Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions

Definitions

• An electrically conductive medium for the electrodeposition of metals which comprises an aqueous solution of a composition comprising (1 a complex consisting of a metal ion and an tetra( methylene phosphonate) ligand, and (2) a complex consisting of a metal ion and a l-hydroxy, ethylidene-l,l-diphosphonate liquid.
• the present invention relates to the electrodeposition or electroplating of metals and to novel media which may be employed in the electrodeposition or electroplating of metals.
• the invention further relates to novel processes for the preparation of such media and to novel processes for the electrodeposition of metals.
• Electrolyzing an electrically conductive medium e.g., an electroplating bath also known as a galvanic solution
• an electrically conductive medium e.g., an electroplating bath also known as a galvanic solution
• the metal of the metal salt dissolved in such a medium is usually the metal which it is desired to electrically deposit upon a substrate.
• the electrodeposition or electroplating system consists of an electroplating bath and two or more electrodes in which the cathode or cathodes comprise the object upon which the metal is to be deposited.
• the anode usually, although not necessarily, consists of a solid metal or metal alloy containing metal identical to the metal of the plating metal ions in the electroplating bath. Such metal ions will be transformed into a film or plate of elemental metal as they are electrically deposited upon the cathode.
• Electroplating baths are usually aqueous alkaline solutions or dispersions of metal cyanides and often have disadvantages (depending upon the particular metal ion and/or the particular surface on which the metal ion is to be deposited) of producing relatively dull or lusterless plates or coatings and/or deposits of coatings of uneven thickness.
• the use of metal cyanide solutions can be hazardous since, if the pH of the electroplating medium should drop to neutral or below, there is a danger of poisonous hydrogen cyanide gas being produced.
• the use of metal cyanides presents a disposal problem due to their toxicity and such disposal, unless the cyanides are dumped into sewers or streams in which they cause pollution, is expensive. 1
• 2,195,409 to partially overcome some of the disadvantages of dull plates or plates of uneven thickness by adding to an electric bath, containing a metal cyanide, a nuclear alkyl derivative of an aromatic sulfonic acid of the benzene series (as distinguished from nuclear alkyl derivatives of condensed polynuclear aromatic sulfonic acids such as those of the naphthalene series).
• a metal cyanide a nuclear alkyl derivative of an aromatic sulfonic acid of the benzene series (as distinguished from nuclear alkyl derivatives of condensed polynuclear aromatic sulfonic acids such as those of the naphthalene series).
• an alkyl aromatic sulfonate eliminates pitting (e.g., uneven thickness) and the formation of pin holes in the metal plate.
• the plates are bright, uniform deposits of metal.
• the present invention provides, in part, an electrically conductive medium comprising an aqueous solution (or dispersion) of a composition comprising (1 a complex consisting of a metal ion and an ethylenediarnine tetra(methylene phosphonate) ligand of the formula:
• M is hydrogen, alkali metal (such as sodium, potassium, lithium and the like) ammonium, alkylammonium and amine; and (2) a complex consisting of a metal ion and a l-hydroxy, ethylidene-1,ldiphosphonate ligand of the formula:
• the two complex"-containing composition is present in suchsolution (or dispersion) in an amount sufficient to electrically deposit the metal of a metal ion when an electric current is passed through said solution (or dispersion). More specifically, it is found that the use of this two complex-containing composition results in a unique cooperative effect as contrasted to the use of either complex (1) or (2) above on an individual basis. This cooperative effect is quite unexpected as will be seen from the results hereinafter described in the Examples.
• a. aqueous solution includes and means both a solution and a dispersion of the composition (described below).
• aqueous solution of a) compsition includes and means both of the complexes l and (2)" described above, and/or a single complex consisting of a metal ion, the ethylenediamine tetra- (methylene phosphonate) ligand, and the lhydroxy, ethylidene- 1 1 -di'phosphonate ligand.
• EDTMP or ethylenediamine tetra(methylene phosphonate) ligan includes and means all of the compounds falling within Formula I above (e.g., full acid, salts and partial salts).
