THE EFFECT OF MANGALESE ON

ELECTRODEPOSITED NICKEL

By
Robert J. Rowe

AN ABSTRACT

Submitted to the School of Graduate Studies of Michigan
State University of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY
Department of Metallurgical Engineering

Year , , 1956

//
APPROVED: %
, v 7‘,

 

ABSTRACT

Using highly purified buffered nickel sulfate plating
solutions of four different types, the effects of manganese in
solution on the physical properties of electrodeposited nickel
was studied. The physical properties used for a basis of comparison
were: appearance, adhesion, ductility, salt spray (fog) and
electrochemical corrosion resistance, hardness and throwing power.
Watts' nickel solution of pH 2.2 and 5.2, nickel-cobalt, and
organic nickel solutions were used, with concentrations of
manganese up to 300 mg./l. The removal of manganese was studied
both electrolytically and by high pH precipitation methods.
Internal stress of the deposits was measured at varying thicknesses
as well as the strain imposed on the basis metal during the plating

cycle.

TABLE OF CONTENTS

PAGE
INTRODUCTION...................... 1
MRIMENTAL...................... 5
EFFECTS OF IMI-ZGMIESE ON EIECTRODEPOSITED NICKEL . . . . 9

REMOVAL OF MANGANESE PROF-I NICKEL SOLUTIOI‘JS . . . . . . . 25
STRESS IN EILECTRODEPOSITEID NICI$3L o o o o o o o o o o o 29
COIICLUSIONSO o o o o o o o o o o o o o o o o o o o o o o 1.18

REITEREI; CF18 O O C O O O O O O O O O O O O O O O O O O O O 51

IKTRODUCTION

The metal finishing industry has for a number of years utilized
the electrodeposition of metals for many applications without
cognizance of the effect of metallic impurities which may be present
in the electrolyte. In the field of nickel electrodeposition, the
general effect of the deposit on the physical properties due to
metallic impurities common to most solutions, namely copper, iron,
and zinc, were known but not studied extensively nor on an individual
basis. The presence of these metallic impurities in the nickel
plating solution, upon electrolysis, codeposit with the nickel,
thereby changing the physical and mechanical properties of the
deposited metal, dependent upon the type and concentration of the
impurities present. The codeposited material may directly influence
the properties of the deposit or affect its structure to produce
a fine grained deposit with internal stresses and lattice dis-
tortion (l). The physical and mechanical properties of the deposit
can be influenced both directly and indirectly by these latter two
factors.

It has been observed in some instances that a direct correlation
exists between the amount of impurity in the solution and the
variation in the properties of the deposits. A well known example
is the rapid decrease in corrosion resistance of nickel deposits
by the addition of small amounts of copper as an impurity to the
electrolyte (2). However, the correlations are not always consistent.

Two reasons may be advanced: (l) The degree of dispersion of the

 

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impurity in solution, and (2) equal contents of impurities may not
produce equivalent effects as in the dull and bright nickel solutions.

In industry, modern methods of refinement produce purer products
than were formerly attainable, and with increasing purity of product,
there is often a desirable refinement of properties. However, not
many metals are used in the pure form. Present practice in the
metallurgical field is for the production of metals in purest form
with the subsequent addition of amounts of other metals which may
be beneficial. Just as the properties of metals can be varied
considerably by metallurgical treatments, the properties of electro-
deposited metals may be varied by the inclusion of metallic impur-
ities in the electrolyte. Thus electrolytic copper is characterized
by its high conductivity, but small amounts of gold and silver, in
themselves good conducting materials, markedly depreciate the
conductivity of copper. In other words, very small amounts of
impurities may seriously impair the properties of metals.

The properties which determine the merit of metallic coatings
for decorative or corrosion resistant purposes are appearance,
adhesion, ductility, hardness, throwing power, 1d those chemical
properties which determine the corrosion resistance. The properties
which are of value in heavier deposits, usually for engineering
purposes, are of a mechanical type and are internal stress, tensile
strength, hardness, and ductility. A considerable amount of research
has been carried out on the properties of electrodeposited metal
‘by industry and educational institutions, and it was through a

fellowship grant that the present work was made possible.

The main objective of this study was the determination of the
effect of manganese as an impurity in nickel plating solutions
on the physical properties of the deposits. The occurance of
manganese in these solutions usually is brought about by the
addition of potassium permanganate or its presence in the nickel
anodes. This investigation was one of a series carried out under
the supervision of the American Electroplaters' Society on the
determination of the effect of impurities on the physical properties
of electrodeposited nickel. Previous studies included the invest-
igation of the effects of copper, zinc, iron, chromium, lead and
aluminum (3, h, S, a, 7, 8).

The purification of plating solutions by the addition of an
oxidizing agent such as potassium permanganate to overcome organic
contamination of nickel plating solutions has frequently been
suggested. The use of this oxidizing agent has gradually lost
its position as a purifier in plating solutions since about 1930
and has been largely replaced by hydrogen peroxide as the reduction
product of the latter is merely water. The advantage of using
potassium.permanganate over other oxidizing agents is that the
permanganate acts as its own indicator, denoting when enough has
been added. If an excess of permanganate is added to the solution,
a precipitate of manganese dioxide is formed, which will eventually
dissolve in the bath if not filtered out.

Another source of manganese in plating solutions is from the

anodes. Manganese is sometimes added to deoxidize the molten nickel

before casting. A survey of commercial installations of nickel
plating solutions has determined that the greatest concentration
of manganese occurs in the nickel solutions which have been
purified with potassium permanganate. In spite of the widespread
use of the latter as an oxidizing agent, there has been little
information published as to the effect of manganese on the
properties of the nickel deposit.

In the correlated review and abstract of the literature on
the effects of impurities in nickel plating solutions, it was
noted that the presence of manganese in nickel plating solutions
had little effect on nickel deposits other than roughness occurring
in the presence of undissolved manganese dioxide (9). Thomas and
Blum found that potassium permanganate additions did not markedly
decrease porosity (10). Campbell and others showed that it was
possible to form alloys of manganese and nickel by electrolysis (ll).
However, Campbell's solution contained 7h grams per liter of
manganese and only 1h grams per liter of nickel, while other alloy
solutions contained up to forty times as much manganese as nickel.
In all cases, as the nickel concentration increased, the current
efficiency of the solution increased with a resulting decrease in
the manganese content of the deposit. The current efficiency of
these solutions ranged from about 10 to 50 percent. The addition
of ammonia salts were evidently necessary for a satisfactory
deposit. No references on the removal of manganese as an impurity

in nickel solutions were found.

