US2966448A - Methods of electroplating aluminum and alloys thereof - Google Patents
Methods of electroplating aluminum and alloys thereof Download PDFInfo
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- US2966448A US2966448A US739680A US73968058A US2966448A US 2966448 A US2966448 A US 2966448A US 739680 A US739680 A US 739680A US 73968058 A US73968058 A US 73968058A US 2966448 A US2966448 A US 2966448A
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- cyanide
- alkali
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- 229910052782 aluminium Inorganic materials 0.000 title claims description 51
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims description 51
- 238000000034 method Methods 0.000 title claims description 30
- 229910045601 alloy Inorganic materials 0.000 title description 13
- 239000000956 alloy Substances 0.000 title description 13
- 238000009713 electroplating Methods 0.000 title description 5
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 55
- 229910052725 zinc Inorganic materials 0.000 claims description 55
- 239000011701 zinc Substances 0.000 claims description 55
- 238000000576 coating method Methods 0.000 claims description 46
- 239000011248 coating agent Substances 0.000 claims description 45
- 239000003513 alkali Substances 0.000 claims description 32
- 229910052751 metal Inorganic materials 0.000 claims description 30
- 239000002184 metal Substances 0.000 claims description 30
- GTLDTDOJJJZVBW-UHFFFAOYSA-N zinc cyanide Chemical compound [Zn+2].N#[C-].N#[C-] GTLDTDOJJJZVBW-UHFFFAOYSA-N 0.000 claims description 24
- 229910001854 alkali hydroxide Inorganic materials 0.000 claims description 23
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 23
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 claims description 17
- 239000002585 base Substances 0.000 claims description 13
- 238000006073 displacement reaction Methods 0.000 claims description 13
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 9
- 239000002659 electrodeposit Substances 0.000 claims description 7
- AVTYONGGKAJVTE-OLXYHTOASA-L potassium L-tartrate Chemical compound [K+].[K+].[O-]C(=O)[C@H](O)[C@@H](O)C([O-])=O AVTYONGGKAJVTE-OLXYHTOASA-L 0.000 claims description 5
- 239000001472 potassium tartrate Substances 0.000 claims description 5
- 229940111695 potassium tartrate Drugs 0.000 claims description 5
- 235000011005 potassium tartrates Nutrition 0.000 claims description 5
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 39
- 239000000243 solution Substances 0.000 description 28
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 20
- 239000003792 electrolyte Substances 0.000 description 12
- LJCNRYVRMXRIQR-OLXYHTOASA-L potassium sodium L-tartrate Chemical compound [Na+].[K+].[O-]C(=O)[C@H](O)[C@@H](O)C([O-])=O LJCNRYVRMXRIQR-OLXYHTOASA-L 0.000 description 11
- 229910052709 silver Inorganic materials 0.000 description 11
- 239000004332 silver Substances 0.000 description 11
- 235000011006 sodium potassium tartrate Nutrition 0.000 description 11
- KXZJHVJKXJLBKO-UHFFFAOYSA-N chembl1408157 Chemical compound N=1C2=CC=CC=C2C(C(=O)O)=CC=1C1=CC=C(O)C=C1 KXZJHVJKXJLBKO-UHFFFAOYSA-N 0.000 description 9
- 238000007747 plating Methods 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 239000000203 mixture Substances 0.000 description 6
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 description 6
- 229910000838 Al alloy Inorganic materials 0.000 description 5
- 239000002253 acid Substances 0.000 description 5
- 238000000151 deposition Methods 0.000 description 5
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- 238000013019 agitation Methods 0.000 description 4
- 238000004140 cleaning Methods 0.000 description 4
- LFAGQMCIGQNPJG-UHFFFAOYSA-N silver cyanide Chemical compound [Ag+].N#[C-] LFAGQMCIGQNPJG-UHFFFAOYSA-N 0.000 description 4
- 229940098221 silver cyanide Drugs 0.000 description 4
- 239000001476 sodium potassium tartrate Substances 0.000 description 4
- 239000004372 Polyvinyl alcohol Substances 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 229920002451 polyvinyl alcohol Polymers 0.000 description 3
- 229910052979 sodium sulfide Inorganic materials 0.000 description 3
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 229910052793 cadmium Inorganic materials 0.000 description 2
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- NNFCIKHAZHQZJG-UHFFFAOYSA-N potassium cyanide Chemical compound [K+].N#[C-] NNFCIKHAZHQZJG-UHFFFAOYSA-N 0.000 description 2
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 description 2
- 238000002203 pretreatment Methods 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- RNAMYOYQYRYFQY-UHFFFAOYSA-N 2-(4,4-difluoropiperidin-1-yl)-6-methoxy-n-(1-propan-2-ylpiperidin-4-yl)-7-(3-pyrrolidin-1-ylpropoxy)quinazolin-4-amine Chemical compound N1=C(N2CCC(F)(F)CC2)N=C2C=C(OCCCN3CCCC3)C(OC)=CC2=C1NC1CCN(C(C)C)CC1 RNAMYOYQYRYFQY-UHFFFAOYSA-N 0.000 description 1
- 229910001369 Brass Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 241001479489 Peponocephala electra Species 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- PTFCDOFLOPIGGS-UHFFFAOYSA-N Zinc dication Chemical compound [Zn+2] PTFCDOFLOPIGGS-UHFFFAOYSA-N 0.000 description 1
- 230000001464 adherent effect Effects 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004070 electrodeposition Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- IPJKJLXEVHOKSE-UHFFFAOYSA-L manganese dihydroxide Chemical compound [OH-].[OH-].[Mn+2] IPJKJLXEVHOKSE-UHFFFAOYSA-L 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 239000004323 potassium nitrate Substances 0.000 description 1
- 235000010333 potassium nitrate Nutrition 0.000 description 1
- 229940074439 potassium sodium tartrate Drugs 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 description 1
- 235000019345 sodium thiosulphate Nutrition 0.000 description 1
- ZKMQXMFJRJPCMY-UHFFFAOYSA-N sodium zinc dicyanide Chemical compound [Zn+2].[C-]#N.[C-]#N.[Na+] ZKMQXMFJRJPCMY-UHFFFAOYSA-N 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 150000004763 sulfides Chemical class 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/34—Pretreatment of metallic surfaces to be electroplated
- C25D5/42—Pretreatment of metallic surfaces to be electroplated of light metals
- C25D5/44—Aluminium
Definitions
- This invention relates to methods for electroplating aluminum and alloys thereof. More particularly, it relates to improved methods for providing articles of aluminum and alloys thereof with a firm, dense, nonporous zinc coating which serves as a firmly adhering base for metal deposited on said articles.
