American Electroplaters Society
Publication and Editorial Office
3040 Diversy Ave., Chicago
XVII AUGUST, 1930 No. 8
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
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
society as a whole.
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.”
DEPOSITION OF SILVER-CADMIUM ALLOYS
By Colin G. Fink and Basil G. Gerapostolou
Read at the A. E. S. Convention, Washington, D. C.
process for electrodeposition of cadmium-silver alloys was first developed
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.
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.
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
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:
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).
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.
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
a little hydrochloric and a little nitric acid, and after thorough
washing we coated with mercury by dipping for a few seconds in mercury
(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
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.
of the cadmium and silver found from analysis in each case did not
differ from the amount of deposit used by more than l%.
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
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
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
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
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
these globules increases with increase of the cadmium percentage of
the deposit. When the cadmium percentage reaches about 80% and over,
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
there is deposited only one part of cadmium approximately, and partly
because the ionic concentration of the metals in solution is decreased.
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.
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.
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
Education of Electroplaters
By Dr. Wm. Blum, Bureau of
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
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.
symposium on education showed that while many Branches lave had very
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.
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.
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
at once and make at least tentative plans for the coming fall and winter.
The slogan should be
Class in Every Branch”
IMPROVEMENTS IN BLACK RUSTPROOF
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
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
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
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,
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
around these samples which were produced, and any of you gentlemen
that are interested in following out the ideas presented to you can take
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
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.
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
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
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
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
in view of the misstatements passing around I wish to say that there
can be but
little difference in solutions used today
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.
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.
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
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:
- Modernization of the electro-plating department so that
its mechanical efficiency is placed on the same basis as that of other
of the polishing department—improving
compositions and buffs.
- Adoption and application of a definite electrolytic
coatings of proved value.
- 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
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.
finishing department is usually ”nobody’s
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
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.
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.
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.
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.
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.
consecutively to all the other departments in which the necessary operations
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:
- After the first polishing
and buffing operations there must be presses in the line up to
do all the piercing necessary on the bodies.
buffing lathes for the rebuffing operations.
- Then the brass color
- Then the inspecting line up. (Bodies that are not buffed
quite right in the first operation. Arrangement must be made to touch
without the bodies ever going back over the first cycle.)
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
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.
- From there the material is unracked and transferred
to another conveyor for the nickel buffing cycle.
- 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.
- The material is
again unracked and transferred to another conveyor which takes the
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
So much for the transfer of materials; now let us consider
the investments. In buffing lathes alone for heavy cutting down operations
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
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
generators runs about one dollar per ampere the cost of generators,
starters and exiders would be $36,000. Other costs are:
would be required at the cost of $12,500.
The anodes required for these tanks would amount to 60,000 pounds or
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.
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.
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
is the highest in the polishing and buffing department, the plating
department must so adjust its conditions to take care of the unsaponifiable
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
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
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
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.
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.
plating department one must study cleaners and cyanide dips, nickel,
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.
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
Let us illustrate by a formula in existence at the present
grams of CrO3 per liter
3 grams of Cr(SO4)3 per liter
6 grams of Cr(OH)3 per liter
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
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.
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.
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
We did not know anything about the chemicals that this
gentleman added. He added ounce of a fine white powder which, of course,
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
his formula. We were not interested and here is what we found when
checking our solution after the gentleman had gone. First, the density
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
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
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.
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.
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 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.
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.
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
86 degrees Fahrenheit
Throwing power just as good as in No. 1
is a little brighter due to more cleaning action
3. Temperature 96 degrees
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
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
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
7. Temperature 136 degrees Fahrenheit
Practically no throwing power and brown color showing on what little
there is plated
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
1. Temperature 66 degrees Fahrenheit
Good throwing power
Burnt around the edge and about two inches in on the face
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
Cannot see any difference in throwing power or appearance
98 degrees Fahrenheit
100% perfect in color and throwing power
7. Temperature 100 degrees Fahrenheit
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
surface of the article either due to insufficient nickel or being not
properly colored. We do not know but will try and find out.
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.
Plating time—5 seconds
Good throwing power—just a little frost around the outer edge.
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.
ratio of 150 to 1 we had one hundred percent throwing power from 90° to 110° F.—color
was also very good.
ratio of 122 to 1 and 100 to 1 we received the best results. The color
was perfect at a temperature of 112-1/2° F.
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
as chromium plating did some years ago.
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
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
All of you gentlemen have doubtlessly noticed how easily
some pieces in a tank receive less plate than others; very often considerably
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
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
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.
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
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
of the same dimensions, the temperature of the cadmium plated piece
will be higher. The limit of the usefulness of cadmium depends on the
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
My second topic is soldering to cadmium plate. We all know
the importance of proper cleaning of a steel or copper surface before
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.
are all degrees of adherence of a plate, and while blistering is a
criterion of poor adherence, a medium adherence is not always accompanied
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
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
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
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
case of soldered electric connections. There are, however, special
non-corrosive soldering fluids on the market, which have proven entirely
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
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
aluminum, the effect being less marked on very bright surfaces. If
the base metal is porous, spotting out may occur. Lacquering is the
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.
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
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.
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
without changing its properties and adherence to the cadmium. These
three enamels stand up well on indoor exposure. Our outdoor exposure
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
all. Except for the acidity both had the same properties.
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
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.
how many platers could give an
intelligent and convincing answer if their employer asked them the
facts regarding our research fund.
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
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
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
table discussion in Washington that board will be kept busy.
if every member was just like me what kind of a Branch would my Branch