• HEDP or I-hydroxy, diphosphonate ligand includes and means all of the compounds falling within Formula II above (e.g., full acid, salts and partial salts).
• the metal ion is advantageously a metal ion from the group cobalt, silver, tin, gold, copper, iron, nickel, zinc and cadmium ions.
• the particular metal employed to form the aforementioned complexes with the EDTMP and HEDP ligands will generally depend upon the metal which it is desired to electrically deposit.
• metal ions to be employed are preferably those water-soluble metal compounds which form chelates with EDTMP and HEDP, i.e., the chelate constituents.
• metal compounds used in the present invention can be (1) simple ionic metal salts which, when dissolved, set free a metal ion capable of a chelate formation, for example, coppersulfate, or (2) they are more complex salts which, when dissolved, give a metal ion capable of a chelate formation, for example, sodium zincate, or (3) metal salts, such as the carbonates, which react with the EDTMP and HEDP chelate constituents, and form metal chelate salts.
• the plating of alloys can be accomplished according to the invention by the use of two or more difi'erent metals capable of a chelate formation used in correct proportions.
• the plated alloys of the invention there may be mentioned copper-nickel alloys and copper-zinc alloys yellow brass and white brass.
• the amounts of metal ions (in the form, for example, of water-soluble metal salts) and the EDTMP and HEDP ligands utilized in the electroplating medium or galvanic baths can vary depending upon several variables such as bath temperature, pH, substrates to be plated, water-solubility of the composition, i.e., the metal ion EDTMP and HEDP complexes, and the like. 0f the above-described composition, it is preferred to be water soluble to an extent such as to provide from about 0.1 percent to about 5 percent by weight, preferably 1 percent to about 5 percent by ethylidene-1,1-'.
• suitable electroplating baths of the invention can also be prepared by using from about 0.01 to about 400 grams of the EDTMPHEDP (chelate constituent) per liter; a concentration of 50 to .150 grams per liter is utilized effectively.
• EDTMPHEDP chelate constituent
• the mole ratios of EDTMP and I-IEDP to metal ion be within a certain range in order to produce the cooperative effect heretofore described.
• the mole ratio of BBB? to metal ion is from about 1:1 to about 4:1, preferably from about 1.5:1 to about 3:1.
• EDTMP the mole ratio of BBB? to metal ion
• the amount of the composition comprising a metal ion and the EDTMP-HEDP ligands which may be present in the electrically conductive medium may vary considerably and will usually depend upon the solubility of the composition; Generally speaking, the amount 0 composition is based upon the amount of metal employed and the composition is usually present in an amount which is sufficient to provide from about 0.1 percent to about 5 percent by weight, based on the weight of the aqueous solution of metal in the form of metal ion. Such compositions comprising these metal complexes are usually substantially soluble under these circumstances. The particular concentration of the composition within the above range will depend primarily upon the particular metal of the metal complexes.
• the concentration of the composition preferably is a concentration sufficient to provide from about 1 percent to about 5 percent by weight of copper or iron.
• the concentration of the composition is preferably a concentration sufficient to provide from about 1.5 to about 3 percent by weight of the nickel.
• the concentration of the composition is preferably such as to provide a concentration from about 2 percent to about 5 percent by weight of the zinc; and in the case of cadmium theconcentration of the composition is preferably such as to provide a concentration from about 1 to about 4 percent by weight of cadmium.
• the electrically conductive medium which comprises an aqueous solution of the composition comprising the metal complexes
• has a wide pH range for example, a pH range of from about 6.0 to about 13.0; however, lower and higher pI-ls are operative.
• the pH of the medium will depend to some extent upon the metal ion of the metal complexes, the alkali metal or hydrogen cation and also to some extent upon the substrate upon which the metal ion is to be electrically deposited in the elemental state.
• the pH of the medium may be in the range of from about 6.0 to about 13.0, the higher pl-ls being attained when M in the above described Formulas l or II is an alkali metal cation instead of a hydrogen cation.