- a number of plating processes are known for the deposition of metal plate, such as silver plate, upon aluminum.
- the aluminum is first anodically cleaned in a solutionof phosphoric acid after which a coating of silver is applied or electroplated thereon. While the oxide coating on the aluminum base resulting from the anodic treatment in the acid bath results in an improved adherence of the silver plate, the final product is not particularly useful for electrical applications due to the high electrical resistance of the intermediate oxide film.
- Another known method for applying silver to an aluminum article comprises the preplating of the aluminum with a layer of zinc from a suitable zincate plating bath. This is commonly known as the zinc immersion process. The zinc coating, as a base for the ultimate silver plate, has been found to be necessary if proper adhesion is to be obtained.
- the known zincate pretreatments have not been completely satisfactory in being both cumbersome and in many cases quite unreliable. In many of the known zincate pretreatments, as many as 8 or 10 individual steps are involved before actually depositing the silver coating. Furthermore, the zinc coatings applied by the previously known zincate methods are inherently porous and spongy, making it diflicult, if not impossible, to com- ,pletely rinse away all traces of the alkaline zincate solution. The residual alkali, along with the natural galvanic action between silver, zinc and aluminum, causes the silver plate to blister, particularly when the plated articles are subjected to elevated temperatures or used in electrical applications where a current flows between the aluminum base and the silver coating.
- a principal object of this invention is to provide improved means for electroplating metals on aluminum and its alloys and for preparing the basis metal for the reception of the plated metal.
- the aluminum containing article to be plated is first cleaned or etched in an alkaline bath, which is heated to about 160 F. and rinsed. It is then immersed in a modified zinc cyanide solution, preferably at a temperature of from about 70 F. to F. for a short period of time, during which time, the water from the rinse is dissipated, the solution etches the article slightly and a thin, superficial displacement Zinc coating is deposited thereon.
- a suitable displacement coating is of the order of 0.000015 mil thick and ranges from about 0.00001 to 0.001 mil. Generally, this action takes place in any time over 1 second to times up to 15 seconds or more which have been found suitable although much longer times can be used if desired.
- the current time limits are from about 10 ampere seconds to about 15,000 ampere seconds, it being realized, of course, that this depends upon the particular solution composition, bath temperature, agitation and the cathode current density employed. Generally speaking, above 15,000 ampere seconds per square foot, adhesion becomes spotty with gentle agitation. Even though up to 150,000 ampere seconds may be used with high agitation, the results tend to be erratio.
- Example 1 Aluminum articles of pure E.C. aluminum and alloys 1100 and 6061 were cleaned in a bath containing, by weight, per gallon of water solution, 10 ounces of sodium hydroxide and 10 ounces Rochelle salt or potassium sodium tartrate, the bath being maintained at 160 F. for about 30 to seconds.
- the sodium hydroxide serves to clean and etch the surface of the article and dissolve or'remove the oxide film therefrom.
- the Rochelle salt serves to keep in solution any alloy con stituents such as magnesium and manganese which would otherwise form gel-like hydroxides which would adhere to the article and prevent adequate cleaning and satisfactory subsequent treating.
- the articles were next removed from the cleaning bath and rinsed in cold water. They were then immersed in a bath having the following composition.
- the articles were allowed to remain in the bath for seconds during which time a thin, adhesive, dense coating of zinc was acquired by the article. Following this, the articles were made the cathode while current was passed through the solution and an additional thin electro-deposit of zinc was applied for a period of about 6 seconds.
- the aluminum articles were exposed during the 6-second period in such manner as to provide a range of current density varying from about 2 amperes per square foot to about 500 amperes per square foot, it being realized that higher current densities can be used with a corresponding reduction in plating time as is well known to those skilled in the art.
- the articles were next rinsed in cold water. Thereafter the zinc-coated aluminium article was removed from the electrolyte and washed under clean running Water in preparation for silver plating.
- a silver strike is recommended if the aluminum is to be plated in a still tank although the strike is not required when the Work is plated by the use of a high speed plating machine.
- a suitable typical silver plating solution for depositing a hard, dense silver plate by the tank method comprises 12 ounces silver cyanide, 18 ounces potassium cyanide and from 0.05 to 0.1 ounce sodium thiosulfate per gallon of solution with the solution operated at a temperature in the neighborhood of 100 F. Proper physical characteristics of the silver are best obtained at current densities of 0.5 to 0.80 amp. per square inch. Adequate solution agitation and filtration should be supplied.
- the silver plating solution employed may typically be one containing about 10 ounces of silver cyanide, 8 ounces free potassium cyanide and about 20 ounces potassium nitrate per gallon of solution with an operating temperature of the solution from 80 F. to 120 F. and a current density range of from 0.1 to 4.5 amps. per square inch.
- the silver-plated products were characterized by a hard, dense, bright silver plate which was relatively nonporous and which adhered to the aluminum article at all temperatures up to the melting point of aluminum. No blistering was noted in the plate at elevated temperatures.
- the silver plate applied over the above-described zinc coating withstood the passage of electric currents of high amperage.
