Apparatus for plating a layer onto a metal strip

An improvement in a device for plating a thin layer of a first metal onto the surface of a generally flat metal strip formed of a second metal as the strip is moving in a selected direction along a given path, wherein the device includes an anode in the chamber and means for supplying electrolyte containing ions of the first metal between the anode and the moving strip. The improvement involves providing the anode as an electrically conductive, non-consumable, anode element having an outer surface with a transverse width substantially as great as the width of the strip. A plenum chamber is formed behind the anode element and generally coextensive with the outer surface of the element so that apertures in the anode element direct jets of electrolyte through the anode element and directly against the surface being plated to provide a uniformly turbulent flow of electrolyte at the surface of the strip.

The present invention relates to the art of plating a layer of metal on a 
moving thin metal strip and more particularly to an improved apparatus or 
device for accomplishing this purpose and the method of using the 
apparatus or device. 
The invention is particularly applicable for plating zinc onto a moving 
steel strip and will be described with particular reference thereto; 
however, it is appreciated that the invention has broader applications and 
may be used in other plating installations wherein a cathodic moving metal 
strip is plated on at least one surface by a spaced, generally parallel 
anode. 
BACKGROUND OF INVENTION AND PRIOR ART 
The art of plating zinc onto a moving metal strip is well developed. 
Normally, a consumable anode is provided in the plating cell so that the 
zinc forming the anode is electrically deposited on the moving strip which 
is connected to a negative D.C. potential with respect to the anode. 
Representative patents illustrating this concept are U.S. Pat. Nos. 
2,382,018; 2,509,304; 2,569,577; 2,690,424; and U.S. Pat. No. RE 23,456. 
In some instances, the anode is non-consumable and the electrolyte is 
provided with the zinc compound which provides zinc ions for electrolysis. 
Representative patents showing non-consumable anodes for use in 
electroplating are U.S. Pat. Nos. 3,354,070 and 3,483,113. In many 
instances, the strip is moved longitudinally through one or more plating 
traps which include an electrolyte and are continuously provided with 
electrolyte from a lower reservoir into which the electrolyte overflows 
from the tray. In this manner, an elongated line of trays can be used to 
plate the desired thickness of material onto a moving strip. Generally, 
the anodes are provided in the tray and the strip is provided with a 
negative potential. A representative patent showing this general concept 
is U.S. Pat. No. 3,468,783. Another patent showing the tray arrangement is 
U.S. Pat. No. 3,287,238. The current density of the plating process 
determines the rate at which zinc or other metal is placed onto the strip. 
As the current density is increased, the plating process is more rapid and 
the speed of processing of a metal strip is increased. This reduces the 
length of the line used to obtain a given thickness of plated material or 
increases the speed at which the strip can be passed through the apparatus 
during the plating process. Generally, a current density of between 
500-2000 ampers per square meter are common. To increase the current 
density, it is known to increase the velocity of the electrolyte along the 
strip as shown in U.S. Pat. No. 3,975,242 wherein the strip is passed 
through a narrow vessel and the electrolyte is passed through this same 
vessel. 
The above discussion is the general background of the present invention and 
the patents mentioned above are incorporated by reference for the 
illustrated background information. 
The prior art described above does not illustrate a plating device or 
apparatus wherein one or both sides of a strip can be selectively plated 
in a tray type plating device using a non-consumable anode and capable of 
current densities substantially greater than the normal current densities 
of 500-2000 ampers per square meter. Also, the prior art discussed above 
does not illustrate a non-consumable anode for use in a tray type of 
plating process wherein the anode is economical to produce, allows high 
current densities and produces uniform results across the width of the 
strip. 
THE INVENTION 
The present invention relates to an improvement in the prior apparatus as 
described above which improvement includes the provision of an anode which 
is formed from an electrically conductive, non-consumable anode element 
transversely aligned with the moving strip and extending along the path in 
which the strip is moving. This anode element has an outer surface with a 
width substantially as great as the strip width and a plenum chamber is 
provided coextensive with the outer surface of the anode element. 
