CA1070260A - Method of electroforming on a metal substrate - Google Patents
Method of electroforming on a metal substrateInfo
- Publication number
- CA1070260A CA1070260A CA249,212A CA249212A CA1070260A CA 1070260 A CA1070260 A CA 1070260A CA 249212 A CA249212 A CA 249212A CA 1070260 A CA1070260 A CA 1070260A
- Authority
- CA
- Canada
- Prior art keywords
- acid
- master substrate
- solution
- aluminum
- nickel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D1/00—Electroforming
- C25D1/02—Tubes; Rings; Hollow bodies
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D1/00—Electroforming
Abstract
METHOD OF ELECTROFORMING
ON A METAL SUBSTRATE
ABSTRACT OF THE DISCLOSURE
A metal article is produced by: (1) providing an aluminum master substrate, the surface of which may be smooth or patterned; (2) making the aluminum matter substrate cathodic, in an acid or acid salt solution which will not etch aluminum, at a current density of between about 10 to 500A/sq. ft., at solution temperatures of up to about 50°C;
(3) coating the surface of the aluminum master substrate with a thin metal layer and (4) dissolving the aluminum master substrate, to provide a metal foil article that is a negative duplicate of the smooth or patterned aluminum master substrate surface.
ON A METAL SUBSTRATE
ABSTRACT OF THE DISCLOSURE
A metal article is produced by: (1) providing an aluminum master substrate, the surface of which may be smooth or patterned; (2) making the aluminum matter substrate cathodic, in an acid or acid salt solution which will not etch aluminum, at a current density of between about 10 to 500A/sq. ft., at solution temperatures of up to about 50°C;
(3) coating the surface of the aluminum master substrate with a thin metal layer and (4) dissolving the aluminum master substrate, to provide a metal foil article that is a negative duplicate of the smooth or patterned aluminum master substrate surface.
Description
BACKGROUND OF THE INYENTIC)N
Extremely thln~ patterned or irregular shaped metalllc ~oils are dlr~lcult to ra~ricate by con~entional--manufacturing techniques. Patterns can be pressed into metal ~oll using a metal embossing cyllnder, but such methods are orten not suitable ror e~tremely fine detalled patterns.
Plating thin metal coatings on aluminum substrate~
is one method of maklng thin wall shapes. Most platlng processe~, such as that tauæht by Coll-Palago~ in U.S.
3,726,771, require removal ~r the oxi~e on the aluminum, ror examp~le`by a HF dip, and then, metal deposltion under conditions that prevent~reoxidatlon ~f the aluminum ~ubstrate surrace.
In such ~ proces~, ~he deoxidizing can easily~de~troy the origlnal ~ini~h and detalled p~ttern or grain o~, the meta}
'substrate. The pattern on the ele~ctro~ormed ~oll w111 be Puzzy and iack r~ ne detail.~ -.. ~ - .. . .. .
' ' ' ` ' ~ : ` .
.
' ' 45, 777 7V~:iO
Cleaning processes, such as a simple room temperature nitric acid dip followed by application of a zinc petrolatum compound, as taught by Bonwitt ln U.S. 2,437,2~0, while cleaning without removing all the oxlde, do not provide a particularly suitable electro-deposit~on surface.
Cooke et al, in U.S. 3,718,547, teaches a con~inuous process for selectively removing m~gne~ium oxide rrom a magnesium containing aluminum substrate, and then reformlng an anodic oxide fllm by alternating current electrical treatment in sulfuric acid at 90C, prior to lacquering.
Such initial oxide removal could easily destroy the original finish at many points on the surface. ~-Bailey et al, in U.S. 3,844,906, rather than remove the aluminum oxide layer from a cylindrical mandrel, plates chromium over it and polishes the chromium, prior ko electroforming a nickel coating from a nickel sul~amate bath at 200 to 500 A/sq. ft. This process generates high bath temperatures requiring cooling, and involves the expense of chromium plating and polishing, which plating would not conform to any fine detail present on the mandrel.
What is needed then, is ~ method cf manufacturing thin metal foil which can successfully reproduce an extremely - -~
fine detailed pattern or mirror finl~h on the foil, from a ~-specially treated patterned, çmbossing pla~e or mandrel having a surface conducive to metal electro-coating. -SUMMARY OF TH~ INVENTION
... .. ..
This invention solves the above problem by electro-forming a metal foil upon the natural oxide of a dissolvable, patterned, smooth and/or mirror finished master substrate, preferably a tubular or cup shaped metal mandrel. The criti-
Extremely thln~ patterned or irregular shaped metalllc ~oils are dlr~lcult to ra~ricate by con~entional--manufacturing techniques. Patterns can be pressed into metal ~oll using a metal embossing cyllnder, but such methods are orten not suitable ror e~tremely fine detalled patterns.
Plating thin metal coatings on aluminum substrate~
is one method of maklng thin wall shapes. Most platlng processe~, such as that tauæht by Coll-Palago~ in U.S.
3,726,771, require removal ~r the oxi~e on the aluminum, ror examp~le`by a HF dip, and then, metal deposltion under conditions that prevent~reoxidatlon ~f the aluminum ~ubstrate surrace.
In such ~ proces~, ~he deoxidizing can easily~de~troy the origlnal ~ini~h and detalled p~ttern or grain o~, the meta}
'substrate. The pattern on the ele~ctro~ormed ~oll w111 be Puzzy and iack r~ ne detail.~ -.. ~ - .. . .. .
' ' ' ` ' ~ : ` .
.
' ' 45, 777 7V~:iO
Cleaning processes, such as a simple room temperature nitric acid dip followed by application of a zinc petrolatum compound, as taught by Bonwitt ln U.S. 2,437,2~0, while cleaning without removing all the oxlde, do not provide a particularly suitable electro-deposit~on surface.
Cooke et al, in U.S. 3,718,547, teaches a con~inuous process for selectively removing m~gne~ium oxide rrom a magnesium containing aluminum substrate, and then reformlng an anodic oxide fllm by alternating current electrical treatment in sulfuric acid at 90C, prior to lacquering.
Such initial oxide removal could easily destroy the original finish at many points on the surface. ~-Bailey et al, in U.S. 3,844,906, rather than remove the aluminum oxide layer from a cylindrical mandrel, plates chromium over it and polishes the chromium, prior ko electroforming a nickel coating from a nickel sul~amate bath at 200 to 500 A/sq. ft. This process generates high bath temperatures requiring cooling, and involves the expense of chromium plating and polishing, which plating would not conform to any fine detail present on the mandrel.
What is needed then, is ~ method cf manufacturing thin metal foil which can successfully reproduce an extremely - -~
fine detailed pattern or mirror finl~h on the foil, from a ~-specially treated patterned, çmbossing pla~e or mandrel having a surface conducive to metal electro-coating. -SUMMARY OF TH~ INVENTION
... .. ..
This invention solves the above problem by electro-forming a metal foil upon the natural oxide of a dissolvable, patterned, smooth and/or mirror finished master substrate, preferably a tubular or cup shaped metal mandrel. The criti-
-2-:. - . ~ . - . .-45,777 Z~
cal part of the method is the electrochemical cleaning of the mandrel prior to electroforming.