- A" x 4" aluminum bus bars having their ends zinccoated and silver-plated in accordance with the present invention were bolted in overlapping relationship with an overlapping area of about eight square inches.
- a current in excess of 200,000 amps. was passed through the bars for one-half second with no apparent effect on the silver plate or the electrical resistance of the joint.
- Example 2 Aluminum articles comprising E.C. aluminum and aluminum alloys 6061, 6063, 7075, 3003, 2024 and 2014 were etched in a caustic solution similar to that of Example 1, except that the Rochelle salt was omitted. This treatment was followed by a dip in a solution of one volume of concentrated nitric acid and one volume of water for about 5 seconds. The articles were then immersed in a bath having the following composition.
- Optimum Con- Preferred centration Range (Ounces per (Ounces per Gallon) G lon Zine Cyanide 10 1 to 30 Sodium Cyanide. 8.5 4 to 54 Sodium Hydroxide. 10 5 to 20 Sodium Oarb0nate 6 0.1 to 12 Sodium Sulfide 0. 05 0.01 to 0. 07 Temperature 75 F. 50 to F.
- Example 2 The time of treatment and current densities in this example were the same as Example 1, and the silver plate was plated thereon in a similar manner.
- Example 3 Aluminum articles of E.C. aluminum and alloy 6101, 6063, 7075, 3003, 2024, 2014, 355, 356 and 380 were processed similarly as in Example 1 except that again the Rochelle salts were eliminated in the preliminary cleaning or etching solution, and this was followed by a dip in one volume of 48% hydrofluoric acid, four volumes of concentrated nitric acid and five volumes of water. The articles were then rinsed and immersed in a bath having the following composition.
- the sodium cyanide and sodium hydroxide in the bath or water solution serve as solvents for the zinc cyanide which the latter in turn serves to provide the zinc ion which is deposited as zinc metal.
- the sodium cyanide and sodium hydroxide also serve to control the degree of ionization of zinc.
- Sodium hydroxide, and, to some extent, sodium cyanide provide proper pH conditions of the cathode film on the aluminum during the zinc displacement step and during electrodeposition of the zinc.
- the ratio of zinc cyanide to sodium cyanide may vary with the concentration.
- the ratio of zinc cyanide to sodium cyanide should be of the order of 1 to 3.8, lower concentrations requiring higher ratios.
- the required ratios of zinc cyanide to sodium cyanide for best results are of the order of 1 to 4 and 1 to 5, respectively.
- the ratio may range from 1 to 0, and as high as 1 to 3.1. If, in the bath, the concentration of sodium cyanide is less than the stoichiometric amount required to dissolve the zinc cyanide, sutlicient sodium hydroxide is necessary to complete the solution.
- concentration of sodium cyanide is less than the stoichiometric amount required to dissolve the zinc cyanide, sutlicient sodium hydroxide is necessary to complete the solution.
- below about 4 ounces of zinc cyanide per gallon chemical creates control problems and operating sensitivity increases inversely proportional to the concentration. Above 5 ounces per gallon of zinc cyanide,
- the choice of bath concentration largely becomes a matter of economics, though, of course, such higher concentrations can be used.
- Some sodium hydroxide is required in the bath.
- the amount of sodium hydroxide can vary over wide limits. For example, with the zinc cyanide concentration as low as 0.25 ounce per gallon, the sodium hydroxide may be as low as 2 ounces per gallon. Higher concentrations of sodium hydroxide are preferable for higher zinc cyanide concentrations and the desired range lies between 4 and ounces per gallon. Higher concentrations than 10 ounces per gallon, of course, may be used although no significant advantages appear to be obtained. It will be realized that other alkali metals may be used in lieu of sodium in the bath compounds.
- the Rochelle salt in general, where used, serves to aid, as pointed out above, in the removal of insoluble compounds like magnesium and manganese hydroxide.
- the zinc electrolyte will function satisfactorily without it, but it is useful again, as pointed out above, for alloys having a rather large concentration of elements which are insoluble in sodium hydroxide.
- the sodium carbonate in the bath helps to stabilize the pH of the bath and aids in producing uniformly bright deposits of good texture. Under many conditions, this salt is not essential but to some degree it does improve the quality of the electrodeposited zinc coating. In many cases, sodium carbonate is produced in the bath by reaction with carbon dioxide in the air.
- the sodium sulfide serves in the role of a bath purifier [precipitating lead, cadmium and other sulfides which are insoluble in cyanide solutions. Such metals in sufficient quantity would reduce the brightness of the zinc coating. However, if the chemicals originally used in the bath are of suitable purity, the sodium sulfide may be omitted.
- the brightener or polyvinyl alcohol used generally improves the brightness, density and tensile strength of the zinc coating and provides for better over-all bonding.
- the method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises 1) immersing said aluminum base article in a hot bath containing alkali hydroxide and alkali potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution of zinc cyanide, alkali cyanide, alkali hydroxide and alkali sulfide until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath with the article as the cathode at current densities up to the order of 1500 amperes per square foot at temperatures ranging from about 50 F. to 120 F. until a thin eleetrodeposit of zinc is applied thereto, and (5) electrodepositing a metal coating on said zinc coated article.
- the electrolyte bath contains about from 1 to 30 ounces zinc cyanide, 4 to 54 ounces alkali cyanide, 5 to 20 ounces alkali hydroxide and 0.01 to 0.07 ounce alkali sulfide per gallon of electrolyte.
- electrolyte also contains from 0.1 to 12 ounces of alkali carbonate per gallon of electrolyte.
- electrolyte also contains from 0.1 to 12 ounces alkali carbonate, from 4 to 12 ounces sodium potassium tartrate, from 0.001 to 0.1 ounce silver cyanide and 0.01 to 0.4 ounce polyvinyl alcohol per gallon of electrolyte.
