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Патент USA US2503218

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April 4, 1950
A. F. PRUST
2,503,21 7
PROCESS FOR TREATING BRIGHTENED ELECTROTINPLATE
Filed Dec. 15, 1944
INVENTOR.
A L V/N ‘FEEDER/CK P/PUST
BY
MM
Patented Apr. 4, 1950
2,503,217
UNITED STATES
$503,217}v
PROCESS FOR‘TREATINGBRIGHTENED‘
ELECTROTINPLATE/
Alvin 1 Frederick Pru‘stk Warren, . Ohio; assignor, to
Republic. Steel Oorporation,-,. Cleveland,‘ Ohio,’
a. corporation of NewnvJte'rscyv
Application'Decemberfl5, 194.43.,SerialiNo;~ 5683415.
5 ‘ Claims. . (01. 2049-141)
1
2,
This‘ invention relates generally; to the tin,-v
platevartand‘particularlyto a new and-improved?
method-of and apparatus for treating, the sur
current.75%--byweight~of,potassiumichromate;
about
of between about 10 and about 15, amper-esi
persq; fit. and at avoltage of; about-7.5 volts-was
faces of ‘ electro-tinplate.
Electro-tinplate, ‘that is; steel having’ surface;
coatingsofelectro-deposited tin; asmade here
passed thru; the electrolyte andv piece- of tinplate';
for» about; one: second. The strip was, then;
washed; largely dried; in a steam~ atmosphere,"
tofore; does-‘not adhere strongly or uniformly tov
?nally and rapidly dried, and- immediately;
enamel, or lacquer.
coated! with ‘ oil. ~ The- electrotinplate so heated
When‘such surfaces have,
been brightened; .asby beingfused after electro->
did not? exhibit: any: tendency: to develop ayellowv
deposition‘ of.. the tin. they often become- dis 10v coloration‘ when heated?‘ at‘v about 420°- F; for‘
colored with a yellow discoloration, and there is‘
about twenty; minutes and enameli and lacquer‘
a-tendency for lacquer‘or enamelwhieh has been
baked on‘ the»: thus treated tinplatev adhered‘
baked thereon‘, to loosen fromthe tin or actually.
toi?ake o?. I-lbelieve‘ that when electro-tinplate
is brightened‘thesurface-layers of» the tin are;
activated and oxidized; and that when-‘such. 3.";
surface is~enameled; or lacquered; at’ tempera‘
tures-whichvmay‘ rangenupeto about 420° F., the
oxide on or: the oxidationof the tin surface layer
forms a weak connectionbetween the enamel, or‘.
lacquer andthe tin-whichis. not strong'enoughi
to‘prevent the coating-material» from loosening or“
?aking off;
The present, invention aims to“ avoid those;
causes of‘. poor- adherence and provides-a- method
of and-apparatus for treatment of: brightened;
electro-tinplate so that enamel. or lacquer will
adhere tenaciously-due,. I-believe-,; to thepassive or:
non-oxidized condition of’ the. surface layers; of‘
the tin.
Brie?y. stated, the present invention- comprises,
astreatment of brightened e-lectro-tinplate» which;
converts “the surfacelayer of the: tin intea -de-
oxidized and passive state, that is, deoxidizes it:
tenaciously and; uniformly: to the: tinplate and;
exhibitedanovtendency to: ?ake o?; ,
ltvwillibevunderstood that the speci?c, condi-.
tions set; out: in»the~foregoing= example may- be
m'cdiiied considerably and. within:the-‘following?
limits:
The? temperature‘ of- the-~>electroly-t,eI may: range
betweeneabout 150° F: and; about 200° F. Tem
peratures lower than about 150° F. may be used;
butiare non-desirable. In general, temperatures
much. below aboutF18Q9-F. are not’desired because:
the"- cur‘rent requirements increase‘ in inverse?
proportions- to. the decrease in temperature.
The‘? length» of' time1 the, current‘ is ?owing-i
thru any part of the article may range‘: from‘?
about one-half? second" to‘ about‘ ten seconds.