• the pH of the medium is preferably in the range of from about 7.0 to about 10.5.
• the electrically conductive medium containing copper EDTMP-HEDP complexes is to be used for plating, for example, copper on aluminum the pH of the medium may be in the range of from about 7.0 to about 12.
• the electrically conductive medium comprises an aqueous solution containing iron ions and the EDTMP-HEDP ligands
• the medium preferably has a pH in the range of from about 7.0 to about 10.0.
• the pH of the medium preferably is in the range of from about 6.0 to about 11.0
• the pH of the medium preferably should be in the range of from about 7 to about 10.
• the electrically conductive medium comprises an aqueous solution of a complex containing nickel ions and the EDTMP-HEDP ligands
• the pH of the medium preferably should be in the range of from about 6.5 to about 11. Media having pHs within this range have been found to be particularly advantageous when it is desired to deposit nickel on zinc, brass or steel.
• the electrically conductive medium comprises an aqueous alkaline solution of a composition containing divalent zinc ions and the EDTMP-HEDP ligands
• the pH of the medium usually should be in the range of from about 6.5 to about 12, preferably in the range of from about 7.5 to about 10, and such a medium has been found particularly advantageous in the electrodeposition of zinc on steel and brass.
• the electrically conductive medium comprises an aqueous alkaline solution of a composition containing divalent cadmium ions and the EDTMPHEDP ligands
• the pH of such medium usually should be in the range of from about 7.0 to about 1 1.0, preferably in the range of from about 8.0 to about 10.0, and such medium has been found to be particularly advantageous in the electrodeposition of cadmium on steel or brass.
• the electrically conductive medium comprising the aqueous solution of the composition
• the metal complexes may be synthesized prior to its dissolution or dispersion in water, it has been found generally desirable to dissolve component precursors of the complexes in water to form the composition containing the desired metal ion and the EDTMPHEDP ligands.
• the components of the composition which usually comprises the EDTMP-HEDP ligands, an alkali metal ion and a divalent metal ion, may be dissolved in the aqueous medium (usually water) simultaneously or in any order.
• aqueous medium usually water
• the metal (ion) in the form of a water soluble salt consisting of the metal (ion) and a nonoxidizing anion.
• the metal (ion) salt in the acid form, may be dissolved in water, the metal (ion) salt added'to the solution and thereafter the alkali metal is dissolved in the solution.
• the anions of the metal salts are preferably nonoxidizing anions such as, for example, sulfate, chloride, phosphate, citrate, carbonate, oxide, or acetate anions.
• anions such as carbonate or sulfate anions are preferred for copper cations.
• the alkali metal in the form of a water soluble alkali metal 'salt, containing any of the anions referred to above.
• a plating bath which has been found particularly advantageous may be prepared by first dissolving the full acids of EDTMP and HEDP in water. To the resulting solution there is added the desired amount of metal salt and the resulting solution may then be adjusted to the desired pH by the addition of an alkali metal carbonate.
• the present invention further provides a process for the electrodeposition of a metal (ion) which comprises the steps of electrolyzing an aqueous solution of a composition comprising metal complexes consisting of any of the metal ions hereinbefore described and the EDTMP-BED? ligands.
• the amount of composition present in the solution is, for example, an amount sufficient to provide from about 1 percent to about 5 percent by weight, based on the weight of the disperl060l l 0266 sion, of said metal.
• metals such as copper, iron, nickel, zinc and cadmium may be electrically deposited on a cathode comprising substrates such as steel, aluminum, brass, zinc and the like.
• the bath is maintained at a temperature of from just above the freezing point to just below the boiling point of the aqueous solution, generally from room temperature to 90C.
• a temperature of the electrically conductive medium inthe range of from about 40C to about 80C.
• the amount of current employed in the electrodeposition may vary widely depending upon the particular metal ionin the form of complexes with the EDTMP--HEDP ligands, the particular EDTMP HEDP ligands, the temperature of the medium and whether or not the medium is agitated during the passage of the electric current therethrough.
