1|

H

\NU‘VHW “M

a
\

__‘_——
f
’
____———
_—’—
’
’—
I‘—
f
._ -__——
"“
’
_—_/
f_——
__———-—-
—
__'_——-
___—————
__’—’
—
__’—
__————
__‘_—._
f_———
__————
_———'—-
f
—
__’——-
_—_——
#—
__————-
—

 

EWEVENTICN CF
CF LEAD SHE-.1
ENSTALLED U

“10:35 for We 4
MlCi‘iiCAN ST

}Chn E

¥
:9

V...«.:...:V F. 1.3V.

 

.. ..‘ : . , . . . . . I 2 22:22. ._ 3...... ._
w”u_.r,....§.__,.22.r...313.:2: w.“._...~....:.3x..... .....£..:.T4uzt. g a ., _ .. . .A ,_ ‘

fi‘ '1.

 

333:3; . ,. .3%?..§._33§23::£22233:

4":

.. P‘L
a II a
'1' .
1‘ \‘F r
1 tn
4". h a 1 v1.
#0.“ . ..:
D . f l
. ._ r ~
OI
- .. \ «r W -
m. . ,
A

 

 

in

.o

PREVENTION
OF THE
CORROSION OF LEAD SHEATHED CABLES

INSTALLED UNDERGROUND

_ A Thesis Submitted to
the Faculty of
Hichigan State College
of

Agriculture and Applied Science

by
John Ellis Egan

Candidate for the Professional Degree of

Electrical Engineer

June 1939

THfiSFS

 

4

INTRODUCTION

The underground distribution engineer, faced by the problem of pre-
venting the corrosion of lead covered cables installed underground, is not
so much concerned with the chemical theory by which to explain corrosion
as he is in determining the extent and the methods of curbing it. A study
of the literature reveals that there is some difference of opinion as to
the exact mechanism Operating to produce corrosion. It is not the purpose
of this paper to enter this matter, but father, to find a counon ground on
which to base satisfactory, practical methods of dealing with the problem
of corrosion prevention. r

The following statistics on cable failures, due to corrosion of the
lead sheath, are taken from the report on Cable Operation in 1937, pre-
pared by the Transmission and Distribution Committee of the Edison Electric
Institute. The total number of cable failures on nearly 15,500 miles of.
cable, operated by 49 companies, was 7.1 per 100 miles of cable per year.
25.1% of these failures was attributed to corrosion of the lead sheath.

The real significance of this figure may be better seen by comparison with
some of the other causes of cable failure. For instance, deterioration
of the insulation was the cause of 12.3% of all cable failures, while the
largest single cause, next to corrosion, was mechanical damage of the
sheath due to external causes, amounting to 15.8%. The latter is not
under the control of the Utility and little can be done to reduce it. It
would seem that, since corrosion is the major cause of lead sheathed,

. paper insulated, cable failures, it might well be the concern of the under-
ground distributicn engineer.

12147-1

-2-

HISTORICAL REVIEW

The distribution of electric power by means of lead covered cables
installed underground came into being shortly after the birth of the
electric light and power industry. The streets and alleys of our large
cities were already crowded with the overhead circuits of the telegraph
and telephone companies, and, with a new utility looking for right-ofdway
it was apparent that this could only be found underground. The Edison
Underground Tube System seemed the answer for a time but soon A.c., with
its higher voltages and the need for better insulation, led to the only
other econmmical solution - paper insulated, lead covered cables. Once
the problems of right-of-way, and suitable cables to install therein, were
solved another serious situation was uncovered - electrolysis. An inter-
esting account of the difficulties encountered is contained in an address
by Capt.‘wm. Brcphy, before the N.E.L.A. in 1896. Quoting in parts

”Having now been compelled, as we will assume, to go underground,
what are the difficulties to be met with? After placing your wires under-
ground, if there are no stray currents to disturb them, you are reasonably
safe for a number of years; for the manufacture of insulated cables for
underground work has now been brought to a very high state of perfection,
and you can get almost any required degree of insulation. But unfortunately,
in this country, where we want everything of the most approved type, and
where, in order to get it, we will run almost any risk, we have, co-existing
with the electric light, the single trolley electric railway system, which
has done wonders in building up cities and towns, and in bringing people of
small means within the reach of comfortable homes where they can get a

reasonable amount of fresh air and God's sunlight. The horse, as a motive

-3-

power for propelling street cars, is fast disappearing. It is a pity
that the rail of the electric street railway was adopted as a part of the
circuit, and those who introduced it little knew what the consequences
would be. -------- Owing to imperfect bonding, or to the lack
of conductivity of one side of the circuit, these large currents sought
and found the earth; in other words, the potential of the earth was raised
at places distant from the station, and was lowered again.within a radius
of a half or quarter of a mile, more or less, depending largely on the
state of the soil on'which the station was built. The earth's potential
there became lower than the cables; these lead covered cables affording a
much easier path to the negative side of the dynamos than portions of the
earth. Large volumes of current were conveyed through them. No diffi-
culty occurs at the point where the current seeks the cable, but at the
point where it seeks to leave the cable - where the earth's potential is
lower - here the trouble begins.

”Electrolysis. What is it? Can it be prevented, and how? Elec-
trolysis proceeds on the same line, and under somewhat similar conditions,
as the well-known method of electroplating; the moist earth being an imp.
mense electro—plating bath of various resistances, while the lead covering
of the cable, metal gas and water pipes, are the negative and positive poles.
Corrosion of metals, due to the electrolytic current, goes on as surely as
fate. There is a difference, and perhaps a wide one, between the working
effects of an electro-plating bath and the destructive corrosion of iron and
lead pipes and lead covered cables. All currents of electricity flowing
into the earth seek the best conducting medium, and cause the destruction of
the latter at the point where they seek the earth again.

”The corrosion of metals is due to the following conditions:- A thin

-4-

film of water surrounds these metals, and it is decomposed into oxygen
and hydrogen by the electric current. Oxygen, when freely released, is
always intensely active in combining with any metal present. The lead
covering of the electric conductor within the ducts, or buried in the
earth is, as a rule, covered with a thin film of water, and it is not ‘_
infrequently the case that the ducts and manholes are filled with water.
In every case, the lead takes the place of the positive and negative
plates in the electro-plating bath. If the current of electricity,
after touching along the surface of the lead, leaves it to seek a point
where the earth‘s potential is lower than that of the lead, water is de-
composed, and the free, nascent oxygen immediately enters into combination
with the lead surface to produce lead oxide in the forms of paste, and
iron oxide or rust in iron. The crust of oxide being permeable by water,
a fresh surface of the metal is in contact and presented to the moisture;
and the process is continued indefinitely until the lead covering is
destroyed. The amount of metal thus decomposed depends on the amount of
current flowing from metal to the ground. - - - - - - -

"What is the remedy? The only real remedy is to cease using the
rail as a part of the circuit and to use a metallic circuit. But te
bring about this condition of affairs is a task not easy of accomplish-
ment. The Courts have already decided that the electric railways have
a perfect right to use the earth if they see fit. Now that we have the
electric railway with us - and we would not part with it under any circum-
stances - let us do what we can under these present conditions to reduce

the evil".

The references given to the literature take up the problem of elec-

-5-

trolytic corrosion at this point and bring it up—to-date in a thorough
fashion. However, to the writer's knowledge, the patent field has not
been covered and a brief review of some of the more interesting patents

'11]. nov be madae

Robt. Berry. #132,746. November 5, 1872.
Improvement in Coating Lead Pipes.

"Tb carry out my invention, I employ a solution of chromate or bi-
chromate of potassa, acidulsted or not, as the case may be, and bringing ,
it in contact with the lead to be protected by any of the processes known.
In this manner an insoluble chromate of lead will be formed on the surface

of the lead to be protected“.

Arthur E. Colgate. Assignor to Western Electric Company.