This‘ range ofJtimeis apparently determinedby/
the time " required 1 for? the-‘electrolyte to change“
sufficiently to attack'the tin'; It appears that
the nature-'ofthe diffusion’ layer or, cathode ?lm
is'la‘v-function of‘the applied current density and:
With a, constant current‘
density;- the pH" value or alkalinity of the dif;
fusion layer rises in proportion to the time of“
and makes it resistant to oxidation, and protects . . time“ of? treatment.
it against-- oxidation as evidenced by discolora
tion, even when heated to a lacquering.temperature of about 420° F; This method of treatment
treatment until its alkalinity becomes high‘
atmosphere while washing'andlarg'ely dryingcin;
bytheielectrolyte;
been» satisfactorily practiced is as: follows:- A
Since the-voltage is a'flunctioneof the required;
current density and'the-concentrationand tem-a
peratureioiéthe electrolyte. ‘the; ranges; oil-voltages;
are-fairly wellldeiined by those; factors: Howe.
enough to, attack the tin. With. current densities
comprises the steps of making a brightened
electro-tinplate article the‘ cathode in-a. heated: 40 within‘ therange later speci?ed herein, a treat'-.
menttimiei'off as mllQhjasI about, ten seconds is;
electrolyte containing hexavalent chromium and
not" sufficiently 1_"(_),1’1'gf12f()v causeany bad effects on,
passing a low density current thru the electrolyte,‘
the; tin'platefresultingjfrom an‘ attack of the tin
surrounding, the article with a non-oxidizing‘
?ash heating. it toacomplete drying; and! 1711511. 45 Current 'deiris'ities,v may be‘ used which» range
from about; etc‘ about 25‘ amperes per sq; ft! with}
coating it‘ with a protective‘ coating;
An illustrative, but not-limiting-rsetof(2011;:
the-bestlresults being obtained, within the'raneei
of ‘from abcut 1.0; to 18,"amperes;'p€r sq. ft.‘
'
ditionsaunder which" the. present invention» has‘
piece of electro-tin-plate; with brightened» sur~ '
faces, the brightening having; beingaccompl-ished
by fusing the‘depositedtinnwasmadethe cathode
in-lan electrolytic bath; the anodesr-b'eingicomi
ever,
posedof-llo-w carbonsteelL I Theelectrclyte com»
ransea-ofricurrent density‘and-ccncentrationand
general-i it may be: Said: that - for: the.
sisted-of water-containingbetweenabout .5Y%,~andi 55. temperature of! the» solutions-asset out-herein
2,508,217
3
the ordinarily available voltages of from about
.5 volt to about 18 volts are satisfactory.
In lieu of the potassium chromate mentioned
in the foregoing illustration any other water
soluble hexavalent compound of chromium may
be used including sodium chromate, a dichromate
of either sodium or potassium, or chromic acid.
The concentration of the chromium ions in the
electrolyte may range between those present in
from about .5% to about 5% by weight of po
tassium chromate. However, it will be under
stood that these limits are not necessarily con
between ?ash heater tubes 16 which extend along
the strip for a distance of a little less than two
feet. Then the trip passes into a spray chamber
H’ where an oil emulsion is sprayed onto the
surfaces of the strip thru perforations in tubes
[8. Excess oil emulsion collects in tank 19 below
this spray chamber l1 and may be repumped
thru pipes [8. When the strip l leaves chamber
I‘! it passes under roll 20 which dips into water
10 in rinse tank 2| therebeneath and then passes
upwardly between inclined heating tubes 22.
It will be understood that the flow brightened,
oxidized, tinplate surfaces are deoxidized in pass
ing between anodes 5 in the electrolyte in cell 8;
ing on the voltage employed, the manner of '
rinsing the treated tinplate and the speed of 15 that the strip is then protected against contact
with the air while passing from the electrolyte
travel of the tinplate thru the electrolyte. The
‘into and out of the liquid in cell II; that the
limits just stated have been found to be satis
electrolyte is washed from the strip by the liquid
factory with tinplate traveling thru the elec
in cell Ii and most of the moisture is removed
trolyte at the rate of about 100 to about 800 ft.
per minute, with ordinary rinsing practice and 20 from the strip by the jets of steam from steam
pipes l5; that the remaining moisture on the
with the voltages maintained within the fore
trolling because they will obviously vary depend
going limits.
strip is driven off by ?ash heating, that is, by
being heated for not more than about one second
The present process has been carried out suc
by the heater pipes [6; that immediately there
cessfully on a commercial scale under_the fol
lowing set of conditions: Electro-tinplate in end 25 after the surfaces of the strip are coated with a
water-oil emulsion and the emulsion is spread
less strip form was passed at a speed of 250 ft.