In the method o~ this invention: (1) an aluminum master substrate i5 provided~ having a patterned, gralned, smooth and/or mirror finish which is desired to be reproduced;
the surface being covered wlth ~n oxldlzed layer; (2) option-ally, olls and organic matter are removed by a sultable sol-vent; (3) the master substrate is made cathodic (negative) in an acld or acid salt solution which will not etch the aluminum beneath the oxide layer. A curren~ density of between about lOA/sq. ~t. to about 500A/sq. ft. is applied at solution temperatures of up to about 50C, to cause evolution of hydrogen gas upon the master substrate surface.
This combination electrochemical and mechanical process cleans the surface without removing all of the natural oxide layer at any point on the sur~ace, or destroying the original surface finish or any fine detail of the pattern, yet "electro-chemically activates" the sur~ace to prepare it for later metal deposition; (4) the treated master substrate is coated with a thin metal layer, preferably by electroforming in a suitable metallic solution, at a current density and for a tlme effective to plate the surface of the master substrate;
(5) the support substrate is then dissolved, preferably by a suitable alkali hydroxide solution and (6) optionally, any impurities or residue remainin~ on the patterned metal plating are removed by ultrasonic techniques or by a suitable acid or acid salt solution.
This method provides a metal ~oil article between about 0.2 mil to 50 mil$ thick, ~hich is a negative dupli-30 cate of the master substrate and which can have faithfully -~3-45,777 iO702~0 transferred thereto the smooth finish or all of the fine detailed pattern from the master substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the lnvention, reference may be made to the preferr-ed embodiments, exemplary of the inventlon, shown ln the aocompanylng drawlngs, in which:
Figure 1 shows, in magnif`ied cross section, a patterned master substrate, with a mirror smooth finish between the protuberances and lndentations ~orming the pattern;
Figure 2 shows, in magnified cross section, the master substrate made cath~de in acid or acid salt solution, with hydrogen gas evolution at the master substrate surface during the electro-cleaning step of this process;
Flgure 3 shows, in magnified cross sectlon, the -master substrate made cathode in a mçtallic solution with a -~
metal coating layer ~orming thereon, Figure 4 shows, in magnified cross section, the -~ -20 master substrate being dissolved by an alkali hydroxide ~
solution; and - i -~:. . .
Figure 5 shows, in magnified cross section, the - -, formed metal foil sheet, which is a negative duplicate of -~
the master substrate. -~ .
Referring now to Figure 1 of the drawings, a master substrate, having at least one finished surface which is desired to be reproduced, is shown as 10. In the method of this invention, the master substrate will be aluminum.
The aluminum may contain about 1/2-S wt.% copper or other l~5,777 ~ 2 ~ ~
metals, to improve machining properties. The master substrate can have a pattern of proturberances 11 and indentations 12, as well as a smooth or mirror flnished surface 13. Generally the surface will be smooth. The pat~ern can bo lmpressed by engraving or by a metal embosslng cyllnder and can be of extremely flne detall. A smooth surrace can be ach~eved by sanding and a polished mlrror ~lnished sur~ace can be lmpressed by a suitable die. The finiæhed surface will be covered by a natural oxldlzed layer 14.
The thlckness of ~he master substrate can range from about 0.001 inch ~o 0.25 inch (0.0025-0.62 cm.). It would be dlfficult to handle or pattern master substrates having a thickness less than about 0.001 inch, and difficult to dissolve the aluminum mandrel in a commercially feasible time at thicknesses greater than about 0.25 inch. The master alumlnum substrate can be flat, cylindrical, cup shaped with a hollow closed end or of an irregular configura-tion having grooves, slots and the like.
Figure 2 shows the master substrate in acid or acid salt electro-cleaning solution 21. The solutlon 21 will generally be a bath in a container and must be main- -tained at a temperature below about 50C. At higher tem-peratures the solutlon will easily allow the temperature at the solution-master substrate surface interface 22 to become high enough for the ac~id or acid salt solution to etch the aluminum master substrate surface.
The master substrate 10 is connected to the nega- -tive terminal of a power supply, and made cathodic in the solutlon 21 at a current density of between about lOA/sq.
ft. to about 500 A/sq. ft., preferably 10-120A/sq. ft. i.e., ~ -45,777 ~ 2 amps per square foot of master substrate surface area to be cleaned and plated (107-5,4Q0 A/sq. meter).
At current densities above 500A/sq. ~t., the acld or acid salt solut~on 21 wlll. completely d~.~solve the oxidlzed layer at points along the surface and attack and etch the aluminum surraae, causing loss o~ pattern de~inition and 6,`~ possibly ruining ~he surrace fln.ish.ev~r about 120A/~q. ft., ~or prolonged time periods, may generate heat surficient to cause the acid to start etchin~ the alumlnum. At current densitles below about 10A~sq. ft, no hydrogen will be formed, possibly due to reduction reactions in which hydrogen is not a by-product.
These current density ranges are critical in pro~
viding hydrogen gas 23 evolution, ~rom the oxldized, finished -~surface interface 22, effective to clean the aluminum surface without causing chemical or electrochemical attack of the aluminum surface by the solutio~ 21. The master substrate ~ ~
cannot be made anodic, or the solution may etch ~he base :~ -aluminum sur~ace. The anode may be a carbon, platinum, or other suitable material not attacked annodically by the acid or acid salt solution.
Only certain mineral, carboxylic, hydroxy, and ~;~
dicarboxylic acids and acid salts can be used as the solution 21 in the electro-cleaning step of this process. These acids should be relatively soluble in water so that the solution will have good conductivity, i.e., their solubility should be at least abou~ 9g/lOOg H20 at 20C. These acid and acid salts should not etch aluminum, i.e., they should offoc~
not chemically ~ h the aluminum sur~ace to make it soluble in the solution or cause the solid to change to an ionized ~5,777 ~7V260 DAase in solution, a drastic form of which would be complete dissolution. However, the term etch as used herein should not be considered an absolute term. The electro-cleaning solution should not substantially de~erlorate the surface rinish o~ the aluminum within ~he current densikies and time periods herein set forth.
Suitable electro-cleaning materials would lnclude solutions of nitrio acid, acetic acid, citric acid, oxalic acid, formic acid, propionic acid, butyric acid, tartaric acid, malic acid, glyceric acid, lactic acid, glycolic acid, malonic acid~ maleic acid and their sodium or potassium salts i.e., sodium nitrate, potassium nitrate, sodium acetate, potassium acetate, sodium citrate, potassium citrate, sodium oxalate and potassium oxalate, etc~ and mixtures thereof.
Sulfuric, hydrochloric, phosphoric and hydro-fluoric acid solutions will generally attack and etch the aluminum surface and are not suitable as an electro-cleaning material in this process, i.e., they will randomly break through the oxide layer and at least start to dissolve or degrade the base aluminum. The Preferred electro-cleaning solution is 2 wt.~ to 70 wt.% nitric acid (HNO3) in water, which provides very effective "electrochemical activation"
without complete oxide removal. Depending on the current density, the cathodic aluminum surface will be cleaned effectively after about 10 seconds to 1200 seconds treatment -(20 minutes) in the electro-cleanin~ solution, generally up to 600 seconds is sufficient.