#403,418. May 14, 1889.

Method<f protecting the Lead Pipe of Telegraph-Cables from Corrosion.
Method consists of forcing sulphureted hydrogen into the ducts con-

taining cables. The resulting lead sulphide formed is supposed to prevent

corrosion.

Lucien I. Blake. #661,165. November 6, 1900.

Protecting Underground Metallic Structures from Effects of Electrolysis.
”It is well known that a current which leaves a metallic surface by

a conducting path which is non-ionisable or not chemically decomposible

will prodtme no electrolytic effect on that surface, and I have taken ad-

vantage of this fact in carrying out my plan of protecting underground

metallic structures against electrolytic corrosion by interposing between

the metallic surfaces and the surrounding soil an electrically-conducting

-6-

medium which is non-ionisable and which will prevent access to such sur-
faces of the products of electro-decomposition of any solution which may

be present in the soil. The protective medium may be coup osed of one or
more of a large number of materials and may be applied in many ways. I
may, for example, employ carbon in any suitable form, preferably a.mixture
of graphite with some binding material by means of which it may be applied
and fixed to the surface of the metallic structure which it is designed to
protect. I have found, for example, that a.mixture of graphite and paraf-
fin is well adapted for this purpose.

"It is not essential that the substance of the protective medium
should be itself a conductor of electricity, provided only it permit the
passage through it when applied for use of the current while preventing
the access to the metal surface of the products of decomposition. Such
substances are now well known and have been employed as nonsperous elec-
trolytic diaphragms in galvanic batteries and electro-decomposition cells.
Among such substances may be mentioned precipitated chalk, pulverized
anthracite coal, gelatinized compounds of silica and the like which when
used in layers of sufficient thickness, and moistened if by nature they
are dry, permit the ready passage of current, but prevent the recombination
of the products of electro-decomposition.

"The protective medium may be applied to the metallic structures in
any convenient manner. It may be applied in a thin layer with brushes or
suitable tools, or it may be deposited in larger amounts in a trench and

the metal structure embedded in it”.

Rob't :1. Burns. #1,903,975. larch 16, 1929.

Process of Making Concrete.

-7-

“This invention relates to concrete ducts which are used for pro-
tecting lead cable sheath, and to the process of making the same.

”The object of this invention is to provide a cable duct in which
the corrosive effect of lime on the lead cable sheath is prevented or
retarded.

"Applicant discovered that certain substances tend to protect lead
or lead alloy cable sheath from corrosive attack and that this effect is
due to the presence of the silicate ion, that it is induced by so low a
concentration as is afforded by a saturated calcium silicate solution
and that it is effective within a relatively wide range of hydrogen ion
concentration.. Applicant further discovered that the corrosion of lead
cable sheath resulted in the formation of red crystalline lead monoxide
which crystallizes from saturated solutions of lime or alkali plumbites
or plumbates. The alkali responsible for corrosion may be produced by
a solution of lime or alkali salt, sodium chloride or ordinary table salt
which is used to thaw out street car switches in winter and occasionally
finis its way into cable ducts where it is converted into caustic soda
at the surface of the cable sheath as a result of current flow from.earth
to the sheath. This type of corrosion also occurs in newly manufactured
concrete ducts owing to the presence of free lime in the concrete. Appli-
cant further discovered that distilled water exposed to air readily corrodes
cable sheath alloys and that this corrosive action may be prevented by the
introduction of solid silicate or by the addition of finely divided silica
flour.

"According to this invention concrete cable ducts are constructed by

introducing a certain quantity of soluble silicate as water glass silica

-3-

or silicious slag in the concrete mixture while constructing the cable
duct. The silicate has the property of neutralising or preventing the
corrosive effect of lime on the cable sheath through the formation of a
silicate film on the surface of the cable sheath. Cable ducts after
being constructed or laid may be impregnated with a solution of soluble
silica or coated on the inside duct surface with soluble silica. How-
ever, in the case where soluble silicate is introduced in the concrete
mixture, the concrete should be of such composition that water permeating
through it or forming a solution by contact with it should have silicate
ion content of not less than that of saturated calcium silicate; hydrogen
ion content of not less than 1 x 10’11 grams per liter of solution.

”What is claimed is:
l. The method of preventing the corrosion of lead alloy cable sheath
enclosed in concrete ducts which consists in producing a saturated sili- T
cate condition adjacent the lead sheath which forms or causes to be formed

a coating of an insoluble film on the lead sheath.

2. The method of preventing the corrosion of lead alloy cable sheath en-
closed in concrete ducts which consists in producing a saturated silicate
condition adjacent the lead sheath which forms or causes to be formed a

coating of lead silicate on the sheath".

Henri Benit. z§41,94,4,773. say 7, 1931.
Method of Protecting Lead Against Corrosion.
”The method consists in rendering the lead unattackable by destructive

agents by creating on its surface, chemically, a protective layer formed

by a very stable lead salt which resists chemical changes. The lead salt

-9-

thus produced will form a very thin layer protected mechanically by the
usual covering which might now be tar or other inexpensive material which
will not be chemically neutral. There will be no longer any liability of
corrosion of the lead in case of cracking of the waterproof covering even
if corrosive products are present in this coating because the lead salt
formed on the surface of the lead will prevent attack by the latter.

“The lead salt which forms the protective coating should be very
stable and be easily and cheaply formed. Lead sulphide fulfills these
conditions; it is insoluble in water and is unattackable'or almost un-
attachable by acids and mineral and organic salts. It is formed easily
from pure sulphur or from natural or artificial sulphide derivatives in

contact with lead, the reaction being very rapid with the aid of heat.

”For example, there may be applied to the lead directly at a temper-
ature a little above 100°C. a layer of ordinary tar mixed with pure
sulphur in a proportion greater than 3%. Under these conditions there
will be formed instantaneously on the lead a film-like coating of lead
sulphide and the reaction will cease of its own accord leaving an excess
of sulphur in the tar. - - - - - ~2-

"Where the protective covering of the lead consists of concrete or
cement another form of the invention consists in incorporating in the
cement during the preparation of the mortar a small proportion of sodium
sulphide. It will be understood, from what has been stated above, that

the lead will thus be protected against attack of the most highly basic

cements”.

Vladimir Grodsky. #2,007,969. Patented July 16, 1935.
Filed October 14, 1933.

-10-

lbthod of Protecting Underground Pipes and Conduits.

-------- ”This is accomplished preferably by mixing a
portion of the soil remw ed from the trench or excavation with a proper
percentage of an inhibiting compound usually an alkali, whereby the acidity
is neutralized in the case of acid soils, and the potential acidity is
balanced in the case of alkaline soils. The soil as conditioned will
comprise a small percentage of the total earth removed from the trench or
excavation and is returned in its loose absorbent condition to the trench
in the usual manner to fill the same and cover the pipe.

'I find it desirable and economical to isolate the portion of the
soil so conditioned and returned to the trench for two reasons. First,
by isolating the conditioned soil from the remainder of the adjacent soil
it is possible to maintain a substantially constant mixture. Again, by
isolating or confining the conditioned soil with positive means, I prevent
any possibility of the leaching out of the neutralising agent due to the
presence of excess water.

"The means which I employ to accomplish this isolation will prefer-
ably comprise a waterproof material, such as textile or paper fabric,
providing a liner in the lower portion of the trench, and in some cases.
forming an envelope to completely isolate the pipe and conditioned soil.