more or less uniformly over the surfaces by the
per minute, thru an electrolyte containing about
water in the rinse tank, after which heaters 22
.'75% of potassium chromate by weight while a
evaporate water from the emulsion and dry the
current of about 4.5 volts and an amperage of
about 10 to 18 amperes per sq. ft. was flowing 30 oil of the emulsion which remains as an ad
herent coating on the strip.
thru the electrolyte and tinplate. The tempera
As has been stated above, I believe that the
ture of the electrolyte was about 180° F. The
foregoing treatment not only reduces any oxides
strip moved from the electrolyte thru a steam
which may be on the surface of the brightened
atmosphere into and out of a body of wash water
and between steam jets which removed practi
electro-tinplate but also makes the surface lay
cally all the wash water and electrolyte from
ers of the tin passive or protects them to such
an extent that they do not become oxidized to a
its surfaces. Then it was heated for a fraction
of a second and thereby made substantially dry ‘ material extent either before or during subjec
tion to the oven temperatures at which lacquer
and immediately thereafter it was coated with
an oil emulsion and heated to dry out that coat 40 or enamel is baked thereon. I believe that it is
due to this reduction and passivation of the sur
mg.
face layers of the tin and the protection afforded
' The present invention will be better under
by the non-oxidizing atmosphere and the ?nal
stood by those skilled in the art from the follow
coating that the strong, tenacious adherence of
ing description of the construction and opera
tion of the apparatus illustrated in the drawing I enamel and lacquer to tinplate treated by this
method is largely, if not entirely, traceable.
which is attached to and forms a part of this
This application is a continuation-in-part of
speci?cation.
my copending application Ser. No. 520,783 ?led
In the ?gure tinplate in the form of an elon
February 2, 1944, now abandoned.
gated strip l passes from roll stand 2 between
Having thus described my invention so that
roll 3 and cathode roll 4 which constitutes part others skilled in the art may be able to under
of an electric circuit. From roll 3 strip I moves
stand and practice the same, I state that what
vertically down between anodes 5, also in the
I desire to secure by Letters Patent is de?ned
electric circuit, and around roll 6 and thence
in what is claimed.
upwardly to roll 1. The anodes 5 and roll 6 are
positioned in a cell 8 which is substantially full 55 What is claimed is:
of electrolyte. The strip l passes from roll 1
1. The method of treating elongated brightened
down to and around roll 9 and thence up to roll
electro-tinplate which comprises the steps of
10. Roll 9 is located near the bottom of cell H
making the tinplate a cathode, moving such tin
plate endwise and successively deoxidizing tin
which is partly ?lled with condensed steam con
taining more or less electrolyte. The tempera 60 surfaces thereof electrolytically in an aqueous,
ture of the electrolyte is controlled by heating
hexavalent chromium electrolyte, covering the
coils I2 in the upper portion of cell 8 and the
thus deoxidized surfaces with a steam atmosphere
while passing the tinplate from the electrolyte
temperature of the liquid in cell II is controlled
into and out of a body of washing liquid and
by heating coils [3 near the bottom of that cell.
thereby protecting said surfaces by said atmos
A hood l4 encloses the upper end of cell H and
phere against oxidation and substantially com
part of cell 8, and serves to retain a steam atmos
pletely drying them after they pass out of the
phere around the strip ‘in both cells abovethe
washing liquid, heating said surfaces for less than
surface of liquids therein. Just below roll in
about one second to remove ?nal moisture there
pipes l5 are disposed on opposite sides of the
from and forming an oil coating on said surfaces.
strip I and are provided with openings thru
2. The method of treating elongated brightened
which steam may be discharged against the sur
electro-tinplate which comprises the steps of
faces of the strip at an acute angle and in a
making the tinplate a cathode, moving such tin
direction opposite to the direction of travel of
plate endwise and successively deoxidizing tin
the strip as it moves from roll 9 to roll ID.