In the electro-cleaning step, oil and grease remaining in the aluminum oxide matrix, on the surface of 45,777 10~702ti0 c~ r~
r~ the aluminum substrate, ~ dissolved and oxide agglomerates mechanically removed or displaced by H2 gas evolution. The surface ls "electrochemically activated", i.e., the alumlnum oxide layer remains, but i9 thinned out to provlde a uniform~y thick, relatively smooth oxide layer 24 without large agglom-erates, which closely conforms to the finish on the master substrate. This uniformly thick aluminum oxide layer has a uniform resistance which will allow even, pin hole free nickel electrodeposition. In this step the aluminum oxide layer remains, no other ions being substituted for the aluminum.
Prior to electro-cleaning in solution 21, an initial degreasing step may optionally be used. This can be . , - .
accomplished by dipping the master substrate in a suitable solvent which effectively removes oil and organlc matter. ~;~
Suitable solvents would include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol and the like, ketones such as acetone, methyl ethyl ketone and the like, trichlorethylene, -~ -perchlorethylene and the like. A 10 second to 120 second -20 dip will generally be effective for cleaning and should be ~ -~
followed by air drying.
The cleaned and activated aluminum master substrate is next placed in a metallic solution bath and made cathodic, as shown in Figure 3. The master substrate 10 is connected to the negative terminal of a power supply. A-DC potential is applied at a predetermined current density and for a time effective to deposit a metal layer 31, which coats the surface of the master substrate. The current density range is a function of the individual plating system. Effective current densities will range between about 5A/sq. ft. to 1~70260 about 150A/sq. ft. of surface area to be plated. Processing difficulties start to occur in this system at over about 150A/sq. ft.
The anode may be a nonconsumable carbon electrodo or one that will replenish metal ions to the bath such as nickel when nickel ls to be plated. The anode ~an be in bar, plate, mesh or chip form~ When a nickel anode is used it may contain a small propor~ion of sul~ur, about 0.02% to 0.04%, to promote dissolution. At about 20A/sq. ft, the metal layer will be deposited at a rate of about O.OOl inch per hour. Pinhole free metal layers can be coated to thick- -nesses of between about 0.0002 inch to about 0.050 inch (0.000005-0.00125 mm.) over a time period of about 1/2 hour to 50 hours. ~ -The metal layer can be applied by suitable spraying techniques, but an electroforming technique from a metallic solution 32 is preferred. The solutiQn should be maintained at a temperature of between about 20C to about 85C de-pending on the metallic solution use~. Suitable metal coating materials must be compatible with aluminum, yet not attacked by the alkali hydroxide or other solution used to dissolve the master substrate. Suitable metal coating materials would include solutions of nickel sulfamate, nickel sulfate, gold cyanide, silver cyanide, copper cyanide, copper sulfate, copper fluoroborate, tin sulfate, cadmium cyanide, cadmium-fluoroborate3 cobalt sulfate, cobalt sul-famate, platinum sulfamate, and thç like to provide nickel, gold, silver, copper, tin, cadmium, cobalt or platinum foil.
The preferred metal coating materials are solutions selected from nickel sulfamate or nic~el sulfate, whlch have _g_ 4S,777 107~Z~i~
a pH of between about 2 to 5~. The nickel bath temperature should range between about 35G to about 65C. Hydrolysls of the nlckel solutlon bath can occur at temperatures over about 65~
The characterlstlcs and operatln~ conditlons of the nickel solutlon bath and the others ~hat can be used are well known in the platlng art. For example, suitable nickel sulfamate bath~ could contain a buffer such as boric acld, present in amounts raneing from lOg/llter to saturatlon ln addition to between about 200 to 700g/liter of nickel 8ul-phamate. A typical nlckel electrocoating bath would contain about 300g/liter of nickel sul~amate (about 55g/llter of nlckel lon); about 40 g/liter of borlc acid and the balance water operated at a pH of about 4. -~ -Chlorlde or bromide ion, in amounts up to about 25g/liter, may be present, generally as nickel chloride or nickel bromide, to increase anode dissolu~ion. The bath may also contain up to about lg/liter of a wetting agent such as sodium lauryl sulfate or sodium lauryl sulfoacetate, which ~-provides effective surface tension properties in the bath for superlor platlng. The usual impurities known to be -harmful in nickel plating, such as zinc, chromium and lead should be controlled ko low levels. When electrocoating from gold, silver, copper, tin, cadmium, cobalt or platinum baths suitable ad~ustments known to those in the art can be made regarding the amount of buffer if any to be added.
Referring now to Flgure 4, an alkali hydroxlde or other suitable solution 41 known to dissolve aluminum and its oxides is applied to the aluminum master substrate 10, for a time effective to dissolve the master substrake 10 and -.
1~5,777 ~O'~UZ~
its thinned adherent oxidized coating 24, leaving the metal foil sheet, shown as 51 in Figure 5. The aluminum dissolving solution should be maintained at a temperature of between about 20~C to about 85C. Clenerally khe coated master substrate will be placed in a bath of khe dissolvin~ solutlon for a time period of ~bout 2 hours to about 6 hours dependin~
on the thickness of th~ aluminum substrate. The preferred dlssolving solutlons are 10 wt.~ to 50 wt.% sodium hydroxide or potassium hydroxide in water. Selected acid solutlons may be used to dissolve the aluminum master substrate but they must not attack the metal coating 31.
After dissolution of the aluminum master substrate, some copper impuritles from the aluminum may be attached to the metal foil sheet 51 at the surface 52. Most other im-purities do not seem tq presen~ this problem. These impurities ~ -are in the form of a single atomic layer of atoms and as small amounts of microscopic agglomerates. These impurlties may be removed by ultrasonic techniques using water or by applying an acid or acid salt which will not attaçk the primary metal of the metal foil sheet. Suitable materials for this selective etching step would include solutions of nitric acid, mixtures of nitric acid and sulfuric acid, sodium cyanide, potassium cyanide and the like. For a nickel foil sheet, a 5 second to 20 second dip in 1.5 wt.%
to 45 wt.% nitric acid (HNO3) in water at between about 25C
to 35C is preferred, The resulting metal foil, shown in Figure 5, is between about 0.0002 inch to 0.050 inch thick and a negative duplicate of the master aluminum substrate. It can be flak, cylindrical, cup shaped or of highly irregular configuration.
45~777 ~0702~0 It will have exactly reproduced the surface flnlsh on the master substrate. The finished foil article will be pinhole free, structurally strong and ductile. Thls me~hod is particularly useful in maki~g crack ~ree, theoretically dense, -thin-wall nlckel cups o~ varylng diameters which can be concentrically stacked and used in vacuum multi-foil insulation applications. The ~ollowing non-llmit1ng example is illustratl~e o~ the metal foil~ that can be ~ormed using this method.
A high-density, thin wall n~ckel GUp, having a smooth interior, was fabricated by an electroforming technlque using a nickel sulfamate plating bat~ and a polished, specially ~ -cleaned and "electrochemically activated" aluminum mandrel substrate.
