electrodeposition of the various alloys we used current densities from 10 to 80 amps. per sq. ft. (1.08 to 8.6 amps/sq.dm.). In each set of experiments we used the three solutions, A, B, and C, in cells (beakers 250 c.c. each) arranged in series. We changed the time of electrodeposition with the various current densities employed in such a way that the same amount of current in ampere hours approximately would pass from the cathode in each case The deposits we obtained for analysis were from 0.4 g. to 0.9 g. per square inch cathode surface. We used mechanical stirring with glass rods in order to avoid excessive anode polarization and to keep the solutions around the cathode homogeneous.

1. Effect of current density. The effect of current density is to increase the percentage of cadmium in the deposit. I will not read to you the numerical results; it will be too tiresome. With three curves I am going to give you the whole story.

The upper curve (Fig. 1.) shows the change of molecular percentage of cadmium with the current density for Solution A. The percentage by weight is very nearly the same because the atomic weights of cadmium and silver are very close, 112.5 for cadmium and 108 for silver.

The curve in the middle shows the increase of cadmium percentage in the deposit with increased current density for the deposits obtained from Solution B with higher silver content. The lower curve is for deposits from Solution C, with still higher silver content.

From the shape of the upper curve it is seen that the rate of cadmium percentage increase in the deposit falls off after a current density of 55 amperes per square foot. This is due to the fact that the cathode polarization sets in at current densities above 50 amps/sq. ft. and gas evolution (hydrogen) starts. Voltage measurements could not be obtained at that current density because the voltage was fluctuating, but the voltage for the current density 80 amps/sq.ft. was 11 volts, much higher than with the other solutions.

(Turn to Fig. 2.)

2. Effect of the mole ratio, Cd/Ag, of the bath. These three curves may be plotted in another way, Cd/Ag in the bath, against Cd/Ag in the deposit. The curves are nearly straight lines and show an increase in the metal ratio in the plate much faster with the high metal ratio baths than with the lower.

3. Effect of agitation. Agitation decreases the grain size of the deposits in the case of lower current densities, increases anode corrosion, and increases the silver percentage in the deposits especially in the case of high cadmium deposits.

4. Appearance of the deposits. Deposits obtained at the lower current densities are fine crystalline and non-metallic in appearance. As the current density is increased, the deposits become coarser and darker. Under the microscope, the deposits obtained with the lower current densities appear even and non-metallic, and as the current density increases, tiny, shining, metallic globules make their appearance. The number of these globules increases with increase of the cadmium percentage of the deposit. When the cadmium percentage reaches about 80% and over, the deposits become finer and of metallic appearance.

5. Effect of the free cyanide of the bath. Increase of the free cyanide of the bath increases the cadmium percentage of the deposits a little. This point has not been completely investigated. The weight of the deposit decreases this latter effect, partly because for every two parts of silver there is deposited only one part of cadmium approximately, and partly because the ionic concentration of the metals in solution is decreased.

6. Effect of temperature. The effect of temperature is to decrease the percentage of cadmium in the deposit. In addition, higher temperatures make the deposits very brittle especially in the case of deposits obtained from baths with higher silver content.

7. Addition of glue. Glue, added in the baths, increases the cadmium polarization as has been observed from the high rate of gas evolution even at lower current densities. The deposits become metallic in appearance even at lower current densities, but we did not obtain even deposits as in the case of baths without glue.

8. Resistance to corrosion. A few of the deposits with relatively low cadmium content were exposed for a month in the laboratory after being polished and washed with alcohol. It seems that they are not much more resistant to atmospheric corrosion than pure silver deposits.

A series of samples with cadmium content from 5% to over 90% were exposed to hydrogen sulphide fumes by hanging in a covered beaker and adding a few sodium sulphide crystals in the bottom of the beaker. After twenty hours exposure, the low cadmium deposits did not show any better resistance to tarnishing than silver. The high cadmium deposits were - covered with a greenish film, as cadmium.

DR. BLUM: Mr. Chairman, if it is in place,—I know we are crowded, but there is a point I want to speak of in connection with this. This represents a survey of the whole field of silver and cadmium alloys, but practically the need or demand today which a good many people are interested in is an alloy of at least sterling silver composition which has to have 92-1/2% silver, but which will be more resistant to tarnish than pure silver. Now, plated alloys of silver and cadmium and silver and zinc, with 92-1/2% of silver do have more resistance to tarnish than pure silver, and the few tests that we made on deposits, just such as are spoken of here today show that the deposited alloys have also greater resistance, that is in the case of cadmium. But the difficulty there, if you have to have as narrow a margin as 7-1/2% of cadmium and the composition varies with the current density, is to be able to plate on different parts of an article and still have not more than 7-1/2% cadmium. So that the range in which most people are interested would be a very small part of the work you have done.

MR. GERAPOSTALOU: For that I may answer that from our investigation, a solution which will be high in silver,—I mean the mole ratio—should be very high in silver, is much better than that, because as the slope of the curve is very much smaller, a little variation of current density would not greatly vary the composition of such an alloy. We examined some of these samples and have found that we had a very small spot, well distributed throughout. This alloy probably had 8% or 10% of cadmium. But there were egg-shaped spots all around which were either themselves alloy of cadmium and silver, or pure cadmium. We cannot say very well now.


