US20210115586A1

US20210115586A1 - High surface area anode and method of manufacturing

Info

Publication number: US20210115586A1
Application number: US16/148,966
Authority: US
Inventors: Randy Frank Klein
Original assignee: University of Pennsylvania Penn
Current assignee: University of Pennsylvania Penn
Priority date: 2018-10-01
Filing date: 2018-10-01
Publication date: 2021-04-22

Abstract

The invention described herein shows a high surface area anode. The high surface area anode contains a flat surface on one side and a ribbed surface on the opposite side. On the ribbed surface there is a first edge-lip on its first-end and a second edge-lip on its second-end. Both the first edge-lip and the second edge-lip run parallel to each other. The high surface area anode further contains a plurality of ribs and groves between the first edge-lip and the second edge-lip also running parallel to each other. The high surface area anode is manufactured using a continuous casting method that includes the following steps; dissolving the anode metal into the holding furnace shaping the anode metal using a high surface area graphite mold; solidifying the anode metal using a liquid while extruding the anode metal through the high surface area mold; solidifying the anode metal by using a secondary cooling source; and extracting the now solidified and shaped high surface anode metal.

Description

BACKGROUND

Field of the Invention

The present invention is directed to a high surface area anode and a method of manufacturing the high surface area anode to electroplate the surface of various products.

Description of the Related Art

The electroplating process consists of the immersion of an object to be coated in a bath containing an anode. The object itself functions as the cathode. The bath is usually a solution of salts of the metal to be deposited. An electrolytic cell is produced when voltage is applied to the anode. The cathode being negative. Metal ions formed in the solution are attracted to the cathode where they gain electrons and deposit out of the solution onto the cathode surface as pure metal.
Electroplating is widely used in various industries for coating metal objects with a thin layer of a different metal. The layer of metal deposited has some desired property, which the metal of the object lacks. For example, chromium plating is done on many objects such as car parts, bath taps, kitchen gas burners, wheel rims and many others for the fact that chromium is very corrosion resistant, and thus prolongs the life of the parts. Electroplating has wide usage in industries, including in the making of inexpensive jewelry. Electroplating is primarily used to change the surface properties of an object (e.g. abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities, etc.), but may also be used to build up thickness on undersized parts or to form objects by electroforming.
Silver anodes are used to plate the surface of various products from jewelry to precision military and aerospace parts. Electroplating uses electric current to reduce dissolved metal cations so that they form a coherent metal coating on an electrode. The term is also used for electrical oxidation of anions onto a solid substrate, as in the formation silver chloride on silver wire to make silver/silver-chloride electrodes.
The process used in electroplating is called electrodeposition. It is analogous to a galvanic cell acting in reverse. The part to be plated is the cathode of the circuit. In one technique, the anode is made of the metal to be plated on the part. Both components are immersed in a solution called an electrolyte containing one or more dissolved metal salts as well as other ions that permit the flow of electricity. A power supply supplies a direct current to the anode, oxidizing the metal atoms that it comprises and allowing them to dissolve in the solution. At the cathode, the dissolved metal ions in the electrolyte solution are reduced at the interface between the solution and the cathode, such that they “plate out” onto the cathode. The rate at which the anode is dissolved is equal to the rate at which the cathode is plated, vis-a-vis the current through the circuit. In this manner, the ions in the electrolyte bath are continuously replenished by the anode.
There are many kinds of anodes. Typical bar anodes when spent form a “sword” shape which for many reasons are a disadvantage, as described in prior art U.S. Pat. No. 2,802,702.
Unfortunately, plating with the aforementioned variable surface area anode “sword” design, dissolves the anode unevenly and there is a lot of waste of metal. Moreover, when the anode is dissolved unevenly, it makes the electrodeposition of the metal also uneven thus creating an irregular coating.
One way to solve the aforementioned issues is to make the current distribution uniform, so if the current distribution is uniform, the plating thickness will be uniform. But to even out the thickness when geometry favors higher or lower current density to certain areas, three “mechanical” techniques are shielding (the use of plastic shields to block off the shortest path), thieving (the use of conductive wires as cathodes to steal some of the current away from high current areas, and auxiliary anodes (anode material in close proximity to the work in the areas which need more current). These techniques are antiquated when performing high volume plaiting and it also consumes time and money.
What is needed in the industry is an anode that consumes from the front surface closest to the plated part to the back surface furthest from the plated part, reduces or eliminates the need for the addition of additional salts in solution, maintains an even current density throughout the life of the anode, results in a more uniform plating or coating, and at the same time causes less waste of the anode metal. Available art does not provide an anode with the aforementioned properties. Therefore, a need exists to overcome the problems with the prior art as discussed above.