Apertures within the anode element and extending between the plenum 
chamber and the outer surface over substantially the complete area of the 
outer surface allow pumping by positive force of an electrolyte containing 
an appropriate supply of plating ions through the apertures in the form of 
jets impinging directly upon substantially the total surface of the strip 
being plated to provide uniformly turbulent flow at the surface. If a 
single side of the strip is to be plated, a single anode of this type is 
provided or only one of two anodes is activated. If both sides of the 
strip are to be plated, two anodes are provided, one on each side of the 
strip. By providing the high velocity jets impinging directly against 
substantially the total surface of the strip being plated, the thickness 
of the ion transfer layer at the strip is decreased substantially. As is 
well known, the current density in the plating process varies inversely 
with the thickness of the ion transfer layer at the surface of the strip. 
By reducing the thickness of the ion layer in accordance with the present 
invention, the mass transfer rate of the electrodepositing-metal ion is 
significantly increased and the current density is correspondingly 
increased for the same applied voltage, such as 12 volts D.C. Thus, the 
practical effect is the same as though electrolyte resistance is 
decreased. With respect to this aspect of the invention, three prior 
patents are pertinent. U.S. Pat. No. 4,030,999 illustrates a plating 
process wherein a screen is the anode and electrolyte is forced through 
the anode screen as jets directed against the strip. This provides single 
side deposition on the strip in a selected area. However, the anode screen 
does not include a plenum chamber coextensive with the screen so that the 
electrolyte is distributed equally on the reverse side of the screen and 
is directed in power jets against the surface to decrease the thickness of 
the ion transfer layer at the strip. Indeed, the strip is not completely 
submerged in a manner to give a constant ion transfer layer over at least 
the entire surface of one side of the strip. U.S. Pat. Nos. 2,989,445 and 
3,038,850 relate generally to anodizing the aluminum on one side in the 
first instance and both sides in the second instance. In U.S. Pat. No. 
2,989,445 an upper reservoir is provided with a negative potential and 
directs electrolyte by gravity through orifices against the upper surface 
of the strip which is at a positive potential. This concept relates to a 
gravity flow which distributes electrolyte in a thin layer over the upper 
surface of the strip. The strip is not submerged in the electrolyte of the 
tray, nor is the electrolyte directed in high velocity jets toward the 
surface of the strip to decrease the thickness of the ion transfer layer 
as contemplated by the above-mentioned aspect of the present invention. In 
U.S. Pat. No. 3,038,850, the aluminum anodizing process incorporates 
carbon anodes on each side of the moving foil or strip. Electrolyte is 
pumped through orifices at the center of the strip only. From there, the 
electrolyte flows outwardly in the space between the strip and the carbon 
anodes. This patent does not show the concept of a perforated anode having 
a coextensive plenum chamber therebehind so that a plurality of high 
velocity jets can be directed to all surface areas of the strip as the 
strip is moving through a tray type of electroplating process. These prior 
art patents are incorporated by reference herein as background information 
for the anode aspect of the present invention. 
With respect to another aspect of the present invention, the electroplating 
device includes a first anode facing a lower surface of the strip and a 
second anode facing the upper surface of the strip. Means are provided for 
selectively changing the electrolyte level in the chamber or tray between 
a first level covering the strip and both anodes and a second level 
covering only the lower anode and the strip. In this manner, the 
electroplating process can be changed between a single side plating and a 
two side plating process by the provision of an arrangement for reducing 
the level of electrolyte in the tray of the plating apparatus. By using 
this concept, especially with the anodes as previously described, it is 
possible to utilize the novel method of plating a metal strip moving along 
a longitudinal path with a selected different layer thickness on the upper 
and lower surface of the strip. In accordance with this method, the strip 
is provided with a negative potential and there is provided a series of 
plating cells each including an upper and lower non-consumable anode 
facing each of the surfaces of the strip. By selecting the number of cells 
and controlling the level of the electrolyte in each of the cells, the 
respective cells plate only one side or both sides of the moving strip. In 
this manner, a desired thickness of plated material can be provided on 
each side of the strip in a manner heretofore not obtainable. By using 
this process, one side of the strip can be plated with one metal and the 
other side of the strip can be plated with another metal. Also, the 
thickness of the plating on each side of the strip can be controlled to a 
different thickness irrespective of the type of material plated on both 
sides of the moving strip. 
