Historical Articles



Washington, D. C., Nov. 15, 1924.

To Members of the American Electroplaters Society:

The Research Committee is very pleased to be able to offer the following report of the Joint Conference with the staff of the Section of Electrodeposition of the Bureau of Standards.

In addition to the Bureaus staff and the Research Committee there were present about twenty-five platers and chemists and about twelve engineers representing manufacturers interested in plating and plating materials.

The morning session of Friday, Nov. 14, at which Dr. Blum presided, was given over to a summary of Bureau work and the purpose of the conference, with a review and discussion of work already published in the form of letter circulars, which are still available for free distribution.

Discussion of the "Control of Acidity in Nickel Deposition" (Letter Circular No. 82, B. of S.) indicated that many platers are using the Gillespie drop-ratio method with very satisfactory results. Careful control at a suitable pa value materially assists in assuring high cathode efficiency, good solubility of anodes, maintenance of clear solutions, and a deposit of uniformly excellent quality. There is no proper PH value applicable to all conditions, but it must be determined for each set of conditions. In general increased current density, higher temperature, agitation, hard and bright deposits require a lower PH (higher acidity) than the reverse conditions.

Attempts to calculate mathematically the amount of acid or alkali needed to correct the acidity to a definite PH have not been satisfactory on account of the widely varying composition of solutions, both as to main constituents and impurities. It bas been found practical, however, to maintain good shop practice by establishing an empirical table of corrections applicable to any standardized solution formula.

Much interest was shown in the Sterling Wedge apparatus f~)r pH measurements. Discussion seemed to indicate, however, that its users were usually disappointed with it on account of its lack of accuracy and the instability of the solution. It was stated that the addition of a drop of formaldehyde to the brown-cresol-purple solution used in this and the drop-ratio method seemed to considerably increase its stability. It is hoped that these defects can be overcome in the near future, in which case the wedge apparatus would be of very great value in the plating room. "Throwing Power" (MONTHLY REVIEW, Aug., 1923) and Bureau of Standards, Letter Circulars 125, discussion reviewed general principles governing, and also gave the form of a simple piece of apparatus called the "distribution box" for the determination of the relative values of different solutions and different conditions. It was emphasized that all values thus determined are purely relative and will vary widely under varying conditions. In general the throwing power is increased by lowering the current density, temperature, agitation and metal iron concentration, and is decreased by reversed condition. Addition agents have varying effects. Those tending to increase polarization give a marked increase in the throwing power. The beneficial effects of magnesium sulphate and sodium sulphate, sometimes used, is ascribed to this fact, although it has not previously been understood in this light. Several persons present reported having improved their plating practice in various respects after checking their operating conditions with the distribution box. The Bureau has available several sets of this apparatus, which it is glad to loan to concerns otherwise equipped with the necessary laboratory apparatus for making use of them. The desired standard of "Purity of Nickel Salts" (Letter Circular No. 93) was given as the following:

  • Zinc, maximum: 05 %
  • Copper, maximum: 02
  • Iron, maximum: 10
  • Free Acid, as H2SO4 max: 10
  • Total Nickel, Single Salts, min.: 21.39
  • Total Nickel, Double Salts, min.: 14.72

It was stated that nearly all samples of commercial salts examined had been up to the above specifications, and several had been considerably better. All of those present dealing in nickel salts agreed that the commercial articles should conform to this specification and could do so without any increase in cost to the user. The Bureau and Research Committee therefore particularly urge that as many manufacturers as can do so incorporate the above in their purchase specifications on double and single salts.

It was also brought out that there was a need of a specification limiting the amount of organic matter. The commercial salts may contain such impurities or contamination as glue, sugars, resins, tannins and other organic substances of indefinite and undeterminable composition, which give rise to serious trouble, chiefly pitting. Two persons present stated independently that they had prevented pitting on new solutions or after addition of new salts by treating the solution with peroxide and permanganate of potash respectively in small amounts, thus effectively oxidizing the organic matter. It was pointed out that permanganate had one advantage of giving a brown precipitate of manganese deoxide when a very slight excess over the required amount was added. This precipitate disappeared in a short time, as soon as enough hydrogen was generated in the solution to dissolve it.