The aluminum mandrel substrate was made of 2024 aluminum which contained about 96 wt.% aluminum and about 4 wt.% copper. The mandrel had a hollow 8 inch (20.3 cm.) long cup shape, with a 1.0 inch (2.54 cm.~ outside diameter and a 1/8 lnch (a.32 cm.) wall thicknessO The closed outside end of the cup shaped mandrel was machined to a 1/8 inch radius so that it would have sm~oth corners, The outside of the mandrel was polished to a Mo t 6 surface finish, i.e. a smooth finish, where the distance between ad~acent microscoplc ridges and valleys on the surface is about 0. ooooo6 inch.
The aluminum cup shaped mandrel was cleaned by dipping it in room temperature trichloroethylene, rinsing it of~ in room temperature acetone and then letting it drip dry.
The cup shaped aluminum mandrel was then placed in a tank contalning 14 wt.% aqueous HN03 solution. The mandrel 45,777 ~ 07 V ~ ~ 0 was made cathodic at 60A~s~. ~t. Or outslde cup sur~ace, by connecting lt to a direct current power supply. The anode was a platlnum mesh. The bath temperature was 25C and the cleaning-"activating" tlme was 60 ~econds.
During thl~ electrocleaning-activatlng step, hydrogen gas was evolved at the mandrel surrace-solution lnterrace. The hydrogen ~as scrubbed the surrace clean o~
any resldual pollshing compound and other sur~ace debrl~
including aluminum oxide agglomerates. The nitric acld slowly reacted wlth the alumln~m oxide layer on the aluminum base mandrel, thlnning lt out, and making it a uni~orm thickness with a smooth sur~ace, but not removlng it. ~he aluminum base surface o~ the mandrel was not etched, ~ttacked or degraded in any way. The smooth, unlform agglomerate ~ree oxide surface provides an "activated" surface for electro~orming, since the oxide resistance i8 uni~orm. Thl~
will result in very smooth, even, pinhole free subsequent metal coat~ng.
The cleaned-activated, cup shaped, aluminum mandrel-; 20 was rinsed and air dried. It was then placedg closed bottom side down, so that the solution only contacted the outs~de walls, ln a tank contalning nickel sul~amate ~etal plating solution. The solution contained about 300 g ~f nickel ~ulfamate~
liter o~ water and about 40 g of boric acid/liter o~ water, operated at a pH o~ about 4. The mandrel wa~ made cathodlc -at a current density o~ 20Aisq. ft. of outslde cup sur~ace, by connectlng lt to a dlrect current power supply~ The anode wa~ a 95 wt.% pure nickel bar conta~ning an er~ective - small amount o~ sulrur to help electrode dissolutlon and replenishment o~ nlckel ions ln the bath. Thc bath temper-45,777 10702~i0 ature was 50C and the plating tlme was 120 minutes. During this metal coating step nickel was deposited on the outslde surface of the cup as a layer about 0.002 inch (0.005 cm.) thick.
The nickel plated, hollow, cup shaped aluminum mandrel was then plaoed in a tank contalning 150g NaOH/liter of water, l.e , 15 wt.%, at 90C. A~ter about 3 hours the aluminum mandrel and its attached oxide layer was dissolved, leaving a thin metal foil cup. It appeared that some copper from the mandrel coated the interior of the nickel cup. To eliminate the copper, the cup was rinsed, drip dried and placed in a tank containing an aqueous mixture of 14 wt.%
nitric acid and 53 wt.% sulfuric acid, at 25C for about 10 seconds. This solution dissolved the copper deposits but did not etch or attack the nickel surface.
The finished nickel cup had a bright interior surface finish with a low porosity. The finish was similar to that on the polished surface of the aluminum -cup used as the dissolvable mandrel. Microscopic examination at 400 power revealed no pitting. The open end o~ the free standing cup could be repeatedly flexed without permanent deformation or work hardening.
A second cup was made as described above except for activating in 5 wt.% aqueous HNO3 solut~on, for 180 seconds and nickel pla~ing for 30 minutes at 20A/sq. ft. of outside cup surface. A cup having a wall thickness o~ -0.0005 inch was obtained, having a bright, very smooth interior surface flnish with nQ pitting.
Other electra-cleaning acids have been used to electrochemically activate 2024 aluminum mandrels having a 45,777 ~0~()2~;0 No. 6 surface finlsh, using the same procedures followed above. Acetic acid was used at 15 wt.% concentratlon for 10 minutes at 35A/sq. ft.; citric acid was used at 10 wt.%
concentration for 10 minutes at 50A/s~. ~t.; oxalic acid was used at 10 wt.% concentration .ror ~ minutes at 120A/~q. ft.;
~ormlc acid was used at 10 wt.% concentration ~or 10 minutes at 63A/sq. ft. In all cases a platinum mesh anode was used wlth a bath temperature of 25C. During these electrocleaning-"activatlng" experiments, evolved hydrogen gas scrubbed the aluminum mandrel surfaces and the acids provided a uniform oxlde thlckness wlthout etching or degrading the mandrel.
The cleaned-"actlvated" cup shaped mandrels were then rlnsed, air drled and coated with 0.0005 inch thlck nickel from a nlckel sul~amate bath similar to that described above, using a 30 minute plating time. The plating was smooth and pin- - -hole free.
The inside of a cup shaped aluminum mandrel could also be el~ctro-plated using this process. Similarly, flat aluminum substrates, having a sm~oth or patterned surface could be coated using this process. For example, the non-patterned side-of a flat mandrel could be coverçd, prior to lntroduction into the plat ng bath, with a ~ilm of material, such as petroleum ~elly, which would provide a non-plateable surface. This ~aterlal could then be removed prior to dis- .
solution of t~e mandrel. A~ter the mandrel is dissolved, a sheet o~ thin, smooth or patterned nickel, gold, platlnum, silver, copper, tin, cadmium or cobalt foil would remain, Such foil could be used in ~ewelry and many other applications.
Cups made by the method described above have pro-vided the only solution for producing vacuum multi-foil con-.
45, 777 1070Z~:iO
centric cup thermal insu~ati~n in a completely implantable nuclear powered artl~iclal heart. This fabricatlon technique provldes ultra dense, ultra thln, ultra smooth cups, utilized to ellminate high heat 108~ areas ~uoh as mltred corner Joint 8 .
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cal part of the method is the electrochemical cleaning of the mandrel prior to electroforming.
In the method o~ this invention: (1) an aluminum master substrate i5 provided~ having a patterned, gralned, smooth and/or mirror finish which is desired to be reproduced;
the surface being covered wlth ~n oxldlzed layer; (2) option-ally, olls and organic matter are removed by a sultable sol-vent; (3) the master substrate is made cathodic (negative) in an acld or acid salt solution which will not etch the aluminum beneath the oxide layer. A curren~ density of between about lOA/sq. ~t. to about 500A/sq. ft. is applied at solution temperatures of up to about 50C, to cause evolution of hydrogen gas upon the master substrate surface.
This combination electrochemical and mechanical process cleans the surface without removing all of the natural oxide layer at any point on the sur~ace, or destroying the original surface finish or any fine detail of the pattern, yet "electro-chemically activates" the sur~ace to prepare it for later metal deposition; (4) the treated master substrate is coated with a thin metal layer, preferably by electroforming in a suitable metallic solution, at a current density and for a tlme effective to plate the surface of the master substrate;
(5) the support substrate is then dissolved, preferably by a suitable alkali hydroxide solution and (6) optionally, any impurities or residue remainin~ on the patterned metal plating are removed by ultrasonic techniques or by a suitable acid or acid salt solution.