The primary object of the present invention is the provision of a 
non-consumable anode for use in plating metal onto a moving metal strip, 
which anode directs jets of electrolyte containing the plating metal 
through orifices encompassing the total width of the strip for decreasing 
the thickness of the ion transfer layer or barrier at the surface to be 
plated. 
Another object of the present invention is the provision of an anode, as 
defined above, which anode includes a conductive metal element having 
apertures therein and a plenum chamber behind the anode for forcing 
electrolyte from the plenum chamber through the anode onto the moving 
strip. 
Still a further object of the present invention is the provision of a 
non-consumable anode for a plating process, which anode directs jets of 
electrolyte against a moving strip within a bath of electrolyte to 
increase the current density of a plating process by decreasing the 
thickness of the ion layer at the surface of the strip without requiring 
complicated flow directing mechanisms. 
Still a further object of the invention is the provision of an anode, as 
defined above, which anode includes within the plenum chamber an 
arrangement for rendering the velocity of electrolyte flow through the 
anode somewhat uniform over the total surface of the perforated anode. 
Still a further object of the present invention is the provision of an 
anode which can be positioned above and below a moving strip to plate one 
or both sides of the strip as it moves through a plating tray. 
Another object of the present invention is the provision of a method of 
controlling which anode is active in the above-mentioned arrangement by 
controlling the level of the electrolyte in the tray. 
Yet another object of the present invention is the provision of a method of 
plating a metal onto a moving metal strip, which method can control the 
thickness of the coated metal on each side of the strip by controlling the 
level of the electrolyte in successive trays in a processing unit. 
A further object of the present invention is the provision of an anode and 
method of operating same, which anode and method increases the current 
density possible in a plating process and provide a convenient way of 
shifting from one side to two side plating. 
Another object of the present invention is the provision of a device for 
plating metal onto a moving strip wherein a non-consumable anode is spaced 
from the surface of the strip to be plated, which device maintains the 
spacing between the anode and strip filled with an appropriate electrolyte 
which electrolyte is acted upon by high velocity jets from another source 
of electrolyte. The jets extend from the anode and unite in a high 
velocity flow across the surface of the strip being plated over its total 
width. In this manner, the ion transfer layer adjacent the surface being 
plated is decreased to a minimum and in effect decreases the electrolyte 
resistance between the anode and the strip and thus allowing higher 
current densities for the plating process. 
Another object of the present invention is the provision of an apparatus 
and method for plating a moving metal strip which apparatus and method 
substantially decrease the thickness of the ion transfer layer adjacent 
the strip being plated. 
These and other objects and advantages will become apparent from the 
following description which includes the drawings set forth in the next 
section.