A second important phase of this project was the determination
of the internal stress of the deposit as plated from purified
nickel solutions. The presence of internal stress in electrodeposited
nickel is of great concern in commercial installations, as it may
be responsible for the failure of plated parts through peeling,
cracking, or distortion. The main purpose of this portion of the
project was to determine the stress present in electrodeposits
of nickel as deposited from highly purified nickel solutions, and
to determine if a nickel deposit as plated from a nickel-cobalt
solution producing highly stressed coatings cracked during depos-
ition to relieve the internal stress. Previous work by Owen on
his investigation of the effects of lead in nickel solutions brought
out the fact that on micrographic examination, several of his
nickel deposits exhibited cracking (12). It was thought that these

cracks might be due to the relief of internal stresses.

EXPERIMENTAL

Procedure: The methods for the preparation and purification of
the solutions and the subsequent testing of the physical properties
were those described in previous publications of this project (13).
The methods and techniques utilized for these measurements will
be briefly explained as the effects of manganese no nickel deposits
are described.

In this investigation, manganese was added as the impurity

(as manganese sulfate) to each of four representative nickel

solutions shown in Table I. They consisted of the watts' pH 2.2
and 5.2 producing gray deposits, and bright deposits from an organic
type pH 3.2 and a nickel-cobalt alloy type pH 3.75. The organic
solution used nickel benzene disulphonate and triaminotolydiphenyl-
methane as addition agents. Sodium lauryl sulphate was used in
amounts which just prevented pitting on the face of the panel in
all solutions except the nickel cobalt.

The deposits obtained were analyzed qualitatively for changes
in the physical properties by measurements of the panels produced
from the pure solutions compared to those from solutions containing
varying amounts of manganese. Since trends were the objective
instead of absolute data, deviations were reported as percent
change from the properties of the pure deposit. Additions of
manganese to the four nickel solutions were made in amounts of O,
S, 20, 80, 160, and 300 milligrams per liter. The manganese content
of the nickel solutions was determined by the colorimetric method
developed by Project #2 of the American Electroplaters' Society
research program. (1h). The method consisted of oxidizing the
manganese to permanganate by sodium periodate in a strong acid
mixture containing nitric, sulfuric, and phosphoric acids. The
sodium periodate oxidizes the manganese, and then the excess
periodate stabilizes the color. Manganese is oxidized according
to the equation:

2MnSOh + SKIOh + 3H20'-9 ZHMnOb + SKIO3 + 2 HQSOb

TABLE I

NICKEL PLATING SOLUTIONS

 

 

Nickel Sulfate
Nickel Chloride
Boric Acid

Nickel Formate
Cobalt Sulfate

Nickel Benzene
Disulfonate

Triamdnotolyl-
diphenylmethane

Temperature °F.
pH (electrometric)

Current Density
amperes per square foot

 

‘Watts' Nickel-
Type Cobalt Organic
2&0 g./l. 2h0 g./l. 262 g./l.
LS hS 60
30 30 3h
AS
15
7.5
O.lh ml./l.
SS 60 60
2.2 a 5.2 3.75 3.2
LO LO LO

 

 

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th;

The survey of commercial installations using nickel plating

solutions indicated a range of manganese concentrations from 6

to 30 milligrams per liter, with the greater percentage of these

solutions having concentrations of less than 20 milligrams per

liter.

To determine the quantity of manganese in solution after

an axidizing treatment of permanganate, a procedure patterned

after a commercial method was used (15). This consisted of:

l.

2.

5.
6.

Adding 2 lb/lOO gal. of potassium permanganate at 50

to 55°C. while stirring for one hour.

‘While stirring, bringing the temperature of the solution
up to 70 to 75°C.

'When the temperature had reached 70 to 75°C., adding

h lb/lOO gal. of activated carbon to the solution and
stirring for two hours keeping the solution temperature
at 70 to 75°C.

Adding the necessary amount of nickel carbonate to raise
the pH of the solution to at least 5.0 and continuing
agitation for 2 to h hours.

Cooling to 50 to 55°C. and filtering.

Analyzing the solution for manganese content.

The following results were obtained. The second figure represents

the manganese content of the solution after a second treatment

to the same solution.

Nickel Solution Manganese Concentration

Milligrams Per Liter

watts' pH 2.2 bath 26h - 300
Watts' pH 5.2 bath 385 - 396
Nickel-Cdbalt pH 3.75 bath 225 - 235
Organic pH 3.2 bath 267 - 272

Repeating the treatment did not appreciably increase the manganese
content of the solution. As these nickel solutions contained no
metallic or organic impurities, the addition of the large amount
of permanganate represented a very drastic treatment. Even with
this large excess of permanganate the manganese content remained
very close to the limits used in the experimental phase of this
project. High pH treatment and low current density electrolysis
were evaluated for removal of manganese from nickel plating

solutions.

EFFECTS OF MANGANESE ON ELECTRODEPOSITED NICKEL
Appearance: Several methods for evaluating the appearance of
nickel deposits have been proposed. These methods may be the
measure of leveling as determined by a surface analyzer, or the
measure of reflecting power and brightness. For the purpose at
hand, it was found sufficient to compare the appearance of the
gray deposits to the Eastman Gray scale and to classify the bright
deposits from dull to mirror bright. Any change in appearance

was compared to the deposit as produced from a pure solution.

10

The use of a bent cathode permitted one to note any change in
appearance with change in current density, as well as any change
in the flat surface of the panel deposited at a current density
of LC amperes per square foot.

The'Watts' 2.2 pH deposits showed the only significant change
in appearance. 0f the three sets of panels plated from each
solution, 0.0003, 0.0010, and 0.0015 inch, only the heavier
deposits appeared to be finer grained with a correspondingly less
tendency to tree on the edge of the lip. This trend was observed
with increasing amounts of manganese in solution. The series of
panels from the Watts' 5.2 pH were uniform in appearance with a
slight darkening effect in the low current density area from those
solutions at manganese concentration of 80 to 300 milligrams per
liter. The smoothing effect was not as pronounced at the high
current density area as the'Watts' 2.2 pH series. These two series
of panels were judged to have an Eastman gray scale rating of
from 1 to 2. No change was noted in the appearance of the deposits
from the nickel-cobalt or organic solutions. These two series

of panels were rated as mirror-bright.

Adhesion: The qualitative tests for adhesion can be classed as
bend tests and blister tests. The bend tests comprise bending

or flexing of the plated panel in such a manner as the specimen
will permit. Any evidence of peeling, chipping, or flaking of the

deposit is taken as lack of adhesion. The blister test takes

advantage of the difference between the coefficients of expansion
of the plate and the basis metal. The difference, on heating,
results in a severe straining at the interface which produces
cracks, blisters, or peeling when the plate adhesion is poor.
This method does not injure the plated piece and is adaptable to
specimens which cannot be bent or flexed.