”Instead of conditioning the soil by mixing a neutralising agent
therewith, I in some cases provide the pipe or conduit with a surround-
ing layer of the neutralising or inhibiting agent, and preferably enclose
the loose absorbent mass in an envelope of the lining material. - - - -

”The soil having been removed and its nature detemmined, I add
thereto one or more of a group of corrosion inhibiting compounds se-

lected from the oxides, hydroxides and carbonates of the alkali metals-

-11-

or alkali earth metals. I prefer to use calcium hydroxide but sodium
hydroxide and potassium hydroxide may be employed, as well as calcium
oxide, barium oxide, calcium and barium bicarbonate, and in some cases,
sodium carbonate. Phosphorous and chromium compounds may also be

employed I! e

THEORIES 0F CORROSION

At first the corrosion of lead (other than by electrolysis) was
supposed to take place entirely by chemical action. There are a whole
series of lead oxides beginning with the suboxide Pb20, followed by lead
monoxide or litharge PbO. Then comes lead sesquioxide Pb203, formed when
lead hydroxide, in an alkaline solution, makes contact with an oxidising
agent. It sometimes happens that the cable sheath may become negative
to its surroundings and at the same time sodium chloride, la01, may find
its way into the duct, usually at street intersections where salt and
sand are spread when the streets are icy, or near street car switches
which are kept from freezing through the use of salt. The result of the
action of the negative potential is to decompose the sodium chloride, re-
leasing nascent chlorine which is an excellent corroding agent. The
following reaction is believed to take place under such conditions -
2Pb0 + NaOClvrhaCl e Pb203. There is also red lead which appears to be
Pb304 + nPbO or has an approximate formula Pb405. Now here arises a
peculiar situation; the chemist describes these oxides of lead as
amphoteric oxides; that is to say, that lead monoxide, for example, may
act either as a base or an acid. Lead monoxide reacts with potassium
hydroxide to form potassium.plumbite, Pb(OK)2, or with an acid to form a
lead salt. In the same way lead sesquioxide, Pb203, appears to be lead

metaplumbate, Pbng03, and red lead similarly appears to be lead artho-

-12-

plumbate, Pb2PbO4. This dual role that lead plays was used to explain
why lead was attacked by weak acids, particularly acetic, and also by
alkalies.

The older, or as it may well be called 'Chemical Theory of Corrosion',
served very well for some time; however, as corrosion became a more serious
problem and greater attention was given to its causes there were cases
that could not be satisfactorily explained. In time sufficient evidence
was produced, both experimentally and in the field, to support an electro-
chemical theony of corrosion. Oliver P. Watts, writing on, 'Voltaic
Couples and Corrosion', (page 235, Electrical Chemical Society, Volume
47, 1935), states, ”the electro-chemical theory of corrosion now seems
to have been adopted as agreeing better with the known facts of corrosion
than any of the theories previously proposed. Whether corrosion of
metal takes place in a solution of HaCl, IH4Cl, sea water, H2304, or
alkali, or the metal dissolves as a double salt, these experiments dis-
close no difference in the nature of the corrosion process. As far as
can be detected with the naked eye, removal of air prevents corrosion.

In these particular cases, either for a single metal or a couple of two
or more metals in contact, corrosion appears to depend on the ability of
the metal to displace hydrogen from the electrolyte”.

In reply, Benough and wermwell'wrotes- ”It is probable that a
choice between these alternatives cannot be made with certainty until it
is possible to experiment on an atomic scale, since differences on such
a scale may start corrosion".

Experimentation on such a scale was approached by Frink and Kenny.
(The Passivity Produced by Chromic Acid on 18-8 Chromium-Nickel Alloy.

Transactions Electra-Chemical Society, Vol. 60, page 235, 1931). "The

-13-

actual elimination of point to point galvanic couples, or, in other words,
the equipotentialization of the metal surface was demonstrated by direct
potential measurement for the first time. This equipotentializing
principle may be of general application to other metals and alloys, no
metal or alloy being corrosion proof without the elimination from its sur-
face of point to point galvanic couples". (The capillary electrode had an
area of cross-section of 0.012 sq. mm.).

Wm. Blumt Transactions Electra Chemical Society. Volt. 52, page
432, 1927. "According to the electrolytic theory there can be no cor-
rosion except as there is a difference in potential between two parts of
the surface, due either to initial difference in composition, in physical
condition or in the surrounding mediums".

w. H. Hatfield. Transaction. Electro Chemical Society. Vol. 54,
page 123, 1933. “Acceptance of the electro chemical theory in regard
to corrosion of a specimen in a uniform aqueous electrolyte necessitates,
in my opinion, the assumption of the existence of some variation in the
potential across the metal surface".

Considering for the moment purely electrolytic corrosion we imagine
that the stray current flowing from the cable sheath to ground causes the
ionisation of the electrolyte adjacent to the sheath, releases ions some
of which attack the lead. The electromotive force causing this electro-
lytic corrosion was assumed to be derived from the street railway tracks.
One day someone asked, ”why must the electric current come from some out-
side source?" "Why, if cables are installed in ducts and we know that
moisture is present, cannot the necessary potential be generated locally
by cell action?" An experiment to prove this point was conducted in the

laboratory. A lead specimen, supported on a glass rod in a dilute

-14-

solution of sodium chloride, was found to corrode at the point of contact
with the glass rod. The problem was, then, to discover how the potential
was generated. One theory is that the glass rod tends to exclude the
dissolved oxygen from the point of contact with the lead, thereby making
it positive to the remainder of the specimen. This potential may, under
proper conditions, amount to as much as 0.1 volt. Due to the small
physical dimensions of the field the resistance is low and electrolysis
may readily take place.~ There are many possible ways in which corrosion,
due to cell action, may take place, but they all have a common charac-
teristic - inhomogeneity of field. A few illustrative examples are: a
cable only partly submerged in water; the sheath of a cable in contact
with solutions of two different concentrations or, in the case of cable
buried in direct contact with the soil; the natural difference in soil
particles has been shown to cause corrosion.

Tiers appears, then, to be two very general classifications of lead
corrosion, vis., by direct chemical reaction which is rather complicated
by the amphoteric nature of lead, and electrolytic corrosion, due to self-

generated electromotive force through cell action.

STATEMENT OF PRESENT PROBLEM

One is finally forced to conclude that lead, instead of being a very
stable element and one not easily destroyed may, under unfavorable circum-
stances, become the very opposite. For a long time all corrosion of lead
underground was blamed on stray current electrolysis. When it was recog-
nised that there were other causes and a theory involving the electro-
chemical corrosion of lead was proposed it became apparent that stray
currents may have had a beneficial effect. It has been shown that in
order for cell action to take place a small portion of the lead must be-

come positive. Now, when stray currents are present, it is necessary to

-15-

install drainage cables in order to keep the sheaths negative. This
appears to prevent, to a large degree, the formation of corrosion cells.
Now, with gasoline driven busses replacing the street cars, the protection
afforded through keeping cable sheaths negative to their surroundings by
control of stray currents is disappearing. Furthermore, it is not eco-
nomically feasible, except in very special cases, to maintain the cable
sheath negative to ground. Where the cables are remote from all other
underground structures it is entirely possible to provide facilities in
the form of rectifiers, motor generator sets, or other sources of D.C. to
maintain the sheath at a potential of not more than 0.2 volts.

The present problem, then, consists of recognising that the sheaths
of underground cables, whether pulled into ducts or buried direct in the
ground, may be attacked by corrosion due to stray current or produced by
cell action or by direct chemical action. McCallum and Logan, of the
Bureau of Standards, in Technical paper #355, have presented a comprehen-
sive view of electrolysis testing. Bureau of Standards Technical Paper
#358: by Logan, Ewing and Yeomans, Soil Corrosion Studies, discusses the
damage likely to occur to cables buried directly in the soil. I. A.
Denison reports on Electrolytic Measurement of the Corrosiveness of Soils -
Bureau of Standards Research Paper #RP918.