Education of Electroplaters

By Dr. Wm. Blum, Bureau of Standards

That this is a timely theme, is indicated not only by the lively consideration of it at the conference on this subject, but even more so by the extent and type of the discussions in all of the Convention sessions. During recent years some concern has been expressed over the fact that more of the Convention papers have been presented by chemists than by platers. The program this year also illustrated this trend. Instead of this condition being an indictment of the platers, it is a tribute to their progressiveness and broad-mindedness. It represents in effect an admission by the platers that most of them have neither the education, time nor facilities to conduct researches. But it represents also a determination on their part to increase their education and to avail themselves of all new and useful information from every source. How far they have succeeded is well illustrated by their earnest, intelligent discussions of the “high-brow” papers presented by chemists. Further progress will depend largely on the efforts made in each Branch to develop the members so that they can still better understand and apply the results of such researches.

The symposium on education showed that while many Branches lave had very successful classes, some of which have been operated for many years, the smaller branches, or those in which no one has taken the initiative, have either had no classes, or have held them with only partial success. It was therefore very wisely recommended to and approved by the business session, that the ”Bureau of Education” that is provided by the Constitution but has been inactive for many years, be revived in order to stimulate interest in classes for platers.

The activities of such a Committee may well include the preparation of a ”manual” of experiments for platers’ classes, and suggestions for adapting such a course to the needs of any Branch. Such needs will obviously vary, depending upon the progress made by previous classes, the experience of the instructor, the equipment available, and the types of plating carried on in that vicinity. Any such manual can therefore serve only as a guide, leaving ample opportunity for modification or extension of the course to meet local conditions. In short, it may represent the combined experience of those who have taught and studied in such classes and thus constitute a ”definite program,” for which the need was so forcibly expressed at the Convention.

When this Committee is appointed and organized, it will no doubt take steps to learn from all Branches not only what has been done, but also what the members think should be done. At best it will be difficult if not impossible to make very definite recommendations in time for the fall classes. Each Branch should therefore consider its educational activities at once and make at least tentative plans for the coming fall and winter. The slogan should be

”A Class in Every Branch”


IMPROVEMENTS IN BLACK RUSTPROOF FINISHES

Read at the Annual Convention held in Washington, D. C., 1930
By C.H. Proctor

If we go back into the history of rustproof blacks, of course we have to go back as far as Bauer & Barf in 1854. Bauer & Barf, of course, introduced the first real black rustproof finish. You will find such a finish in the hotels today. Hundreds of architects specified that finish, because there is no question it is the most remarkable black rustproof finish we have in the metal fabricating industry today.

Some thirty years ago, Bradley and Bon Tempi sought to improve the Bauer & Barf finish. They used the same methods, a closed retort heated to between 1100 and 1200 degrees Fahrenheit, but with superheated steam; they injected a hydrocarbon such as benzine. They claimed they got a more rustproof finish and got quicker results. The Bon Tempi and the Bradley finish, however, are not used commercially as I know of today.

There are a number of firms, I think Yale & Towne, Penn Hardware Co., Pacent Manufacturing Co. in Chicago, and several other firms that still produce hardware under the practical results obtained from the Bauer & Barf finish, though I understand some of them still do inject a small amount of a hydrocarbon factor.

The finish that I have in mind today is one that follows along the line of the finish I gave out about four years ago, and such a finish has been used quite extensively in the automobile industry, especially for producing a black rustproof finish upon rims. I think a good many of you remember that the basis of that finish was a zinc cyanide deposit, and after we obtained the deposit in three or four or five minutes, whatever time the current factor was, we immersed the rim after washing thoroughly in cold water in a sodium hydroxide antimoniac solution, consisting of sodium hydroxide 2-4 ounces and antimony oxide 1/4 to 1/2 ounces per gallon. That has given good results and is still used quite extensively, though in some plants they have substituted the Parker rustproof finish. I question whether they get as good a rustproof finish by that method as they do when they deposit zinc and then put black on obtained from antimony oxide first and then enamel it.

This finish I have in mind to present to you today is a modification of a solution developed some few years ago, and is still being used near Philadelphia in the production of a black finish upon steel. This firm at one time did a very great amount of Parker rust proofing upon their product. The matter was discussed several times in regard to using zinc with a black nickel solution, and that \\as finally adopted, and I believe is in use today though they run into problems once in a while. I happened to be in their plant one day they were having some problems, and I decided to change their black nickel solution to a chloride solution, because evidently they were getting no anodic reduction with the alkaline solution, so nearly alkaline, and I thought perhaps that we would be able to get some nickel in solution by using a chloride solution. I am going to pass around these samples which were produced, and any of you gentlemen that are interested in following out the ideas presented to you can take these along and make a test, salt spray test. I have been unable to make that test on account of being in the West, and our Research Division have been very busy. As you know, the chemists can always keep busy. So I had to go down the other day and produce this finish myself so I could bring them with me. You can take samples so far as they go, with you and make a rust test, atmospherically or with the salt spray.

Now, coming down to the solution factors, I used an ordinary zinc cyanide solution,—most any type will do, but I found the best solution is one that is composed of say four ounces sodium cyanide, five ounces zinc cyanide, four ounces of caustic soda, and a very slight trace of mercury. The anode that gives the best results, and keeps the cleanest for this particular purpose is one of Prime Western Spelter, containing one half of one percent mercury. I don’t care to get much mercury in the deposit, but there is a little which is a factor.