The qualitative test used herein consisted ofliending the
lip of the cathode, as cut from the 0.001 series of panels, upper
side outward, 180 degrees around a 3/16 inch mandrel in the middle
and across the short dimension (9). The bend was examined under
a microscope at 20 diameters. Flaking was considered indicative
of poor adhesion. The results showed good adhesion of the nickel

deposit to the steel base metal in all cases.

Ductility: Ductility in a deposit is of prime importance in case
the plate is subjected to occasional or periodic deformation or

to forming or machining operations. Qualitatively, ductility of

a deposit is judged by means of a fingernail test, which is made

on a section of the metal 0.001 inch thick deposited on and stripped
off a passive metallic surface. The number of times that the foil
can be creased and opened is a measure of ductility. Another
possible method for measuring the comparative ductility of an electro-
deposited metal is the Modified Erickson Cup Test (16). This method
involves plating on a flat strip of basis metal and elongating a
small section of the test specimen by transmitting a load to the

flat section by a hardened steel sphere.

12

The ductility of deposits are markedly influenced by many
variables which enter into the plating process. As a matter of
fact, the relative importance of each of the many variables has
not yet been evaluated. Thus there are bound to be discrepancies
in the matter of testing among the various reports on this subject.

The ”fingernail test" was used for evaluating the 0.001 inch
stripped deposits. The test was carried out until fracture occurred.
The number of bends was then recorded. Table II is a summation
of the results obtained from several individuals who tested portions
of the same deposit. The results are reported in percent change
from that of the pure deposit.

The significance of these figures is somewhat in question,
as, in the case of the nickel-cobalt deposits, the average number
of bends before rupture was about two. Therefore, a small change
in the number of bends would have caused a fairly large percentage
change. Another factor that could have been responsible for the
random distribution of results was the lack of control over the
amount of wetting agent in solution. An attempt was made to
produce the deposits used for this test at about the same sequence
from all solutions, but this varied due to the number of trial
panels necessary to produce pit free deposits. On the basis of the
above qualitative test results, the Watts' 5.2 pH and nickel-cobalt
series showed a decrease in general. The values obtained from the

organic series of deposits established no trend.

13

TABLE II

EFFECT OF MJZGAT‘ESE ON DUCTILITY OF NI CIiEL DEPOSITS

 

 

Percent Change

 

 

Manganese ,
Concentration ‘Watts' 'Watts' Nickel-Cobalt Organic
mg./l. pH 2.2 pH 5.2 pH 3.75 pH 3.2
O O O O O
5 113.1: -19.5 -18.5 5.3
20 1.1.6 0 -bb.5 -7.9
80 52.1 -22.h -51.8 0
160 18.? 1.3 -59.3 0
300 5.8 -33.3 -7.b 18.h

TABLE III

EFFECT OF MANGANESE 0N ELOKGATION CF NICKEL DEPOSITS*

 

 

 

 

Manganese Percent Elongation
Concentration ‘Watts' 'Watts' Nickel-Cobalt Organic

mg./l/ pH 2.2 pH 5.2 pH 3.75 pH 3.2
o 1; 3 6 8
S 3.5 3 6.5 7

20 3 3 h 7

80 3 3 5.5 8

160 3 3 h 7

300 3 3 5 7

 

*Measured by Research Division of Chrysler Corporation by L. Morse.

15

The property most frequently associated with ductility is
elongation. The elongation of the specimen when stretched to
fracture in a tensile strength machine is measured and is expressed
as percent elongation in a specified gage length. The elongation
values in Table III show no trend with regard to manganese con-

centration as measured on deposits from all four nickel solutions.

Hardness: Reliable and significant hardness measurements are
difficult to make on electrodeposits because the concepts of
hardness are neither simple nor definite, and the various methods
employed may measure different properties. The results by any
method are likely to be influenced by the hardness of the underlying
metal unless the deposits are relatively thick. If heavy deposits
are produced for hardness measurements, there is no indication

that the properties are necessarily the same as those of the thinner
layers used in actual plating.

It is interesting to note that the hardness of electrOdeposited
metals often equals or exceeds the hardness of severely cold worked
metals. This may be taken as another indication, other than the
presence of internal stress, that the metallic lattice formed during
deposition is more or less distorted, for the lattice formed in
cold worked metal is severely distorted. The hardness of electro-
deposited metals is not a property of a metal alone, but is influenced
by the condition for deposition, the solution composition, and the

other plating variables. For this latter reason, care was exercised

16

during the plating operation to produce comparable conditions for
the four series of deposits.

Hardness measurements were made on deposits of 0.002 inch
thickness with a Tukon hardness tester at the National Bureau of
Standards. The results are presented in Table IV as percent
change in hardness from those of deposits from pure solutions.

In general, the nickel deposits from the manganese containing
solutions did not establish a trend. The values represented are
small and the variation falls within the range of experimental

error.

Throwing Power: The inclusion recently in many specifications
of requirements for a minimum thickness of deposit on significant
surfaces has emphasized the importance of securing as nearly
uniform metal distribution as practicable. With the exception
of a few simple shapes, a uniform distribution of current over
the entire electrode surface is not possible. The distribution
of metal, which is the significant result, depends upon: (1)
the distribution of the current, and (2) the respective cathode
efficiencies at the prevailing current densities. If, over the
current range involved, the cathode efficiencies are equal, the
metal distribution is the same as the current distribution.

In order to minimize the number of variables, the throwing
Power of the solutions was measured by utilizing the lip of the

0.002 inch deposit as plated for the hardness measurement. In

17

TABLE IV

EFFECT OF IVIAI‘IGAI‘CESE OI.T WIRDNESS OF NICKEL DEPOSITS

 

 

 

 

Manganese Percent Change
Concentration 'Watts' hatts' Nickel-Cobalt Organic
mg./l. pH 2.2 pH 5.2 pH 3.75 pH 3.2
0 0 0 0 0
5 4407 205 705 1109
20 0 1-009 -303 307
80 '1300 5.5 008 -506
160 '1203 ‘8014 11.8 10.0

300 _ -. -l2.3 15.8 -3.5 0

 

18

this manner, existing equipment was used, and conditions were
maintained as in the other operations. As described in an earlier
paper on this project, the throwing power measurements were per-
formed on both the top and bottom of the lip to minimize the
variation in the results due to the tilting of the lip of the
cathode during plating (8).

A comparison of these results with those of the deposits
from the pure solutions gave a measure of throwing power. With
proper pH control, no gassing was observed at the cathode during
the preparation of the test panels in the solutions. It was
assumed that no change occurred in cathode efficiency, and that
any change in the deposit thickness was due to a change in the
throwing power of the solution. The results are summarized in
Table V.

With an estimated error of 10 percent in the measurement of
these values, a general observation of the above table indicates
no definite trend for either an increase or decrease in throwing

power with an increase of manganese in solution.