PREFERRED EMBODIMENTS 
Referring now to FIGS. 1-4, wherein the showings are for the purposes of 
illustrating the preferred embodiment of the invention and not for the 
purpose of limiting same, there is disclosed a device or apparatus A for 
plating the lower surface 10 of a steel strip B moving in a path P. The 
strip includes an upper surface 12, parallel edge portions 14, 16 and a 
center portion 18. The width of the strip W can vary according to the size 
of the strip being processed by the device A. In accordance with standard 
practice, contact rolls 20 coacting with back-up rolls 22 apply a negative 
potential to strip B as it moves along path P through device A. In 
accordance with somewhat standard practice, a plurality of trays 30, two 
of which are shown are used for plating strip B. Often these tray types of 
plating devices plate both surfaces of the strip as it passes through an 
electrolyte and adjacent a consumable zinc anode. Since the trays 30 are 
substantially identical, only one of these trays will be described in 
detail and this description will apply equally to the other tray or trays 
used in the plating process which in accordance with the present invention 
plates only the under surface 10 of strip B as it passes through the trays 
in succession. As will be explained later, if both surfaces of the strip 
are to be plated in a tray, a second anode arrangement is provided in 
accordance with the present invention. Within tray 30 there is provided an 
appropriate electrolyte L which, in practice, is a solution of sulfuric 
acid containing zinc sulfate which provides zinc ions for electroplating 
onto surface 10 of moving strip B. Electrolyte L is maintained in tray 30 
to an appropriate level 32 which in practice is above upper surface 12 of 
strip B. Since only the lower surface of the strip is being plated, it is 
essential that the electrolyte contact only the lower surface of the 
strip; however, since the strip may form a catenary in the tray, level 32 
is maintained above the upper surface 12 of strip B. At each end of tray 
30 there is provided standard dam rolls 34, 36 which allow an overflow of 
electrolyte from between the rolls or over the top of the rolls to remove 
the electrolyte from tray 30 and maintain level 32 within certain general 
limits. In accordance with the invention, there is provided a hollow anode 
50 formed from non-consumable materials. The electrical circuit is 
completed at the non-consumable anode because water is oxidized to give up 
electrons to the external electrical circuit in the same amount as 
required to neutralize the positively charged zinc ions for deposition at 
the strip surface. An electrolyte inlet 52 directs electrolyte from 
reservoir 54 through conduit 60 which includes a filter 62 and an 
appropriate pump 64. As schematically illustrated in FIG. 1, and as will 
be described in more detail later, hollow anode 50 includes a plurality of 
orifices or apertures 70 which create high velocity liquid jets 72 formed 
from electrolyte forced through orifices or apertures 70 against surface 
10 by the pressure created with pump 64. This pressure is sufficient so 
that the jets actually impinge at high electrolyte flow rates across the 
lower surface 10 of strip B. By this direct contact effect of the jets 
impinging upon strip B, the ion transfer layer thickness at surface 10 is 
decreased to a relatively low amount which approaches zero. Of course, the 
layer does not reach zero and includes at least a single molecular layer 
which can not be scrubbed from surface 10 by the action of the several 
liquid jets 72. As will be explained later, the number of orifices or 
apertures 70 is selected so that the total surface of strip B over anode 
50 is acted upon by the liquid scrubbing action of jets 72 being propelled 
through electrolyte L within tray 30. 
As so far explained, as strip B passes along path P through device A, the 
strip is cathodic and a non-consumable anode 50 is provided. This anode is 
electrically positive with respect to the cathode strip and is spaced only 
slightly therefrom to create a space 80 which is filled with electrolyte 
and continuously agitated by the high velocity jets of electrolyte passing 
in straight uninhibited, unobstructed paths from the orifices or apertures 
70 to surface 10. This combined submersion of surface 10 and agitation by 
high velocity unobstructed electrolyte jets from the anode decreases the 
thickness of the current density controlling ion transfer layer. By 
maintaining surface 10 submerged in electrolyte and agitated by high 
velocity jets, the thickness of the ion layer is decreased and high 
electrodeposition rate can be provided. Accordingly jets 72 are created at 
each of several apertures covering the upper surface of anode 50. As will 
be explained later, these jets have sufficient velocity to travel through 
electrolyte L and provide high solution flow over surface 10. By retaining 
the same voltage which in practice is approximately 12 volts D.C., the 
higher solution flow across the strip surface in space 80 permits 
substantially increased current flow between the anode and surface 10. 