The steel articles are prepared under normal conditions, cleaned, —of course if you want to sand blast them or pickle them, you can do so. Then after they are cleansed and ready for the plating, you plate them. Of course you must remember when you have two factors on top of the zinc coating, you don’t have to put on very much zinc. We find perhaps a thirty-second, or a sixteenth of an ounce of zinc per square foot of surface is ample for the purpose. So we plate from three to four or five minutes in such a solution which I have mentioned, at about 5 volts, 25 amperes per square foot. As soon as the articles are plated sufficiently, based upon our discretion in the matter, what we want to get, they are taken out of the solution, washed very thoroughly and then immersed in a black nickel solution by simple immersion. I found for such a solution one composed, based on water one gallon, or four ounces nickel chloride, six ounces of ammonium chloride, two ounces of sodium sulphocyanide and a half ounce zinc chloride, did very well. The solution is heated to about 100 and the maximum should be 110 degrees Fahrenheit. The articles zinc coated, when they are immersed in the black nickel dip, become immediately black coated. If you hold them in the air for a moment you will find they turn black very quickly and then you can oil them or lacquer them as you may desire.

On the upkeep of this solution, as you know, with an ordinary black nickel solution, you do not get very good anodic reduction, so it is practically building up the solution with the factors based upon the original formula. In this particular solution, I find that about the only factors that we have to add are nickel chloride and sodium sulphocyanide. When you fail to get a black, put in some sodium sulphocyanide, and of course your nickel must be replenished from nickel chloride.

I think this solution is worth while because it makes a simple solution. In many plating departments where they don’t operate the Parker rustproof finish, or Bondurite, or some other such basic finish, this gives them a quick action, as long as they have a cyanide solution. I other words, I started the other day and we plated say five or ten minutes, took them out and washed them, and I had the finish all done probably in about ten minutes or so. And you can coat the surface with an ordinary black lacquer, or you can use an oil finish. This particular oil finish that I have on the surface, it is not exactly dried. After the articles were finished, I wrapped them in a paper very soon afterwards and put them in this box. I made up that finish with benzol. To every gallon of benzol, I used four ounces of beeswax and four ounces of a black oil, soluble dye. And this gives you a coating in a moment, and of course it dries very quickly; you can handle it in a few minutes. And we hope eventually to go into this finish a little more deeply and determine its comparative values as a rustproof factor as compared with the ordinary rustproof black finishes that are still in vogue. That is all I have to say.


CHROMIUM PLATING ON A LARGE COMMERCIAL SCALE
IN MODERN PRODUCTION

By Jacob Hay
Read at Milwaukee Annual Meeting, April 1929

Chairman, Ladies, and Gentlemen:

When Mr. H. G. Binder requested me to write something about chromium plating for the meeting this afternoon I felt rather embarrassed as there is very little left to say about chromium plating or chromium solutions at the present time that has not already been stated by some other writer.

Mr. H. L. Farber and William Blum in their article about ”The Throwing Power of Chromium” and Richard Schneidewind in his late article, and other writers have covered the subject so thoroughly that there is very little left for me to say. I feel that what I have to say to you will not have any material effect on that which already has been said by others.

But in view of the misstatements passing around I wish to say that there can be but little difference in solutions used today in commercial chrome plating whether they are operated under certain principles or patents, or whether they are operated under the chemist’s own formulas. These formulas should consist of nothing more than chromic acid and sulphuric acid and it does not matter whether a solution of high or low concentration of chromic acid is used, as long as the proportion of the chromic acid and sulphate is correct. To find the exact ratio it will depend entirely upon the plater as different sulphate ratios are required for the different kinds of material that he intends to chrome plate.

Although the efficiency of a chromium solution as compared with copper, nickel, silver, and cadmium is very low; this fault is somewhat offset by the stability of the chromium solution as it requires less attention than any other solution in operation. If the preceding operations—cleaning copper and nickel plating—are very carefully done and the preceding coats of plate are applied heavily enough to withstand corrosion there will be little trouble in applying chromium successfully.

Experience is of more value in chromium plating than in any other metallic plating. Carelessness and incompetence on the part of the plater always results in expensive losses. To overcome these losses the articles to be plated must be properly cleaned and racked, the bath must be of the right temperature, and the current density must be kept in proper adjustment at all times.

Three major factors confront those intending to plate their products with chromium:

  1. Modernization of the electro-plating department so that its mechanical efficiency is placed on the same basis as that of other fabricating departments.
  2. Modernization of the polishing department—improving compositions and buffs.
  3. Adoption and application of a definite electrolytic coatings of proved value.
  4. The creation of a new chromium bath which not only would have a high degree of efficiency but also would be less harmful to the health of the operator.

The accomplishment of the above four factors to replace the present unsatisfactory situations is absolutely imperative if chromium plating is to be permanently established on a sound basis.

The finishing department is usually ”nobody’s child.”

I have not yet seen a manufacturing plant where the metal finishing department is as efficient as the fabricating department. The reason for this probably is that business executives, managers and superintendents all are or have been either mechanical engineers or skilled mechanics and as it is natural for man to do the things he knows and likes; the departments that these executives are not vitally interested in are usually neglected. Consequently in the iron, steel and metal working industries the machine shop is favored; and in the chemical industry the chemist and plater have just as much difficulty in seeing the need for rearranging a group of presses to speed up production, as the manager of a brass mill has in appreciating the requirements of the plating department.