Corrosion resistance: In most cases electroplated metal coatings
are applied because they have properties different from the basis
metal, especially greater resistance to tarnish, or because they
protect the basis metal against corrosion. Even when appearance
is a primary consideration, protection against corrosion is also

significant. Many tests have been devised and used for predicting

19

service life of metal coatings. The tests chosen and the criteria
for evaluation of the results depend to a large degree on the
mechanism of protection of specific coatings. Nickel coatings
must be continuous and completely cover the basis metal for
maximum protection. 'When pinholes or cracks extend through the
coating, corrosion of the basis metal is accelerated.

Of the many methods devised for testing the corrosion resistance
or protective qualities of electrodeposited coatings, the salt
spray test is the most widely used. It is presently the subject
of a considerable amount of controversy and of intensive efforts
at standardization. The rate of corrosion in the salt spray has
been shown to be directly related to the rate of condensation of
the fog or mist upon the surface tested. Specifications for the
salt spray test provide for the measurement and control of the
volume of liquid that settles on a horizontal surface per hour,
as well as the density and purity of the salt solution and the
temperature of operation.

The acetic acid modification of the salt spray was developed
originally for nickel-chromium deposits on zinc base-alloy die
castings. Later modifications of lower temperature and salt
concentration were found to give more realistic results for most
of the deposited coatings, and in less time than the standard
salt spray method.

Other accelerated testing methods include the recent develop-

ment of an electrochemical method which utilizes a cell in which

TABLE V

20

EFFECT OF 3&NGANESE ON THE THRG'IING PCI'E‘ER OF NI CICEL SOLUTIONS

 

 

Percent Change

 

 

Manganese
Concentration Watts ' Watts' Nickel-Cobalt Organic

mg./l. pH 2.2 pH 5.2 pH 3.75 pH 3.2
O O O O O
5 -3.5 7.5 17.5 5.0
20 -l.5 -l.0 114.0 11.5
80 14.5 -17.0 44.0 14.5

160 1.0 —o.5 6.5 7.5

300 h.5 11.5 12.5 9.5

 

21

the nickel coating is the anode, a copper wire for the cathode
with an electrolyte of sodium chloride (17).

Three series of panels were prepared for testing in the above
named corrosion testing means. The latter two tests were under-
taken for verification purposes when it was observed that more
than usual inconsistent results were obtained from the salt spray
test.

The salt spray (fog) corrosion resistance was carried out as
set forth in ASTM Tentative Method of Salt Spray (fog) Testing
Bll7-h9T, and the system of rating as described in a previous paper
was used (9). Triplicate panels of 0.0003, 0.0010, and 0.0015 inch
thickness were prepared from each solution to be tested. The
heavier deposits exhibited no apparent change in corrosion
resistance. The thin deposits (0.0003 inch) produced erratic
results with no apparent trend established for each thickness
series, the 0.0003 inch panels corroded so quickly that the results
so obtained were erratic and exagerated. A uniform corrosion
pattern was obtained on most of these deposits. In both the 0.001
and 0.0015 inch series, however, one or two rust spots appeared on
the face of the panel and no further corrosion took place other than
in depth. It is highly probable that these spots became highly
anodic and protected the rest of the panel by maintaining it
relatively cathodic. It was also noted that after a period the
panels exhibited a water insoluble gray film. This film seemed

to stop all further corrosion. The same phenomena was also noted

 

22

by Dow in which the crystalline material on the panels was found
by qualitative analysis to be basic nickel carbonate (8).

A series of nine panels of 0.001 inch thickness from each
solution were prepared for the acetic acid salt spray. This test
was carried out at the General Motors Research Laboratory under
the direction of Mr. C. F. Nixon. The testing was done in an
acetic acid salt spray chamber controlled essentially as covered
in ASTM 3287-SLT. Findings are reported in terms of Performance
Index Numbers. The panels were exposed for eight 2h-hour periods
to a 5 percent sodium chloride solution, pH 3.2 with acetic acid,
at BS’C. At the end of each interval, the panels were rinsed
with cold running water and inspected. A rating number was assigned
to each panel at each interval. The rating scheme was as follows:

Amount of Failure Rating

None -- No failure 5

Slight -- l to 10% of significant surface affected h

Moderate 10 to 3053 of significant surface affected 3

Severe 30 to 70% of:3ignificant surface affected 2

Total Over 70% of significant surface affected 1
The Performance Index Number was based on these ratings for each
of the eight inspections. An example is illustrated.

Hours: 2h LB 72 96 120 ILL 168 192

Rating: 5 h h b 3 3 2 2
The sum of the ratings (26) is multiplied by an arbitrary constant
of 2.5. The product is by definition the Performance Index Number.
In this example: 26 x 2.5 = 65. The possible values range from

a minimum of 20 to a maximum of 100.

23

Number 20 represents a part which had totally failed at 2h
hours and a value of 100, a part which showed no evidences of
corrosion at the conclusion of 192 hours of testing. As necessary
for comparison purposes, all panels were tested at the same time.
Table VI gives the average, range, and standard deviation of the
Performance Index. On the basis of the data from the acetic acid ‘
salt spray test, a comparison of the average performance index
numbers within each group indicated agreement with those corrosion
results obtained by other testing methods in that no significant
change in corrosion resistance occurred due to the presence of
manganese in nickel solutions.

In order to avail ourselves of an additional check on corrosion
resistance and to evaluate it for future use on the American
Electroplaters' Society Project #5: the electrochemical method of
Pierce and Pinner was utilized (17). This method was based on
the work of Shome and Evans (18). These investigators formed a
cell consisting of a copper electrode, a thinly nickel plated steel
electrode, and an electrolyte of sodium chloride. To increase the
potential of the cell so that it could be used on thicker deposits,
a potential of 0.3 volts was connected in series with the cell.

At this voltage, the amount of nickel dissolved was negligible

and there was no danger of anodic attack on the plate, but was great
enough to insure consistent test results. The electrolyte was three
percent sodium.chloride solution.