This method provides a metal ~oil article between about 0.2 mil to 50 mil$ thick, ~hich is a negative dupli-30 cate of the master substrate and which can have faithfully -~3-45,777 iO702~0 transferred thereto the smooth finish or all of the fine detailed pattern from the master substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the lnvention, reference may be made to the preferr-ed embodiments, exemplary of the inventlon, shown ln the aocompanylng drawlngs, in which:
Figure 1 shows, in magnif`ied cross section, a patterned master substrate, with a mirror smooth finish between the protuberances and lndentations ~orming the pattern;
Figure 2 shows, in magnified cross section, the master substrate made cath~de in acid or acid salt solution, with hydrogen gas evolution at the master substrate surface during the electro-cleaning step of this process;
Flgure 3 shows, in magnified cross sectlon, the -master substrate made cathode in a mçtallic solution with a -~
metal coating layer ~orming thereon, Figure 4 shows, in magnified cross section, the -~ -20 master substrate being dissolved by an alkali hydroxide ~
solution; and - i -~:. . .
Figure 5 shows, in magnified cross section, the - -, formed metal foil sheet, which is a negative duplicate of -~
the master substrate. -~ .
Referring now to Figure 1 of the drawings, a master substrate, having at least one finished surface which is desired to be reproduced, is shown as 10. In the method of this invention, the master substrate will be aluminum.
The aluminum may contain about 1/2-S wt.% copper or other l~5,777 ~ 2 ~ ~
metals, to improve machining properties. The master substrate can have a pattern of proturberances 11 and indentations 12, as well as a smooth or mirror flnished surface 13. Generally the surface will be smooth. The pat~ern can bo lmpressed by engraving or by a metal embosslng cyllnder and can be of extremely flne detall. A smooth surrace can be ach~eved by sanding and a polished mlrror ~lnished sur~ace can be lmpressed by a suitable die. The finiæhed surface will be covered by a natural oxldlzed layer 14.
The thlckness of ~he master substrate can range from about 0.001 inch ~o 0.25 inch (0.0025-0.62 cm.). It would be dlfficult to handle or pattern master substrates having a thickness less than about 0.001 inch, and difficult to dissolve the aluminum mandrel in a commercially feasible time at thicknesses greater than about 0.25 inch. The master alumlnum substrate can be flat, cylindrical, cup shaped with a hollow closed end or of an irregular configura-tion having grooves, slots and the like.
Figure 2 shows the master substrate in acid or acid salt electro-cleaning solution 21. The solutlon 21 will generally be a bath in a container and must be main- -tained at a temperature below about 50C. At higher tem-peratures the solutlon will easily allow the temperature at the solution-master substrate surface interface 22 to become high enough for the ac~id or acid salt solution to etch the aluminum master substrate surface.
The master substrate 10 is connected to the nega- -tive terminal of a power supply, and made cathodic in the solutlon 21 at a current density of between about lOA/sq.
ft. to about 500 A/sq. ft., preferably 10-120A/sq. ft. i.e., ~ -45,777 ~ 2 amps per square foot of master substrate surface area to be cleaned and plated (107-5,4Q0 A/sq. meter).
At current densities above 500A/sq. ~t., the acld or acid salt solut~on 21 wlll. completely d~.~solve the oxidlzed layer at points along the surface and attack and etch the aluminum surraae, causing loss o~ pattern de~inition and 6,`~ possibly ruining ~he surrace fln.ish.ev~r about 120A/~q. ft., ~or prolonged time periods, may generate heat surficient to cause the acid to start etchin~ the alumlnum. At current densitles below about 10A~sq. ft, no hydrogen will be formed, possibly due to reduction reactions in which hydrogen is not a by-product.
These current density ranges are critical in pro~
viding hydrogen gas 23 evolution, ~rom the oxldized, finished -~surface interface 22, effective to clean the aluminum surface without causing chemical or electrochemical attack of the aluminum surface by the solutio~ 21. The master substrate ~ ~
cannot be made anodic, or the solution may etch ~he base :~ -aluminum sur~ace. The anode may be a carbon, platinum, or other suitable material not attacked annodically by the acid or acid salt solution.
Only certain mineral, carboxylic, hydroxy, and ~;~
dicarboxylic acids and acid salts can be used as the solution 21 in the electro-cleaning step of this process. These acids should be relatively soluble in water so that the solution will have good conductivity, i.e., their solubility should be at least abou~ 9g/lOOg H20 at 20C. These acid and acid salts should not etch aluminum, i.e., they should offoc~
not chemically ~ h the aluminum sur~ace to make it soluble in the solution or cause the solid to change to an ionized ~5,777 ~7V260 DAase in solution, a drastic form of which would be complete dissolution. However, the term etch as used herein should not be considered an absolute term. The electro-cleaning solution should not substantially de~erlorate the surface rinish o~ the aluminum within ~he current densikies and time periods herein set forth.
Suitable electro-cleaning materials would lnclude solutions of nitrio acid, acetic acid, citric acid, oxalic acid, formic acid, propionic acid, butyric acid, tartaric acid, malic acid, glyceric acid, lactic acid, glycolic acid, malonic acid~ maleic acid and their sodium or potassium salts i.e., sodium nitrate, potassium nitrate, sodium acetate, potassium acetate, sodium citrate, potassium citrate, sodium oxalate and potassium oxalate, etc~ and mixtures thereof.
Sulfuric, hydrochloric, phosphoric and hydro-fluoric acid solutions will generally attack and etch the aluminum surface and are not suitable as an electro-cleaning material in this process, i.e., they will randomly break through the oxide layer and at least start to dissolve or degrade the base aluminum. The Preferred electro-cleaning solution is 2 wt.~ to 70 wt.% nitric acid (HNO3) in water, which provides very effective "electrochemical activation"
without complete oxide removal. Depending on the current density, the cathodic aluminum surface will be cleaned effectively after about 10 seconds to 1200 seconds treatment -(20 minutes) in the electro-cleanin~ solution, generally up to 600 seconds is sufficient.
In the electro-cleaning step, oil and grease remaining in the aluminum oxide matrix, on the surface of 45,777 10~702ti0 c~ r~
r~ the aluminum substrate, ~ dissolved and oxide agglomerates mechanically removed or displaced by H2 gas evolution. The surface ls "electrochemically activated", i.e., the alumlnum oxide layer remains, but i9 thinned out to provlde a uniform~y thick, relatively smooth oxide layer 24 without large agglom-erates, which closely conforms to the finish on the master substrate. This uniformly thick aluminum oxide layer has a uniform resistance which will allow even, pin hole free nickel electrodeposition. In this step the aluminum oxide layer remains, no other ions being substituted for the aluminum.
Prior to electro-cleaning in solution 21, an initial degreasing step may optionally be used. This can be . , - .
accomplished by dipping the master substrate in a suitable solvent which effectively removes oil and organlc matter. ~;~
Suitable solvents would include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol and the like, ketones such as acetone, methyl ethyl ketone and the like, trichlorethylene, -~ -perchlorethylene and the like. A 10 second to 120 second -20 dip will generally be effective for cleaning and should be ~ -~
followed by air drying.