Customers are demanding permanent finishes, and this in turn is bringing about a radical change in general manufacturing methods. Duco, vitreous enamels, and chromium now produce a finish that surpasses in quality any that were formerly being produced. The plater of today that wishes to ”toe the mark” in modern production realizes that his department must be so laid out and synchronized that the line up in the metal finishing department will be just as straight and as free from breaks and reversals in direction as it is in any other department.

Chromium plating can be done so much more rapidly than other forms of plating that the handling of work is one of the outstanding problems to be considered in the installation of equipment. By ”handling” I mean not only a steady flow of work through the department, but also an adequate provision for the inspection of the polished and plated parts before the final chrome plating is done. Then and then only can the department function properly and keep losses down to the minimum.

If you are asked to produce thirty-six thousand lamps per day— including the parts of the lamp that are plated but not polished— you have no small job on your hands and you must know plating, polishing and costs in order to be able to figure out the best means of leading up to this production; especially if you have only sixty days to do it in. So if we had 9,000 head lamps per day it would require about thirty buffing lathes and sixty automatic stands for the first buffing operation; and eighteen buffing lathes and thirty six automatic stands in the second operation for the brass finish alone. In other words four hundred buffing lathes, and four hundred automatic stands, and four hundred men are required for buffing and polishing alone on a production of about 36,000 lamps.

As it is not possible to handle this amount of material by trucking alone, conveyors must be installed. In order that the conveyors may be conveniently installed in the buffing department the blower system must be either overhead or underneath the floor. The conveyors must be so arranged that the material will run from the Press Dept. to the Buffing Dept. and then consecutively to all the other departments in which the necessary operations are performed.

The operations must naturally follow each other and the conveyors must be so arranged that no material will have to go over the same place twice; and all movements must be forward. For instance:

  1. After the first polishing and buffing operations there must be presses in the line up to do all the piercing necessary on the bodies.
  2. Then buffing lathes for the rebuffing operations.
  3. Then the brass color buffer.
  4. Then the inspecting line up. (Bodies that are not buffed quite right in the first operation. Arrangement must be made to touch up defects without the bodies ever going back over the first cycle.)
  5. Cleaning and dipping operations for plating. As the material is all carried on conveyors to the nickel plating cycle it is then transferred to hooks on the conveyors for the nickel plating. The conveyor carried the plating hooks with the material to be plated to the cleaner and then through the plating tanks and it is then transferred back to the conveyor of the plating cycle.
  6. From there the material is unracked and transferred to another conveyor for the nickel buffing cycle.
  7. After nickel buffing the material again is transferred to a conveyor that takes the material to the rackers and the chrome plating conveyor, which again carries the plating hooks to the cleaning and chrome plating cycle for chrome plating.
  8. The material is again unracked and transferred to another conveyor which takes the finished material to the inspectors and the Assembly Room, where all riveting operations are performed under the conveyor; and then the parts’ are carried by the conveyor to the shipping room.

So much for the transfer of materials; now let us consider the investments. In buffing lathes alone for heavy cutting down operations 15 horsepower motor is required for each lathe and 10 horsepower motors for the second operation and 72 horsepower motors for lighter operations and in some instances only 5 horsepower motors are necessary. This would mean an investment in the huffing department alone of 150,000 dollars for buffing lathes and blowers and 75,000 dollars for automatic stands and other expenses. It is quite a problem to try to figure out ways and means for improving and increasing production, but it is still a harder problem to try to convince your employer that this equipment is really necessary.

Then in the plating room when plating 72,000 pieces per day or 7200 pieces per hour one will have to consider cleaning, nickel plating, cleaning for chrome and chrome plating. These processes will require about 36,000 amperes of plating generators; and as the average size of the parts is about one square foot in actual surface and the average cost of the plating generators runs about one dollar per ampere the cost of generators, starters and exiders would be $36,000. Other costs are:

5 plating machines—semi-automatics would be required at the cost of $12,500.
The anodes required for these tanks would amount to 60,000 pounds or about $27,600.
20,000 gallons of nickel solution at $9,000.
Chromium installation alone would cost $15,000.
Additional investment in copper buss bars, plating barrels and units etc. would bring the total investment up to about $500,000.

The secret of good chromium plating in the first place can be traced to polishing and buffing. The metal to be plated must be polished and buffed to a very good finish and all metals polished and buffed should be as near non-porous as possible. In order to do this one must furnish his help with the proper tools and the proper compositions.

The buffing compositions that are used in the polishing and buffing department are a problem for every production man to study very carefully; as a composition that may work one hundred percent in the polishing and buffing department will not do for the plating department. But as the labor cost is the highest in the polishing and buffing department, the plating department must so adjust its conditions to take care of the unsaponifiable greases that are necessary to use in the buffing department, of course, for good economical advantage. One can save much in money and labor if he is- willing to study composition and buffs.

I can state with confidence that in one case we saved as high as seventy-five percent on material alone and the labor cost went down to an unbelievable level. In some cases where it took four polishers to polish one hundred pieces we now have one man doing the same work. By simply designing the proper tools and by using the proper composition we can get these results without any extra effort on the part of the operator.