SUMMARY

The invention provides a High Surface Area Anode and Method of Manufacturing that overcomes the previously mentioned disadvantages of the heretofore-known devices and methods of this general type.
The anode described herein includes a method of manufacturing; wherein the anode created generates superior electrodeposited coatings. Furthermore, the design of the anode allows the electrolyte to dissolve it more uniformly and it doesn't have the diminishing effects of the prior art sword.
Specifically, the invention includes a high surface area anode including, at least one flat surface and at least one ribbed surface on its short end; the ribbed surface further comprising at least one edge lip on the long end. The ribbed surface further comprises a plurality of ribs and groves and at least one edge lip is larger in height and width than one of the ribs. The at least one edge lip contains more material by volume than one of the ribs, wherein the plurality of ribs and groves define the width of the high surface area anode.
The invention also describes a high surface area anode including a flat surface on one side and a ribbed surface on its opposite side; the ribbed surface further including a first edge lip on its first end and a second edge lip on its second end opposite and parallel from each other. The ribbed surface further comprises a plurality of ribs and groves and the first edge lip and second edge lip are larger in height and with than one of the ribs. The first edge lip and second edge lip contain more material by volume than one of the ribs, and the first edge lip and second edge lip contain more material by volume than the plurality of ribs. The plurality of ribs and groves define the width of the high surface area anode.
The invention al so includes a method of manufacturing, the method of manufacturing a high surface area anode includes the steps of; 1) dissolving the anode metal into the holding furnace; 2) shaping the anode metal 801 using a high surface area graphite mold; 3) solidifying the anode metal using a liquid while extruding the anode metal through the high surface area mold; 4) solidifying the anode metal by using a secondary cooling source, and 5) extracting the now solidified and shaped high surface anode metal. The shape of the high surface area anode further includes a flat surface on one side and a ribbed surface on its opposite side, and the ribbed surface further including a first edge lip on its first end and a second edge lip on its second end opposite and parallel from each other.
Other features that are considered as characteristic for the invention are set forth in the appended embodiments. As required, detailed embodiments of the present invention are disclosed; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the invention. While the specification concludes with claims defusing the features of the invention regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawing figures, in which like reference numerals are carried forward. The figures of the drawings are not drawn to scale.
Before the present invention is disclosed and described, the terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting. The terms “a” or “an,” as used herein, are defined as one or more than one. The term “plurality,” as used herein, is defined as two or more than two. The term “another,” as used herein, is defined as at least a second or more. The terms “including” and/or “having,” as used herein, are defined as comprising (i.e., open language). The term “coupled,” as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically.
As used herein, the terms “about” or “approximately” apply to all numeric values, whether or not explicitly indicated. These terms generally refer to a range of numbers that one of skill in the art would consider equivalent to the recited values (i.e., having the same function or result). In many instances these terms may include numbers that are rounded to the nearest significant figure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a tridimensional orthogonal cross-sectional diagram showing the high surface area anode.

FIG. 2 is a photograph of the “sword” anode found in the prior art.

FIG. 3 is a tridimensional orthogonal cross-sectional diagram showing the circuit density of the “sword” anode, previously shown in FIG. 2, found in the prior art.