This current flow in practice has been found to be substantially above 
approximately 10,000 ampers per square meter using the anode concept as 
generally described above and which will be described in more detail 
hereinafter. In addition to the substantial increase of the permissible 
current density because of uniform turbulence of electrolyte flow due to 
the anode jets, the electrolyte flow through the anode also decreases the 
anode polarization by sweeping away oxygen gas that forms at the anode 
surface due to oxidation of water. In this manner, the electrical energy 
will be minimized for accomplishing zinc plating on the moving strip. 
Referring now more specifically to FIGS. 2 and 3, anode 50 is a hollow 
structure including a conductive element 100 formed from a non-consumable, 
electrically conductive material. The term "non-consumable" indicates that 
sheet 100 does not change form or weight while functioning as an anode in 
relation to surface 10 of moving strip B. In practice, anode 100 is formed 
from perforated steel coated with a layer of metal including 90% lead and 
10% tin. Anode 100, as shown in FIG. 3, is curved so that the space 80 
increases outwardly from the center portion 18 of strip B to the outer 
edge portions 14, 16, respectively. This allows a more even distribution 
of current density which will reduce the general tendency of the strip to 
overplate along the edges of the strip. By curving the anode, the 
resistance of the electrolyte adjacent the edges is increased by 
increasing the spacing through which the electrical current must flow 
between surface 102 and surface 10. Anode 50 is hollow and is closed by a 
rearward housing 110 forming a plenum chamber 112 for directing 
electrolyte from inlet 52 through the apertures or openings 70 within 
conductive sheet 100. Housing 110 is electrically non-conductive and also 
non-consumable in the plating process. In practice, the housing is formed 
from a high strength plastic such as CPVC which is a high strength 
polyvinylchloride well known in the trade. Of course, the housing could be 
formed from steel having an outer coating of rubber or other materials 
including plastics which are common practice in the plating art. As so far 
described, conductive anode 100 has a width D which is generally the same 
as but greater than the width of the strip being plated. Of course, the 
width of the strip W varies according to the strip being plated. The 
spacing between surface 102 and surface 10 is such that jets 72 cause 
turbulent agitation at surface 10 before being dissipated by the body of 
effluent within space 80. In the center, the spacing may be relatively 
small in the neighborhood of approximately 2-3 centimeters. To control the 
velocity of jets 72, the pressure differential between outer surface 102 
and inner surface 104 of sheet 100 is equalized and is not affected by the 
position of inlet 52 for housing 110. To accomplish this, an appropriate 
baffling arrangement is provided within plenum chamber 112. In the 
illustrated embodiment of FIG. 3, the baffling arrangement includes 
vertically depending, longitudinally extending baffles 120 extending the 
total length of housing 110 and element 100. The baffles are provided with 
downwardly angled deflectors 122. These baffles and deflectors equalize 
the pressure within plenum chamber 112 so that the pressure differential 
between surfaces 102, 104 is stabilized. Consequently, the velocity of 
liquid jets 72 is relatively constant and is controlled by the size of the 
openings 70. As the openings are made larger, the velocity of the jets 
becomes less. In each instance, it is anticipated that the jets actually 
cause turbulent agitation at surface 10 to reduce the thickness of the ion 
transfer layer on this surface which allows a drastic increase in the 
current density for electrodeposition of a metal on surface 10. This 
increase in the current density together with the uniformity of the 
current density created by the curvilinear contour of element 100 provides 
a relatively uniform, high current density for the plating process which 
reduces the time which the metal must be subjected to the electrolysis 
process to obtain a given thickness of plated material on surface 10. 
Thus, a fewer number of cells may be used and/or the speed of the strip 
may be increased to produce a preselected plated thickness for the metal 
being plated onto the strip. 
