By George B. Hogaboom.
(Secretary of the National Electroplaters’ Association.)
Transactions of the American Electrochemical Society
1911
- Image by Chemical Heritage Foundation via Flickr
There has existed for such a long time a separation of the practical plater using electroplating kits and the electrochemist that it is a pleasure to present this paper, as suggested by your secretary, and it is hoped that the practical end of electroplating, as represented by the National Electroplaters’ Association, and the scientific end as represented by this Society, will be brought into a closer relation. As is well known, electroplating was the beginning of the science of electrochemistry, but it has lingered by the wayside and been neglected as a science, and today the unsolved problems are many.
Electroplating has been looked upon more as a trade than a science, and it is only during recent years that much study has been given to it by scientists, and that attention has been directed more to the electrolytic refining of metals than to the deposition of metal for decorative purposes. The solutions published by Roseleur in 1854 have been improved upon but little, and those who have published treatises upon the subject often give only a repetition of his formulas. Nickelplating, as invented by Dr. I. Adams, is probably the only exception.
The field is broad, but its development has been left to the practical man, guided only by “rule of the thumb.” An electrochemist in the plating room of a factory is so rare that it probably can be said without fear of contradiction that they can be counted on the fingers of one’s hands. The need today is mutual assistance in solving these problems and developing of new ideas. To a great extent they are “useless each without the other”— the plater producing results which he cannot duplicate—the electrochemist creating solutions that are not a commercial success.
So many phenomena have been encountered that to include the perplexing problems would necessitate a history of nearly every known solution and finish. The varying of the temperature and the electric current often prove a stumbling-block, and these conditions cannot always be controlled. There is a vast difference between producing a homogeneous deposit at a minimum cost from a solution where the amount of cathode surface is being changed every twenty minutes, and a solution in which the amount of cathode surface is always the same and the rapid deposit of the metal is more desired than a deposit that can be easily burnished. Such would be the difference, for instance, between the surface of a sheet of electrolytic copper and that of a cast lead and antimony electrolier with its deep reliefs and where a coarse crystalline structure would destroy its beauty. In the discussion of electroplating problems, it must be borne in mind that a mere deposit of a metal is not all, but that the deposit must be soft and smooth and lend itself to a decorative process; the anodes should be capable of being reduced easily; the electrolyte must offer little resistance to the electric current, and, last, but not least to the plater, who hears it so often that it becomes a part of him, the cost must be nominal.
The automobile industry has brought about, more than anything else, the need of a heavy deposit of brass. At present this is done in solution of cyanide of Cu and Zn. The deposit is not only slow, but unsatisfactory, because of what is known as “spotting out”—a discoloration in spots which appears on the work after it has been polished and lacquered. Deposits on cast metal give the most trouble. It is probably caused by the acids or alkaline solutions being absorbed in the pores of the metal, or in the small blow-holes, and the deposit covering these holes partially, leaving minute holes through which the solution oozes out. Several remedies have been suggested and tried, such as boiling out in some neutralizing chemical solution, placing in a drying oven for several days, but a satisfactory remedy has not been found.
An acid brass solution would be a great advantage. There is an acid copper and an acid zinc solution, but no acid brass electrolyte. The difference between the deposit from a cyanide and a sulphate of copper solution well illustrates the advantage of having an acid brass solution.
Tin.—The formula for a tin solution published by Roseleur is the most generally used today, as little, if any, improvement has been made upon it, although a good solution which would give a heavy deposit is much desired. In Roseleur’s solution the electrolyte is not replenished by the anode, but by the constant addition of a concentrated solution. This should be overcome, and would be appreciated by manufacturers of tinware.
Aluminum.—While several solutions have appeared from time to time for plating upon this metal, none of them are in general use, and a good electrolyte that would deposit gold, silver, brass or copper so that it would stand burnishing and not peel off in time could be used.
Nickel.—The successful removal of a deposit of nickel from another metal without affecting the latter has not been accomplished.
To give all the unsolved problems in detail would make a lengthy paper, and a simple statement of those most desired will be given:
An electrolyte that will remove the fire-scale from brass; also one that will produce a bright or a matte surface in place of using the present acid dips.
An electric cleaner that will saponify the grease and take it into solution instead of driving it to the top, where it has to be constantly removed to prevent it adhering again to the work as the latter is removed from the solution.
A heavy deposit of lead on the inside of iron pipes, to prevent rapid corrosion.
A method to coat electrogalvanized iron or steel with decorative metals without destroying the rust-resisting properties of the zinc.
An alkaline nickel-silver solution that can be worked with a low voltage.
A method of etching steel without destroying a resistance film of gelatin.
Some alkaline substance that would replace cyanide of potassium. This would be universally welcomed.
For the above suggestions, the writer is indebted to 100 different platers, who were kind enough to answer a request for unsolved problems. It may be interesting to note that 80 percent of them requested an acid brass solution.
