IMPROVEMENTS IN THE MODE OF AND MEANS FOR THE PROTECTION AGAINST CORROSION OF THE INTERNAL SURFACES OF STEAM BOILERS, AND OTHER IRON AND STEEL VESSELS CONTAINING WATER."
Year: 1877

page_text: LETTERS PATENT to David Phillips, of Brompton, in the County of Middlesex,
for the Invention of "IMPROVEMENTS IN THE MODE OF AND MEANS FOR THE
PROTECTION AGAINST CORROSION OF THE INTERNAL SURFACES OF STEAM
BOILERS, AND OTHER IRON AND STEEL VESSELS CONTAINING WATER."
PROVISIONAL SPECIFICATION left by the said David Phillips at the Office
of the Commissioners of Patents on the 7th April 1877.
DAVID PHILLIPS, of Brompton, in the County of Middlesex.
"IMPROVEMENTS
IN THE MODE OF AND MEANS FOR THE PROTECTION AGAINST CORROSION OF THE
INTERNAL SURFACES OF STEAM BOILERS, AND OTHER IRON AND STEEL VESSELS
CONTAINING WATER."
Heretofore zinc and zinc alloys have been at various times proposed to be applied
for the purpose of preventing or counteracting the corrosion of the internal parts of
steam boilers and other vessels, and especially since the more general introduction
of surface condensers the question has assumed more importance, because it is
supposed that under certain conditions of working, the steam boilers, where surface
condensers are used, corrode more rapidly on their internal surfaces than was
formerly the case, which is attributed among other causes to the presence of the fatty
matters which are carried from the cylinders through the condenser into the boiler,
and to galvanic action being set up between the boiler and the copper or brass
tubes in the condenser, and the brass fittings and copper pipes, and to the absence
of any efficient or even scale protection which in other cases is formed by the lime
in the water. Thus, pieces of zinc or alloy have been proposed to be used, and are
used, but in an undefined vague manner as to quantity, surface, or distance apart,
being simply placed in some cases on the bottom of the boiler or suspended loosely
from the stays in one or more places in the boiler, or placed in the path of the feed
water, either in or out of the boiler, in order, as it was supposed, to act upon the water
before it got into contact with the surfaces of the boiler, or in order to intercept or
"throw down" any particles of copper which might be carried into the boiler by
the feed water from the wear and tear of the copper pipes, or which might be

page_text: carried in in solution produced by the oxydation of the copper and brass surfaces,
or in order to prevent galvanic action being set up between the condenser tubes and
other parts and the boiler. Nevertheless, the object sought has neither been efficiently
nor partly attained, except accidentally in most cases, so that the zinc, as hitherto
applied, has had no even or anything approaching a thorough action on the surround-
ing parts, but only at most a local uncertain action, confined to the spot where it was
placed or suspended, or if a more extended action, then a very weak action through the
water itself. Now the object of my Invention is to apply zinc or zinc alloys so as
to cause an even, certain, and efficient influence or action of the same through
the steel or iron plates on the surrounding surfaces, and I attain this object by 1
establishing perfect metallic continuity between the zinc or zinc alloy and the iron
or steel plates to which it is applied or secured, to the exclusion of water between
then, and also by so distributing the zinc or alloy equally at distances in inverse
proportion to the amount of saline matters in the water, as to spread its influence
or action evenly over the whole surface of the boiler (under water), thus rendering
the metal of which it is made negative to the zinc. Mere contact of the zinc or
alloy and the plate, though intimate, is not sufficient, but I have found that when
the zinc is applied to a clean surface (that is, a surface free of scale, oxydation, or
other impurities), and when a perfect metallic contact is insured by pressure, so
that the water and its impurities be kept out from between the surface of the iron
and the zinc or zinc alloy (which entry of water would cause oxydation of the zinc,
and thus gradually destroy the metallic continuity), that then a perfect and con-
tinuous protection (while the zinc remains) is afforded to the internal surfaces of
steam boilers and other vessels now liable to corrosion. However, as the protection
of the boiler is only insured at the expense of the zinc, it will be necessary to watch
the latter, and renew it at intervals. The wasting or oxydation of the zinc or zinc
alloy will very much depend on the condition of the water used in the boiler, on the
proportion of zinc surface to that of the iron or steel exposed, and on the purity of
the zinc or alloy.