As the width of the strip being plated changes, the effective width D' of 
surface 102 on element 100 must be changed accordingly to prevent 
overplating along the outer edges of the strip. To adjust the effective 
width D' of element 100 with respect to the width W of strip B, there is 
provided electrically non-conductive, non-consumable sheet baffles 130, 
132 extending along the edges of sheet 100. Material forming these sheet 
baffles 130, 132 may be the same material as used in forming the housing 
110. To change the effective width D' of sheet element 100, baffles 130, 
132 are adjustable in a transverse direction by an appropriate 
arrangement, schematically illustrated as a plurality of wing nuts 134 
coacting with transversely extending slots 136. When plating strip B, 
baffles 130, 132 are adjusted inwardly until there is no wrap-around or 
overplating at the edges of strip B. It has been found that the effective 
width D' is less than the width W of the strip being plated. As will be 
explained later, this decrease in width D' apparently reduces the current 
paths passing through the electrolyte and concentrated at the edge 
portions of strip B. By adjusting the non-conductive shields or baffles 
130, 132 inwardly, the thickness of the plating adjacent edge portions 14, 
16 is reduced somewhat to prevent overplating at these surfaces. This is 
also a factor of the current paths formed from the positive surface 102 to 
the negative surface 12. 
In accordance with another aspect of the invention, the apertures 70 of 
anode element 100 are angled backwardly in a direction opposite to the 
path P of moving strip B. This is schematically illustrated in FIG. 4. 
This backward angled direction of openings, orifices or apertures 70 
causes a sliding action of the liquid jet as it impinges directly upon 
surface 10 to coact with the movement of strip B to produce a higher 
velocity differential between the impinging jets 72 of electrolyte and 
moving strip B. The effective electrolyte velocity at surface 10 is 
increased by this angled direction of the high velocity electrolyte jets 
extending through space 80 and impinging upon surface 10 because the 
relative velocity includes a component of the liquid velocity of the jet. 
In the preferred embodiment of this aspect of the invention, the angle of 
the jets is approximately 45.degree. with respect to a vertical direction 
as schematically illustrated in FIG. 4. In FIG. 4A, a preferred anode 100a 
includes a plurality of angled non-consumable anode bars 102a defining 
transverse slots 104a through which electrolyte passes in sheet-like jets 
72a. Element 100a operates essentially like anode element 100. 
Referring now to FIGS. 5-9, another aspect or modification of the present 
invention is illustrated. In this concept, a lesser amount of electrolyte 
is pumped as electrolyte jets in the area of the outer portion of surface 
10 than in the area of the center portion thereof. A variety of 
arrangements could be used to provide greater electrolyte volume for the 
jets as the distance from the center of surface 10 increases toward the 
edge portions of the surface. Various arrangements for this purpose are 
illustrated in FIGS. 5-9 wherein the orifices or openings 70a-70e are 
provided on surfaces 102a-102e of sheet elements 100a-100e. As can be 
noted, by spacing the orifices a greater transverse distance, as shown in 
FIGS. 5, 7 and 8, the volume of electrolyte being jetted to the surface of 
the strip is decreased from the center portion of the anode sheet element 
to the outer portion of the anode sheet element. This feature can also be 
accomplished by decreasing the size of the orifices or openings as shown 
in FIG. 6. A contoured orifice or opening may also be provided as shown in 
FIG. 9. In each of these instances, a decreased volume of electrolyte is 
provided in space 80, in a gradual manner, as the orifice distance 
increases from the center portion of anode sheet 100 and the edge portions 
of this sheet. By this modification, the volume rate and, therefore, the 
velocity of the electrolyte flow adjacent the strip is maintained uniform 
even though there is a larger spacing between the anode and strip adjacent 
the outer edge portions of the strip. This uniformity can be controlled 
also by the taper of the anode. 