Several methods of establishing a standard test for organic matter were suggested, such as a carbon determination, loss on ignition, pitting test, and permanganate absorption value. The Bureau will appreciate the opportunity to check any method which may be submitted to them in this connection, and to consider it as an addition to the specification on nickel salts.

On "Nickel Anodes" (Letter Circular No. 115) a specification for the 95-97% cast anode was suggested as follows:

  • Nickel, min.: 95.00%
  • Carbon, Min.: 1.25
  • Sulphur, max.: .10
  • Copper, max.: .25
  • Iron, Tin Silicon, max. ea.:1.00

Carbon is the active ingredient tending to decrease passivity and polarization, and increase uniform corrosion and solubility. Surphur and copper are injurious, inducing disintegration and streaking and therefore should be kept at the low limits. Iron, tin and silicon have no particularly harmful effect other than lowering the nickel content and increasing the sludge. Their presence is therefore not recommended over a nominal amount.

Several persons present stated that they were getting very satisfactory results with electrolytic sheet nickel anodes, particularly in chloride solutions. This form of nickel has the advantages of lower cost per pound, less tank load, high purity and freedom from sludge and slime. It has the disadvantage of disintegration and peeling of the nickel laminations and irregular corrosion. The logical need therefore is for a high purity anode which will combine the advantages of both of the above types, that is a 99 % cast anode Of good solubility and uniform corrosion. Attempts to produce an anode of this type seem to have been not entirely successful in the past. It is thought, however, that much interest was aroused by this discussion with several anode producers, and we have considerable hope that they may be more successful in the near future.

In addition to the Letter Circular indicated above, the following are also available for free distribution, and should be in the hands of every plater and plating chemist:

  • L.C. 121, Publications on Electro-deposition from the Bureau of Standards.
  • L.C. 120, Conductivity of Nickel Solutions.
  • L.C. 33, Structure of Alternately Electro-deposited Metals.
  • L.C. 34; Lead Plating from Fluoborate Solutions.
  • L.C. 4, Electro-Deposition of Lead-Tin Alloys.

This review of discussion of this session emphasized the particular point that wherever it is being applied the work of the Bureau is of great value in improving manufacturing practice.

The first subject of the afternoon session was a progress report by Mr. C. T. Thomas on the "Protective Value" of Nickel Plating on Iron and Steel." -

Mr. M. R. Thompson outlined some preliminary work on the "Nickel Plating of Zinc and Die Castings," the feature of which was the use of a high concentration of sodium or magnesium sulphate. The particular solution which he suggested had the following composition:

  • Single Salt: 19. oz. per gal.
  • Ammonium Chloride: 1.8 oz. per gal.
  • Boric Acid: 2.1 oz. per gal.
  • Sodium Sulphate (crystals): 64.0 oz. per gal.
  • Or Sodium Sulphate (anhyd.): 28.0 oz. per gal.

The characteristics of this solution which makes it particularly adapted for plating on metals of high solution pressure, such as sheet zinc and die castings, is its high polarization, excellent throwing power and freedom from streaking. One person present who had used the solution for a short time on production work, reported favorably in this respect, but also noted increased tendency to burn under ticularly adapted for plating on cathodes of low conductivity, such as sheet zinc and die castings, is its high polarization, excellent throwing power and freedom from streaking. One person present who had used the solution for a short time on production work, reported favorably in this respect, but also noted increased tendency to burn under the ordinary current density used for his particular work. However, reducing the single salt content from 19 to 10 oz. per gallon, overcame this difficulty to a large extent. He also stated, in his opinion, the value of the method lay not in the use of the particular formula given, but merely in the use of a higher content of sodium sulphate which might be added to advantage to any solution designed for die casting without varying the other components of the solution. No unusual trouble in peeling or blistering was experienced. Further work will be done on this subject to coordinate the data already obtained so that more definite conclusions can be drawn therefrom.