The mode I prefer to employ for carrying out this Invention, as applied to the
plate surfaces of the boiler or other vessels, is the following -I drill and tap holes
through the plates of the boiler or other vessel at as regular or equally distanced
intervals as possible, and below the water level (by preference below the lowest
ordinary water level), and I screw studs tightly into these holes from the inside,
and by preferenee further secure them by nuts on the outside, the plate and
the screwed stud thus being in perfect inetallic contact. The stud is formed with a
square or hexagon shoulder, by which it is screwed into the plate, forming under
any pressure a perfectly water-tight joint. On the inner part of each of these studs
is fixed a plate, disc, or strip of zinc or zinc alloy, and it is also of special importance
that the contact surface between the stud and the zinc plate should be clean and
perfect, so as to exclude the water from between the zinc and the part of the stud
on or against which it fits.
The holes in the zinc plates are by preference drilled, and the plates thicker at
their central parts, where the corroding or wasting action is greatest, than at their
outer edges, and 1 prefer to use many sinall studs and zinc plates rather than fewer
and larger ones in order to ensure even action, and for convenience of application,
especially in narrow spaces.
For ensuring protection to some stayed surfaces, and where such stays can be
conveniently placed in the boiler, I make use of specially constructed stays, to
which zinc protectors are attached, and perfect metallic continuity insured. The
long stays, as ordinarily fitted, are not suitable for the purpose, because the ends are
usually passed through clearing holes in the plates, and are secured by a nut on
each side of the plate, with a "grummet" and putty or other suitable material round
the stay and under the nut for making a tight joint, by reason of which and also by
reason of the oxide or scale which is generally attached to the surface of the plates
and the stay when the zinc is attached, continuity between the metals is almost
out of question, or at best very uncertain; I therefore face or lay bare the surface

page_text: of the plates in immediate contact with the inner nut, or both, or tap the holes in
the plates and screw the tightly fitting screwed ends of the stays through the clean
tapped holes, which are then nutted and tightly screwed on the outside only, or
both, and I fit or clamp on zinc protectors to ono or more parts of the stays.
For the convenience of adjusting the latter stays I have adopted the following
modes:-
1st. The stay is made in two pieces which are connected to each other by a
coupling nut, having a screw coarser in pitch than at the ends, which are screwed
through the boiler plates.
The next mode is to make the stay in one piece, one side or plate being made
sufficiently large in the hole to allow one end of the stay to pass through, which
end is screwed with a slightly coarser thread than the other end.
The modes of attaching the zinc to the stays are numerous, but amongst the
simplest and best are the following:-.
According to one mode I clamp a piece of zinc to the stay, and as near to each
plate as convenient by a strap of iron placed round it, and held tightly against the
stay by a tapered cotter put through the ouds of it, either above the stay or below
the zinc plate. The stay must be perfectly clean and free from scale at these places,
and the pieces of zinc must also be clean, and fit fairly and well against thein, and
be held up tightly against the stay, as aforesaid.
Another efficient mode of attachment is that of passing a narrow staple, clamp, or
strap of iron round a plate of zinc which, as well as all other such plates, aro
preferably thicker where they fit against the stay than at its other edge, and which
also in the opposite direction is thicker in the middle part, where the staple fits
round it, than at each side thereof. The ends of this clamp are screwed and passed
through a cross piece over the stay, and the zinc is held by nuts screwed tightly up
on the ends of the clamp, which serves as a convenient means for holding the zinc
protector tightly against the stay.
For the protection of the tubes and tube plates however I prefer to fit those parts
of the tube plates most convenient for the distribution of the zinc with solid stays
(not stay tubes), which I make.portable and easy to attach and detach, and on which
the zinc protectors are secured. For this purpose the holes in the tube plates are made
as large at least as the tubes; these holes are screwed and fitted with tightly fitting
screwed plugs, through which the ends of the stays are screwed or passed, and by
which their lengths are nicely adjusted, say, in one of the following modes:-
According to one mode the plugs and tube plates at both ends are screwed to fit
each other with right-handed threads of any convenient number to the inch, and
the stays with right-handed threads at one end, and left-handed thread at the other
end for adjustment only, and I screw the stay through the plugs with a jam nut on
the outside at each end, but for convenience and simplicity the pitch of thread at
the front end should be the same on both plug and stay.