The cleaned and activated aluminum master substrate is next placed in a metallic solution bath and made cathodic, as shown in Figure 3. The master substrate 10 is connected to the negative terminal of a power supply. A-DC potential is applied at a predetermined current density and for a time effective to deposit a metal layer 31, which coats the surface of the master substrate. The current density range is a function of the individual plating system. Effective current densities will range between about 5A/sq. ft. to 1~70260 about 150A/sq. ft. of surface area to be plated. Processing difficulties start to occur in this system at over about 150A/sq. ft.
The anode may be a nonconsumable carbon electrodo or one that will replenish metal ions to the bath such as nickel when nickel ls to be plated. The anode ~an be in bar, plate, mesh or chip form~ When a nickel anode is used it may contain a small propor~ion of sul~ur, about 0.02% to 0.04%, to promote dissolution. At about 20A/sq. ft, the metal layer will be deposited at a rate of about O.OOl inch per hour. Pinhole free metal layers can be coated to thick- -nesses of between about 0.0002 inch to about 0.050 inch (0.000005-0.00125 mm.) over a time period of about 1/2 hour to 50 hours. ~ -The metal layer can be applied by suitable spraying techniques, but an electroforming technique from a metallic solution 32 is preferred. The solutiQn should be maintained at a temperature of between about 20C to about 85C de-pending on the metallic solution use~. Suitable metal coating materials must be compatible with aluminum, yet not attacked by the alkali hydroxide or other solution used to dissolve the master substrate. Suitable metal coating materials would include solutions of nickel sulfamate, nickel sulfate, gold cyanide, silver cyanide, copper cyanide, copper sulfate, copper fluoroborate, tin sulfate, cadmium cyanide, cadmium-fluoroborate3 cobalt sulfate, cobalt sul-famate, platinum sulfamate, and thç like to provide nickel, gold, silver, copper, tin, cadmium, cobalt or platinum foil.
The preferred metal coating materials are solutions selected from nickel sulfamate or nic~el sulfate, whlch have _g_ 4S,777 107~Z~i~
a pH of between about 2 to 5~. The nickel bath temperature should range between about 35G to about 65C. Hydrolysls of the nlckel solutlon bath can occur at temperatures over about 65~
The characterlstlcs and operatln~ conditlons of the nickel solutlon bath and the others ~hat can be used are well known in the platlng art. For example, suitable nickel sulfamate bath~ could contain a buffer such as boric acld, present in amounts raneing from lOg/llter to saturatlon ln addition to between about 200 to 700g/liter of nickel 8ul-phamate. A typical nlckel electrocoating bath would contain about 300g/liter of nickel sul~amate (about 55g/llter of nlckel lon); about 40 g/liter of borlc acid and the balance water operated at a pH of about 4. -~ -Chlorlde or bromide ion, in amounts up to about 25g/liter, may be present, generally as nickel chloride or nickel bromide, to increase anode dissolu~ion. The bath may also contain up to about lg/liter of a wetting agent such as sodium lauryl sulfate or sodium lauryl sulfoacetate, which ~-provides effective surface tension properties in the bath for superlor platlng. The usual impurities known to be -harmful in nickel plating, such as zinc, chromium and lead should be controlled ko low levels. When electrocoating from gold, silver, copper, tin, cadmium, cobalt or platinum baths suitable ad~ustments known to those in the art can be made regarding the amount of buffer if any to be added.
Referring now to Flgure 4, an alkali hydroxlde or other suitable solution 41 known to dissolve aluminum and its oxides is applied to the aluminum master substrate 10, for a time effective to dissolve the master substrake 10 and -.
1~5,777 ~O'~UZ~
its thinned adherent oxidized coating 24, leaving the metal foil sheet, shown as 51 in Figure 5. The aluminum dissolving solution should be maintained at a temperature of between about 20~C to about 85C. Clenerally khe coated master substrate will be placed in a bath of khe dissolvin~ solutlon for a time period of ~bout 2 hours to about 6 hours dependin~
on the thickness of th~ aluminum substrate. The preferred dlssolving solutlons are 10 wt.~ to 50 wt.% sodium hydroxide or potassium hydroxide in water. Selected acid solutlons may be used to dissolve the aluminum master substrate but they must not attack the metal coating 31.
After dissolution of the aluminum master substrate, some copper impuritles from the aluminum may be attached to the metal foil sheet 51 at the surface 52. Most other im-purities do not seem tq presen~ this problem. These impurities ~ -are in the form of a single atomic layer of atoms and as small amounts of microscopic agglomerates. These impurlties may be removed by ultrasonic techniques using water or by applying an acid or acid salt which will not attaçk the primary metal of the metal foil sheet. Suitable materials for this selective etching step would include solutions of nitric acid, mixtures of nitric acid and sulfuric acid, sodium cyanide, potassium cyanide and the like. For a nickel foil sheet, a 5 second to 20 second dip in 1.5 wt.%
to 45 wt.% nitric acid (HNO3) in water at between about 25C
to 35C is preferred, The resulting metal foil, shown in Figure 5, is between about 0.0002 inch to 0.050 inch thick and a negative duplicate of the master aluminum substrate. It can be flak, cylindrical, cup shaped or of highly irregular configuration.
45~777 ~0702~0 It will have exactly reproduced the surface flnlsh on the master substrate. The finished foil article will be pinhole free, structurally strong and ductile. Thls me~hod is particularly useful in maki~g crack ~ree, theoretically dense, -thin-wall nlckel cups o~ varylng diameters which can be concentrically stacked and used in vacuum multi-foil insulation applications. The ~ollowing non-llmit1ng example is illustratl~e o~ the metal foil~ that can be ~ormed using this method.
A high-density, thin wall n~ckel GUp, having a smooth interior, was fabricated by an electroforming technlque using a nickel sulfamate plating bat~ and a polished, specially ~ -cleaned and "electrochemically activated" aluminum mandrel substrate.
The aluminum mandrel substrate was made of 2024 aluminum which contained about 96 wt.% aluminum and about 4 wt.% copper. The mandrel had a hollow 8 inch (20.3 cm.) long cup shape, with a 1.0 inch (2.54 cm.~ outside diameter and a 1/8 lnch (a.32 cm.) wall thicknessO The closed outside end of the cup shaped mandrel was machined to a 1/8 inch radius so that it would have sm~oth corners, The outside of the mandrel was polished to a Mo t 6 surface finish, i.e. a smooth finish, where the distance between ad~acent microscoplc ridges and valleys on the surface is about 0. ooooo6 inch.
The aluminum cup shaped mandrel was cleaned by dipping it in room temperature trichloroethylene, rinsing it of~ in room temperature acetone and then letting it drip dry.
The cup shaped aluminum mandrel was then placed in a tank contalning 14 wt.% aqueous HN03 solution. The mandrel 45,777 ~ 07 V ~ ~ 0 was made cathodic at 60A~s~. ~t. Or outslde cup sur~ace, by connecting lt to a direct current power supply. The anode was a platlnum mesh. The bath temperature was 25C and the cleaning-"activating" tlme was 60 ~econds.
