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
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/562—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of iron or nickel or cobalt
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F10/00—Thin magnetic films, e.g. of one-domain structure
  • H01F10/06—Thin magnetic films, e.g. of one-domain structure characterised by the coupling or physical contact with connecting or interacting conductors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
  • H01F41/24—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates from liquids
  • H01F41/26—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates from liquids using electric currents, e.g. electroplating

Definitions

• Patent Faulkner [54] METHOD OF ELECTRODEPOSITING FERROMAGNETIC ALLOYS [72] Inventor: John P. Faulkner, Thousand Oaks, Calif.
• ABSTRACT Deposition of cobalt-phosphorus and cobalt-nickelphosphorus alloys, on conductive carriers, from an aqueous bath containing the metal ions and at least hypophosphite ions as the source of phosphorus.
• the deposition is solely the result of electrolysis.
• the aqueous bath has a pH of from 3.2 to 5.0.
• the current density is maintained in the range of 10 to 120 amperes per square foot.
• the products have magnetic properties rendering them valuable for application as high-density digital recording media.
• An improvement over the basic process involves the use of both phosphite ions and hypophosphite ions as the source of phosphorus.
• the phosphite ions decrease the concentration of hypophosphite ions required and increases stability of the electrolyte.
• This invention relates to ferromagnetic coatings and more particularly to an electrolytic method of depositing ferromagnetic coatings and the composition thereof. 1
• Digital computers handle large volumes of information at high speeds and this information is generally coded in binary form which may be recorded on a ferromagnetic coating embodied in one of the well known forms.
• a piece of binary information in a digital computer is generally identified as a bit" and these bits are usually recorded in tracks which are produced by the passage of a magnetic recording head over the ferromagnetic surface.
• the number of bits per square inch of coating which may be recorded is an important factor in determining the cost of recording equipment.
• the recording density is generally specified as the number of bits per linear inch of recording track and stated in bits per inch. It will be recognized, then that the magnetic characteristics of a ferromagnetic coating for recording information are important as to the number of bits per inch which may be recorded and intelligently reproduced. To this end, an important characteristic of the ferromagnetic coating is the coercivity thereof.
• the recording information exists in the ferromagnetic coating as large numbers of very small magnetized areas and the presence of these magnetic poles induces within the surface of a field which tends to demagnetize these areas.
• the coercivity of the ferromagnetic coating be controlled to provide a level which will minimize the effects of the self-induced demagnetizing field and, at the same time, will not be excessively great.
• other magnetic characteristics of the ferromagnetic coating are also of importance in determining the maximum recording density which may be achieved. Increasing the squareness ratio of the magnetic hystersis loop characteristic of the ferromagnetic coating results in a reduction in the minimum coercivity necessary to minimize the demagnetizing effect.
• a proportional decrease in the thickness of the coating may be achieved without a decrease in the read-back signal amplitude. Since a reduction in the thickness of the ferromagnetic coating results in a reduction in the minimum magnetic field to be produced by the recording head and improved resolution of the recorded infonnation, the maximum obtainable remanence is to be desired. Therefore, for any given combination of recording head and recording mode, there is an optimum combination of coercivity, squareness ratio, remanence and thickness of the ferromagnetic coating.
• the basic form of the present invention provides an improved method of depositing a ferromagnetic coating, having superior high-density recording qualities over those heretofore known.
• the improved method involves deposition solely through electrolytic action, by which the coercivity of the resultant coating can be predicted by controlling the composition of the electrolyte.
• the method of the present invention is inexpensive and very rapidly produces ferromagnetic coatings.
• a coating suitable for high-density binary recording applications is deposited in a period of time on the order of l minute.
• the method of the present invention allows the coercivity of a ferromagnetic carrier to be controlled and predicted through the control of the quantity of hypophosphite ions that is placed in the electrolyte to produce a coating which permits high recording densities, on the order of 2,000 binary bits per inch, that are readily reproducible.
• the pH of the plating bath is maintained in the range of 3.2 to 5.0 and the current density at the cathode is maintained in the range of l to 120 amperes per square foot.
• the aforementioned basic form of the present invention is of considerable importance to high-density recording techniques and is a significant stride forward in the art of plating high-density magnetic recording films. However, it has become necessary to plate films capable of recording at even high densities in the order of 3,000 bits per inch and higher. This also can be achieved in accordance with the aforementioned basic form of the invention by increasing the concentration of hypophosphite ions in the bath.
• hypophosphite ions which have been oxidized from the hypophosphite ions.
• Hypophosphite ions are to 30 times as an effective source of phosphorus as phosphite ions therefore the phosphorus and hence the coercivity of the film will change markedly as the hypophosphite ions oxidize to phosphite ions.
• phosphite ion may be employed as a partial source of phosphorus for electrodeposition of cobaltphosphorus and cobalt-nickel-phosphorus alloys from these baths. Therefore, high coercivity recording films may be electrodeposited from electrolyte containing a smaller concentration of hypophosphite ion that would be required if hypophosphite ion alone is employed as the source of phosphorus.
• recording films deposited from baths which employ both hypophosphite and phosphite ions as sources of phosphorus are, in fact, as suitable for high-density magnetic recording media as are those deposited from baths which employ only hypophosphite ion as a source of phosphorus.