All the parts that have to be polished and buffed must be carried to the operators so that the operator does not have to lose time looking or reaching for these parts. We found that by applying tripoli in paste form under pressure, fifty percent of the material could be saved over the old way of using tripoli. This is quite an item since the cost of tripoli is around four hundred dollars per day. Another item which is well worth your thought is the fact that if you were to investigate matters you would find that it is not necessary to use cotton for buffs. The other material that can be used is not only much cheaper but will outlast a cotton buff in use to the extent of from 48 to 60 hours in its life and on account of its long life will save labor and material.

In the plating department one must study cleaners and cyanide dips, nickel, silver, cadmium, chrome, in fact, any condition that arises the plater: must be ready to meet. One will find that by studying nickel anodes and having the proper electrolyte for these anodes you will not only save money in the plating department but automatically cut the cost in the buffing department. I am wandering off of my subject but let me give you this warning—the plater of today cannot afford to confine himself to the operations of the plating department alone; as every finishing operation in any organization rightly should be under his supervision. With the proper chemical training and practical experience and common sense it is your duty to be the general of all finishing divisions.

Research and study on chromium solution up to the present time revealed some very interesting facts about the so-called patents and addition agents to chromium solutions. In all cases, the addition agents, so far as found through actual experience by the writer, only served either one of two purposes. It was either a case of overcoming high acid content or else increasing acid content. But, in any case, if the ratio of H2SO4 to CrO3 was correct at the time these additions were made no material effect on throwing power or efficiency could be noticed at any time.

Let us illustrate by a formula in existence at the present time:

250 grams of CrO3 per liter
3 grams of Cr(SO4)3 per liter
6 grams of Cr(OH)3 per liter

This solution would give a very good deposit and good throwing power as long as the sulphate ratio to chromic acid was about 100 to 1, but the author of this formula took things for granted, and he did not explain what the sulphate ratio had to be in the 250 grams of chromic acid per liter, in order that after adding Cr(SO4)3 and Cr (OH)3, one would have a ratio of 100 to 1.

This was one of the great reasons why all of us could not see the light when chromium plating came into existence. Most of us cannot see the light and the reason for failures to the present day. Let me illustrate.

A short while ago, I was approached by some gentleman from a well-known corporation who makes it his business to sell these patented solutions and chromium formulaes. He wanted to know if I was interested in throwing power. I told him I was. In fact, I told him, we are interested in anything that is new and interesting in the plating and finishing line. I was asked if I had a small tank and if I could make up a chromium solution of 40 ounces of chromic acid per gallon. So we made up a solution in our laboratory of 32 gallons. After we had this solution made up we checked for H2SO4 before this gentleman had a chance to make his addition. Our sulphate ratio at the time was 438 of chromic acid to 1 of sulphate or about .01 ounces per gallon. We checked this solution for density also before addition was made, and-the density at the time was 1.22 or 25.17 (Beaume) which checked correctly as far as the chromic acid content was concerned.

We did not know anything about the chemicals that this gentleman added. He added ounce of a fine white powder which, of course, he was very careful that we could not get our hands on it. The throwing power and the plating looked very good, although we had to admit we did as well ourselves with our own solution. The gentleman was very much interested in selling us his formula. We were not interested and here is what we found when checking our solution after the gentleman had gone. First, the density of the solution had changed to 1.26 or to 50 ounces per gallon of solution. I want you gentlemen to understand that this chromic acid content was calculated from the hydrometer and the chromic acid content was not checked by actual analysis, so there is chance for doubting whether this was correct or not, but just the same these additions showed this difference as far as the hydrometer was concerned. The next surprise to us was the radical change in the sulphate ratio to chromic acid which changed from 438 to 135. Naturally, we were not now surprised to find that we had such good throwing power. We tried to calculate what kind of acid radical this gentleman added, but could not get any place due to the fact that we did not figure on his having added two different kinds of acid radicals. Here is what we finally discovered: in place of adding /2 of an ounce of the powder, he added 8/10 of an ounce of anhydrous sodium sulphate and 4/10 of an ounce of boric acid. In the next few days the good effect of adding this catalyzer was offset by very poor work, and after checking this solution again it was found that the ratio of sulphate to chromic acid had increased to the point where good chromium plating could not be done. Another vision on throwing power went up in the air.

I might give here a number of organic and inorganic substances or addition agents which have been patented. All kinds of claims were made for them, but all of them have been tried by the writer, and none of them have any merit. In fact, they are all detrimental to any chromium solution if added for production work.

Here are some of them: ammonia hydroxide, sodium fluride, chromium chromate, iron chromate, iron sulphate, chromium hydroxide, phosphate, boric acid, hydrofluoric acid, fluro, salicylic acid, sodium iodate, and others.

Gentlemen, I have here a few reflectors which were plated chromium without any inside anode. You may notice that the throwing power was very good. I will try and give some data on how this plating was done and the different results we obtained by changing our sulphate ratio and also the temperature. The voltage in all this data was kept at 5 volts, and the amperes, of course, varied with the change of temperature from 60 amperes to 150 amperes per square foot.

No. 1:
Data on chrome plating reflectors direct on brass solution in experimental tank—32 gallons—density 1.230 S. P. at 60 degrees Fahrenheit—ounces per gallon 44.2 chromic acid—sulphate ratio 245 H2SO4—distance from anode to cathode 7”—plating time 2”—5 volts.