• the amount of current employed will be a current suffi cient to provide a current density of from about 0.5 to about 300 amperes per square foot of electrode surface.
• the current employed will be an amount sufficient to provide a current density of from about 1 to about 150 amperes per square foot and when the electrically conductive medium is agitated the current employed will be an amount sufficient to provide a current density in the range of from about 1 to about 300 amperes per square foot of electrode surface.
• the amount of current employed will depend to some extent on the metal (ion) which it is desired to deposit.
• the electrically conductive medium will comprise an aqueous alkalinesolution containing complexes of divalent copper ions and the FDTMP- HEDP ligands and the current employed will be preferably an amount sufficient to provide a current density of from about 1 to about 120 amperes per square foot of electrode surface.
• the preferred amount of current will be an amount preferably sufficient to provide a current density in the range of from about 2 to about 60 amperes per square foot.
• the amount of current employed will be an amount sufficient to provide the current density of from about 2 to about 120 amperes per square foot.
• the electrically conductive medium when it is desired to electrodeposit copper, will comprise an aqueous alkaline solution containing divalent copper ions and EDTMP-HEDP ligands.
• the current employed preferably is an amount sufficient to provide a current density of from about 1 to about 100 amperes per square foot of electrode surface.
• the preferred amount of current When the medium is not agitated the preferred amount of current will be an amount sufficient to provide a current density in the range of from about 2 to about 50 amperes per square foot of electrode, whereas when the medium is agitated, the preferred amount of current employed will be an amount sufficient to provide a current density of from about to about 100 amperes per square foot of electrode.
• the electrically conductive medium will comprise an aqueous alkaline solution containing divalent nickel ions and EDTMP-HEDP ligands, and the current employed will usually be an amount sufficient to provide a current density of from about 1 to about 300 amperes per square foot of electrode surface.
• the amount of current will be that which preferably will provide a current density in the range of from about 5 to about amperes per' square foot,
• the amount of current will preferably be an amount'sufficient to provide a current density of from about 2 to about 50 amperes per square foot of electrode surface.
• the electri cally conductive medium will comprise an aqueousalkaline solution containing complexes of divalent zinc ions and EDTMP-HEDP ligands, and the current employed will be an amount sufiicient to provide a current density of from about 1 to about 50 amperes per square foot of electrode surface.
• the preferred amount of current employed will be an amount sufficient to provide a current density of from about l to about 25 amperes per square foot whereas, when the medium is agitated, the current employed will be an amount sufficient to provide a current density of from about 1 to about 50 amperes per square foot of electrode surface.
• the electrically conductive medium When it is desired to electrodeposit cadmium, the electrically conductive medium will comprise an aqueous alkaline solution containing complexes of divalent cadmium ions and EDTMP-HEDP ligands.
• the current employed will be an amount sufficient to provide a current density of from about I to about 50 amperes per square foot of electrode surface.
• the electrically conductive medium When the electrically conductive medium is not agitated the preferred amount of current will preferably be an amount sufficient to provide a current density in the range of from about 2 to about 40 amperes per square foot whereas if the electrically conductive medium is agitated, the amount of current will preferably be an amount sufficient to provide acurrent density of from about 1 to about 50 amperes per square foot of electrode surface.
• the time required to electroplate or to electrically deposit the metals will vary with the current density in the medium and will depend upon the thickness of the plate or deposit which it is desired to obtain. Generally, the greator the current density, the shorter will be the time required to produce a deposit or plate comprising a given thickness of electrically deposited metal.