- the method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide and alkali potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution of zinc cyanide, alkali cyanide, alkali hydroxide and alkali sulfide until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at a temperature of from about 50 F. to about 120 F. with the article as the cathode in the amount of from about 10 to 15,000 ampere-seconds per square foot whereby a thin eleetrodeposit of Zinc is applied thereon, and (5) electrodepositing a metal coating on said zinc coated article.
- the method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises 1) immersing said aluminum base article in a hot bath containing alkali hydroxide and sodium potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution of zinc cyanide, alkali cyanide, and alkali hydroxide until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at 50 F. to 120 F. with the article as the cathode at current densities up to the order of 1500 amperes per square foot whereby a thin eleetrodeposit of zinc is applied thereto, and (5) electrodepositing a metal coating on said zinc coated article.
- the method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide and sodium potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution containing by weight per gallon of solution about 10 ounces zinc cyanide, 8.5 ounces alkali cyanide, 10 ounces alkali hydroxide, 6 ounces alkali carbonate and 0.05 ounce alkali sulfide until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at a temperature of from about 70 F. to F. with the article as the cathode at current densities up to the order of 1500 amperes per square foot until a thin eleetrodeposit of zinc is applied thereto, and (5) electrodepositing a metal coating on said Zinc coated article.
- the method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide and alkali potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution containing by weight per gallon of solution about 10 ounces zinc cyanide, 8.5 ounces alkali cyanide, 10 ounces alkali hydroxide, 6 ounces alkali carbonate, 8 ounces Rochelle salt, 0.03 ounce silver cyanide, 0.05 ounce alkali sulfide and 0.15 ounce polyvinyl alcohol until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at a temperature of from about 70 F.
- the method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide and alkali potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution containing by weight per gallon of solution about.
- the method of preparing an aluminum'containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum article in a hot bath containing alkali hydroxide and sodium potassium tartrate, (2) removing said article from said bath and rinsing said'article, (3) immersing said article in a bath comprising an;aqueous.solution containing by weight per gallon of solution from about 0.25 to 40 ounces of'zinc' cyanide, from 1.3'ounceupto the saturation amount of alkali cyanide, and from 2.5 ounces to the saturation amount of alkali hydroxide, until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at a temperature from about 50 F. to 120 F. with the article as the cathode at current densities up to the order of 1500 amperes per square foot until a thin electrodeposit of zinc is applied thereto, and (5) electrodepositing a metal coating on said zinc-coated article.
- the method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide, (2) treating said article with an acid dip, (3) rinsing said article, (4) immersing said article in a bath comprising an aqueous solution of zinc cyanide, alkali cyanide, alkali hydroxide, and alkali sulfide, until a thin displacement coating of zinc is deposited thereon, (5) passing a direct electric current through said bath at a temperature of from about 50 F. to 120 F. with the 8 articleasthe cathode at current densities up to the order of. 1500 amperes per square foot until a thin electrodeposit of zinc is applied thereto, and (6) electrodepositing a metal coating on said zinc-coated article.
- the electrolyte bath contains from about 1 to 30 ounces of zinc cyanide, 4 to 54 ounces alkali cyanide, 5 to 20 ounces alkali hydroxide, and 0.01 to 0.07 ounce alkali sulfide per gallon of electrolyte.
- the method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide, (2) treating said article with an acid dip, (3) immersing said article in'a bath comprising an aqueous solution of zinc'cyanide, alkali cyanide, alkali hydroxide, and alkali sulfide, until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at a temperature of F. to F. with the article as the cathode at current densities up to the. order of 1500 amperes per square foot until a thin electrodeposit of zinc is applied thereto, and (5 electrodepositing a metal coating on said zinc-coated article.
- the electrolyte bath contains from about 1 to 30 ounces of zinc cyanide, 4 to 54 ounces alkali cyanide, 5 to 20 ounces alkali hydroxide, and 0.01 to 0.07 ounce alkali sulfide per gallon of electrolyte.
Description
United tates Patent:
METHODS OF ELECTROPLATIN G ALUMINUM AND ALLOYS THEREOF Thomas J. Connor, Penn Wynne, Pa., assignor to General Electric Company, a corporation of New York No Drawing. Filed June 4, 1958, Ser. No. 739,680 '15 Claims. Cl. 20433 This invention relates to methods for electroplating aluminum and alloys thereof. More particularly, it relates to improved methods for providing articles of aluminum and alloys thereof with a firm, dense, nonporous zinc coating which serves as a firmly adhering base for metal deposited on said articles. While the examples herein are directed to the electrodepositiou of silver on aluminum or aluminum alloy articles prepared as described herein, it will be appreciated that the invention applies as well to the deposition of other metals including brass, copper, cadmium, tin, and combinations thereof among others.
A number of plating processes are known for the deposition of metal plate, such as silver plate, upon aluminum. In one of these, the aluminum is first anodically cleaned in a solutionof phosphoric acid after which a coating of silver is applied or electroplated thereon. While the oxide coating on the aluminum base resulting from the anodic treatment in the acid bath results in an improved adherence of the silver plate, the final product is not particularly useful for electrical applications due to the high electrical resistance of the intermediate oxide film. Another known method for applying silver to an aluminum article comprises the preplating of the aluminum with a layer of zinc from a suitable zincate plating bath. This is commonly known as the zinc immersion process. The zinc coating, as a base for the ultimate silver plate, has been found to be necessary if proper adhesion is to be obtained. However, the known zincate pretreatments have not been completely satisfactory in being both cumbersome and in many cases quite unreliable. In many of the known zincate pretreatments, as many as 8 or 10 individual steps are involved before actually depositing the silver coating. Furthermore, the zinc coatings applied by the previously known zincate methods are inherently porous and spongy, making it diflicult, if not impossible, to com- ,pletely rinse away all traces of the alkaline zincate solution. The residual alkali, along with the natural galvanic action between silver, zinc and aluminum, causes the silver plate to blister, particularly when the plated articles are subjected to elevated temperatures or used in electrical applications where a current flows between the aluminum base and the silver coating.