Since the electro-chemical theory of corrosion has come to play such
an important part in explaining the causes of sheath damage it is only
logical that electro-chemical means should be used in locating corroded
areas. One such method that shows great promise is described in U.S.
Patent #l,865,004, granted to H. E. Haring of the Bell Telephone Labora-
tories. A non-polarisable electrode, or half cell, is pulled through a

vacant duct and the variation in potential between the cable sheaths and

-15-

the electrode at regular intervals is noted. Field experience has shown
that marked variations in potential indicate areas of corrosive attack.
The electrode may take several different forms. The British Post Office
uses a copper-sulphate half cell, while the Bell Telephone Laboratories
have used a lead chloride half cell. A modification of the latter, as
used by the writer, is described in the appendix.

When the non-polarisable electrode, or half cell, is pulled into a
vacant duct and the electrical circuit completed through a potential
indicating instrument the equivalent of an electro-chemical cell is set
up with the lead cable sheaths as one pole and the non-polarizing electrode
as the other; hence,its name - half cell. The material separating the
two poles consists of the duct material and, in some cases, may be of
rather high resistance. In addition, any attempt to draw current from
the non-polarizing electrode will tend to change its normal voltage and
lead to erroneous results. Therefore, a potentiometer or vacuum tube
voltmeter is recommended for use in the field. These instruments have
certain drawbacks, however, and the writer has used a voltmeter designed
to make hydrogen ion determinations. The meter is readily portable and
has a resistance of two megohms/volt. Considerable skill, apparently,
is necessary in interpreting the results and for that reason several tests
were conducted under known conditions. First of all, a section of conduit
was surveyed which, it was quite certain, was located in a non-corrosive
location. The curve A (page 25), plotted from the readings obtained,
seemed to verify the assumption inasmmch as there were no marked changes
in potential. The next test was conducted on a conduit in which two cable
failures, attributed to chemical corrosion, had occurred. Furthermore,

the conduit section was located in an alley and it was quite certain that

-17-

sodium chloride was not a factor, nor was it likely that stray currents
were present (see page 26, Curve D). Cable A failed at Point #1 and was
replaced four years before the test was made and Cable B failed at Point
#2 only two years before. The remaining cables have been installed in
this location for eight to ten years without failing. Cable A was
severely corroded for several feet each side of the fault, the remaining
portion being in good condition; Cable B, however, was badly corroded for
217 feet. This much was scrapped because of the condition of the sheath.
The condition of the sheath of the four remaining cables is not known, but
the potential from.the 240 ft. point to the manhole would indicate serious
corrosion. The reason that failures did not occur in this region, it is
supposed, is due to the fact that the corrosion was not highly localised
as the potentials at the 70 and 150 ft. points would indicate. The
potentials obtained after the cable sheaths had been treated with a cor-
rosion inhibiting gel, Curve 2, will be discussed later. Turning now

to the curves on page 25, Curve B shows the potentials existing when
street cars are operating on a track adjacent to the conduit. The read-
ings taken were the average value as the potentials varied quite widely
due to the stray current. Curve c shows the conditions existing some
time later after street car service had been discontinued. The potentials,
of course, did not fluctuate and the values are those actually indicated.
This set of curves shows that stray current, if controlled, may be an
actual aid in preventing corrosion by maintaining cable sheaths negative
to earth. While, in all probability, the cable sheaths are not danger-
ously positive to earth after the removal of street car service, never-
theless the conditions are definitely less desirable from the standpoint
of possible sheath corrosion due to chemicals in contact with the lead,

or cell action. Finally, Curve F, page 26, shows the potentials exist-

-13-

ing on a section of cable in a residential section where corrosion due
to any cause would be least expected. Examination of the physical sur-
roundings showed a sewer adjacent to the thirty foot point. The general
contour of the duct section rose from the 0 foot point to the end of the
duct section. Further investigation disclosed that the sewer had backed
up on previous occasions undoubtedly discharging highly corrosive material
into the lower end of the conduit section. The condition of the half
cell upon removal from the lower and showed the presence of decayed matter.
So far as the writer is aware the half cell method of exploring a
vacant duct is the only way to determine the presence of corrosion in situ.
The other methods commonly used depend upon chemical analysis or micro-
scOpic examination of the products of corrosion. One such method in-
volves the use of a 5% solution of tetramethyldiaminodiphenylmethane con-
taining dilute acetic acid. When this indicator is dropped on the cor-
roded area a blue color is produced in the presence of lead peroxide.
Some authorities question the reliability of this test and for this
reason it must be used with discretion. Photograph No. 1 shows a typi-
cal case of stray current electrolysis. The oval, sharp edged pits are
typical of this form of corrosion. Photograph No. 2 shows another case
of stray current electrolysis but here the cable sheath was cathodic.
The presence of sodium chloride in the duct was shown and it seems proba-
ble that the redeposit of lead was due to the wide difference in conduc-
tivity of the electrolyte at several points along the duct. Differential
aeration is a cause of corrosion in some localities and may be identified
by the symmetry of the affected areas. In some cases the damage may at
first be attributed to foreign material in the ducts scoring the sheath

when the cable was installed, so regular is the region of attack. Some-

-19-

times, it is true, mechanical damage may be a contributing factor
through changing the crystal structure, thus leading to concentration

cells in the presence of an electrolyte.

METHODS OF PREVENTING CORROSION

The most logical way to prevent corrosion of lead sheathed cable
is, of course, to isolate the cable from all corroding media by means of
a protective covering of some impervious material. Jute wrappings im-
pregnated with asphalt have long been used for cable buried directly in
the ground and, for the most part, when conscientiously applied have
withstood the test of time. Armored cable, made of alternate wrappings
of jute and steel wire, are generally used in crossing streams, lakes or
other bodies of water. What is desired is an inexpensive covering that
will protect the cable sheath from corrosion under the average conditions
of installation. The practice of pipe line companies has been followed
with some degree of success. The flexibility of cable as compared with
rigid pipe must be considered and bitumastic enamels or other brittle
coatings are to be avoided. Rubber or rubberized fabrics, sold under a
variety of trade names, have been advocated. A series of tests conducted
on a number of such coverings produced by several different manufacturers
revealed that the average life of the coatings in submerged ducts was
approximately five years. Some of these coverings represented an ad-
ditional cost of between 5% to 2071. of that of the cable. If these cables
‘were to be buried directly in the ground some form of mechanical protection
‘weuld be required. Photograph No. 3 shows one form of protection, a
cathedral tile, which seems very promising both as regards cost and pro-
‘tection. lore commonly, concrete or wood slabs are placed over the

'buried cable. One method of protecting buried cable that has several

advantages consists of laying tar paper on the bottom of the trench to
keep the cable out of contact with the soil, both while the protective
coating is being applied and after the installation is completed. The
cable is pulled into the trench and supported out of contact with the

tar paper by means of pieces of old crossarms or other suitable support.
If the trench is narrow and deep the cable may be supported above the
trench while the coating is applied. One coating, now under test, con-
sists of a grease, about the consistency of cup grease, in which is in-
corporated sodium silicate (1 gallon), and sodium bichromate (1 lb.) to

10 gallons of grease. The function of the two chemicals will be dis-
cussed under the action of inhibitors. The grease was applied up to a
thickness of l/lG of an inch. Grease can be applied by unskilled labor
and with close supervision a satisfactory coating is obtained with a
minimum of expense. The cable is then covered with cathedral tile.

Where the ground is not likely to be flooded this covering is considered
satisfactory. Another coating under test consists of emulsified asphalt,
(clay type), in which has been incorporated 1% each of sodium silicate

and sodium bichromate. For use in cold weather alcohol must be added

to keep the emulsion from fressing. The advantage of asphalt over grease
lies in its drying to a comparatively moisture resistant state. Cathedral
tile is again used for mechanical protection. The costs of these types
of coating are approximately equal and will be found to be considerably
less than that of most other types. Examination of one installation,
after it had gone through the winter and spring seasons, revealed that the
‘tile, when properly laid with little or no gaps between adjacent sections,
had prevented the ingress of loose soil.