•
Or, according to another mode, the plugs and zinc protectors are fitted as just
named, the plugs screwed with any convenient pitch of thread, and right-handed,
and the stay ends screwed with threads of different pitch for adjustment only. The
zinc protectors are fitted on the ends of the stays well clear of the plugs, and are
screwed hard against collars by a nut at each end, by which means perfect metallic
continuity between the zinc tube plates and tubes is insured.
Again, in finished boilers, new or old, where it would be deemed inadvisable
to disturb the stays or stay tubes for the aforesaid purpose, I adopt another
mode of attachment, which is this:-I take out, say, two or more tubes, and the
screwed plugs are fitted in these tube holes, as before, but the plugs are in this
instance forined with a small projecting end or stud on the interior side of them, on
which the zinc ferrules or protectors are fitted and held tightly against the ends of
the plugs by nuts, and by which means perfect metallic continuity is insured
between the zinc and tube plates; these, as well as the stays, are made portable, for
the purpose of renewing the zinc protectors whenever it should become necessary to
do so on account of oxydation or disintegration of the metal..

page_text: In order to make the zinc ferrules or protectors which are attached to the stays,
and also the plugs as thick and as durable as possible, I make the stays as small in
diameter as practicable, and because of the protection which is given to them
against corrosion a smaller factor of safety may be safely adopted in calculating
their strength.
The length of the zinc ferrules or protectors is determined by the amount of tube
surface which is necessary for each of them to protect.
To insure perfect protection to the tubes it is most important that all the ends or
parts which fit in the tube plates are made clean, and free from scale or oxide; this
I do by filing the scale off after annealing.
I believe that four or five stays fitted as described will be all that are necessary
to protect all the tubes in a nest, but if not the rest, that is, the outer top, bottom,
and side rows, will or may be protected by the aforesaid short studs placed on or
secured to the plate surfaces in convenient contiguity thereto.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said David Phillips in the Great Seal Patent Office on the 6th October
1877.
DAVID PHILLIPS, of Brompton, in the County of Middlesex. "IMPROVEMENTS IN
THE MODE OF AND MEANS FOR THE PROTECTION AGAINST CORROSION OF THE
INTERNAL SURFACES OF STEAM BOILERS, AND OTHER IRON AND STEEL VESSELS
CONTAINING WATER."
Heretofore zinc and zinc alloys have been at various times proposed to be applied
for the purpose of preventing or counteracting the corrosion of the internal parts of
steam boilers and other vessels, and especially since the more general introduction
of surface condensers the question has assumed more importance, because it is
supposed that under certain conditions of working, the steam boilers, where surface
condensers are used, corrode more rapidly on their internal surfaces than was
formerly the case, which is attributed among other causes to the presence of fatty
matters which are carried from the interior wearing surfaces of the engines through
the condensers into the boilers, and to galvanic action being set up between the
boilers and the copper or brass tubes in the condensers, or between the brass fittings
or copper pipes between the engines and boilers, and to the absence of an efficient
or even scale on the interior surfaces of the boilers, a protection which in other
cases is formed by the presence of lime in the water. Thus pieces of zinc or alloy
have been proposed to be used and are used, but in an undefined and vague manner,
as to quantity, surface, or distance apart, it being simply placed in some cases on the
bottom of the boiler, or suspended loosely from the stays in one or more places in
the boiler, or placed in the path of the feed water, either in or out of the boiler, in
order, as it was supposed, to act upon the water before it got into contact with the
surfaces of the boiler, or in order to intercept or "throw down" any particles of
copper which might be carried into the boiler by the feed water from the wear and
tear of the copper pipes, or which might be carried in, in solution produced by the
oxidation of the copper and brass surfaces; or in order, as before stated, to prevent
galvanic action being set up between the condenser tubes and other parts and the