During thl~ electrocleaning-activatlng step, hydrogen gas was evolved at the mandrel surrace-solution lnterrace. The hydrogen ~as scrubbed the surrace clean o~
any resldual pollshing compound and other sur~ace debrl~
including aluminum oxide agglomerates. The nitric acld slowly reacted wlth the alumln~m oxide layer on the aluminum base mandrel, thlnning lt out, and making it a uni~orm thickness with a smooth sur~ace, but not removlng it. ~he aluminum base surface o~ the mandrel was not etched, ~ttacked or degraded in any way. The smooth, unlform agglomerate ~ree oxide surface provides an "activated" surface for electro~orming, since the oxide resistance i8 uni~orm. Thl~
will result in very smooth, even, pinhole free subsequent metal coat~ng.
The cleaned-activated, cup shaped, aluminum mandrel-; 20 was rinsed and air dried. It was then placedg closed bottom side down, so that the solution only contacted the outs~de walls, ln a tank contalning nickel sul~amate ~etal plating solution. The solution contained about 300 g ~f nickel ~ulfamate~
liter o~ water and about 40 g of boric acid/liter o~ water, operated at a pH o~ about 4. The mandrel wa~ made cathodlc -at a current density o~ 20Aisq. ft. of outslde cup sur~ace, by connectlng lt to a dlrect current power supply~ The anode wa~ a 95 wt.% pure nickel bar conta~ning an er~ective - small amount o~ sulrur to help electrode dissolutlon and replenishment o~ nlckel ions ln the bath. Thc bath temper-45,777 10702~i0 ature was 50C and the plating tlme was 120 minutes. During this metal coating step nickel was deposited on the outslde surface of the cup as a layer about 0.002 inch (0.005 cm.) thick.
The nickel plated, hollow, cup shaped aluminum mandrel was then plaoed in a tank contalning 150g NaOH/liter of water, l.e , 15 wt.%, at 90C. A~ter about 3 hours the aluminum mandrel and its attached oxide layer was dissolved, leaving a thin metal foil cup. It appeared that some copper from the mandrel coated the interior of the nickel cup. To eliminate the copper, the cup was rinsed, drip dried and placed in a tank containing an aqueous mixture of 14 wt.%
nitric acid and 53 wt.% sulfuric acid, at 25C for about 10 seconds. This solution dissolved the copper deposits but did not etch or attack the nickel surface.
The finished nickel cup had a bright interior surface finish with a low porosity. The finish was similar to that on the polished surface of the aluminum -cup used as the dissolvable mandrel. Microscopic examination at 400 power revealed no pitting. The open end o~ the free standing cup could be repeatedly flexed without permanent deformation or work hardening.
A second cup was made as described above except for activating in 5 wt.% aqueous HNO3 solut~on, for 180 seconds and nickel pla~ing for 30 minutes at 20A/sq. ft. of outside cup surface. A cup having a wall thickness o~ -0.0005 inch was obtained, having a bright, very smooth interior surface flnish with nQ pitting.
Other electra-cleaning acids have been used to electrochemically activate 2024 aluminum mandrels having a 45,777 ~0~()2~;0 No. 6 surface finlsh, using the same procedures followed above. Acetic acid was used at 15 wt.% concentratlon for 10 minutes at 35A/sq. ft.; citric acid was used at 10 wt.%
concentration for 10 minutes at 50A/s~. ~t.; oxalic acid was used at 10 wt.% concentration .ror ~ minutes at 120A/~q. ft.;
~ormlc acid was used at 10 wt.% concentration ~or 10 minutes at 63A/sq. ft. In all cases a platinum mesh anode was used wlth a bath temperature of 25C. During these electrocleaning-"activatlng" experiments, evolved hydrogen gas scrubbed the aluminum mandrel surfaces and the acids provided a uniform oxlde thlckness wlthout etching or degrading the mandrel.
The cleaned-"actlvated" cup shaped mandrels were then rlnsed, air drled and coated with 0.0005 inch thlck nickel from a nlckel sul~amate bath similar to that described above, using a 30 minute plating time. The plating was smooth and pin- - -hole free.
The inside of a cup shaped aluminum mandrel could also be el~ctro-plated using this process. Similarly, flat aluminum substrates, having a sm~oth or patterned surface could be coated using this process. For example, the non-patterned side-of a flat mandrel could be coverçd, prior to lntroduction into the plat ng bath, with a ~ilm of material, such as petroleum ~elly, which would provide a non-plateable surface. This ~aterlal could then be removed prior to dis- .
solution of t~e mandrel. A~ter the mandrel is dissolved, a sheet o~ thin, smooth or patterned nickel, gold, platlnum, silver, copper, tin, cadmium or cobalt foil would remain, Such foil could be used in ~ewelry and many other applications.
Cups made by the method described above have pro-vided the only solution for producing vacuum multi-foil con-.
45, 777 1070Z~:iO
centric cup thermal insu~ati~n in a completely implantable nuclear powered artl~iclal heart. This fabricatlon technique provldes ultra dense, ultra thln, ultra smooth cups, utilized to ellminate high heat 108~ areas ~uoh as mltred corner Joint 8 .
- -'' , -". : ~' - . ~
. . ' ' -. ' ', - . , ".
: - ~ - . - .
- - - .. .
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.
, ,- " ', .
.
Claims (10)
1. A method of making a metal article comprising the steps of:
(1) providing an aluminum master substrate having at least one surface which is desired to be reproduced, said surface being covered with an oxidized layer;
(2) making the aluminum master substrate cathodic at a current density of between about 10A/sq. ft. to about 500A/sq. ft., in an aqueous electrically conducting solution selected from the group consisting of an acid solution or acid salt solution or mixtures thereof which will not etch aluminum, said solution having a temperature of up to about 50°C, said current causing evolution of gas at the solution-oxidized surface interface and chemical activation effective to thin and smooth the oxidized layer without removing it;
(3) coating the smoothed, oxidized surface of the aluminum master substrate with a thin metal layer; and (4) dissolving the aluminum master substrate and the attached oxidized layer, to provide a metal article having a surface that is the negative duplicate of the surface of the master substrate.
(1) providing an aluminum master substrate having at least one surface which is desired to be reproduced, said surface being covered with an oxidized layer;
(2) making the aluminum master substrate cathodic at a current density of between about 10A/sq. ft. to about 500A/sq. ft., in an aqueous electrically conducting solution selected from the group consisting of an acid solution or acid salt solution or mixtures thereof which will not etch aluminum, said solution having a temperature of up to about 50°C, said current causing evolution of gas at the solution-oxidized surface interface and chemical activation effective to thin and smooth the oxidized layer without removing it;
(3) coating the smoothed, oxidized surface of the aluminum master substrate with a thin metal layer; and (4) dissolving the aluminum master substrate and the attached oxidized layer, to provide a metal article having a surface that is the negative duplicate of the surface of the master substrate.
2. The method of claim 1 wherein the metal layer coacted in step (3) is selected from the group consisting of nickel, gold, platinum, silver, copper, tin, cadmium and cobalt, the aluminum master substrate is dissolved in an aqueous alkali hydroxide solution and the acid or acid salt of the electrically conducting aqueous solution in step (2) has a solubility of not less than about 9g/100g H2O at 20°C.