1. Temperature 76 degrees Fahrenheit
Good throwing power
Plate a little grey deep in the recess due to too much lime in coloring and not enough cleaning action in solution
Throwing power approximately 5-1/2” or more No burning

2. Temperatures 86 degrees Fahrenheit
Throwing power just as good as in No. 1
Color is a little brighter due to more cleaning action

3. Temperature 96 degrees Fahrenheit
No appreciable difference in throwing power
Deposit a little lighter at 5” mark

4. Temperature 106 degrees Fahrenheit
Very good throwing power as yet but can notice the plating is lighter at about a depth of 4”

5. Temperature 116 degrees Fahrenheit
Throwing power fairly good
Brown spots showing at the outer edge of the reflector
Acid content not high enough to correspond with the temperature
Plate very thin and with a pronounced brassy tinge deep in the recess

6. Temperature 126 degrees Fahrenheit
Brown spots very pronounced around the outer edge extending inward about 1/4 of an inch
Throwing power cut down to about 4”
The back part of the reflector only plated in spots
The rest is very brown
While the face which is polished and buffed has taken the plate, it seems a highly finished surface takes a better plate than one in the rough state

7. Temperature 136 degrees Fahrenheit
Practically no throwing power and brown color showing on what little there is plated

No. 2:
Cadillac 5 1/4”—Chrome plating nickel plated reflectors—density 1.240 S. P. at 60 degrees Fahrenheit—ounces per gallon 46.2 CrO3—sulphate ratio 243 H2SO4—Distance from anode to cathode 6/2”—voltage 5—amperes 135 per square foot—plating time 2”

1. Temperature 66 degrees Fahrenheit
Good throwing power
Burnt around the edge and about two inches in on the face

2. Temperature 72 degrees Fahrenheit
Good throwing power
Burning about 1” in from the rim

3. Temperature 80 degrees Fahrenheit
Very good results
The rim just slightly milky in appearance

4. Temperature 86 degrees Fahrenheit
Throwing power perfect
Very little of the frosty appearance around the edge

5. Temperature 92 degress Fahrenheit
Cannot see any difference in throwing power or appearance

6. Temperature 98 degrees Fahrenheit
100% perfect in color and throwing power

7. Temperature 100 degrees Fahrenheit
100% perfect
We had to try three samples at this temperature. I do not think it was due to a bad connection. I think it was more in the condition of the surface of the article either due to insufficient nickel or being not properly colored. We do not know but will try and find out.

8. Temperature 106 degrees Fahrenheit
Have tried four samples but cannot get a satisfactory plate only about 1/4” around the outside, the rest all having an etched appearance, fairly uniform.

Changing of sulphate ratio:

All experiments that we have tried so far have been done with a ratio of 243 CrO3 to 1 of H2SO4.

We then added enough H2SO4 to bring the ratio to 200 to 1 and plating with a temperature of 90° Fahrenheit we seem to get the best results.

Temperature—90°
Ratio—200 to 1
Plating time—5 seconds
Good throwing power—just a little frost around the outer edge.

At a sulphate ratio of 177 to 1 the plating was getting clearer— throwing power was very good at 90° F.—at 150 no throwing power—and brown spots formed all over the surface.

At a ratio of 150 to 1 we had one hundred percent throwing power from 90° to 110° F.—color was also very good.

At a ratio of 122 to 1 and 100 to 1 we received the best results. The color of the chrome was perfect at a temperature of 112-1/2° F.

Reducing our ratio to 77 to 1 we lost all throwing power and could only get very little throwing power at about 135° Fahrenheit; but the color of the plating we did get was very good.

This data on throwing power was only given to show you how very small the plating range is. This is of course, very well illustrated by Faber and Dr. William Blum in their table on throwing power.

In regard to the adoption and application of a definite electrolytic coating of proved value, I might state here that I have seen work done on zinc die castings where from one hundred to three hundred amperes were used per square foot in a nickel solution; and the nickel coatings are so perfect that it is not possible to break down these nickel coatings in a 1000 hour salt spray test. I feel that we have a big surprise coming to us in the nickel plating field that will again give the world a surprise as chromium plating did some years ago.

Thank you.


PROBLEMS IN CADMIUM PLATING

By Gustaf Soderberg
Read at Washington D. C. Convention

The title of this paper is somewhat misleading. I do not propose to deal with the problems met with in plating with cadmium, but rather with a few problems which we have encountered when articles which are already cadmium plated are further handled in the course of a manufacturing process.

I must point out from the beginning that I have limited myself to the kind of plate which is obtained by means of the Udylite process whereby pure cadmium is deposited. This distinction is quite essential in case of some of the topics which I am going to dwell on. We have, for example, experimented with one type of cadmium plate to which solder does not seem to adhere. Another type offers serious complications in regard to lacquering.

All of you gentlemen have doubtlessly noticed how easily some pieces in a tank receive less plate than others; very often considerably less. The reason is often found to be due to oxidation of the hook) or the hook may be bent a little differently from the others, giving a looser contact. This illustrates the importance of my first topic, which is contact resistance.

The initial value of the resistance of the working contacts of contactors and circuit breakers is often from 5 to 20% of the total resistance of the device. If oxidation sets in, the contact resistance may entirely overshadow the ohms resistance. Overheating with further increase of the resistance follows until something breaks down.