It has also been found that while particular zincate baths as developed heretofore are suitable for pure aluminum or particular aluminum alloys, they are specialized in that such factors as the type of alloy treated is generally limited and that treating parameters such as temperatures, times, current densities and solution compositions must be kept under close control.
A principal object of this invention is to provide improved means for electroplating metals on aluminum and its alloys and for preparing the basis metal for the reception of the plated metal.
Briefly, by the present invention, there are provided improved processes for electroplating aluminum and various alloys thereof in which there is provided a dense,
firm, thin, zinc coating on the basis metal which serves as an adherent substrate for the subsequently deposited metal.
Those features of the invention which are believed to be novel are specifically pointed out in the claims appended hereto. The invention will, however, be better understood and other advantages and benefits thereof appreciated from a consideration of the following description. It will be understood that wherever the term aluminum is used, its alloys, such as those mentioned herein, are included.
According to one aspect of the present process, the aluminum containing article to be plated is first cleaned or etched in an alkaline bath, which is heated to about 160 F. and rinsed. It is then immersed in a modified zinc cyanide solution, preferably at a temperature of from about 70 F. to F. for a short period of time, during which time, the water from the rinse is dissipated, the solution etches the article slightly and a thin, superficial displacement Zinc coating is deposited thereon. Typically, a suitable displacement coating is of the order of 0.000015 mil thick and ranges from about 0.00001 to 0.001 mil. Generally, this action takes place in any time over 1 second to times up to 15 seconds or more which have been found suitable although much longer times can be used if desired. For example, times of from 6 to 10 seconds have been'found suitable at a bath temperature of 75 F. At higher bath temperatures, shorter times can be used. Articles of aluminum alloy such as 2024 containing appreciable copper are advantageously treated after the first alkaline cleaning to an acid dip for several minutes.
While the article is still immersed in the modified zinc cyanide solution, direct electric current is passed therethrough with the article being made the cathode, and thereby an additional thin, dense electrodeposit of zinc is applied to the article. This layer of zinc ranges typically from about 000008 to 0.03 mil thick with a normal coating being of the order of 0.003 mil. The current density is found to be advantageously varied from several amperes per square foot to over, or the order of, 1500 amperes per square foot. At the higher current densities, a shorter time of deposition is required to provide a dense, thin deposit, while at lower current densities a longer time is required. Generally, per square foot of article or cathode, the current time limits are from about 10 ampere seconds to about 15,000 ampere seconds, it being realized, of course, that this depends upon the particular solution composition, bath temperature, agitation and the cathode current density employed. Generally speaking, above 15,000 ampere seconds per square foot, adhesion becomes spotty with gentle agitation. Even though up to 150,000 ampere seconds may be used with high agitation, the results tend to be erratio.
The following examples will illustrate the practice of the invention, it being realized that such examples are illustrative rather than limiting of the invention.
Example 1 Aluminum articles of pure E.C. aluminum and alloys 1100 and 6061 were cleaned in a bath containing, by weight, per gallon of water solution, 10 ounces of sodium hydroxide and 10 ounces Rochelle salt or potassium sodium tartrate, the bath being maintained at 160 F. for about 30 to seconds. The sodium hydroxide, of course, serves to clean and etch the surface of the article and dissolve or'remove the oxide film therefrom. The Rochelle salt serves to keep in solution any alloy con stituents such as magnesium and manganese which would otherwise form gel-like hydroxides which would adhere to the article and prevent adequate cleaning and satisfactory subsequent treating. The articles were next removed from the cleaning bath and rinsed in cold water. They were then immersed in a bath having the following composition.
The articles were allowed to remain in the bath for seconds during which time a thin, adhesive, dense coating of zinc was acquired by the article. Following this, the articles were made the cathode while current was passed through the solution and an additional thin electro-deposit of zinc was applied for a period of about 6 seconds. The aluminum articles were exposed during the 6-second period in such manner as to provide a range of current density varying from about 2 amperes per square foot to about 500 amperes per square foot, it being realized that higher current densities can be used with a corresponding reduction in plating time as is well known to those skilled in the art. The articles were next rinsed in cold water. Thereafter the zinc-coated aluminium article was removed from the electrolyte and washed under clean running Water in preparation for silver plating.
A silver strike is recommended if the aluminum is to be plated in a still tank although the strike is not required when the Work is plated by the use of a high speed plating machine. A suitable typical silver plating solution for depositing a hard, dense silver plate by the tank method comprises 12 ounces silver cyanide, 18 ounces potassium cyanide and from 0.05 to 0.1 ounce sodium thiosulfate per gallon of solution with the solution operated at a temperature in the neighborhood of 100 F. Proper physical characteristics of the silver are best obtained at current densities of 0.5 to 0.80 amp. per square inch. Adequate solution agitation and filtration should be supplied. If a high speed plating method is employed, the silver plating solution employed may typically be one containing about 10 ounces of silver cyanide, 8 ounces free potassium cyanide and about 20 ounces potassium nitrate per gallon of solution with an operating temperature of the solution from 80 F. to 120 F. and a current density range of from 0.1 to 4.5 amps. per square inch. The silver-plated products were characterized by a hard, dense, bright silver plate which was relatively nonporous and which adhered to the aluminum article at all temperatures up to the melting point of aluminum. No blistering was noted in the plate at elevated temperatures. The silver plate applied over the above-described zinc coating withstood the passage of electric currents of high amperage. For example, two A" x 4" aluminum bus bars having their ends zinccoated and silver-plated in accordance with the present invention were bolted in overlapping relationship with an overlapping area of about eight square inches. A current in excess of 200,000 amps. was passed through the bars for one-half second with no apparent effect on the silver plate or the electrical resistance of the joint.