Referring now to FIGS. 10 and 11, if the anode C is spaced uniformly from 
surface 10 of strip B, the current density adjacent the outer edge is 
increased. This causes a heavier plated layer at the edge portions 14, 16 
and also a certain amount of metal deposition around these edge portions 
during the plating process. By providing a curvilinear surface as shown in 
FIG. 11 for anode element 100, the current density is more uniform in that 
a longer electrolyte path is provided adjacent the outer portions of the 
strip. The current paths are schematically illustrated as R1-R6. The 
current path R7 represents parallel resistance paths adjacent the edge 
portions of the strip. These paths increase the plating at the edge 
portion even with a controured surface. Because of the extra current paths 
adjacent the edge portion, the baffles or shields are used as previously 
described. FIG. 11 schematically illustrates one concept found to exist in 
the preferred embodiment. The baffles 130, 132 shown in FIG. 3 can be 
moved transversely to change the current paths for reducing the 
overplating along the edges of the strip and the thickness of the plated 
layer adjacent the edge portions of the strip. 
Referring now to FIGS. 12-15, the preferred transverse contour and 
construction of the anode sheet element is schematically illustrated. 
Anode element 200 is formed from standard expanded metal such as steel 
having a general upper surface 202 and a general outer surface 204. Of 
course, these surfaces are not smooth and include the normal rippled 
texture of expanded metal. The expanded metal is steel coated with a lead 
alloy, as previously described. Of course, other metals, such as 
nickel-cobalt-silicon alloy, could be used. The expanded metal has 
openings or apertures 206 which openings form approximately 25%-50% of the 
total surface 202. Element 200 tapers outwardly from the center portion of 
an angle indicated on FIG. 12. The anode as schematically illustrated in 
FIGS. 12 and 13 functions in accordance with the description of the 
embodiment of the invention illustrated in FIGS. 1-4. Referring to FIG. 
14, the tapered element 200 increases the spacing of the anode from the 
center to the outward portions of the moving strip. This contour has a 
tendency to equalize the current density, as schematically illustrated in 
FIG. 15, wherein the spacing of the vertical lines illustrates current 
density distribution over surface 10 of strip B as the spacing of the 
lines in FIG. 10 shows a variable current density. 
Referring now to FIGS. 16 and 17, these figures show the action of the 
electrolyte jets propelled from the orifices or apertures in the anode as 
they impinge upon surface 10 of moving strip B. As can be seen, jets 210 
are propelled from openings or apertures 206 to impinge at an angle on 
surface 10. These jets are propelled through the electrolyte filling space 
80 so that the electrolyte of the jets after direct impingement upon 
surface 10 combines with the existing electrolyte to cause a composite 
liquid flow as indicated by the arrows in FIG. 16. This flow is outwardly 
from the center of space 80. As shown in FIGS. 17, jets 210 wipe the ion 
layer 200 to decrease the thickness of this layer to a minimum thickness 
on surface 10 and in effect substantially reduces the resistance of the 
plating operation. This allows an increase of the current density from 
normal 500 to 2000 ampers per square meter to over 10,000 ampers per 
square meter for the same 12 volt D.C. potential applied across the anode 
and cathode of the plating apparatus. By providing a larger volume of 
electrolyte toward the outer edges of the anode and strip as used in one 
embodiment of the invention, the velocity of electrolyte flow is 
maintained as the thickness of space 80 increases. In the embodiment shown 
in FIGS. 12-17, which is preferred, the apertures or openings are 
uniformly distributed over element 200. Thus, the electrolyte flow is 
generally the same for all areas of surface 202. The increased spacing of 
surface 202 still allows uniform electrolyte flow, as the center jet 
electrolyte combines with the outer jet electrolyte. The taper or surface 
202 takes this factor into consideration to allow generally even flow from 
space 80. Of course, modified anode openings could also be used to assist 
in maintaining a uniform velocity of electrolyte along the strip. 
Referring now to FIG. 18, an arrangement for using the invention as so far 
described to plate either lower surface 10 or upper surface 12 of strip B 
or both surfaces is schematically illustrated. Lower anode 300, 
constructed like the anode of FIGS. 12 and 13, extends along the lower 
surface of strip B in tray 304 in the manner previously described. In this 
embodiment of another aspect of the invention, a second anode 302 extends 
along upper surface 12 of moving strip B. In this instance, tray 304 
includes sidewalls 306, 308 including side openings 310, 312 having upper 
edges 310a, 312a, respectively. These upper edges serve as auxiliary weirs 
to control the level of electrolyte L in a manner to be described later. 