~ Immediately after leaving roll l0, strip l passes 75 surfaces thereof electrolytically in an aqueous,
2,503,217
5
6
hexavalent chromium electrolyte, covering the
of from about 100 to about 800 feet per minute
and successively treating increments thereof as
follows: removing oxides from surfaces of such
tinplate by making it the cathode in an aqueous
electrolyte containing dissolved hexavalent chro
mium ions equivalent to those in from .5% to
.75% by weight of alkali chromate and main
thus deoxidized surfaces with a steam atmos
phere while passing the tinplate from the electro
lyte into and out of a body of washing liquid‘ and
thereby protecting said surfaces by said atmos
phere against oxidation and substantially com
pletely drying them after they pass out of the
washing liquid, heating said surfaces for less than
tained at a temperature of between about 150° F.
and about 200° F. and passing an electric current
about one secondto remove ?nal moisture there
from, forming an oil coating on said surface, rins 10 of from about 4 amps, to about 25 amps. per sq.
ing said coating in water and drying the coating.
ft. thru said electrolyte and tinplate for between
3. The method of treating elongated brightened
about one second and about ten seconds, remov
electro-tinplate which comprises the steps of
ing electrolyte from the tin surfaces by passing
making the tinplate a cathode, moving such tin
the tinplate in a steam atmosphere into and out
plate endwise and successively deoxidizing tin 15 of a body of water at a temperature of about
surfaces thereof electrolytically in an aqueous,
180° F., removing water from said tin surfaces by
hexavalent chromium electrolyte, covering the
directing jets of steam under pressure at an acute
thus deoxidized surfaces with a steam atmos
angle thereagainst, drying the tin surfaces by
phere while passing the tinplate from the elec
trolyte into and out of a body of washing liquid
and thereby protecting said surfaces by said at
mosphere against oxidation and substantially
completely drying them after they pass out of
the washing liquid, heating said surfaces for less
heating them for less than one second, covering
the tin surfaces with an oil emulsion ?lm, rinsing
than about one second to remove ?nal moisture
therefrom, forming an oil coating on said sur
The following references are of record in the
1c of this patent:
faces and drying the coating.
4. The method of treating brightened electro
tinplate which comprises the steps of removing
oxides from surfaces of such tinplate by making
in water and heating said ?lm.
ALVIN FREDERICK PRUST.
REFERENCES CITED
UNITED STATES PATENTS
30
the tinplate the cathode in an aqueous electro
Number
1,827,204
Name
_
Date
Mason ___________ __ Oct. 13, 1931
lyte containing dissolved hexavalent chromium
ions equivalent to those in from .5% to 75% by
weight of alkali chromate and passing an electric
1,872,614
2,125,387
2,142,486
2,203,062
Wirshing _________ __ Aug. 16,
Mason _____________ __ Aug. 2,
Antisell ___________ __ Jan. 3,
Schueller _________ __ June 4,
current of from about 4 amps. to about 25 amps. 3 i)
1932
1938
1939
1940
2,215,143
Clayton ________.____ Sept. 17, 1940
per sq. ft. thru said electrolyte and tinplate for
vbetween about one second and about ten seconds,
2,215,165
2,234,593
removing electrolyte from the tin surfaces by
2,255,859
Sumner __________ __ Sept. 17, 1940
Ferm et a1 ________ __ Mar. 11, 1941
Quigley __________ __ Sept. 16, 1941
passing the tinplate in a steam atmosphere into
2,266,330
2,274,963
2,306,143
2,314,818
2,317,242
2,327,127
2,327,885
2,424,718
and out of a body of water, removing water from -
said surfaces by directing jets of steam under
pressure at an acute angle thereagainst, drying
the tin surfaces by heating them for less than
one second and immediately protecting the tin sur
faces against contact with air by covering them
with an adherent oil emulsion ?lm and remov
ing moisture from said ?lm.
5. The method of treating elongated brightened
electro-tinplate, which comprises the steps of
moving said tinplate endwise at a lineal speed
Nachtman ________ __ Dec. 16, 1941
Hopper ____________ __ Mar. 3, 1942
Stevenson ________ __ Dec. 22, 1942
Cook et a1 _________ __ Mar. ‘23, 1943
Allen et a1 ________ __ Apr. 20, 1943
Rath ____________ __ Aug. 17, 1943
Grace et al ________ __ Aug. 24, 1943
Stevenson ________ __ July 29, 1947
FOREIGN PATENTS
Number
. 479,746
Country
Date
Great Britain ______ __ Feb. 7, 1938
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