The value of inhibitors for the control of corrosion is well

established in practice. Their protective action has been attributed
to rendering'the metal passive or, according to some experimenters, to
the polarisation of the anodic or cathodic areas. R. M. Burns, of the
Bell Telephone Laboratories, in a technical publication, Monograph B-912,.
The Corrosion of Metals - I, discusses the subject from the electro-
chemical point of view. He states the case for the use of silicate as

a means of controlling the corrosion of lead in these words, ' -----
the highly protective film of silicate which presumably forms upon lead
and lead rich alloys when immersed in water or soil solutions containing
as little as ten parts per million of silicate. As is well known,
distilled water is corrosive to these metallic materials. were it not
for this fortunate effect of silicates upon lead it is doubtful that it
or its alloys could be used for cable sheathing in the present type of
underground construction which permits exposure to soil surface waters

at times”.

The British Post Office has taken advantage of this fact and has
incorporated sodium silicate in the pulling grease used when telephone
cables are installed in corrosive locations. Cables so coated are un-
doubtedly less subject to chemical attack, but when sodium silicate is
emulsified in a grease the electrical resistance of the resulting mixture
when applied as a film to a lead covered cable may be decreased. If
this be so, then the cable is subjected to stray current. An effort
was made to find a suitable grease that would not only protect lead
against chemical attack but also reduce the hazard from stray currents.
It was discovered that sodium bichromate had a beneficial effect and has
been used with sodium silicate as a pulling grease for cables installed

in ducts and, emulsified in grease or asphalt, as a coating for buried

.., I I'Flh‘

-22-

cables. Under the action of stray current a protective layer of lead
chromate is quickly formed. This layer of lead chromate adheres so
firmly that patches of it have been found even after the cable sheath
had been sand blasted. Specimens of lead sheathed cable coated with

a silicate-chromate-grease have been installed in ducts flooded with a
saturated solution of sodium chloride and maintained at a potential of
6 volts, some positive and some negative to ground, for a period of six
months without showing appreciable signs of attack. Such protection
can be afforded to cables only at the time of installation and is not
applicable to cables already in service. Therefore, a search was begun
for some method that would permit the use of silicate and chromate on
cables already operating in ducts.

The following process has been developed over a period of several
years and about 1,000 feet of cable have already been treated as an
experiment. Because it can be applied to operating cables and because
of the gratifying way it has withstood accelerated tests under highly
corrosive conditions seems to merit description. The process is based
on the formation of a silica gel through the action of sulphuric acid
on a water solution of sodium silicate. Sodium bichromate is added to
the acid to secure the beneficial action of this chemical as an inhibiting
agent. The process is carried out as follows. The duct, containing the
cable to be protected, is plugged at the lower end and vented to the atmos-
phere through a small flexible tube. A rubber hose is inserted at the
high end of the duct and carried to the surface of the street where it
terminates in a funnel. The dust is then filled with a solution of water,
sodium silicate, sulphuric acid and sodium bichromate. The ratio of the

constituent parts of the solution is not critical but is usually as follows:-

-23-

'water - 20 gallons; sodium silicate - 1 gallon, (20° Ban-d); sulphuric
acid, l/B pint (1400 Sp. gr.); sodium bichromate, one pound. This so-
lution gels in about 15 minutes at ordinary temperatures. Some concern
was felt as to the difficulty that might be encountered should it become
necessary to remove a treated cable. Trial has shown that the pulling
stress is not increased by the presence of the gel. Furthermore, the

gel is easily converted back into a liquid so that any of it carried into
a.manhole may be readily removed. The effect of syneresis, loss of water
by the gel, has not been fully determined. The high thermal conductivity
and thermal capacity of the gel are an aid in increasing the KVA rating of
cables protected.

Cathodic protection of underground pipe lines has been discussed in
the literature and its application to lead covered cables is clearly indi-
cated. The chief difficulty in the case of the latter, however, is that
cables are usually installed in urban areas, which means that the effect
of the protective potential on other underground structures cannot be
ignored. Where cathodic potentials may be applied without jeopardizing
other preperty, great care must be exercised to control the magnitude and
gradient of the voltage applied to the sheath. Should the sheath become
appreciably more than 0.2 V. negative to earth cathodic corrosion may take
place, especially if there are chloride ions present. At potentials of

much less than 0.2 V. the voltage developed by local cell action may not
be neutralized.

CONCLUSION

A study of the cable operation record of a typical Utility operating
approximately 2,000 miles of lead covered cable reveals that for the 10

year period, 1927 to 1936 inclusive, the rate of cable failures due to all

I 'itli \ alga '3 .. .. u. blta.

1.7.. . Ecljlflllfli
c . 1.4.17

»
a
. .. 41‘:

 

 

-24-

causes was 6.5 failures per 100 miles per year. Of this total figure
0.76 failures per 100 miles per year were attributed to stray current
electrolysis and 0.47 to corrosion. The figures for 1936 were: 5.35,
0.23, and 0.41. The reduction in electrolysis failures from 0.76 to

0.23 per 100 miles of cable per year shows what can be done through the
cooperative efforts of a Committee on Electrolysis. 0n the other hand,
the total number of failures dropped from 6.5 to 5.35, while the corrosion
failures remained practically unchanged. The writer believes that these

figures show the advisability of taking steps to curb the losses due to

corrosion.

. t e t \r a!“
1.35 I .
. j

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

iii--411 4 1 _-:--- kI4-l-ul-5-tl -.11!-1-- - 4 . a . . 4
. . e _. . _ . _ . 4 .
4 .. _ . , c _ . . . .
-. . .4 . 4 .. _ ....... 4 - - ...... . _.. . - -. 4- - . 4 . 4 4 4. 4 . H . 4
_ . . . . 4
a . 4 _ . _ H _ __ 4 4 . 4 4 u 4 . ...... .
. *O- Ill ll- v+olvilin t tittil. 4|!- !!ovlti A. tuft-94f: -O-ilt' in!" J I lax tini‘ill OI 41||1Ivt 11941:: lT.‘ lie. till I t - on H 1.?!T1- 4:14. A - ., .r- IlatDl 1“
H _ 4 n n 4 . _ a: .
. a . . 4 . . . . . 4
vi vv - I. F “I n A ¢I4 4 . la . .. vi a - W s r .. . u .
m . - .. . 4 _ . _ 4 . 1 _
. ... ,h . . . 4 . 4 . _ . u 4
fit... + > s) . LFIPOI'-’ 311....91". V+ll1'1.|-11‘t-I1«.|7‘v.‘o:1 I’ll! .Iu.:v..'l.l +3 tlll‘ ..Ille-'e. ‘l'e31|.4_\.|r3. ‘N’t.!...1)l|a
. _ - - . _ . _ 4 . . . . . . -.. . 4
_ 4 . .. . . 4 u 4 4 . 4 4- 4
4 . . . n 4 _ .4 r .
.' Q9: I.* leh-t... . o‘ Flt? 1e ' IAY ~‘Vt-A ill Ill 11 -onl|te. . _¥ I-ii A I a '1: t v0 .v ..M, a 9 o H
. . . 4 4 4 . . 4 . . 4 v
m a fit. . . .... u H . M 4 w. m an”. ,4
. . . .. .. - 4}, -.-.---4-.--..-,- -._-..-..-- --.-4---.- i
4. _ 4 .4 . .. ... . . . 4 4. .4 ... _
T. ..... u! .9 . luv I-“ etl .? u \ 4 .4 ....... k .Puh roe ~..|a-,-. .10 r I? t O .4 t 4! . e. n . .
a . .. . - . . w _ 4
o - .. . fi _ ... .- u _ Hi _ a .
ll. ‘4 t'tt-n’AWLJI‘III‘WITt'seOI-..qdlllnbllelelL #Jntl1_ W :01”. IWll-ilad L50 . t v vfitlllllf' “OI h .4
. .. a e . 4 4 IL
.- 1 -4 a . it” [4.1. .- .- -.34 Ls.- - - - -. - - 4. -.-..-V .- 4 4 u- - _
. . 4 . : . . . 4 . . . . _
4 . 4 . . 4 4 . . 4 . 4 ...» 4
*0 v’l .P el- ). III» l-sl Int- ill. b 11...- Lotliltlw l 'Vrl.w>|e-:.-Iltilreuli nrb’ltfl‘tlul‘- $ [I a
4 4 .e. .
l.-

 

. .
«Iv-It’- | .
.

e.—

l

.