Openings 310, 312 of sidewalls 306, 308 are closed in FIG. 18 by plates 
320, 322 held in position over the openings by bottom lugs 324 and side 
lugs 326, two of which are shown. With plates 320, 322 in place, the 
electrolyte level in tray 304 is level 330. The electrolyte flows over the 
top of sidewalls 306, 308 as previously discussed. To provide pressurized 
electrolyte within the anodes 300, 302 there is provided a line 340 
connecting reservoir 54 with inlet 52 of anode 300. A valve 342 opens line 
340 for pumping of electrolyte L from the reservoir into anode 300 by a 
pump 344. In a like manner, electrolyte L is provided within anode 302 by 
line 350 having a selectively operated valve 352 and a pump 354. One or 
both of the anodes can be provided selectively with electrolyte L for a 
plating operation as previously described in conjunction with the other 
embodiments of the present invention. To provide the electrical current 
for anodes 300, 302, there are provided leads 362, 360, respectively. 
These leads are connected to a common positive potential lead 370 of the 
D.C. power supply used in the plating process. 
By using the aspect of the invention as illustrated in FIG. 18, the bottom 
surface 10 may be plated by removing plates 320, 322 from openings 310, 
312, respectively. This lowers the level of electrolyte to the level 332 
which is below anode 302 and generally corresponds to level 32 of FIG. 1. 
Thus, anode 302 is inactive even though connected to the positive lead 
370. By closing valve 352, a single side plating process is obtained. If 
both sides are to be plated, the plates 320, 322 are replaced. Valve 352 
is opened and both surfaces 10, 12 are plated. Thus, by using an 
arrangement for reducing the level of electrolyte within tray 304 the 
apparatus as illustrated in FIG. 18 can be easily converted from a single 
side plating arrangement to a two side plating arrangement. It is also 
possible to plate only the upper surface 312 in the apparatus as shown in 
FIG. 18. This can be done by employing the electrical circuitry shown in 
FIGS. 19A or 19B. The showing of FIG. 19 is a schematic illustration of 
the electrical circuitry used in FIG. 18. Referring now to FIG. 19A, a 
second power supply is provided with a positive lead 372 electrically 
distinct from lead 370. If only the upper surface 12 of strip B is to be 
plated, lead 372 is disconnected. This supplies power therefore only to 
anode element 200 of upper anode 302. In this manner, only the upper 
surface is plated even though the electrolyte is at the level 330. Of 
course, in this instance, the electrolyte will not be pumped through lower 
anode 300. To do this, valve 342 is closed. A similar arrangement could be 
accomplished with a single positive potential lead 370 by providing a 
switch 374 between lead 370 and input lead 362 of anode 300 as shown in 
FIG. 19B. By opening switch 374, electrical potential is created only 
between the upper anode 302 and strip B. By using the circuitry as shown 
in FIGS. 19A, 19B and the structure shown in FIG. 18, either the top 
surface, bottom surface or both surfaces can be plated as the strip B is 
passing through tray 304. 
Referring now to FIG. 20, a method utilizing the structure shown in FIG. 18 
for selective plating of both sides of strip B is schematically 
illustrated. By controlling the level of electrolyte within tray 304 and 
electrolyte flow to anodes 300, 302, either the lower side or both sides 
of strip B are plated. In the arrangement illustrated in FIG. 20, five 
units are used for plating the lower surface and only two units are used 
for plating the upper surface. Thus, a substantially heavier layer of 
material is plated on the lower surface of strip B. It is also possible to 
use this concept to plate the upper surface only as previously described. 
Also, different metals can be plated on different surfaces by using a 
series of trays with the controllable electrode arrangement as shown in 
FIG. 18 and containing different electrolyte.