boiler. Nevertheless, the object sought has neither been efficiently nor partly
attained except accidentally in most cases, so that the zinc as hitherto applied has
had no even or anything approaching a thorough action on the surrounding parts,
but only at most a local and uncertain action confined to the spot or surface in
proximity with it or to the part to which it was suspended, or if a more extended
action, then a very weak action through the water itself. Now the object of these
my improvements to apply zinc or zinc alloys so as to cause an even, certain, and
efficient influence or action of the same on the surrounding surfaces through the

page_text: steel or iron plates; and I attain this object by establishing perfect metallic con-
tinuity between the zinc or zinc alloy and the iron or steel plates to which it is
applied or secured, to the exclusion of water between them; and also by so distri-
buting the zinc or alloy equally at distances in inverse proportion to the amount of
saline matters in the water as to spread its influence or action evenly over the whole
surface of the boiler (under water), thus rendering the metal of which it is made
negative to the zinc. Mere contact of the zinc or alloy with the plate is always
insufficient and uncertain; but I have found that when the zinc is applied to a clean
surface (that is, a surface free of scale, oxidation, or other impurities), and when
perfect metallic contact or continuity between the two metals is insured by pressure
so that the water be kept out from between the surfaces of the iron and the zinc or
zinc alloy (which entry of water would cause oxidation of the zinc, and thus
gradually destroy the continuity), that then a perfect and continuous protection
(while the zinc remains) is afforded to the internal surfaces of steam boilers and
other vessels now liable to corrosion. However, as the protection of the boiler is
only insured at the expense of the zinc, it will be necessary to watch the latter and
renew it at intervals. The wasting or oxidation of the zinc or zinc alloy will very
much depend on the condition of the water used in the boiler on the proportion of
zinc surface to that of the iron or steel exposed, and on the purity of the zinc or
alloy.
The mode I prefer to employ for carrying out these my improvements as applied
to the plate surfaces of the boiler or other vessels is the following, and will be fully
understood by reference to the accompanying two Sheets of Drawings:-I drill and
tap holes through the plates of the boiler or other vessel at as regular or equally
distanced intervals as possible, and below the water level (by preference below the
lowest ordinary water level), and I screw studs tightly into these holes from the
inside, and by preference further secure them by nuts on the outside, the plate and
the screwed stud thus being in perfect metallic contact.
Figure 1 shews such a stud as applied to a part of a boiler plate. Figure 1ª is a
plan of the stud with its zinc plate; the stud A is formed with a square or hexa-
gon shoulder A', by which it is screwed into the plate B, forming under any
pressure a perfectly water-tight joint on the inner part of the stud; between the
shoulder and the nut a plate disc or strip a of zinc or zinc alloy is firmly secured;
and it is also of especial importance that the contact surfaces of the stud and the
zinc plate should be clean and perfect, so as to exclude the water as before stated
from between the zinc and the part of the stud; on or against which it fits.
The holes in the zinc plates a are by preference drilled, and the said plates a
thicker at their central parts where the corroding or wasting action is greatest than
at their outer edges, as here shown; and I prefer to use many small studs and zinc
plates rather than fewer and larger ones, in order to ensure even action and for
convenience of application, especially in narrow spaces.
Plates or strips of zinc or zinc alloy might be secured directly to the iron or steel
plate, say, by bolts or studs; but by such an arrangement and mode of attachment
the surface of one side of the zinc plate would not be so fully available for the
desired action; as it will be observed that when the zinc plates are secured to studs
or brackets or other suitable means of attachment, as illustrated in the Drawings,
the largest possible exposed surface of zinc is obtained, practically speaking, with
the smallest amount of zinc made use of; it must be borne in mind that the pro-
tection afforded depends upon the amount of zinc surface, and not upon the
quantity or bulk of the same.