The three compartment cell and the portable battery operated

power supply are shown in Figures I and II. The cell was constructed

2h

TABLE VI

EFFECT OF MAKSAKESE ON THE CULROSlOK hESISTAhCE OP NICLEL
DEPOSITS AS DETEhHINED IN THE ACETIC ACID SALT SPRAY (E03)

 

 

 

Manganese
Concentration Performance Index Standard
mg./1. Average Range Deviation
Watts' 2.2 pH 0 30 25-37.5 3.6
S 31 25-35 2.9
20 31 27.5-37.5 3.1
80 31 27.5-35 2.1
160 33.5 30-35 1.7
300 33 30-37.5 2.5
'Watts' 5.2 pH 0 32.5 25-35 3.5
5 30 225—1.2.5 5.2
20 30 25-35 3.h
80 26 22.5-35 b.1
160 31 22.5-h0 h.6
300 3h 27.5-h0 h.9
Organic 3.2 pH 0 21 20-25 1.7
S 21 20—22.; 1.3
20 21 20-22.5 1.2
80 20.5 20-22.5 1.0
160 21 20-22.; 1.2
300 21 20-22.5 1.3
Nickel-Cobalt 0 SO 37.5-57.5 5.3
3.75 pH
5 39 27.5-52.5 7.0
20 L1 27.5-55 10.5
80 L6 30-60 8.9
160 51 DZvS-és 5.8

300 b2 25-52.5 9.1

25

of lucite having three compartments of equal size to enable the
testing of three panels simultaneously. The bottom plate was
constructed of l/h inch steel plate, and the cover of 1/8 inch
steel plate. The cell was assembled with a l/h inch foam rubber
gasket to seal the cell to the plated panels placed on the bottom
plate. The unit was held together with two bolts extending through
the bottom and cover plates.

Duplicate panels of 0.0003, 0.0010, and 0.0015 inch thickness
were prepared from each of the nickel solutions to be tested and
the procedure as set forth by Pierce and Pinner was followed (17).
The 0.0003 inch panels were tested for two hours and the 0.0010
and 0.0015 inch panels for four hours. Experimental tests indicated
that longer testing (corroding) times were not necessary. The
number of corrosion spots, when examined under a 15 diameter power
microscope, were recorded and used as an index of corrosion. The
results of this corrosion test are illustrated in Table VII.

The results obtained from this method of corrosion testing
were similar to those obtained by the other two methods, in that
the thin deposits produced erratic results, and the two series of
heavier nickel deposits exhibited no significant change in corrosion

resistance.

REMOVAL OF MANGANESE FROM NICKEL SOLUTIONS
Two methods of removal of manganese studied were high pH

precipitation and low current density electrolysis.

 

 

 

26

 

FIGURE 1

THREE COI-lPARTi-ENT CELL ALD PORTABLE BATTERY

OPERATED POTENTIAL SOURCE

 

 

FIGURE 2

THREE COMPARTP’LENT CELL AND PORTABLE BATTERY

OPERATED POTENTIAL SOURCE

27

TABLE VII

EFFECT OF MANGANESE N THE ELECTROCHEEICAL COLPOSION

RESISTANCE OF ELECTRODEPOSITED NICKEL

28

 

Kanganese

Number of Corrosion Spots

 

Concentration (Average of Two Tests)
mg./1. 0.0003" 0.0010" 0.001gg
‘Watts' 2.2 pH 0 1/2 1 0
5 1 2 2
20 7 10 1/2
80 h 2 1/2
160 1-1/2 1-1/2 0
300 1-1/2 5 0
Watts' 5.2 pH 0 7 h 2-1/2
5 S 0 1/2
20 2 2-1/2 0
80 9 1 3-1/2
160 2 1-1/2 2-1/2
300 1 1/2 1-1/2
Organic 3.2 pH 0 13-1/2 .2 0
5 10-1/2 1-1/2 1
20 1 2 0
80 h-1/2 1/2 1
160 35 0 0
300 68 3-1/2 1-1/2
Nickel-Cobalt 0 o h-l/Z 1-1/2
3.75 pH
5 1h-1/2 1/2 3
20 2 2-1/2 1-1/2
80 7 3-1/2 1-1/2
160 2 2 3
300 12 h h-1/2

29

The low current density electrolysis was carried out at 1, 5,
and 10 amperes per square foot for each of the four nickel solutions
containing 300 mg./l. of manganese. This operation was carried
out at the operating temperature of 55°C. for the two Watts' solutions
and 60°C. for the bright nickel solutions. The normal agitation
rate of four feet of solution per minute past the cathode was used
throughout the course of the investigation. The solutions were
analyzed periodically for manganese concentration by means of the
colorimetric method described earlier. Results indicated that no
manganese was removed from the solution by this method.

Current densities of LG and 62 amperes per square foot were
also tested by this method. No significant amount of manganese
was removed from the solution plated at LO amperes per square foot.
A small amount of manganese was removed at the higher current
density, but this method of removal is of no practical value due
to the large amount of nickel that is codeposited.

Removal by the high pH precipitation method was carried out
by raising the pH of the nickel solutions containing 300 milligrams
per liter of manganese to 5.5 to 6.0 by the addition of nickel
carbonate. The solutions were maintained at the high pH for a
period of 72 hours with samples drawn off at periodic intervals
for testing. The sample solutions were filtered and analyzed

for manganese. No manganese was removed by the high pH treatment.

STRESS IN ELECTRODEPOSITED NICKEL
Numerous papers have been published on the experimental deter-

mination of stress in nickel deposits, although stress data are

still somewhat scanty. The following theories have been proposed
for the presence of internal stress in electrodeposits: The
inclusion of hydrogen or its codeposition; formation of nickel
hydrides and their consequent decomposition; the presence of nickel
hydrexide or basic salts as colloids in the cathode iilm; metallic
contamination; or mismatches between the lattices of the basis
metal and the coating may cause the distortion which gives rise
to internal stress (22, 27, 29, 31, 33).

As early as 1877, the presence of stress in electrodeposited
metal coatings was observed and reported by Mills, who called
it electrostriction (19). These residual stresses, often of
considerable magnitude, were demonstrated by Mills, by preparing
deposits on the silvered bulb of a thermometer and noting the
movement of the mercury column caused by the distortion of the
bulb. Deposits of iron, copper, nickel, and silver were formed
in a state of contractile stress, causing the mercury to rise
while the exact reverse was the case with deposits of cadmium and
zinc. Mills showed that the forces involved were considerable.
The effect of the stress in the copper deposit on the bulb was as
great as a uniformly applied hydrostatic pressure of over one
hundred atmospheres.

Stoney, in 1909, made the first quantitative measurements of
stress in electrodeposits, and showed them to be as high as 19.2
tons per square inch parallel to the plane of the cathode (20).

Stoney utilized, as a measuring instrument, a straight metal strip

31

on which he deposited a coating of nickel on one face, allowing
it to bend freely during plating. The strip was insulated with
varnish on the other side. More recently, Hume-Bothery and‘Wyllie
reported that the contractile stresses in chromium deposits may
reach values of nearly 30 tons per square inch (21). It appeared
to them that the internal stresses were clearly connected with
such physical properties as hardness and ductility. Hothersall,
on the other hand, reported that relatively soft deposits from
the Watts' bath may be highly stressed in tension and show good
ductility, whereas an organic type nickel deposit showing zero
stress exhibited a low ductility (22). There is no predictable
relationship among hardness, brittleness, and stress.