3. The method of claim 1 wherein the aqueous, electrically conducting solution in step (2) is selected from the group consisting of nitric acid, acetic acid, citric acid, oxalic acid, formic acid, propionic acid, butyric acid, tartaric acid, malic acid, glyceric acid, lactic acid, glycolic acid, malonic acid, maleic acid and their sodium and potassium salts and mixtures thereof and the current density is applied in step (2) for about 10-1200 seconds.
4. The method of claim 1 including cleaning the master substrate between steps (1) and (2) in a suitable solvent to remove oil and organic matter.
5. The method of claim 2 wherein the master sub-strate is between about 0.001 inch and 0.25 inch thick and is coated by making the master substrate cathodic at a current density of between about 5A/sq. ft. to about 150A/
sq. ft. for a time effective to deposit a metal layer about 0.0002 inch to 0.050 inch thick.
sq. ft. for a time effective to deposit a metal layer about 0.0002 inch to 0.050 inch thick.
6. The method of claim 5 wherein the metal layer coated in step (3) is nickel and as a last step the nickel article is cleaned in a suitable material effective to etch copper but not nickel.
7. A method of making a nickel article comprising the steps of:
(1) providing an aluminum master substrate having a thickness of between about 0.001 inch to 0.25 inch and at least one surface which is desired to be reproduced, said surface being covered with a natural oxide layer;
(2) making the aluminum master substrate cathodic at a current density of between about 10A/sq. ft. to about 120A/sq. ft., in aqueous 2 wt.% to 70 wt.% nitric acid solution, said solution having a temperature of up to about 50°C, said current causing evolution of gas at the solution-nickel oxide coated surface interface and chemical activation effective to thin and smooth the natural oxide layer without removing it;
(3) electrocoating the smoothed, natural oxide coated surface of the aluminum master substrate by making the master substrate cathodic at a current density of between about 5A/sq. ft. to about 150A/sq. ft. in a bath containing a solution selected from the group consisting of nickel sulfamate and nickel sulfate solution for at time effective to deposit a nickel layer about 0.0002 inch to 0.050 inch thick;
(4) dissolving the aluminum master substrate and the attached natural oxide layer in an aqueous alkali hydroxide solution to provide a metal article having a surface that is the negative duplicate of the surface of the master substrate.
(1) providing an aluminum master substrate having a thickness of between about 0.001 inch to 0.25 inch and at least one surface which is desired to be reproduced, said surface being covered with a natural oxide layer;
(2) making the aluminum master substrate cathodic at a current density of between about 10A/sq. ft. to about 120A/sq. ft., in aqueous 2 wt.% to 70 wt.% nitric acid solution, said solution having a temperature of up to about 50°C, said current causing evolution of gas at the solution-nickel oxide coated surface interface and chemical activation effective to thin and smooth the natural oxide layer without removing it;
(3) electrocoating the smoothed, natural oxide coated surface of the aluminum master substrate by making the master substrate cathodic at a current density of between about 5A/sq. ft. to about 150A/sq. ft. in a bath containing a solution selected from the group consisting of nickel sulfamate and nickel sulfate solution for at time effective to deposit a nickel layer about 0.0002 inch to 0.050 inch thick;
(4) dissolving the aluminum master substrate and the attached natural oxide layer in an aqueous alkali hydroxide solution to provide a metal article having a surface that is the negative duplicate of the surface of the master substrate.
8. The method of claim 7 including cleaning the master substrate between step (1) and (2) in a suitable solvent to remove oil and organic matter.
9. The method of claim 7 wherein the current density is applied in step (2) for about 10-1200 seconds, and as a last step the nickel article is cleaned in 1.5 wt.
to 45 wt.% nitric acid at between about 25°C to about 35°C.
to 45 wt.% nitric acid at between about 25°C to about 35°C.
10. The method of claim 7 wherein the aluminum master substrate is cup shaped and the nickel article is cup shaped.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/572,813 US3939046A (en) | 1975-04-29 | 1975-04-29 | Method of electroforming on a metal substrate |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070260A true CA1070260A (en) | 1980-01-22 |
Family
ID=24289454
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA249,212A Expired CA1070260A (en) | 1975-04-29 | 1976-03-30 | Method of electroforming on a metal substrate |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US3939046A (en) |
| CA (1) | CA1070260A (en) |
| GB (1) | GB1545955A (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4067782A (en) * | 1977-05-09 | 1978-01-10 | Xerox Corporation | Method of forming an electroforming mandrel |
| US4534831A (en) * | 1982-09-27 | 1985-08-13 | Inoue-Japax Research Incorporated | Method of and apparatus for forming a 3D article |
| GB2175921A (en) * | 1985-05-14 | 1986-12-10 | Vickers Shipbuilding & Eng | Electroformed tool |
| JPH0317288A (en) * | 1989-06-13 | 1991-01-25 | Daicel Chem Ind Ltd | Electrolytic cleaning solution for stamper |
| GB2246580A (en) * | 1989-09-13 | 1992-02-05 | British Aerospace | Metal components |
| US5772864A (en) * | 1996-02-23 | 1998-06-30 | Meadox Medicals, Inc. | Method for manufacturing implantable medical devices |
| US5932360A (en) * | 1997-06-06 | 1999-08-03 | Servometer Corporation | Hollow shell with internal baffle |
| US7347572B1 (en) * | 2000-05-23 | 2008-03-25 | Media Lario S.R.L. | Telescope mirror for high bandwidth free space optical data transmission |
| US20040031404A1 (en) * | 2002-08-19 | 2004-02-19 | John Dixon | Seamless embossing shim |
| WO2006026989A1 (en) * | 2004-09-10 | 2006-03-16 | Danmarks Tekniske Universitet | A method of manufacturing a mould part |
| DE102004047533A1 (en) * | 2004-09-30 | 2006-04-06 | Carl Zeiss Smt Ag | Device for tempering elements |
| US20070125652A1 (en) * | 2005-12-02 | 2007-06-07 | Buckley Paul W | Electroform, methods of making electroforms, and products made from electroforms |
| US10900136B2 (en) * | 2017-07-18 | 2021-01-26 | Honeywell International Inc. | Additive-based electroforming manufacturing methods and metallic articles produced thereby |
| US11657963B2 (en) * | 2020-09-15 | 2023-05-23 | Enphase Energy, Inc. | Transformer helix winding production |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2433441A (en) * | 1947-12-30 | Electrolytic production of thin | ||
| US880484A (en) * | 1904-06-29 | 1908-02-25 | Edison Storage Battery Co | Process of producing very thin sheet metal. |
| US1515658A (en) * | 1919-12-04 | 1924-11-18 | Cole Thomas Charles | Process for coating aluminum |
| DE1250712B (en) * | 1963-05-22 | 1967-09-21 | International Nickel Limited, London | Galvanic nickel sulfamate bath and process for depositing nickel coatings |
| US3627654A (en) * | 1969-11-19 | 1971-12-14 | Atomic Energy Commission | Electrolytic process for cleaning high-carbon steels |
-
1975
- 1975-04-29 US US05/572,813 patent/US3939046A/en not_active Expired - Lifetime
-
1976
- 1976-03-30 CA CA249,212A patent/CA1070260A/en not_active Expired
- 1976-04-29 GB GB17434/76A patent/GB1545955A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US3939046A (en) | 1976-02-17 |
| GB1545955A (en) | 1979-05-16 |
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