FIG. 4 is diagram that shows a test coupon depicting the uniformity of the coating (in mils) using a “sword” as the anode previously shown in FIG. 2.

FIG. 5 is a photograph of the high surface area anode.

FIG. 6 is a tridimensional orthogonal cross-sectional diagram showing the circuit density of the high surface area anode previously shown in FIG. 5.

FIG. 7 is diagram that shows a test coupon depicting the uniformity of the coating (in mils) of the high surface area anode previously shown in FIG. 5.

FIG. 8 is a diagram showing a schematic of the machine that manufactures the high surface area anode.

FIG. 9 is a flow diagram showing the method how to manufacture the high surface area anode on the machine previously shown in FIG. 8.

FIG. 10 is a tridimensional orthogonal diagram showing the high surface area mold (in open form) used in the manufacturing of the high surface area anode.

FIG. 11 is a tridimensional orthogonal diagram showing the high surface area mold (in closed form) used in the manufacturing of the high surface area anode shown in in FIG. 1.

FIG. 12 is a photograph of the high surface area anode after being manufactured using the high surface area mold of FIG. 11.

FIG. 13 is a diagram showing a schematic how the “sword anode” force fields are unevenly distributed and its concentration at the corners cause the anode to be dissolved unevenly creating an uneven coating.

FIG. 14 is a diagram showing a schematic how the high surface area anode's shape compensated for the increase concentration in force fields.

FIG. 15 is a diagram showing an alternative embodiment of the high surface area anode with both sides include a ribbed surface and edge lips.

FIG. 16 is a diagram showing an alternative embodiment of the high surface area anode wherein one of the sides include a ribbed surface and a single edge lip.