Example 2 Aluminum articles comprising E.C. aluminum and aluminum alloys 6061, 6063, 7075, 3003, 2024 and 2014 were etched in a caustic solution similar to that of Example 1, except that the Rochelle salt was omitted. This treatment was followed by a dip in a solution of one volume of concentrated nitric acid and one volume of water for about 5 seconds. The articles were then immersed in a bath having the following composition.
Optimum Con- Preferred centration Range (Ounces per (Ounces per Gallon) G lon Zine Cyanide 10 1 to 30 Sodium Cyanide. 8.5 4 to 54 Sodium Hydroxide. 10 5 to 20 Sodium Oarb0nate 6 0.1 to 12 Sodium Sulfide 0. 05 0.01 to 0. 07 Temperature 75 F. 50 to F.
The time of treatment and current densities in this example were the same as Example 1, and the silver plate was plated thereon in a similar manner.
Example 3 Aluminum articles of E.C. aluminum and alloy 6101, 6063, 7075, 3003, 2024, 2014, 355, 356 and 380 were processed similarly as in Example 1 except that again the Rochelle salts were eliminated in the preliminary cleaning or etching solution, and this was followed by a dip in one volume of 48% hydrofluoric acid, four volumes of concentrated nitric acid and five volumes of water. The articles were then rinsed and immersed in a bath having the following composition.
the same as those in Example 1 above.
The sodium cyanide and sodium hydroxide in the bath or water solution serve as solvents for the zinc cyanide which the latter in turn serves to provide the zinc ion which is deposited as zinc metal. The sodium cyanide and sodium hydroxide also serve to control the degree of ionization of zinc. Sodium hydroxide, and, to some extent, sodium cyanide provide proper pH conditions of the cathode film on the aluminum during the zinc displacement step and during electrodeposition of the zinc. For any particular concentration of zinc cyanide, there should preferably be a suitable corresponding amount of sodium cyanide and sodium hydroxide. The ratio of zinc cyanide to sodium cyanide may vary with the concentration. For example, with concentrations of zinc around 1 ounce per gallon, the ratio of zinc cyanide to sodium cyanide should be of the order of 1 to 3.8, lower concentrations requiring higher ratios. At 0.5 and 0.25 ounce of zinc cyanide per gallon, the required ratios of zinc cyanide to sodium cyanide for best results are of the order of 1 to 4 and 1 to 5, respectively. At high concentrations, the ratio may range from 1 to 0, and as high as 1 to 3.1. If, in the bath, the concentration of sodium cyanide is less than the stoichiometric amount required to dissolve the zinc cyanide, sutlicient sodium hydroxide is necessary to complete the solution. Generally speaking, below about 4 ounces of zinc cyanide per gallon chemical creates control problems and operating sensitivity increases inversely proportional to the concentration. Above 5 ounces per gallon of zinc cyanide,
the choice of bath concentration largely becomes a matter of economics, though, of course, such higher concentrations can be used. Some sodium hydroxide is required in the bath. When the proper zinc cyanide-sodium cyanide ratio is used, the amount of sodium hydroxide can vary over wide limits. For example, with the zinc cyanide concentration as low as 0.25 ounce per gallon, the sodium hydroxide may be as low as 2 ounces per gallon. Higher concentrations of sodium hydroxide are preferable for higher zinc cyanide concentrations and the desired range lies between 4 and ounces per gallon. Higher concentrations than 10 ounces per gallon, of course, may be used although no significant advantages appear to be obtained. It will be realized that other alkali metals may be used in lieu of sodium in the bath compounds.
The Rochelle salt, in general, where used, serves to aid, as pointed out above, in the removal of insoluble compounds like magnesium and manganese hydroxide. Under many conditions, the zinc electrolyte will function satisfactorily without it, but it is useful again, as pointed out above, for alloys having a rather large concentration of elements which are insoluble in sodium hydroxide. The sodium carbonate in the bath helps to stabilize the pH of the bath and aids in producing uniformly bright deposits of good texture. Under many conditions, this salt is not essential but to some degree it does improve the quality of the electrodeposited zinc coating. In many cases, sodium carbonate is produced in the bath by reaction with carbon dioxide in the air. The sodium sulfide serves in the role of a bath purifier [precipitating lead, cadmium and other sulfides which are insoluble in cyanide solutions. Such metals in sufficient quantity would reduce the brightness of the zinc coating. However, if the chemicals originally used in the bath are of suitable purity, the sodium sulfide may be omitted. The brightener or polyvinyl alcohol used generally improves the brightness, density and tensile strength of the zinc coating and provides for better over-all bonding.
By this invention, there are provided improved processes for electroplating aluminum and alloys thereof. Using such processes, wide ranges of aluminum alloys can be treated under relatively flexible conditions such as time, current density, temperature and solution composition.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. The method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises 1) immersing said aluminum base article in a hot bath containing alkali hydroxide and alkali potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution of zinc cyanide, alkali cyanide, alkali hydroxide and alkali sulfide until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath with the article as the cathode at current densities up to the order of 1500 amperes per square foot at temperatures ranging from about 50 F. to 120 F. until a thin eleetrodeposit of zinc is applied thereto, and (5) electrodepositing a metal coating on said zinc coated article.
2. The method of claim 1 in which the electrolyte bath contains about from 1 to 30 ounces zinc cyanide, 4 to 54 ounces alkali cyanide, 5 to 20 ounces alkali hydroxide and 0.01 to 0.07 ounce alkali sulfide per gallon of electrolyte.
3. The method of claim 2 wherein the electrolyte also contains from 0.1 to 12 ounces of alkali carbonate per gallon of electrolyte.
4. The method of claim 2 wherein the electrolyte also contains from 0.1 to 12 ounces alkali carbonate, from 4 to 12 ounces sodium potassium tartrate, from 0.001 to 0.1 ounce silver cyanide and 0.01 to 0.4 ounce polyvinyl alcohol per gallon of electrolyte.