For ensuring protection to some stayed surfaces, and where such stays can be
conveniently placed in the boiler, I make use of specially constructed stays, to
which zinc protectors are attached and perfect metallic continuity insured. The
long stays as ordinarily fitted are not suitable for the purpose, because the ends are
usually passed through clearing holes in the plates, and are secured by a nut on
each side of the plate with a "grummet" and putty or other suitable material
round the stay and under the nut for making a tight joint, by reason of which and

page_text: also by reason of the oxide or scale which is generally attached to the surface of
the plates or the stay when the zinc is attached, continuity between the metals is,
to say the least, most imperfect, or at best, very uncertain. I therefore face or lay
bare the surface of the plates in immediate contact with the inner nut or both, or
tap the holes in the plates, and screw the well-fitting screwed ends of the stays
tightly through the clean-tapped holes, which are then nutted and tightly screwed
on the outside only, or both.
The first of these two modes is illustrated by Figure 2, where the stay A passes
through clearing holes in the plates B and C, and is secured thereto by nut on cach
side, and washer under the outside nut.
The second of these modes is illustrated by Figures 3 and 4, where the stays aro
screwed through the tapped holes in the plates B and C, and the zinc protectors are
fitted or clamped on to one or more parts of the stays.
For the convenience of adjusting the length of the latter stays I have adopted the
following modes :-
According to one, which is illustrated by Figure 3, the stay A is made in two
pieces, which are connected to each other by a coupling nut D, having a screw with
coarser pitched thread than the ends, which are screwed through the plates B
and C.
The next mode is illustrated in Figure 4, and consists in making the stay A in
one piece, one side or plate B being made sufficiently large in the hole to allow one
end of the stay to pass through, which end is screwed with a slightly finer thread
than the other end, where it is screwed through the plate C.
The modes of attaching the zinc to the stays are numerous, but amongst the
simplest and best are the following :-
--
According to one mode I clamp one or more pieces of zinc to the stay, and as near
to the plate or plates as convenient, by a strap of iron placed round it and held
tightly against the stay by a tapered cotter put through the ends of it, either above
the stay or below the zinc plate.
In Figure 5 is shown a section, and in Figure 5ª a side elevation of a stay A, to
which is clamped a piece of zinc or zinc alloy a by means of a strap E and cotter F.
G is a bolt for holding the strap and zinc together.
Figure 6 is a section, and Figure 6 a side elevation of a similar mode of attach-
ment, the open end of the strap E with its cotter F being below the zinc plate a.
The cotter in both cases socures continuity between the stay A and the zinc plate a.
As before stated, the stay must be perfectly clean and free from scale at these places,
and the pieces of zinc a must also be clean and fit fairly and well against them, and
be held up tightly against the stay, as aforesaid.
Another efficient mode of attachment is illustrated in Figures 6, 7, 7ª, 7b, and 7º,
which are respectively cross sections and side elevations; it consists in passing a
narrow staple clamp or strap of iron E round a plate of zinc a, which, as well as all
other such plates, are preferably thicker where they fit against the stay than at its other
edge, and which also, in the opposite direction, is thicker in the middle part, where
the staple fits round it, than at each side thereof; the ends of this clamp are screwed
and passed through a cross piece F over the stay, and the zine is held by the nuts f
screwed tightly up on the ends of the clamp, which serves as a convenient means
for holding the zinc protector tightly against the stay.
Figure 8 is a cross section, and Figure Sa a side view of a modified arrangement.
The strap E passes round tho stay A, the zinc plates a being secured to the strap E
by means of bolts G, G. F is a cotter for firmly attaching the strap E and zinc
plate or piece a to the stay. The strap E must of course fit well on the stay and
against the zinc plate a in order that the desired continuity may be established.
Figure 9 is a sectional end view, and Figure 0 a side view of a stay A, to which
the zinc plate a is firmly attached by means of a strap E and bolt F, the zinc
plate a being firmly held between the open ends of the strap by means of bolts C, G,
as before.
Figure 10 is an end view, and Figure 10° a side view of a stay A, to which a

page_text: zinc plate a is attached by means of an open clamp, the bolts F, G, and G holding
the two halves of the clamp E to the stay and to the zinc plate a.
Figures 11 and 11ª are respectively end view and side view of a zinc plate a,
which by means of straps or staples E, E, and cotters or bolts F, is firmly attached
to two stays A, A, thus affording protection to both and to the parts of the plates
in proximity to them, to which such plates are secured, the required metallic con-
tinuity being of course insured in all cases.