9
_ s

s

v

v

I

4
4
4

4....
...-
”...-.-

 

 

 

 

 

 

 

?
.r
_i - _
4
I
’-
?
1
e
i
;
i
9
+:
I
1
. T .1 L
D
s
i
;
l
..‘4
I
i
3
l

 

‘ t
¥

 

 

 

O
i
7
l
3
’ 41f-._:.4_

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

         

 

 

 

I

. . .. w _ om . . n V
. .. ts fit . . . u a 4 _
fie .- .6 t O \ e “.lfi‘o‘L-Irlb wiezte: .flullxvoe.owle.(eeu.l. KW..e. ...... h out e ...we I e V t i] l v ‘4r .wul‘l’ w . . .- h
. fin 4.. “.54....” . 4T .4 3
. lb P.. n 4 _ . h . w v 14“ J.‘|I l'l . 4: at“! VII-CL
.. _ . . ... .. . ..H. v v . - . . F
--- ivory-L. -H.-.,-r.-.. 14!.4- -..-.41.!- ...-..I.4.u .1451...- 1 - Alr- ._ - 4 -. 4 , 4 4 -4 .4 . 4 - 1 .7 . . L mi
4. .. . .. . f ..4 , 4.. .... ....4 4 . 4 . 4 .. .- 4 _ W 1.3.
. . . . .47. . . . 4 .
. Itlu'T if? tItFthl b 71!». Int-VII; .wbvll. ...lvltlll \'II I ‘0 .O‘I ‘OII III..- , 0 III- I 'l."[ - It» 0‘.
fix : Mr ...4 . .4. .. . 4. . 4 _ 1- 4 4 f + . 7n n
. .. .4 .4. .. 4 4 4 .
. . . . . . . . . . 4 . . .
fl. »-o.lvl4t-l.l..,i [‘1411 .7; ..l-T-u .. - .....4V toe Y- ..v1.v.. thl-t - +.- .w ..w-I .1-.4T-.-.. . w... . . 4 4 . . ..h ...-4
.4 . . .. ... h. H ... . _ 4. .. _ . . m. 4 V 4 4 Pt I..."
. .- .- . . . . e .. v . . . I” my. 1 .
-b4)-o,--I 4-1- 114114.!- -l- - Ill-1.111-}. x: 1 13.911? --,-- -4
.. 4 - . .. .w .H 4 4 M . . 4 _ .. 7144
. . _ . . _ — o . t.-
..... - . 4-1-” - 4......i: .24.. . -. .... .4 . : . :- ..-...
4.. .. .. .. _ . 4 .4 4 . o .3
h J.- b - L. It» 4 - -,.I.-.-. - -- -.v-IL: ".....r-i-Lru
._ (d. .4. _ 4. 4 4 u r; . In
. .. 4 . _ . t . _ n . .
--.:-...-.-H..-1,4-.1.t.- tut-st. tut-Ti... 3- . -..- -.. ctr-4-..-.. - Jig-4-...- ,..-..-~1+ ....... 4 - .- 4 ...... .4 ....... ., ... 1 _
u; ..... . . ... a . .. r 4 . 4 _ _ .4 a? T4
_. .. . . .w . . . ., 4 4 . .. u
1 .ar. 4 .. a _ .- . -1¢It!-L$¢I- LT: fig-8!...-
. 4. ~. .. . .. H.... a . w 4 . 1 I
. 1m . .41! . To .. - - .. .. w.- .h ..H:
filtrh 4litgx tldn -J.l. ....... Iv «IHM.OI;- .iWewiadn.M v .. . o 4 J 1..M .
I . . . ... . a . .
.- .
. r - . .m-

 

 

e
v

 

 

 

1r*‘
IL; _;
t

«4

 

 

 

 

 

 

 

 

 

_._.—....——._4p- 4.....-—
A—o
. 1 ...‘l y .
‘ '44.;1r4- 4 . -44....

 

 

 

 

 

 

 

f
1
21r—
1
T

 

 

 

 

 

-, H .. iii-41.1% 4.1.
4
.4

 

.-.. ....q»--- A”...
‘ _
' -

. , .

O
.
t
I

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

.-
‘
5'
I .
...
. I
'-
I.-
I
o—
.
.I
J.
.
_ I
' I
s o-
7.
‘. o
'.
-4
.'.
.,
.I
I
|
I
,
-~I
. ..
...4
v
I
o
' o
.
u
..
.0.
4
O
... .
I
I.
"— 4..
I
-
' c
. ‘ .
- - .
.
. u
“- ' I.
..
‘v
I
1 I
.
‘ .
‘V ~¢
-< 4
I“
I
3 V
I
.44
t.
Q

‘ ..
O. O >
.. p

- - . .I
5-

.. I .
-I—. -c.

h .

4,. .
4..- -
.
...“ I».
II'v-o - 0
-...

 

..u DD
‘5, .46
.4 -
4- -

o. o-.
- .-
I-II « --'
o-I

I

.-..

 

A
I—.7 ...-
...
..I .
. 0
-... .
d.- - I
9- I
I
. - I
..-
o. ..
- D I
Y
O
o
I -
v---
- a
-
..
~o¢
I ..
4 .4.
. -
u
-- .-..
--
...
.. ,
.-I
. ....
¢r"'~ .t
av~'-'-~
v~ §
v
-~»..
I. o .-..
. I oIIL
b
. ,-_
.¢ .4 -
.q . I
-v I..
"r
6-.

t
.-

 

 

 

It
' 0..
‘Nn.
. ' .‘
Y' ' - .
. .
' h-.
I., .
.._ :"
.. ~ "
I... :'
-N _. I
1..
--
I .
. "I
O...
- . _
‘v.
.

n-.
7.44
I
V
.Al
. a
.-.

-
o

I

.76.
.AI
un~
' r
--
..

Fa

-
<4.
4....
.-.

 

I
l“
- o
v.
o
u-

..
.I.
...
o,
a
on_.
an
'v...
I;

A
....
-..
n
..I
‘.V
L
-.
..1
Oc.
..-
..
...
I
-5

 

-.
r‘y
. .
- .
I
u
-.
V-’
..
I
- o
.
5.
L;
“-
.-.
I .
o.
I. I
.,_.
...
- I
- I
I
.-
. I
. I.
A
- 1
I-..
'-
”T
v
I
.3-
..-
§—¢
0‘!
I.

I .
.-.
..
0
-II
.-
I.
...
,.
I
~..
9- .
..
I.a
d
D
.
I O
—_.
-I
‘ I
-o .
I

...
.A.
3-.
.
O .
-.-
O.‘~
I
...,
.-r
.
, .
. 4
...
..
I
.4.
.
I.
.-
..-
.4...
Io-I
....
.
I ,.
—o
—.
.-.
...
t
..-
4
, .
I .

U...
IIA

u 4
I
-54
b
'r“
l ..
I

..44

a.
.
‘9
..
OOI
....
Io.
6-y-
I.
u-I
I
I
_.’

OH

III
.._
~v
l

I l
v
-v

u .

I .-

l

-I
,-

...

D

~I

- ,-
Y‘
....