5. The method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide and alkali potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution of zinc cyanide, alkali cyanide, alkali hydroxide and alkali sulfide until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at a temperature of from about 50 F. to about 120 F. with the article as the cathode in the amount of from about 10 to 15,000 ampere-seconds per square foot whereby a thin eleetrodeposit of Zinc is applied thereon, and (5) electrodepositing a metal coating on said zinc coated article.
6. The method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises 1) immersing said aluminum base article in a hot bath containing alkali hydroxide and sodium potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution of zinc cyanide, alkali cyanide, and alkali hydroxide until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at 50 F. to 120 F. with the article as the cathode at current densities up to the order of 1500 amperes per square foot whereby a thin eleetrodeposit of zinc is applied thereto, and (5) electrodepositing a metal coating on said zinc coated article.
7. The method of claim 1 wherein said article after step 1 is treated in an acid bath.
8. The method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide and sodium potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution containing by weight per gallon of solution about 10 ounces zinc cyanide, 8.5 ounces alkali cyanide, 10 ounces alkali hydroxide, 6 ounces alkali carbonate and 0.05 ounce alkali sulfide until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at a temperature of from about 70 F. to F. with the article as the cathode at current densities up to the order of 1500 amperes per square foot until a thin eleetrodeposit of zinc is applied thereto, and (5) electrodepositing a metal coating on said Zinc coated article.
9. The method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide and alkali potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution containing by weight per gallon of solution about 10 ounces zinc cyanide, 8.5 ounces alkali cyanide, 10 ounces alkali hydroxide, 6 ounces alkali carbonate, 8 ounces Rochelle salt, 0.03 ounce silver cyanide, 0.05 ounce alkali sulfide and 0.15 ounce polyvinyl alcohol until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at a temperature of from about 70 F. to 90 F. with the article as the cathode at current densities up to the order of 1500 amperes per square foot whereby a thin eleetrodeposit of zinc is applied thereto and (5) electrodepositing a metal coating on said zinc coated article.
10. The method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide and alkali potassium tartrate, (2) removing said article from said bath and rinsing said article, (3) immersing said article in a bath comprising an aqueous solution containing by weight per gallon of solution about.
1.0 ounces: zinc cyanide", 8.5 ounces alkali. cyanide; 10 ounces alkali hydroxide and 0.05 ounce alkali sulfide until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at a temperature of about 70 F. to about 90 F. with the article as the cathode at current densities up to the order of 1500 amperes per square foot until a thin electrodeposit of zinc is applied thereto, and electrodepositing a metal coating on said zinc coated article.
11. The method of preparing an aluminum'containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum article in a hot bath containing alkali hydroxide and sodium potassium tartrate, (2) removing said article from said bath and rinsing said'article, (3) immersing said article in a bath comprising an;aqueous.solution containing by weight per gallon of solution from about 0.25 to 40 ounces of'zinc' cyanide, from 1.3'ounceupto the saturation amount of alkali cyanide, and from 2.5 ounces to the saturation amount of alkali hydroxide, until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at a temperature from about 50 F. to 120 F. with the article as the cathode at current densities up to the order of 1500 amperes per square foot until a thin electrodeposit of zinc is applied thereto, and (5) electrodepositing a metal coating on said zinc-coated article.
12. The method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide, (2) treating said article with an acid dip, (3) rinsing said article, (4) immersing said article in a bath comprising an aqueous solution of zinc cyanide, alkali cyanide, alkali hydroxide, and alkali sulfide, until a thin displacement coating of zinc is deposited thereon, (5) passing a direct electric current through said bath at a temperature of from about 50 F. to 120 F. with the 8 articleasthe cathode at current densities up to the order of. 1500 amperes per square foot until a thin electrodeposit of zinc is applied thereto, and (6) electrodepositing a metal coating on said zinc-coated article.
13. The method of claim 12 in which the electrolyte bath contains from about 1 to 30 ounces of zinc cyanide, 4 to 54 ounces alkali cyanide, 5 to 20 ounces alkali hydroxide, and 0.01 to 0.07 ounce alkali sulfide per gallon of electrolyte.
14. The method of preparing an aluminum containing article for the application thereon of an electroplated metal coating which comprises (1) immersing said aluminum base article in a hot bath containing alkali hydroxide, (2) treating said article with an acid dip, (3) immersing said article in'a bath comprising an aqueous solution of zinc'cyanide, alkali cyanide, alkali hydroxide, and alkali sulfide, until a thin displacement coating of zinc is deposited thereon, (4) passing a direct electric current through said bath at a temperature of F. to F. with the article as the cathode at current densities up to the. order of 1500 amperes per square foot until a thin electrodeposit of zinc is applied thereto, and (5 electrodepositing a metal coating on said zinc-coated article.
15. The method of claim 14 in which the electrolyte bath contains from about 1 to 30 ounces of zinc cyanide, 4 to 54 ounces alkali cyanide, 5 to 20 ounces alkali hydroxide, and 0.01 to 0.07 ounce alkali sulfide per gallon of electrolyte.