For the protection of the tubes and tube plates I prefer to fit those parts of the
tube plates most convenient for the distribution of the zinc with solid stays (not
stay tubes), which I make portable and easy to attach and detach, and on which
the zinc protectors are secured. For this purpose the holes in the tube plates are
made as large at least as the tubes; these holes are screwed and fitted with tightly
fitted screwed plugs, through which the ends of the stays are screwed or passed,
and by which their lengths are nicely adjusted, say, in one of the following
modes :-
According to one mode, as shown at Fig. 12, the plugs D, D, and tube plates B
and C at both ends of the stay A are screwed to fit each other with right-handed
threads of any convenient nuinber to the inch, and the stay A with right-handed
thread at one end and left-handed thread at the other end for adjustment only, and
I screw the stay through the plugs with a jam nut E on the outside at each end, but
for convenience and simplicity the pitch of thread at the front end should be the
same on both plug and stay.
Or according to another mode, as illustrated by Figure 13, the plugs and zinc
protectors are fitted as just nained, the plug or plugs D screwed with any convenient
pitch of thread and right handed, and the stay ends screwed with threads of diffe-
rent pitch relatively for adjustment only, viz., the thread at the B end being finor
than at the C end. The zinc protectors a, a, Figures 12 and 13, are fitted on the
ends of the stays well clear of the plugs, and are screwed hard against collars by a
nut b at each end, by which means perfect metallic continuity between the zinc and
the tube plates and tubes is insured.
Again, in finished boilers, new or old, having either solid stays or stay tubes, the
same arrangement can be applied by the removal of the required number of stays or
stay tubes, and substituting stays fitted with zinc protectors as described. Where
it would be deemed inadvisable to disturb the stays or stay tubes for the aforesaid
purpose, in some cases I adopt another mode of attachment, which is :-I take out,
say, two or more tubes, and the screwed plugs are fitted in these tube holes, as
before, but the plugs are in this instance made as shown in Figure 14, that is, formed
with a small projecting end or stud A on the interior side, on which the zinc ferrule
or protector a is fitted and held tightly against the end of the plug by a nut, and
by which means perfect metallic continuity is insured between the zinc and tube
plates. These plugs, as well as the stays, can be easily removed for the purpose of
renewing the zinc protectors whenever it should become necessary to do so on
account of oxidation or disintegration of the metal.
In order to make the zinc ferrules or protectors which are attached to the stays,
and also the plugs, as thick and as durable as possible, I make the stay ends as small
in diameter as practicable; and because of the protection which is given to them
against corrosion, a smaller factor of safety may be safely adopted in calculating their
strength.
The length of the zinc ferrules or protectors is determined by the amount of tube
surface which is necessary for each of them to protect.
To ensure perfect protection to the tubes it is most important that all their ends
or parts which fit in the tube plates are made as clean and free from scale or oxide
as possible; this I do by filing the scale off after annealing.
I believe that, say, four stays fitted as described will be all that are necessary to
5 protect all the tubes in a nest, but if not, the rest, that is, the outer, top, bottom,
and side rows, will or may be protected by the aforesaid short studs, Figures 1
and 1ª, placed on or secured to the plate surfaces in convenient contiguity thereto.

page_text: Figure 15 is a vertical cross section, and Figure 16 a vertical longitudinal section
of a marine steam boiler provided with the aforesaid zinc protectors, so arranged
that all necessary parts of the boiler are protected thereby. The stay ends and nuts
projecting on the back tubo plate may be protected against the intense flame or
heat by means of caps made of fire-brick. In this case the zinc surface is to the
interior iron surface of the boiler as about one to forty-five.
And having thus described and ascertained the nature of this Invention, I declare
that I claim,-
Firstly. The mode of protecting surfaces exposed to corrosion by zinc or zinc alloy
protectors, fitted and applied substantially as herein-before set forth, for affording
continuity and efficiency of contact.
Secondly. The various means or appliances, substantially as herein-before
described and shewn, when applied for the protection of surfaces exposed to
corrosion.
In witness whereof, I, the said David Phillips, have hereunto set my hand
and seal, this Fifth day of October, in the year of our Lord One thousand
eight hundred and seventy-seven.
DAVID PHILLIPS. (L.s.)