• This preferred process comprises passing an electric current, at a density in the'range of from about 5 to about 150 amperes per square foot of electrode surface, through an aqueous alkaline solution containing complexes of divalent copper ions and potassium salts of the EDTMP-HEDP ligands, i.e., hexapotassium ethylenediamine tetra(methylene phosphonate) and tetrapotassium l-hydroxy, ethylidene-l,l-diphosphonate, having a pH in the range of from about 7.0 to about 10.0.
• the amount or concentration of the composition containing these complexes in the solution is an amount sufficient to provide from about 1 percent to about 5 percent by weight, based on the weight of the solution, of copper and the temperature of the solution is maintained within the range of from about 50C to about 70C during the passage of 5 the electric current therethrough.
• an electric current at a density in the range of from about 5 to about 150 amperes per square foot of electrode surface is passed through an aqueous alkaline solution containing complexes of divalent nickel ions and potassium salts of the EDTMP-HEDP ligands, i.e., hexapotassium ethylenediamine tetra(methylene phosphonate) and tetrapotassium l-hydroxy, ethylidene-l ,1- diphosphonate, having a pH in the range of from about 8.0 to about 10.5.
• the concentration of the composition containing these complexes in the solution is sufficient to provide from about 1 percent to about 5 percent by weight, based on the weight of solution, of nickel and the temperature of the solution is maintained in the range of from about 50C to about 70C during the passage of the electric current therethrough.
• the plating (galvanic) solutions of the present invention can contain the known brighteners, buffers, and leveling agents and other additives. Boric acid. and its salts are the compatible buffers for many formulas of the invention.
• the known brighteners suitable for a certain metal, when present in the galvanic solutions described here, are in general beneficial for the same metal; for example, selenites and arsenites are useful for the copper plating bath and aldehydes and ketones for the zinc plating bath.
• EXAMPLE I Approximately 22 tests were conducted in this Example in order to show the cooperative effect of the l-lEDP and EDTMP ligands in the electrodeposition of metals from an electroplating solution containing such ligands, as contrasted to the utilization of these ligands on an individual basis.
• Twenty two plating solutions were individually prepared in a glass beaker in the following manner.
• the solutions were prepared in deionized water by first adding potassium hydroxide followed by the particular ligand and then a copper salt which was copper sulfate.
• Final adjustment of the pH of each solution was made with the addition of potassium hydroxide.
• the pH of each solution was approximately 8.0. It was noted that considerable heat was evolved during the addition of the ligand to the potassium hydroxide aqueous solution and that the temperature reached 60-70C within a few minutes. This temperature range resulted in a quick dissolution of the ligand and the copper sulfate into the aqueous solution.
• the solution was heated up to 80C and stirred vigorously for an additional 20 minutes.
• the solutions were cooled, if necessary, to the plating temperatures indicated in Table l and transferred from a beaker to a Hull Cell.
• the particular ligand utilized, the ligand to copper mol ratio and the percent copper in solution are all shown in Table I.
• the Hull Cell was constructed substantially as the electrolysis cell described in US. Pat. No. 2,149,344 (which in incorporated herein by reference) and the galvanic deposition was performed with intermittent agitation.
• the Hull Cell utilized in this case had a capacity of 1,000 milliliters.
• This type of Hull Cell is standard equipment for the evaluation of electroplating solutions by the determination of the brightness range. By subjective evaluation, this permits the formulation of a brightness rating which takes into consideration the overall variables utilized in and the end results'obtained from the electroplating test.
• the particular cathodes utilized in this test were brass or steel as so indicated in Table l and were each X 3% inches in size.
• the anode utilized in these tests was made of copper and was 2% X 2% inches in size.
• each test was conducted for a period of 5 minutes at a constant current of 5 amperes.
• the results of these 22 tests are set forth in Table l and particular attention is directed to the column designated Brightness Rating which is the basic criteria for an evaluation of the electroplating effects on an overall basis.