There may be, and probably are, many other possible sources
of lattice distortion in plating operations, but the data which
are available at present are insufficient to characterize all
of these sources. Systematic, extensive, and well controlled
investigations are needed in this field.

On the theoretical aspects, agreement has by no means been
reached, but the evidence in favor of a hydrogen theory seems most
in accord. The fact that hydrogen is associated with the formation
of stresses appears to derive support from a number of considerations.
It is well known that the transitional metals tend most readily
to form stable or metastable alloys with hydrogen. Expansion of
the lattices of such metals during deposition and their subsequent

contraction is therefore quite feasible. The development of a

32

tensile stress in nickel can be ascribed to the deposition of an
expanded form of nickel-hydrogen or hydride lattice at the moment
of deposition, followed by diffusion of the hydrogen out of the
deposit and contraction to the normal nickel lattice. This theory
is supported by the fact that some depolarizers and alternating
current superimposed on the direct plating current both serve
markedly to reduce contractile stress. Their action is almost
certainly the oxidation of hydrogen shortly after it is liberated
cathodically and before it can exert any considerable effect on
the growing metal lattice.

The internal stress in electrodeposited metals can be removed
or decreased by a heat treatment just as the internal stress in
worked metals is removed. Stress removal is the first step in the
annealing procedure and occurs prior to recrystallization. Briefly,
at elevated temperatures, the mobility of the atoms in the lattice
structure is increased to the point where the atoms can resume
the regular pattern of the lattice, and distortion disappears.

With respect to the distance involved in the atomic movements

which result in recrystallization, the distance that the atoms must
move to resume the regular lattice structure is small. Indications
are that for any nickel solution, an increase in stress is accompanied
by an increase in the hydrogen content of the deposit.

Martin showed that the stress in nickel deposits increases with
increase in pH, and on the basis of this data it was claimed that

co-deposited basic material is the cause of stress (23). Nickel

33

deposits prepared at a pH of 5.7 have been found by direct analysis
to contain hydrogen (2b). It would thus appear that some hydrogen

is always evolved if contractile stress is to result. A conclusion
thus appears that hydrogen must be evolved before contractile

stress manifests itself. However, here may be an optimum amount

of hydrogen necessary to produce maximum stress, the amount varying
with temperature, the rate of deposition, agitation, bath composition,
pH, and other factors not readily capable of quantitative evaluation.

There has apparently been very little work done on the role
of internal stress in electrodeposits and its relation to corrosion.
There appears to be no doubt that it is involved in corrosion
phenomena, as a stressed metal is more active (more anodic) than
an unstressed metal. If the stress is distributed uniformly
throughout the coating, it will have little or no effect on the
corrosion resistance. If the stress should be greater at one
location than another, anodic and cathodic areas will be set up,
and corrosion will proceed more rapidly.

It is evident that knowledge of the magnitude of internal
stress in electrodeposits is not sufficient to interpret intelli-
gently the probable behavior of a plated coating. Further,
to correlate the mass of accumulated information on stress in
electrodeposits with any one factor is almost impossible, and
actual measurements should be made for any particular solution
concerned. Regardless of the theoretical mechanism by which

stress are set up, and the conflicting data in the literature,

3b

the majority of the evidence supports the following conclusions
with regard to stresses in nickel deposition (25, 26, 27, 28).

l. Tensile stress decreases with thickness of deposit.

2. Tensile stress increases with an increase in the chloride
content of the solution.

3. The effect on stress of solution temperature varies with
the composition of the bath and current density.

h. The effect on stress of pH varies with composition of
the electrolyte; however, for a watts' bath it is definitely
advisable to keep the pH well below 5, not only because
deposits with lower stress are obtained, but also because
the harmful effects of some impurities on stress may be
much more pronounced at a high pH.

5. Increasing current density generally increases stress.

6. Superimposing alternating current upon the direct plating
current tends to reduce stress.

7. Agitation has little effect on stress.

8. Effects of impurities and addition agents on stress are
conflicting, apparently because these effects change with
variation in solution composition and pH.

9. Some organic additions tend to reduce stress, and some
cause the stress to pass through zero and even to reverse
in direction.

Several techniques and instruments have been used for the

measurement of stress in electrodeposited coatings. Stoney, Phillips,

and Clifton, Soderberg and Graham plated one side of a thin metal

35

strip which was held in a fixture (20, 26, 27). The amount of
deflection of the strip during plating was measured by Stoney,
while the latter two studies held the strip rigid during plating
and measured the change in curvature of the strip after plating
had stopped. Other investigators proposed methods of measuring
the bending of a strip during plating (plating on one side of the
strip only) but most of these required auxiliary gauges and
calibrated microscopes which were quite fragile. The spial
contractometer is a recent development of the Fureau of Standards
and has been subsequently used in a number of investigations (28).
This device is based on the use of a helix in place of a strip.
The change in radius of curvature of the helix is a measure of
the stress in the plate, and is measured by the angular displace-
ment of one end of the helix while the other end is held rigid.
Continuous readings are thus obtainable. It is necessary to
strip the metal coating from the helix after each plating cycle
and to insulate the inside surface with a suitable stop-off
material.

The use of X-rays for evaluating stress in electrodeposited
coatings has been attempted by a number of investigators, but the
results were difficult to interpret owing, among other factors,
to the effect of grain size on X-ray patterns. Thus the diffuse-
ness in X-ray diffraction patterns may result from two causes:
small crystal size, and lattice distortion. The amount of diffuse-

ness contributed by each of these causes cannot be distinguished.

36

Experimental - The method of Phillips and Clifton for measurement

of internal stress was utilized with slight modifications. In

this method, the strip was held rigid and flat during the plating

cycle. If stress exists in the deposit, the strip bows upon

release from the fixture. The jig shown in Figures 6 and 7 was

designed to accomodate the 5/8 inch wide, 5 inches long, and

0.0lb inch thick test sample. The strip was placed in a milled

slot (5/8 inch wide by 0.0lh inches deep) in the lucite backing

plate. The lucite cover was placed on top of the test piece.

The cover was constructed to minimize edge-effect and to permit

plating of an area 9/16 inch wide and 2-5/8 inches long. Rigidity

was obtained by means of a 1/8 inch thick steel plate imbedded

in the lucite back and the 1/2 inch thick lucite jig material.

Cold rolled 1010 steel was used in all tests. Electrical connection

was made by means of a copper wire soldered to the top of the

strip, which extended above the top of the jig and solution level.
Figures 8 and 9 show the measuring device. The strip was

placed in the instrument by pulling out the spring loaded knob

on the back, retracting the four steel pins, putting thesstrip

behind the micrometer tip and against the end stop. Releasing

the knob allows the four steel pins to position the strip against

the knife edges. The pointed tip of the micrometer was then

advanced until contact with the strip was made, indicated by lighting

of the small battery operated neon light. Curvature readings were

made before and after plating, and the difference was the deflection

caused by the stress in the coating.