This fact was brought out very clearly in our experiments. When copper is oxidized for one hour at 210° C the contact resistance between two copper surfaces increases about 40 times at a contact pressure of 20 lbs. per square inch and about 225 times at 500 lbs. per square inch.

There is where cadmium enters the scene. While copper is readily oxidized at room temperature, forming products of high electrical resistivity, cadmium starts to oxidize first at above 250° C. Also the electrical resistance of cadmium oxide is much less than that of copper oxide. Our tests showed that the contact resistance between the copper surfaces increased four times at 20 lbs./sq. in. and 2-1/2 times at 500 lbs./sq. in., when the contacts were cadmium plated. This increase disappears entirely on heating for one hour at 210° C, which eliminates the film resistance between the copper and the cadmium, probably by causing slight alloying. Considering this film resistance, I cannot over-emphasize the importance of perfect cleaning. Bright dipping before plating is highly recommended. I do not doubt that the film resistance can be made to disappear in much shorter time, granted that the cleaning was properly done. If necessary, a slightly higher temperature nay be used’ up to 250 C. Above this point oxidation sets in, increasing the contact resistance, though at a fairly slow rate. At 310° C, which is very close to the melting point (321° C) the contact resistance at 20 lbs./sq. in. has increased four times over that of copper, and at 50 lbs./sq. in. about 2 times, i. e., the resistance is again about the same as that of just cadmium plated surfaces.

The contact resistance between cadmium plated surfaces increased slightly with the temperature at least up to 120° C, and decreased with increasing pressure practically exactly like copper. In order that the contact pressure be maintained, great care must be taken not to deform the pieces, especially in barrel plating.

We find that contacts which operate under oxidizing conditions (most of them do) and which are not automatically cleaned by the wiping action between the moving and the stationary part, should preferably be cadmium plated. Hot tinned surfaces gave higher contact resistance in all cases. The minimum resistance is obtained when the plated parts are heat treated below the oxidation temperature of cadmium.

Parts which are not subjected to oxidation and which must operate within very small temperature intervals should not be cadmium plated. Cadmium does not radiate heat as quickly as copper or copper oxide. If the same amount of heat is evolved in a cadmium plated as in a plain copper object of the same dimensions, the temperature of the cadmium plated piece will be higher. The limit of the usefulness of cadmium depends on the oxidizing conditions. If cadmium plating does not help a higher contact pressure must be employed or larger contact surface must be provided for. In some cases it may be advisable to use cadmium and increase the heat radiation by blackening the radiating surface only, without changing the contact surface.

My second topic is soldering to cadmium plate. We all know the importance of proper cleaning of a steel or copper surface before soldering in order that the solder shall flow well and that a strong joint be obtained. In soldering to a Udylited surface the cadmium is melted and alloys with the solder, and if the base metal was not cleaned right before plating the solder will not flow as it should over the still dirty surface. There are all degrees of adherence of a plate, and while blistering is a criterion of poor adherence, a medium adherence is not always accompanied by blisters. Only the best adherence of a plate will produce a strong soldered joint, just as only such an adherence gives the best rust resistance of a given coating. When the ordinary cleaning procedures are not satisfactory, greatly improved results may be had with the bright dip, originally recommended by Dr. Graham for use on brass. When steel parts are so treated they should be given a water rinse and a dip in 50 percent muriatic acid, which removes stains, before rinsing for plating. It should be remembered that the transfer from the bright dip to the cold water must be made rapidly and that the same bright dip should not be used for both steel and copper or its alloys. If a solder cannot be made to stick to a perfectly cleaned surface of some particular metal, little improvement can be expected from cadmium plating of this material.

The solder used should have such a composition that it easily alloys with the cadmium forming a solid solution on cooling. Too high a lead content of the solder is, therefore, detrimental. In some cases a high tin content may be important from another reason, namely that of corrosion. As far as our knowledge goes, tin is the only more electro positive metal which does not accelerate the corrosion of cadmium, when used as a coating on top of cadmium.

The flux used in soldering has a triple purpose; firstly, it should clean the surface, dissolving the oxides; secondly, it should exclude the air and prevent oxidation, and thirdly, it should make the solder flow freely by lowering its surface tension. The ordinary zinc chloride-sal ammonia flux fulfills these requirements but it has a corroding effect on cadmium and should not be used in this connection. As it creeps into the pores and clings to the surface it is very hard to remove by rinsing. It is very hygroscopic and the residues take up moisture from the air causing not only corrosion of the cadmium plate but also electrical leakage in case of soldered electric connections. There are, however, special non-corrosive soldering fluids on the market, which have proven entirely satisfactory, and are used in exactly the same manner as ordinary dip cleaners. If core solders have to be used, the rosin core solder is the best yet developed and gives good results if the precautions previously mentioned are taken.

In soldering to cadmium plated surfaces it should finally be remembered that the melting point of cadmium is low (321° C.) and that it starts to oxidize with appreciable rapidity at a temperature as low as 260° C. sufficient amount of flux must be used to exclude the air from the molten cadmium, and the temperature and time of application of the soldering iron must be regulated so that the back side of thin gage sheet material does not oxidize or melt.

The third topic comprises lacquering with clear and pigmented lacquers, and painting of cadmium plated surfaces.
Clear lacquers are used for preservation of surface appearance. Although cadmium stands up well in an ordinary room atmosphere, polluted air does cause tarnishing. Cadmium is also easily finger marked just as zinc and aluminum, the effect being less marked on very bright surfaces. If the base metal is porous, spotting out may occur. Lacquering is the only fully satisfactory way to overcome all these troubles.