• Example ll The procedure utilized in the above Example I was also-utilized in this Example ll in order to prepare the solutions and effect the test designated as Nos. 1 14 in Table II. Each electroplating solution was adjusted, however, to a pH 10 in this Example ll as compared to the pH 8 of Example I plating solutions. The Hull Cell was the same in both examples.
• test Nos l 4 show the utilization of the HEDP ligand per se with a brass and steel cathode. The brightness ratings of these tests ranged from fair to good.
• Test Nos 5, 6 and 7 show the effect of utilizing the EDTMP ligand per se with brass and steel cathodes. These tests result in brightness ratings of very bad to poor.
• test Nos. 8, 9 and 10 result in brightness ratings of very good in all three tests with the utilization of both brass and steel cathodes.
• IIEDP+EDTMP (2+0. 25) 1 2 70 0-60 Very good... Ver bright very good adhesion.
• IIEDP+EDTMP (2+0. 2s 1 2 70 0-75 do 15o.
• LCDA low current density area.
• Example ll EDTM P ligands in electroplating solutions is vividly illustrated in this Example ll as with Example land show the uniqueness of this combination as compared to the utilization of these ligands on an individual basis.
• EXAMPLE Ill Where one so desires to achieve the cooperative effect derived from the present invention, other plating solutions can be prepared and different cathode and anode materials utilized all in an electrodeposition process.
• cathodes such as zinc and aluminum can be interexchanged with anodes prepared from copper, nickel, cadmium, iron, zinc, cobalt and cadmiumnickel materials.
• the plating solutions can be prepared utilizing salts (which supply the metal ion for the HEDP-EDTMP complexes) such as copper carbonate, potassium carbonate, nickel carbonate, cadmium carbonate, iron chloride, zinc oxide, cobalt citrate, sodium zincate, nickel sulfate and iron sulfate.
• a process for the electrodeposition of a metal which comprises the step of electrolyzing an aqueous solution having a pH of from about 6.0 to about 13.0 of a composition comprising (1) a complex consisting of a metal ion and an ethylenediamine tetra (methylene phosphonate) ligand and (2) a complex consisting of a metal ion and a l-hydroxy, ethylidene l, l diphosphonate ligand: wherein said composition is present in said solution in an amount sufficient to provide from about 0.1 percent to about 5 percent by weight, based on the weight of said solution, of said metal and wherein said diphosphonate to metal ion mol ratio is from about 1.0:] to about 4.0:], and said methylene phosphonate to metal ion mol ratio is from about 0.121 to about 1.021; said solution being at a temperature in which the solution produces galvanic deposits.
• the metal ion is a transitional metal ion selected from the group consisting of gold, copper, iron, nickel, zinc and cadmium ions.
• a galvanic bath useful for the preparation of galvanic metal deposits which comprises a substantially cyanide free aqueous solution having a pH of from about 6.0 to about 13.0 which contains a composition comprising (1) a complex consisting of a metal ion and an ethylenediamine tetra (methylene phosphonate) ligand and 2) a complex consisting of a metal ion and a l-hydroxy, ethylidene-l, l-diphosphonate ligand; wherein said composition is present in said solution in an amount sufficient to provide from about 0.1 percent to about 5 percent by weight, based on the weight of said solution, of said metal and wherein said diphosphonate to metal ion mol ratio is from about 1.011 to about 4.021, and said methylene phosphonate to metal ion mol ratio is from about 0.121 to about 1.0:1.
• diphosphonate ligand is l-hydroxy, ethylidene-l,1- diphosphonic acid.
• the metal ion is a transitional metal ion selected from the group consisting of gold, copper, iron, nickel, zinc and cadmium ions.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Chemically Coating (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=26894390

Family Applications (2)

Family Applications After (1)

Country Status (7)

Cited By (39)

Families Citing this family (11)

Citations (5)

Family Cites Families (1)

• 0
  • BE BE791401D patent/BE791401A/fr not_active IP Right Cessation
• 1971
  • 1971-11-15 US US199036A patent/US3706635A/en not_active Expired - Lifetime
  • 1971-11-15 US US199028A patent/US3706634A/en not_active Expired - Lifetime
• 1972
  • 1972-11-14 FR FR7240384A patent/FR2160458B1/fr not_active Expired
  • 1972-11-14 CA CA156,727A patent/CA1009177A/en not_active Expired
  • 1972-11-14 GB GB5243972A patent/GB1370387A/en not_active Expired
  • 1972-11-14 JP JP11420272A patent/JPS568113B2/ja not_active Expired
  • 1972-11-14 DE DE2255728A patent/DE2255728C2/de not_active Expired

Patent Citations (5)

Also Published As

Similar Documents