-- I
?“'
-.
A

,.
54..
.. .
.4

.—
A

-..
A.3.
- o
I>$
...
I..

o

..
o.
I...
’ ..
....
I

 

 

»
I
v
..1- .-..
..-. .¢--
. . ...
, II.
. . ..,
I ’-
— 9. $
.- v .. 6
--..
.. 4.-..
-.I .~
I.. .
. .
-. .,
'4.- .-
... .04.
--
T .-...
.f.. . .
.1 I I
. I
. I
o . .
~ I I
»
,. .
_ .. 4..
, I. I
I... .
.I..
.. I
. ...
' Y
.-I.
o '9-4
O
.. . I
I.- I
,-- I.
,. I I
oI . . ,
I. -...
-» I
.A
_ --
-. ...
n . -.
..... L—,
. .. I.
.» ,....
— ..
I-I.. I
. . -.-I
- . ..-
— .. .I
. I..-
..YI . ..A
.
.u .4
.
5-4
4 I .u
. I
.u..
0‘.
It .
~o
'-
0' I
.... ..
I I . I
.
Q
-
.4
...
-
v-
Q
9
.
T
o...
. 4.,-
« o D
V“ ..
w- ...
..
vv I
I. v
-. .I
q.. .
... .
I'I I ’
l
I
.—.
f¢
I
I.
. ....
I, -.
... .
. I I».
.. J..-
I .. l
‘.
A
o
I. .
... . .
I...
. ...
.. .
. ...
.I .-.
. .4,
-.
... .I
'Q
I...
.. ..

4
..
...4
I-.
A4.
I
I
,.
o

v A
.3
...
.4,
‘4
I

. . .
I
- l
. . I
,
K
I -

0.
$.

I
...
..
.-
...
...-I
I
o

O
Q-
I-.
..
,

o
.

.
:

~I-
- I
...
.
I

.
.
In.
.94.

- ,
I
. ..
.-
.4.
.-.
....
..-
~ I
...

 

'.‘O

 

Vi
’?
¢

..-
.

.5—

I».

00
o.

' .
I¢~L
I v.

_‘
I
r“

...-
...
0'1

1'.

5"

Y'V“
I.

7'“

.3.

I
I
I

 

5‘
-..
.

.-. I

..I.

... ..-
no

.

I.

. .

......

H .

t~t vr‘

I

_. ‘

‘

I0-

.I

.

W
D O.
A

0
.

. .
.,

. .

I .

I
.

O
-I<-‘ J-u
.,.. -....
..., J
.

... .-

. ...

ot.‘ ..‘A

A. -.

.

..

-- - I
,_-.
.. ...
-

..., ..

.... .-.-.

4

.... .

III. ,

. . .

~.

I

- ...-,
A.-

". .

.¢.

..4

-.

.

.

v¢~

..

.‘o I

I
.
.

.Qt

I «I

.4.

-. .
,-

- -

o-vc

. ..-

, .
- I

I I.

,.,.

. I.

.. .-

1“

I
I-.. ..
II- ...

.. ..
. .. ....

-..

. ,-

-.I. ,.
. . .I

- o

'0
-, ..
. .

.A I I.

. .', .

....I .<.

.. .

. . ....
. ..

.. ....

. . ...

I ....

O

.4. .-..

09- - -O

.... I_-.

O-l' I
.

.“n o

..

‘v‘ -

5.

1
.-
’ ‘

. .- .

.. .. I

.. .

.- .

'7
..

. .

- 0‘

..4- -.
4.

.. .

' 9‘. .
I~Lo
I. ..

.-. .-

>‘l 6‘

00‘. v-‘0

. 4
_ t ..
..~-.
...-
1 1"
I1 ,.
-O' O
-
...
.
. .

-< p...
I

.I 4.
>04 ...

. a . u
, .

rt: .
fl :1...
1 ‘H

 

. . ....
...

~ 0
, .

- .
-.. .
..... --
..I. .
. I
...”

.... .

O... -

4. ..

. ..
-I'

. .
.

. .
y.

. .
D
' 'Q
0
-
..-
.
.
o| _
b

 

 

‘ u
. .4 .
- .
I.
o -
. .-
p. .
IJ
-.. .4
. .. ...
.-.
0
II I
.....-
u.
,..
IA
..,-
t -
.A'r' I
.....I.
.-.I. .
, .
A
. p. .
..4. ..
o-a .,
ub-.¢ &
.... .
4- I.
. -.,
-.~.
t 7‘
-.- I
O
.4.
.I.
. ..
v— “‘
"O
....
.l I
fi--.,
.
......
. . .
- I .
- ..4-
‘ v
. .. ,.
. ...

. -
...
¢
-

L, .
I
I
-o.
g-
b
"r.
vt‘v
5c(
C--
I
I4
2,-4
,..
to
O
4..
.
. .
...
p
..A

 

g .
...
..,

w
0"
r--
In
'C
c-
I
I
I.--5
"?

III
I-
I.

..
O

n

.4
-9
.4
. I

 

--—-o

-.
' v0
.....
..
.....
v
...
..
....
.7.
.4
O
.
‘.._.
, .
a» .-

. I
I .
.~.4

,,..

._ -

. .

I .
I v

..

. ' ,
...
‘t

l

. .
.-.

D-
.I

. ..,
..-., I
.I. I A'.
.... ..
.-..

...- 4
..I - .
. o I.
.
L. w”.
$~ o
.. -
.. .

d
- d o
.-
. .
Y‘ .4
....
-. ..
4
<0

.1 I,
. , .
.-. t O
.. .

... ..
L—o- -3
-. - I
.- .
. . .

O
.. .-

,— .

.... ..-
.-

A-.. .'
... ..
... .
-.

o... ..
A oc——-u
..

. I
9
O l‘
'0‘ - Q

I
.
. In
I
. .
IN-

-- .L

.. .

O «I

,4.

ll CI

.
I.
‘-
....
. t
I
I. ,
‘~.
4 .
....
,-

. I...
- 4 --.
'.I I—_-
. ...

....
I I6
4 . A

.- ...

I -.
7‘

fi ,—
-.1 .
—O- t-o

..4

....
..4 . .
I u-

. -. .
.. .

.. -

”..-

-..
I
- ,.
. ....
. .. .I.
.- --.
i. .
- O .
.. A. .
I I
I
......
.. . .
-. I
I -
4...
,.
é ..
...!
. 4
o

. ..
.1
..J
..

A .

.1
..l.
4-.
I ..
.-
r4~
->A
~7+
agh-
. I
- v

-I
I
I
.I.

I!
'o I
I- -
-oo
. I
I. .
uLoQ

-c

o
'7‘

...

...
v—a
,.

.I
I-‘-D
' ‘.

Y.

o
.-
4‘

7
.4.
...

to

..
.»‘
a
O
‘>.~
-
v
I
I
I
.O
I-.
.
.9
...

I
-o.
I .4
...

 

O .
u I
up.

I

I...
I. .

 

7
._
I
.I
.——lo
X
“'0-
'91
k.
I
. .

 

.
J.
..
-I
v
I
.
A.
-
.
>- O
0'.-
I
...
O I
,
I
--o
L.
a.
'0‘
I QJ
h.
4...,-
.<'n
ta
‘.

.1.-.
ob
..
--.
o‘lu‘
I
-I I
O
,.
.

-I-
>‘I
I o
‘J.I
II.

I

 

 

 

'
l
.
..{A
.4 .
- I .
.. .4
..-I-
II ..
pa
.
4*
.IA
. .4.
O‘-
\
O
I
I
.
,.
O.
H-I
I.
I C
v
I—
0
I -
. -
y- .
In...
.- ...
. ...
....
. >u.‘
| “
...
.-..
I.
~
4 ,I.
. ...
‘1
I--.
..
‘
VI
I
'9‘
III
. -y
7-94
-. ,
o
- D
g I
-.l
.. -
I4.—
. ..-.
I .
...,
- a ....
_ ...
.—L I
I --.
. .
.—. I l
..
. r ,.
I
——-
o I? .I
. . o...
- .J‘...
.
. 0 I.
.