37

 

FIGURE 6

EXPIDDED VIFII.’ OF PLATING JIG

38

 

FIGURE 7

ASSEI‘BIED VIE-I 0F PLATING JIG

39

The equation used for converting the curvature and weight

of the nickel deposit into stress is: (16)

 

 

N = ‘Wt. nickel in grams = Thickness of deposit in inches
216
S = 25.6 x 1.06 (N g‘inl3 d = Stress in pounds per sq. in.
x
where N = deposit thickness

t - steel base metal thickness

d = change in curvature due to metal coating

Operation of the cleaning and plating cycles was that as set
out previously. To minimize the number of variables, four stress
strips were plated simultaneously in four liters of nickel solution.
After each series of twentyefour strips, a new solution was used.
Measurements were made at deposit thicknesses of 0.0005 and 0.003
inches in 0.0005 inch increments. Three such series were run in
each of the four solutions, to give twelve check points at each
thickness value. Some variations were noted in the thickness of
the strips as plated in groups of four, i.e., due to their relative
position in the plating solution with regard to the anode, the
deposit would vary slightly in thickness. However, no correlation
was noted in the amount of stress with regard to thickness from
each series of four strips. The stress values were grouped accord-
ing to thickness and the root mean square values were plotted.
Figure 10 shows the variation of stress in the deposits as prepared
from the four highly purified nickel plating solutions. A variation
of as high as 25%'was obtained from the curves in a few isolated

cases, the general deviation being about 10% from the mean.

 

 

FIGURE 8

STRESS MEASURING DEVICE

b0

hi

 

 

FIGURE 9

STRESS I‘EASURING DEVICE

WITH STRIP IN POSITION

142

The stress as measured was the average stress for the given
thickness and was not a suitable quantity for studying the change
in stress with thickness of deposit. It should be noted that if
a deposit had a high initial stress, due to the distortion set
up in the lattice structure by the mismatch between the basis
metal and the deposit, stress would then show a continual decrease
with thickness. Several investigators have shown that stress
decreases with deposit thickness (16, 28, 29).

It has generally been believed by some, that the influence
of the basis metal on the distortion of the lattice structure
was the cause for this observed decrease in stress with increasing
deposit thickness. That as the thickness of the electrodeposit
increased, the structure of the metal coating assumed its own
structure, and was the basis for this theory. However, the effect
of the cathode metal, and its influence on the orientation of
deposits can frequently be ignored. It is true, that under certain
favorable conditions a deposit is able to reproduce the structure
and lattice spacing of the basis metal on which it is produced
for some distance, but this effect is generally very limited.
Finch and Sun have shown that the effect of the basis metal does
not extend to a distance of more than 10003 (30). The above
results are not, due to thicknesses of much greater than IDOOR,
dependent on orientations as derived from the basis metal.

Brenner and Senderhoff in their work involving the spiral
contractometer for measuring stress, found a similar effect, namely,

a decrease in stress with increase in deposit thickness (28).

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Their experiments showed that the grain size of the nickel deposit
coarsened with increasing thickness. The same phenomena and
explanation were cited earlier by Kohlschutter and Vuilleumier

and by Vuilleumier (29, 31).

It is interesting to note that the stress in electrodeposited
nickel can vary from one extreme to the other, tensile to com-
pressive. The stress values measured in the deposits as plated
from the two Watts solutions were nearly the same, although the
pH of the solutions was 2.2 and 5.2 electrometric. This was a
mere coincidence in the selection of pH values, as the Watts'
solutions undergo a minimum of stress at about pH 3 to h and a
rapid increase in stress above 5.5 (16).

The stress developed in the nickel-coialt deposit was double
that exhibited by the Watts' nickel deposits. This can be
attributed to use of formaldehyde and nickel formate in this type
of solution, as both of these are strong stress risers (16).

The phenomenon of compressive stress in the organic type nickel
solutions has been reported extensively in the literature (16, 31,
32, 33). Organic type addition agents are known to have a large
effect on the stress in nickel deposits. They may increase the
stress, but some of them decrease the stress and may convert it
from a tensile stress to a Compressive stress. The use of nickel
benzene disulfonate has previously been reported to cause a complete
reversal of stress (32). It is to be noted that the organic type
bright nickel bath used in this experiment contained nickel benzene

disulfonate.

b5

As mentioned earlier, Owen observed cracks in electrodeposited
coatings and attributed them possibly to stress in the coating.

The cracking of deposits, with consequent relief of stress, has
been pointed out to be a source of error in the measurement of
stress in nickel deposits (32). It was considered that the effect
of co—deposited basic material highly dispersed in the deposit
might be to weaken, to some extent, intergranular cohesion and,
therefore, to promote cracking as well as to inhibit plastic
deformation. It is known that the effect of a finely divided
second phase in a matrix is to make plastic deformation, and there-
fore the occurrance of orientation more difficult. Phillips and
Clifton pointed out in their article on stress in nickel coatings
that the thicker coating contained visible cracks (l6).

Cracking of a nickel deposit, is not an indication that the
internal stress is of a large magnitude, but rather it is an
indication that the maximum stress at certain areas exceeds the
tensile strength of the material. By increasing the stress, or
lowering the tensile strength of the deposit, cracking can be
induced. Inclusion, such as oxides or basic salts may lower the
tensile strength of the deposit without affecting the stress and
these deposits may exhibit cracks.

At the outset of the program of measuring stress in highly
purified nickel plating solutions, the phenomenom of deposit crack-
ing was to be included in the investigation. The method of deter-

mining stress, that is, plating the steel strip while being held

 

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rigid in a lucite fixture lends itself to stress relief through
cracking. To determine if the highly stressed nickel deposits
were cracking during the plating cycle and thereby relieving the
stress even partially, strain gages were used to measure the
strain imposed on the basis metal during electrolysis.

Type A-l8, SR-h strain gages as manufactured by the Baldwin-
Lima-Hamilton Corporation,were mounted centrally on the back of
the steel strips. These gages had a gage factor of 1.76:2%'with
a resistance of 1204a_.¢.3_cL. Strains were measured with a
SR-h strain indicator coupled.with a bridge balancing unit. The
lucite back plate was machined out sufficiently to provide clearance
for the strain gage and its wires. Care being exercised to
insure ample supporting surface for the steel strips. Two thick-
nesses of shim stock were used, 0.01hh inch to provide a check
with that material used in the earlier portion of the work, and
0.0035 inch which provided much more flexibility with the fixture
during the plating cycle. The 0.01hh inch strip behaved as in
the previous work whereas the thin stock was visibly curved while
still clamped in the fixture after plating.