Dr. Hildebrand, Chief Chemist of the Chemistry Division, addressed the conference and welcomed those present to the Bureau, urging them to make free use of all its facilities for making their visit of professional and personal value. Many did take advantage of this invitation to visit other departments of the Bureau, and to meet the members of the Research staff with whom they discussed problems of general and personal interest. The courtesy and co-operation of these gentlemen was very much appreciated.

The morning session of Saturday, Nov. 15, at which the chairman of this committee had the privilege and pleasure of presiding, was given over to a general open discussion of subjects for future research, establishment of specifications for plated products, means of advancing the education of the plater, and cooperative measures between the A. E. S., Bureau of Standards, and other technical organizations.

Dr. Blum opened the session by giving a statement of the present status of the staff and their work. The staff itself consists of three graduate chemists, Dr. Blum, Mr. Thompson and Mr. Herlng; one assistant chemist, Mr. Thomas; one research associate, Mr. Winkler, and one consulting plater, Mr. Hogaboom.

Mr. Thompson is at present working on nickle plating on zinc; Mr. Haring has recently started the investigation of chromium plating; Mr. Thomas has further work on rust resisting of steel; Mr. Winkler, supported by the International Electrotypers Association, is concerned with their particular problems; Mr. Hogaboom contributes his wealth of practical experience as called upon in a consulting capacity.

There is much interest in the future possibilities of chromium plate. Its particular characteristics are a hardness greater than heat treated steel, and high resistance to corrosion, particularly at high temperatures. Possible uses fall into four general classifications:

(1) For ornamental finishes requiring high lustre it is hardly to be expected that it will replace nickel extensively on account of its high cost. It also has the disadvantage of being exceedingly hard to buff.

(2) Although in itself it is practically non-tarnishing it offers no particular protection to steel, comparable with zinc.

(3) Its resistance to heat effects may make it of great value where steel and other metals tend to form scales, such as on hot forging dies, furnace linings, thermal couple elements, etc.

(4) Hardness and resistance to abrasion covers its most important field of usefulness, for such work as printing plates, gauges, bearings, scientific and medical instruments, cutting tools, such as shears, punches and machine parts.

The subject of zinc plating merits a general survey, particularly to secure better results from the acid zinc solution. Many of the principles established in connection with the study of nickel are applicable to the study of zinc, which will simplify this research to a marked extent.

In connection with the discussion of the subject of zinc plate, Mr. Wernlund of the Roessler & Hasslacher Research Laboratory demonstrated a simple test for thickness of zinc on steel. In principle the test depends on the length of time it takes for a standard strength solution of peroxide in acetic acid to dissolve the coating of zinc down to the base metal which then shows up as a rusty coloration. In practice the solution is made up of a 2 % solution of sodium peroxide dissolved in 3.5 % acetic acid. For the test this solution is heated just below the boiling point, at which temperature the test piece is immersed. The time necessary for the rust coloration to appear is taken as an index of the thickness of the deposit.

The whole subject of brass plating appears to merit a careful survey. Present methods are largely worked out on the rule-of-thumb basis with little real knowledge of principles governing the plate. The points to be investigated include total metal concentration, ratio of copper to zinc, composition of anodes, temperatures, current densities, use of brighteners, resistance to corrosion, structure of deposits, and particularly, methods of analysis of solutions.

At tills point Mr. Hogaboom outlined a method for the removal of excessive amounts of sodium carbonate from a brass solution, recently developed at the P. & F. Conbin Co. In principle the method depends on the fact that the sodium carbonate is the least soluble component of the solution containing in addition copper cyanide, zinc cyanide and sodium cyanide. In practice the solution of ordinary concentration is evaporated by means of steam coils to about one-half its original volume. When allowed to cool at this concentration the Na., CO:: crystallizes out practically free from the more valuable constituents. The liquor can then be drawn off and used for a new solution, while the crystallized sodium carbonate may be used in cleaning solutions, if desired.