In the selection of lacquers, several points must be kept in mind. Adhesion to the plate is of major importance, and a lacquer which adheres perfectly to brass does not necessarily adhere to cadmium. In fact, a few years ago there was hardly any lacquer on the market which showed any appreciable adherence a few months after the application. Now, a number of the more progressive lacquer manufacturers produce a satisfactory product. A clean surface is a necessary prerequisite for successful lacquering; finger staining and oil destroy the adherence and must be strictly excluded. The importance of flexibility, toughness, body and color changes from one application to another. Flexibility should not be taken for adherence. In order to prevent spotting out the lacquer must be impermeable to water, which is not the case with many lacquers which are perfectly all right except for this purpose. When the shape of the article allows for proper draining, the work may be taken directly from the hot rinse and immersed in a water dip lacquer, i. e., a lacquer so compounded that the solvents start boiling in contact with the hot work, removing the water which sinks to the bottom of the lacquer container. The work comes out without a stain. We know of a couple of companies producing water dip lacquers which are very satisfactory for cadmium, both as to adherence and non-permeability.

Since the public became color conscious, we have worked with a number of lacquer manufacturers in trying to develop suitable pigmented lacquers for cadmium. The problem is not easy, as the adherence of colored lacquers generally is much poorer than that of clear lacquers. It was only half a year ago that we could note any progress, in that the first acceptable sample of black lacquer was received. About three months later we obtained samples with differently colored lacquers from another manufacturer. A third one has developed a special primer of adherent clear lacquer which is followed by a second coat which adheres well to the first coating without changing its properties and adherence to the cadmium. These three enamels stand up well on indoor exposure. Our outdoor exposure tests are not yet conclusive.

Some soft and sticky paints adhere well to cadmium, but hard baking japans do not. Special purpose paints are successfully used by the Navy with very good results.

My fourth and last topic is a special case of corrosion which we call ”white powder corrosion.” I have seen the statement in some technical magazine that a cadmium coating on brass will disintegrate on exposure to a tropical climate and that cadmium is unsuitable under such conditions. A chemical analysis of this nonadherent white powder shows that it contains water soluble organic matters. Knowing that cadmium plated brass normally does not behave in such a manner, and running into similar cases in this country, we set out to assemble all the data we had on this subject and we found that this type of corrosion occurred only in electric meters, electric time clocks, and other electric apparatus and on bottle cap fasteners. All these things contain electrical insulating materials and impregnated papers. When heated to about 100° C. some of this material gives off a very characteristic smell of burnt grease. If cadmium plated parts are present they become rapidly covered with a white-gray powder of the same appearance as the natural corrosion products.

At this point of our investigation we wrote to several manufacturers for samples of their different products. Comparing two kinds of varnished paper, for instance, we found that one, which according to the manufacturer had an acid number of 18-20 to have a distinct corrosive action on cadmium, while the other with an acidity number of 6, did not attack cadmium at all. Except for the acidity both had the same properties.

An electric clock contains a number of different insulating materials. If ”white powder corrosion” has taken place the cause is determined by placing samples of each material in a separate glass bottle with a glass stopper and hang a piece of Udylited steel in the center on a string. All the bottles are heated in an oven for 24 hours and observed at frequent intervals. One or more samples invariably show sign of powder within a few hours and the different materials are graded according to the number of hours required for the formation of powder. Those which do not show any such sign after 8 hours can be regarded as perfectly safe under normal conditions; those which show powder formation within 24 hours may be unsafe in tropical climates. These climates are distinguished by the high temperature, which favors rapid volatilization, and by high humidity, which favors solution and electrochemical-dissociation, both factors increasing the rate of corrosion.

We have found that proper material always can be substituted for the unsuitable ones and recommend that no material is allowed in an enclosed room containing cadmium plate without having been tested by the simple method which I just outlined. In extreme cases packing materials also have to be tested.


A. E. S. PAGE
Assembled Expert Scraps With and Without Significance

I wonder
why some of our members will drive thirty miles to attend a branch meeting, while others think it too much of a hardship to walk down town for the same purpose.

I wonder
how many platers could give an intelligent and convincing answer if their employer asked them the facts regarding our research fund.

I wonder
if you can remember the time plating was ”shrouded in mystery” so the old timer thought, until the A. E. S. came along and turned on the light of education and research. Since its inception in 1910 the platers’ society’s record has been one of achievement and success.

I wonder
about the platers classes. Here is a chance to rejuvenate your branch meetings. Get in touch with the Supreme President or Secretary. The Washington Convention voted to aid all branches that were willing to start these classes for analyzing solutions etc. President Gehling knows the value of these classes. What Philadelphia and Newark has done can be duplicated by all others. ”You show ‘em” Hartford Conn-Valley.

I wonder
if it has been made generally known that our Board of Education is going to function this year. If all our branches get the spirit of the round table discussion in Washington that board will be kept busy.

I wonder
if every member was just like me what kind of a Branch would my Branch be.

I wonder





| Compliance Assistance | Regulations | Directories | Resources | Hot Topics | News | Ask the Experts | Library | Online Training | About NMFRC | Search | Home |

NMFRC