References Cited in the file of this patent UNITED STATES PATENTS 1,147,718 Hall July 27, 1915 1,627,900 Hewitson May 10, 1927 2,171,842 Barrett et a1. Sept. 5, 1939 2,654,701 Calderon et a1. Oct. 6, 1953 2,730,490 Hendrich et al. I an. 10, 1956 2,791,553 Connor et al. May 7, 1957
Claims (1)
1. THE METHOD OF PREPARING AN ALUMINUM CONTAINING ARTICLE FOR THE APPLICATION THEREON OF AN ELECTROPLATED METAL COATING WHICH COMPRISES (1) IMMERSING SAID ALUMINUM BASE ARTICLE IN A HOT BATH CONTAINING ALKALI HYDROXIDE AND ALKALI POTASSIUM TARTRATE. (2) REMOVING SAID ARTICLE FROM SAID BATH AND RINSING SAID ARTICLE. (3) IMMERSING SAID ARTICLE IN A BATH COMPRISING AN AQUEOUS SOLUTION OF ZINC CYANIDE, ALKALI CYANIDE, ALKALI HYDROXIDE AND ALKALI SULFIDE UNTIL A THIN DISPLACEMENT COATING OF ZINC IS DEPOSITED THEREON, (4) PASSING A DIRECT ELECTRIC CURRENT THROUGH SAID BATH WITH THE ARTICLE AS THE CATHODE AT CURRENT DENSITES UP TO THE ORDER OF 1500 AMPERES PER SQUARE FOOT AT TEMPERATURES RANGING FROM ABOUT 50*F. TO 120* F. UNTIL A THIN ELECTRODEPOSIT OF ZINC IS APPLIED THERETO, AND (5) ELECTRODEPOSITING A METAL COATING ON SAID ZINC COATED ARTICLE.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US739680A US2966448A (en) | 1958-06-04 | 1958-06-04 | Methods of electroplating aluminum and alloys thereof |
GB16440/59A GB923579A (en) | 1958-06-04 | 1959-05-13 | Improvements relating to the electroplating of aluminum and alloys thereof |
DEG27190A DE1168735B (en) | 1958-06-04 | 1959-06-02 | Process for pretreating an object made of aluminum or an aluminum alloy for the application of a galvanic metal coating |
Applications Claiming Priority (1)
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US739680A US2966448A (en) | 1958-06-04 | 1958-06-04 | Methods of electroplating aluminum and alloys thereof |
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US2966448A true US2966448A (en) | 1960-12-27 |
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US739680A Expired - Lifetime US2966448A (en) | 1958-06-04 | 1958-06-04 | Methods of electroplating aluminum and alloys thereof |
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US (1) | US2966448A (en) |
DE (1) | DE1168735B (en) |
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3081536A (en) * | 1959-02-05 | 1963-03-19 | Clevite Corp | Method of soldering to aluminum |
US3274080A (en) * | 1962-05-25 | 1966-09-20 | Cowles Chem Co | Brighteners and process for cyanide zinc electrodeposition |
US3694899A (en) * | 1969-10-22 | 1972-10-03 | Chausson Usines Sa | Process for brazing parts of aluminium and aluminium alloys |
US4465561A (en) * | 1982-02-18 | 1984-08-14 | Diamond Shamrock Chemicals Company | Electroplating film-forming metals in non-aqueous electrolyte |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5268078A (en) * | 1991-02-19 | 1993-12-07 | Sumitomo Light Metal Industries, Ltd. | Aluminum plates for automobile body panels and method of pretreatment for painting thereof |
EP2447313B1 (en) | 2010-09-16 | 2013-01-16 | Instytut Technologii Materialów Elektronicznych | Method of silvering surfaces, especially aluminium surfaces |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
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US1147718A (en) * | 1915-02-05 | 1915-07-27 | Joseph A Hall | Process of plating aluminum. |
US1627900A (en) * | 1926-08-23 | 1927-05-10 | Eastman Kodak Co | Process of coating aluminum surfaces |
US2171842A (en) * | 1936-07-13 | 1939-09-05 | Du Pont | Electroplating |
US2654701A (en) * | 1950-06-08 | 1953-10-06 | Edwin R Calderon | Plating aluminum |
US2730490A (en) * | 1951-11-13 | 1956-01-10 | Wire Coating And Mfg Co | Process of zinc coating magnesium articles |
US2791553A (en) * | 1956-02-15 | 1957-05-07 | Gen Electric | Method of electroplating aluminum |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2511952A (en) * | 1950-06-20 | Process of plating zinc on aluminum | ||
AT168102B (en) * | 1950-03-13 | 1951-04-25 | Hubert Vlk | Process for electroplating aluminum and its alloys |
DE888496C (en) * | 1951-12-16 | 1953-09-03 | Julius & August Erbsloeh K G M | Process for applying a corrosion-resistant coating to metals |
-
1958
- 1958-06-04 US US739680A patent/US2966448A/en not_active Expired - Lifetime
-
1959
- 1959-05-13 GB GB16440/59A patent/GB923579A/en not_active Expired
- 1959-06-02 DE DEG27190A patent/DE1168735B/en active Pending
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1147718A (en) * | 1915-02-05 | 1915-07-27 | Joseph A Hall | Process of plating aluminum. |
US1627900A (en) * | 1926-08-23 | 1927-05-10 | Eastman Kodak Co | Process of coating aluminum surfaces |
US2171842A (en) * | 1936-07-13 | 1939-09-05 | Du Pont | Electroplating |
US2654701A (en) * | 1950-06-08 | 1953-10-06 | Edwin R Calderon | Plating aluminum |
US2730490A (en) * | 1951-11-13 | 1956-01-10 | Wire Coating And Mfg Co | Process of zinc coating magnesium articles |
US2791553A (en) * | 1956-02-15 | 1957-05-07 | Gen Electric | Method of electroplating aluminum |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3081536A (en) * | 1959-02-05 | 1963-03-19 | Clevite Corp | Method of soldering to aluminum |
US3274080A (en) * | 1962-05-25 | 1966-09-20 | Cowles Chem Co | Brighteners and process for cyanide zinc electrodeposition |
US3694899A (en) * | 1969-10-22 | 1972-10-03 | Chausson Usines Sa | Process for brazing parts of aluminium and aluminium alloys |
US4465561A (en) * | 1982-02-18 | 1984-08-14 | Diamond Shamrock Chemicals Company | Electroplating film-forming metals in non-aqueous electrolyte |
Also Published As
Publication number | Publication date |
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DE1168735B (en) | 1964-04-23 |
GB923579A (en) | 1963-04-10 |
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