DETAILED DESCRIPTION

Current density is defined as current in amperes per unit area of the electrode. It is a very important variable in electroplating operations. It affects the character of the deposit and its distribution. Current distribution (depicted in FIGS. 1-2 as 302 and 602) is the local current density on an electrode is a function of the position on the electrode surface. The current distribution over an electrode surface will tend to concentrate at edges and points, and unless the resistance of the solution is very low, it will flow to the workpieces near the opposite electrode more readily than to the more distant work-pieces. It is desired to operate processes with uniform current distribution. That is, the current density is the same at all points on the electrode surface.
There are three types of electrolytic metal deposition processes: direct current electrodeposition, pulse plating, and laser-induced metal deposition. In the direct current (DC) electrodeposition, the current source is a power source in the form of a battery or rectifier (which converts alternating current electricity to regulated low-voltage DC current) provides the necessary current. Electroplating is performed in a plating unit. Electrodes, immersed in the electroplating bath (electrolyte), are connected to the output of a DC current source. The workpiece (depicted in FIG. 4 and FIG. 7 as 401 and 701), that is to be plated acts as a negatively charged cathode. The positively charged anode (depicted in FIG. 2 and FIG. 5 as 201 and 500) completes the electric circuit. This type of circuit arrangement directs electrons (negative charge carriers) into a path from the power supply (rectifier) to the cathode (the workpiece to be plated). The geometric shape and contour of a workpiece to be plated affect the thickness of the deposited layer. In general, workpieces with sharp corners and features will tend to have thicker deposits on the outside corners and thinner ones in the recessed areas. The cause of this difference in the resulting layer thickness is that the DC current flows more densely to sharp edges than to the less accessible recessed areas. In other words, the current distribution is not uniform. Therefore, a judicial placement of the anode(s) as well as modifications of the current density are required to overcome the thickness irregularity effects. The invention herein solved both these issues.
When an anode (such as the one depicted in numerals 201 and 500) is charged with power, it becomes similar to the positive end of a magnet, emitting a force field. The workpiece, being connected to the negative side of the power supply, becomes negatively charged and attracts the positive charge from the anode.
The “positively charged” anode dissolves gradually into the solution as it is attracted to the negative workpiece. The dissolved metal is attracted to the workpiece along the lines of force within a force field. An edge creates multiple force fields, hence concentrated at the edge and emitting more metal from that edge. When an object is placed into the force it effects the lines of force, the workpiece diverts the force fields emitted by the anode depending on its shape. Metallic objects, depending on its shape, attracts the force fields a specially at the corners, this concentration of force field produce more plating in these areas. Other reasons why more material concentration is because force field are attracted to edges that we nearest to the anode.
By creating the ribbed surface in the middle with larger first edge-lip on its first-end, and a second larger edge-lip on its second-end, the force fields are made to radiate equally towards all surfaces to be coated. The increase in material at the edge of the high surface area anode compensates for the increase in force fields at the edges, hence transferring more material to the part to be coated. The invention herein contains more material at the edges of the anode, this allow for the force field concertation to transfer material at a larger rate at the edges than in the middle. Since the edges contain more material, it has more to give and therefore the entire high surface area anode part is consumed evenly.
As explained above, the anode has a superior design because 1) it makes the force fields radiate evenly; and 2) the anode is dissolved more uniformly and stays intact as it is consumed until the very end. One of the many advantages of this technology is that it wears more evenly from the front surface than from the edges. Therefore, there is very little dimensional change to the anode as it is dissolved allowing for a more even distribution of the coating layer.
FIG. 1 shows an embodiment of the invention. FIG. 1 is a tridimensional orthogonal cross-sectional diagram showing the high surface area anode 100 hereinafter (“Anode”). The high surface area anode 100 contains a flat surface 111 on one side, and a ribbed surface 112 on the opposite side. On the ribbed surface 112 there is a first edge-lip 108 on its first-end 108, and a second edge-lip 109 on its second-end 109. Both the first edge-lip 108 and the second edge-lip 109 run parallel and opposite to each other. The high surface area anode 100 further contains a plurality of ribs 103 and groves 104 between the first edge-lip 108 and the second edge-lip 109 also running parallel to each other. The first edge-lip 108, the second edge-lip 109, and the plurality of ribs 103 and groves 104 run along the long side 110 defining the length of the high surface area anode 100. The short side 107 defines the width of the high surface area anode 100. Both the first edge-lip 108 and the second edge-lip 109, have a first height 106 that is larger than the plurality of ribs' 103 second height 105, or both the first edge-lip 108 and the second edge-lip 109, have a first volume 106 that is larger than the plurality of ribs' 103 second volume 105
Ribbed surface 112 comprises a multitude of ribs and groves, but it could also be created with “V” shaped typed indentations, that could be stamped or milled. Similarly, edge lips, could be created of multiple dimensions and of different geometries both round or squared, as long as the volume of material is larger 106 that of the ribs 103 inside the ribbed surface 107. The high surface anode can be made of many types of materials, such as: Gold, Silver, Copper, Nickel, Tin, Solder (tin-lead alloy), Brass, Cadmium, Palladium, Zinc, and Chrome.
FIGS. 2-4 are a series of figures that depict the “sword” anode 201 found in the prior art, the circuit density 302 of the “sword” anode 201, and the uniformity of the coating 401 (in mils) after using a “sword” anode 201.
FIGS. 5-7 are a series of figures that depict the high surface area anode 500, the circuit density 602, 603 of the high surface area anode 600, and the uniformity of the coating 701 (in mils) after using the high surface area anode 500. All data shows that if we compare FIG. 4, and FIG. 7, the there is a significant improvement in the current density. In FIG. 3 the current density 302 of the “sword” anode 201, having a relatively flat surface 301, is small. Compared to FIG. 6 where the edge current density is defined by both the edge density 603, coming from the edge lip 604, and the internal current density 601 coming from the of ribs 103. Large current density leads to a better more uniform metal coating as seen by comparing FIG. 4 coating 401 (in mils) after using a “sword” anode 201 and FIG. 7 the coating 701 (in mils) after using the high surface area anode 500.