Figure 11 illustrates the result obtained in a measure of the
strain imposed on the basis metal during the plating of a nickel-
cobalt deposit in which the stress was measured to be 38,000
pounds per square inch tension. The values obtained do not represent
true strain on the basis metal, imposed by the deposition of a
highly stressed metal coating, because the strip was held rigid

during the plating cycle and could not deform freely. The thin

 

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shim stock had much more leeway in the lucite fixture which had
been milled out for a strip four times as thick. The strip,
although held reasonably flat, had more opportunity to bend than
the thicker strip, especially in view of its greater flexibility.
The values obtained show a steady increase in strain on increasing
the deposit thickness. If there were any breaks in the curve or
plateaus, it would indicate that cracking had taken place. It is,
therefore, reasonable to conclude that no cracking had occurred
in the deposits.

Considerable difficulty was experienced in securing a water—
proof coating for the gage. The best results were obtained by
putting a slight excess of Duco cement on the top of the gage
and allowing it to dry thoroughly over night. Great care was
needed in handling the strips with the attached strain gages to
prevent their detachment. Strain in microinches was read directly
from the strain indicator at one minute intervals up through

100 minutes, and every two minutes thereafter to 180 minutes.

CONCLUSIOLS
The results of this investigation on the effects of manganese
as an impurity in four different types of nickel plating solutions

may be summarized briefly as follows:

Appearance - The Watts‘ pH 2.2 and 5.2 panels exhibited a smoothing
effect on the high current density areas of the panels with increas-
ing manganese concentration in solution. No effect was apparent

on the bright deposits from the nickel-cobalt and organic solutions.

L9

Adhesion - The adhesion was unaffected by increasing manganese

concentration.

Ductility - The increase in ductility in the'Watts' pH 2.2 was
attributed to the presence of manganese in solution while the
watts' pH 5.2 and nickel-cobalt deposits in general exhibited

a decrease in ductility. No significant change was noted in the
organic deposits. Elongation values showed no change due to

manganese concentration.

Hardness - The slight variations encountered in the measurement

of hardness were considered to be of little significance.

Corrosion Resistance - Verification of results of three methods
of testing the corrosion resistance was obtained, in that the
presence of manganese in the four types of nickel plating solutions

did not affect the corrosion resistance of the nickel deposits.

Throwing Power - A small increase in throwing power was noted for
the two bright solutions. However, no significant trend was

established with increasing manganese concentrations.

Removal of Manganese - The removal of manganese as an impurity
in the four nickel plating solutions was not effected by either

high pH precipitation methods or low current density electrolysis.

Stress - The internal stress of the nickel deposits from the four

types of solutions ranged from b0,000 pounds per square inch tensile

 

!

“v: u p,

in the nickel-cobalt coating to 5,000 pounds per square inch
compression in the organic bright nickel deposit. The Watts'
nickel deposits were about 18,000 pounds per square inch. Strain
measurements indicated that no cracking occurred in the deposits

during the plating cycle.

 

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(2)

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(S)
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(7)
(8)

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(10)
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(16)

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(18)

(19)

51

RiEEREIJCES
Hothersall, W}, J. Electrodepositors' Tech. Soc. gg, 203
(1950)
Rominski, R. J., Effect of Copper on the Physical Properties
of Electrodeposited Nickel. Thesis for the M.S. Degree,
Michigan State College (l9h9)
Ewing, D. T., et a1., Plating 21, #11, 1157 (1950)
Mng, Do T., et £0, Plating 22, #9, 1033 (1952)
Ewing, D. T., 33 31., Plating g9, #12, 1391 (1953)
Ewing, D. T., 33Ԥ;., Plating 22, #12, 13b3 (1952)
Ewing, D. T., et 21., Plating £1, #11, 1307 (195h)

Dow, W. 0., The Effects of Iron and Aluminum on Electrodeposited
Nickel. Thesis for the Ph.D. Degree, Michigan State University,

(1955)
Ewing, D. T., 33 31., Plating 2Q, #58, 61 (19u9)

Thomas, C. T., and W. Blum, Trans. Am. Electrochem. Soc. fig,

68-87 (19253

Campbell, A. N., J. Chem. Soc. lag, 1713-9 (192D)

Owen, C. J., The Effect of Lead on the Physical Properties
of Electrodeposited Nickel. Thesis for the M.S. Degree,
Michigan State College, (1952)

Ewing, D. T".EE.§l°’ Plating 2Q, #11, 1137 (l9h9)
Serfass, E. J., gt 21., Monthly Review 2h, 320-26 (19h?)

Private communication

Phillips,'w. M., and F. L. Clifton, Proc. Am. Electroplaters'
Soc. 2Q, 97 (19h?)

Pierce, W. J., and W. L. Pinner, Proc. Am. Electroplaters'
Society Q1, 176-8h (l95h)

Evans, U. R., and S. C. Shome, J. Electrodepositors Tech.

SOC. gé, 137 (1950)

Mills, E. J., Proc. Roy. Soc. 2g, SOL-12 (1877)

(20)

(21)

(22)

(23)

(2h)
(25)

(26)

(2?)

(28)

(29)
(30)

(31)

(32)

(33)

52

Stoney, G. G., Proc. Roy. Soc. A82, 172 (1909)

Hume-Rothery,‘w., and M.R. J. wyllie, Proc. Roy. Soc. A181,
331 (19h3). ‘-“'

Hothersall, A. W., Symposium on Internal Stress in Metals
and Alloys, 107, The Inst. of Metals (19h8)

MacNaughtan, D. J., and A.‘W. Hothersall, Trans. Faraday

Soc. Eh, 387 (1928)
Brenner, A. J., Research Nat. Bur. Stand. 18, 565 (1937)

Brenner, A. J. and C. w. Jennings, Proc. Am. Electroplaters'
Soc. 25, 31 (19h8)

Phillips,'w. M., and F. L. Clifton, Proc. Am. Electroplaters'
Soc. 35, 87 (19h8)

Soderberg, K. G., and A. K. Graham, Proc. Am. Electroplaters'
Soc. 2g, 7n (19h?)

Brenner, A., and S. Senderoff, Proc. Am.‘Electroplaters'

3000.2g: 53 (l9h8)
Vuilleumier, E., Trans. Electrochem. Soc. A2, 99 (1922)

Finch, G. E., and C. H. Sun, Trans. Faraday Soc. 22, 852
(1936)

Kohlschutter, V., and E. Vuilleumier, Z.E1ektrochem. 2h,
300 (1918)

Hothersall, A.‘W., and G. E. Graham, J. Electrodepositors
Tech. Soc. 15, 127-1h0 (1939)

Martin, 8., Proc. Am. Electroplaters' Soc. 32, 206-217
(19uu) "'

 

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