There is also a need for more short testing methods similar in nature to that given above for zinc, for use in the plating room to supplement laboratory and service tests. Simple testing instruments, such as the Sterling wedge, would also be of great value. Anyone originating anything along these lines is invited to submit the same to the Bureau.

Conclusions drawn from the discussion were that further research should be applied particularly on chrominum, brass and zinc plating. It was also indicated that certain details of the purity of nickel salts, pH measurements, 99 % cast anodes, and methods of analysis, might be given some further attention.

Dr. Blum is chairman of the sub-committee of the Federal Specifications Board on silver plated products. In this connection, acting at the request of the Navy Department. the Bureau is collecting data from manufacturers in which to base specifications for silver plated tableware. Other specifications should be established for various classifications of products by manufacturers or manufacturers organizations acting in co-operation with the Bureau of Standards and the American Electroplaters Society. A well-written specification would include a statement of the thickness or weight per unit area, together with precise methods for determining the physical characteristics of the same.

Discussion of educational methods aroused a particularly lively interest. Wherever successfully maintained, classes for platers are of great value in strengthening the educational influence and attendance of branch meetings. Philadelphia Branch is particularly fortunate in having all desired facilities at its disposal from the university authorities. Newark Branch also reported a very successful school. Other classes have in the past been attempted with only partial success. One reason has been lack of a properly written text-book. The Committee particularly wishes to call attention to the fact, this lack is now very adequately filled by the publishing of "Principles of Electroplating," and "Electroforming" by Dr. Blum and Mr. Hogaboom. This book is designed to present such theory of chemistry and electricity in connection with the discussion of modern practice as the up-to-date plater need to keep abreast with the present trend of advancement of the scienc. It is published by McGraw-Hill Book Company.

Lack of time prevented extended discussion of co-operative measures during the meeting, although Dr. Blum and the Committee devoted much time to their consideration. It is pointed out that there are other institutions, such as the universities and large industrial concerns, which are doing research on subjects connected with electro-deposition which bring out facts of value to the plater. For the most part researches are reported through the publications of the American Electrochemical Society. After consulting with Mr. Mesle, our editor, Dr. Blum has agreed to prepare non-technical abstracts of such articles for publication in the MONTHLY REVIEW.

The conference was honored by a short address by Dr. Burgess, Director of the Bureau. Dr. Burgess expressed his own and Dr. Blums gratification in the co-operation received in the past from the American Electroplaters Society, and his particular pleasure in the attendance and spirit of the present series of meetings.

The Committee particularly urges that all members of the A. E. S. attending this conference shall at the first opportunity emphasize the fact to their fellow-members that so many platers have improved their plating practice by applying principles and practice worked out and published by the Bureau; and to point out to them how others can take advantage of this same information.

Dr. Blum also requests that any platers running into difficulties in attempting to apply the Bureaus information, shall write him in detail of their conditions. He will be very glad to supplement any published data with a discussion of its application to particular conditions. Criticisms and suggestions will also be at all times welcomed.

This Committee believes that the question raised at the Milwaukee convention as to whether the amount expended by the Bureau of Standards on research on electroplating has been worth while, has been answered by this conference with an emphatic affirmative. It is therefore our earnest desire on behalf of the A. E. S. that this work shall be continued, to a greater degree if possible, and certainly it should be in no respect curtailed.

This work is made possible by a congressional appropriation under the general heading of industrial research. Although no curtailment is anticipated, it is conceivable that in the present spirit of economy at Washington a congress not informed as to the real value of this work might consider it a proper place to cut its appropriations. A very effective means of forestalling any such action will be for every member of the society to write a personal letter to his congressman, calling his attention to the fact that, largely on account of the Bureau of Standards Industrial Research work on electro-deposition in the past five years, the electroplating industry has made tremendous progress in improving the quality of its product and lowering its manufacturing costs. This action is important and should be effective if carried out.

The Research Committee wishes to express the appreciation of the society to Dr. Blum and his associates for their splendid service in its behalf, and to personally thank the members attending for their support of its efforts.

R. L. SHEPARD, Chairman





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