Having a better more uniform metal coating is advantage because the silver (or any other precious metal) is electrolytically plated onto surfaces of parts creating a surface that does not need re-work thus reducing significantly the cost of manufacturing. A more uniform deposition and plating are achieved because the current density 603 and 604, of the anode of FIG. 6 placed into the electroplating baths and solutions is more uniform. With standard prior art anodes 201, the current density 302 such as the one depicted in FIG. 3, is greatest at the edges closest to the cathode. As shown in FIG. 6, since the high surface anode 600 is ribbed 605 it creates a greater number of edges and points from which the current density 603 can be transmitted. Here, the high surface anode 600 contains curved softened edges to create a broader field as opposed to the point source of 301. Furthermore, the ends 604 of the anode 600 are rounded and thicker which help ensure the anode 600 dissolves and electroplates evenly.
FIG. 8 and FIG. 9 are to be seen in conjunction as the method 920 of FIG. 9 refers to the parts in the machine 800 in FIG. 8. FIG. 8 depicts a diagram showing a schematic of the machine 800 that manufactures the high surface area anode previously shown in FIG. 1 as numeral 100. FIG. 9 is a flow diagram showing the method 920 how to manufacture the high surface area anode, on the machine of numeral 800 in FIG. 8.
The continuous casting method 920 of FIG. 9 is to be used with machine 800 of FIG. 8, include the following steps: (1) step-one 111, dissolving the anode metal 801 into the holding furnace 802; (2) step-two 912, shaping the anode metal 801 using a high surface area graphite mold 810; (3) step-three 913, solidifying the anode metal 801 using a liquid 805 while extruding the anode metal 801 through the high surface area mold 810; (4) step-four 914, solidifying the anode metal 801 by using a secondary cooling source; and (5) step-five 915, extracting the now solidified 808 and shaped high surface anode metal 901.
The process 920 described in FIG. 8 allows for the creation of tightly consistent lot to lot solidified metal 808 grain sizes. Most metals are crystalline in nature and contain internal boundaries, commonly known as “grain boundaries.” When a metal or alloy is processed, the atoms within each growing grain are lined up in a specific pattern, depending on the crystal structure of the sample. With growth, each grain will eventually impact others and form an interface where the atomic orientations differ. It has been established that the mechanical properties of metals improve as the grain size decreases. Therefore, alloy composition and processing must be carefully controlled to obtain the desired grain size. Using the method 920 described in FIG. 9, and the machine 800 described in FIG. 8, the grain size is manipulated (increased and decreased) by controlling the speed and cooling rates of the casting process 920.
FIG. 10 depicts the previously described high surface area mold 810, here as numeral 1000, previously shown inside of machine 800 in FIG. 8. Here, the high surface area mold 1000 includes two parts, the top-mold 1010 and the bottom-mold 1020. The top-mold 1010 contains a flat 1021 that creates the flat surface previously shown in FIG. 1 as numeral 111. The bottom-mold 1022 contains the ribbed surface 1020, which is the mirror image of the first edge-lip, the second edge-lip, and the plurality of ribs and groves previously shown in FIG. 1 as numerals 108, 109, 103, and 104 respectively.
FIG. 11 shows a closed high surface area mold 1010, previously shown open as 1000 in FIG. 10. Here, the top-mold 1110 and the bottom-mold 1120 intimately mating to create a mold opening 1133 wherein the anode metal (previously shown as 801 in FIG. 8) enters the high surface area mold 1010 and exits as a final product at the mold exit 1134. The high surface area anode comes out of the end of the mold exit 1134 and is then cut to the customer's length. FIG. 12 shows a photograph of the final product as a high surface area anode 1220 previously shown as 100 in FIG. 1, as it exits the high surface area mold 1010 through the mold exit 1134.
FIG. 13 and FIG. 14 show a comparison between the prior art “sword anode” previously depicted in FIG. 1, and the invention herein, the high surface area anode previously depicted in FIG. 2. FIG. 13 shows the disadvantage of the “sword,” wherein the force fields 1304 within the current density 1303 accumulate at the edge of the anode 1301 and disproportionally dissolves the anode and non-uniformly coats 1322 the target material 1311. The anode 1301 not only dissolves unevenly but it also as it is deforming, the force fields become more and more in disarray. To the contrary, in FIG. 14, the high surface area anode 1401 creates a uniform distribution of force fields 103 and 1404 in order to create an even coating 1422 upon the target material 1411. Here, the first edge lip 1402 and the second edge lip 1404 are larger (more volume) hence can withstand the multiple increased force fields 103 created at the edge of the anode 1401. In the middle of the anode 1401, the ribbed surface creates less force fields 1404 but are targeted and directed towards the target material 1411 in order to create a uniform coating 1422.
The volume of the edge lips 1402 and 1404 depend how large the anode 1401 is, but as a rule of thumb, the height of the lip is approximately 4 times that of a single rib (previously shown in FIG. 1 as 103), located in the middle section of the anode. Multiple variations of the lip volume can be used for the same purpose to achieve a similar result.
FIGS. 15 and 16 show two alternative embodiments of the invention herein. Anode 1500 includes two ribbed surfaces 1507 one in the front and one in the back, and two large edge lips 1501. In this alternative embodiment maximizes the surface are of both sides of the anode 1500, this will create double the current density hence the more force fields at the corners, and the increase in material compensate for the increase in force field created. FIG. 16, is an alternative embodiment of the invention wherein it only contains one edge lip 1601 rather than two, as previously shown in FIGS. 1, 6, 14, and 15. Here, although not evenly balanced, it could work for certain coating applications and would serve the same purpose to achieve a similar result as the ones with two edge lips or more.
A high surface area anode, and method of manufacturing has been disclosed. The manufacturing method and mold creates an anode where the ends of the anode are rounded, and thicker which help ensure the anode dissolves and electroplates evenly. Also, there are multiple center ribs and groves in the high surface area anode that helps ensure there is a more uniform current density in the plating solution. One of the many advantages of this technology is that the high surface area anode is continuously casted which helps control a tight tolerance of silver grain sizes. Furthermore, the high surface area anode allows for a more uniform plating process, which helps reduce the use of silver and provide a better finish with fewer imperfections.