 

 

I
I
O
I.
‘4
.r .
..
A».
t
L
.
...
...
...
'9
0"
t.
o
.
...
IL
I ..
v I
Yi“
...
-9
H
I
I
I
Y
I
-u
I
I...
-I
.
I.
..-.
.
..
...
..
-~.
.
I
.
4...
..
.
...l

 

0
o
.
...
H
o.
I
..
s
I-
.

 

 

.
Q
,
--.-
. ..
I>--
I
A.
.--
-I
.‘v'
I.
I
...
"h‘
I.
.
..
KI
0
.-.
...
o.
I
I
..,,.
V".
...
III
I
-..
.. .
-..
I
I
...
I
.
.
..I
o
.-
I
..
.
O—.
I-
.
5
-v
F?
I
.
I
..-.-

‘4 I
..-.
\ .
9-
,-
.——I
O
4..-
>0
...-
~
-.
Q
...

- ..
‘-
.
. I
0“
I
-..
‘0
44¢.
.-
.a
V
-- .
I

 

h
.
'“fl
.1
o
A 1
.4 4
.—
I
h.
I
I
6
u
I.
-.—-.
o
I.
no.
...,
..--
.I- o
no
I 4
..L
...I.
c
n
u-
-.,.
..'.
v“
99
--II
I. I
I
. .
I

.I

--

3"

.L
,.
I
.

-. 5
.-
-.

'4

C

5

--I

H
I
J O
I
—-
Io.
.-..
o
,.
0 .
t
I —.
.
I.
.I
...
I..
I4
...
4..,
-.I
0
I -
..-
....
.I-
I.I.
,.
h.
-. .

I...
I
I .
..II
I
....
v
.4.
.
...
..
'4
' .A-
oI
I.
-
O
I
o
o
.-
-I
u.
w
A
v
,
w- .

~-r-I
”4
‘.
I.
‘v
— I
II.
--
.-a
- I-
~‘
--.;
>-
"V
.0

...
-..-
. .-
v —I
_ I

7
§

 

 

...
'9
b

..v
0
t‘
I.
g .
.

--
I.-
l
...
l
.14
...
,.
‘0
l»‘&
.-.
-—4
Q.
o
.
d-
”it
1"’
...
I.
I -I
,.
o~IL
o
.9.
...
. .
-._.‘
....
.I
.. .
..-,
n
.
...
.
.-Iq
I
“-G
...
..I
>~ I
s
I
I-.

 

l
I .
r-vI
I I
I
- O.
4.

..
.
~I
- o
...
III.
nv-o—o

.».
o
O
I
4.
I
, .
. u-
t
a
I
‘1
'0'
o...
I.
I
o
b
—I
...
I .
—o—
v
4
..
‘Q
.I
..

v.-

..-
. .

.
.0.
-..:
F.
..

.

.
...
.-
L.
.-..
.
4.
.1.
..

.
O I.
t .I’-.
Y"

...
4.
..
41
‘6

Y
....
-oo

-..
.
..
0“
r‘f
0‘!
\"
.1.
I
.
OH.
V9"Q
O
I"
., I
I..
, --
....
...
-I.
.-
o
‘9
--A.
4H-

.4
.4

BIBLIOGRAPHY
Electrolytic Corrosion

Electrolysis of Cables. F. Fernie. The (London) Electrician. May 13,
1910.

Digest of Publications of The Bureau of Standards on Electrolysis of Under-
ground Structures Caused by Stray Electric Currents from Railways. S.SJWyer.

Electrolysis Testing. Bureau of Standards Technological Paper #355.
McCollum and Logan.

The Practical Solution of Stray Current Electrolysis. C. M. Longfield.
Institution of Electrical Engineers. Vol. 76 - 101 - 1935.

Stray Current Electrolysis, Some Fundamentals. C. M. Longfield. Electri-
cal Eng.nesring. Vol. 57 - 66 - 1938.

Electrolysis. George Cunningham. Journal American Water Works Association.
November 1938.

Chemical Corrosion

Cable Sheath Corrosion. John T. Murray. Electrical World. Vol. 92 -
1295 - 1928.

Determination of the Cause of Sheath Corrosion. W. C. Radley. Electri-
cal Engineering. Vol. 57 - 167, April 1938.

The Corrosion of Underground Cable. W. G. Radley and C. E. Richards.
Accepted but not yet published; Institution of Electrical Engineers.

Electra-Chemical Theory of Corrosion

Electra-Chemical Character of Corrosion. U. R. Evans. Journal of
Institute of Hetals. Vol. 30 - 239 - 1923.

Corrosion Symposium. Industrial and Engineering Chemistry. Vol. 17,
#4, PP- 335. April 1925.

Inhibitors Safe and Dangerous. U. R. Evans. Transactions Electro-
Chemical Society. Vol. 69 - 213 - 1936.

Determination of the Corrosion Behavior of Painted Iron and the Inhibitive
Action of Paints. Transactions Electra-Chemical Society. Vol. 69 - 169 -
1936. R. M. Burns and H. E. Haring.

Bibliography (Cont.)
General

Water Tight Joint for Fiber Conduit. H. G. Hall. Electrical World.
Vol. 109 - 576, February 12, 1938.

Tile Protects Cable in Shallow Trench. Electrical World. October 22,
1938. Page 1183.

APPENDIX

Construction of the Corrosion Testing Cell

The actual physical dimensions of the cell are unimportant, but the

following conditions must obtain.

1.

4..

The cell must be mechanically strong.

The shell must be chemically inert.

The lead slug which acts as the electrode must be well insulated
from ground.

It is highly desirable to provide a means of cleaning the cell in
the field. The cell under description is cleaned by screwing the
and plug into the shell, thereby compressing the Agar Agar and

forcing it out through the small radial holes.

HERCOLITE was chosen as best fulfilling the first two requirements. A

long.leakage path was provided for the lead slug by cutting deep threads in

the shell and casting the slug in place. The end was then sealed with

De Kohtinsky's cement.

The steps in filling the cell are as follows:

1.

2.

4.

Clean surface of lead slug.

Cover it with a paste consisting of KCl. PbClz. a small amount of
distilled water, and a few drops of glycerin.

Dissolve 2 grams PbClz in 100 c.c. of distilled water, then add

38 grams KCl and dissolve; heat the solution to the boiling point
and add 5 grams of Agar Agar; finally add 40 c.c. of glycerine.
When the mixture starts to cool its viscosity increases and at about
70°C. may be poured into the shell without danger of the solution

running out of the radial holes.

The solution dries out readily and so the cell should be kept immersed

in distilled water when not in use. Erratic readings will be obtained un-

less the potential of the cell is regularly checked.

Photograph No. 1

 

Photograph No. 2‘

 

 

 

 

llllllrlnllll I Ilil\

 

Lg‘k.‘

..g k- L-

—#

 

 

., -3

Photograph No. 3

‘0,

 

Finished Installation

 

,‘ , .,
...- --._- J“ T‘_.-_

. a---,‘-W'- c--.v-'.—6!«T""‘ —"’

 

Applying Coating f

 

 

 

Photographs Courtesy
Clark L. Bassett

Corrosion Cell

 

«I 1...! 11‘ I‘ll-v .ljJII j
‘II‘II' [I]

 

Y5
..N.
O
E
S
u
M
O
O
R

 

 

 

.‘Y. 8.9.. a . lulv - .
v .\\.’hP- Jr AJ.I l

\: .H 1.,a» ‘0‘

ifoi-ni $3....__...__:1.

 

; n '
wrl

MICHIGAN STATE UNIVERSITY LIBRARIES

II lfllllllflflil

3070 9 09

i |

3 1293