Claims

What we claim is:

1. A high surface area anode comprising,

a. At least one flat surface and at least one ribbed surface on its short end;

i. the ribbed surface further comprising at least one edge lip on the long end.

2. The high surface area anode, wherein

a. the ribbed surface further comprises a plurality of ribs and groves.

3. The high surface area anode, wherein

a. the at least one edge lip is larger in height and width than one of the ribs.

4. The high surface area anode, wherein

a. the at least one edge lip contains more material by volume than one of the ribs.

5. The high surface area anode, wherein

a. the plurality of ribs and groves define the width of the high surface area anode.

6. A high surface area anode comprising,

a. a flat surface on one side and a ribbed surface on its opposite side;

i. the ribbed surface further comprising a first edge lip on its first end and a second edge lip on its second end opposite and parallel from each other.

7. The high surface area anode, wherein

a. the ribbed surface further comprises a plurality of ribs and groves.

8. The high surface area anode, wherein

a. the first edge lip and second edge lip are larger in height and with than one of the ribs.

9. The high surface area anode, wherein

a. the first edge lip and second edge lip contain more material by volume than one of the ribs.

10. The high surface area anode, wherein

a. the first edge lip and second edge lip contain more material by volume than the plurality of ribs.

11. The high surface area anode, wherein

12. A method of manufacturing a high surface area anode comprising the steps of,

a. dissolving the anode metal into the holding furnace;

b. shaping the anode metal using a high surface area graphite mold;

c. solidifying the anode metal using a liquid while extruding the anode metal through the high surface area mold;

d. solidifying the anode metal by using a secondary cooling source, and

e. extracting the now solidified and shaped high surface anode metal,

f. wherein the shape of the high surface area anode further comprises a flat surface on one side and a ribbed surface on its opposite side;