• hypophosphite ion Since the rate of oxidation of hypophosphite ion to phosphite ion at the catalytic surfaces is proportional to the concentration of hypophosphite ion in the bath and since phosphite ion is not oxidized at the catalytic surfaces, employment of both hypophosphite and phosphite ions as sources of phosphorus to reduce the concentration of hypophosphite ion required for a given coercivity provides a bath which demonstrates a greater chemical stability in the presence of the catalytic surfaces of the anodes.
• the resulting chemical stability is important because the characteristics of the film being plated must be accurately matched to the characteristics of the magnetic recording heads used to record on the recording films. As a result, the coercivity must be accurately reproduced from one plating run to the next. Control has been achieved using the process in accordance with the basic form of the present invention by control over the concentration of hypophosphite ions in the electrolyte. However, the control of the hypophosphite ions alone becomes quite difi'lcult for higher density recording films in the order of 3,000 bits per inch and higher.
• an improved method or process in accordance with the present invention utilizes phosphite ions in addition to hypophosphite ions in the plating bath and the concentration of the phosphite ions (as well as the concentration of the hypophosphite ions) are controlled.
• the hypophosphite ions are controlled within the range of 0 to 4 grams/liter for a cobalt-phosphorus film and within the range of O to 2.0 grams/liter for a cobalt-nickel-phosphorus film.
• the phosphite ions are controlled within the range of 0 to 12 grams/liter.
• the ratio of hypophosphite ions to phosphite ions in the bath is less than 1 to 7 for cobalt-nickel-phosphorus films and 2 to 7 for cobalt-phosphorus films.
• the recording densities in the order of 2,000 and 3,000 binary bits per inch have been achieved from processes in accordance with the present invention with the recording heads spaced up to 100 microinches from the recording film. This is important as it is much more difiicult to achieve higher recording densities when the recording head is spaced away from the recording film than when the recording head is in contact.
• the ferromagnetic coating produced by the method of the present invention may consist of cobalt and small amounts of phosphorus when deposited from an electrolyte made up principally of cobalt, or of a cobalt-nickel alloy containing small amounts of phosphorus when deposited from an electrolyte having cobalt and nickel as the principal constituents.
• the cobalt-nickel alloys may contain up to 25 percent of nickel.
• the substrate or the carrier for the ferromagnetic coatings is utilized as the cathode in an electrolytic plating cell.
• the carrier may be composed of any of the well-known nonferromagnetic materials, such as the brasses bronzes, aluminum and aluminum alloys and magnesium and magnesium alloys; of ferromagnetic material over which is deposited or laminated a nonferromagnetic material or of a nonconductive material over which is deposited or laminated a conductive nonferromagnetic material.
• the anode for the electrolytic cell is characterized as constructed of the principal elements of the bath and in a cobalt-nickel process may be constructed of an alloy of percent cobalt and 20 nickel.
• the anode material may be pure cobalt or pure nickel with the other element being added to the electrolyte proper as a salt of the metal.
• the electrolyte proper as a salt of the metal.
• a pure cobalt anode is utilized, a nickel salt is added to the electrolyte and the electrolyte is diluted at intervals to maintain the proper composition of nickel and cobalt.
• the remaining constituents of the bath must also be added to the electrolyte when dilution is carried out to maintain the proper composition of the electrolyte.
• the electrodes are connected in a direct current circuit in the conventional fashion to cause the electrolytic action to produce the deposit at the cathode functioning as the magnetic coating.
• the composition of the electrolyte is as follows:
• Cobalt-Nickel Alloy Deposition Ranges of Composition Cobaltous lons, Co, as Cobaltous Sulfate, C080 Nickelous Ions, Ni, as Nickelous Sulfate, NiSO, Additional Sulfate lons, S0,”, as Na,SO, Formate lons, CHO ⁇ , as NaCHO, Boric Acid, H 80; Hypophosphite lons, H PO,a-, as NaH,FO,* 0-2.75 g./1.-0.0-0.04N
• the sodium salt is preferred.
• Cobalt Deposition Ranges of Composition Cobaltous lons, Co, as cohaltous sulfate, CoSO, Additional Sulfate Ions, S0,, as Na,SO, Formate lons, CHO ⁇ , as NaCHO, Boric Acid, B0; Hypophosphite lons, H,PO,a-, as NaH,PO,* 0-6 g./1.-0.00.09N
• the sodium salt is preferred.
• the above electrolytes may have a pH within the range of 3,2 to 5.0 and, preferably have a pH of 3.8 which is maintained in a stable condition by the additon of sulfuric acid, H 80
• the cathode current density applied through the electrodes may vary from 10 to 120 amperes per square foot.
• the temperature is maintained in the range of 90 to 140 F. and, preferably, should be maintained in the range of 100 to 110 F.
• the ferromagnetic coatings which are deposited on the cathodes may have thicknesses of 10 to 500 millionths of an inch. When the coatings are to be used for high-density binary recording, the preferred thickness is of the order of 50 millionths of an inch. Thicknesses of 5 millionths of an inch may be desirable as higher density recordings are achieved.
• aqueous electrolytes include sulfate, it is added to improve the electrical conductivity thereof while the boric acid is used in the conventional fashion as a buffer to stabilize the pH of the solution.
• boric acid is used in the conventional fashion as a buffer to stabilize the pH of the solution.
• formate is included, it is added as a brightener.
• hypophosphite ions At this minimum coercivity, the remanence is at a maximum.
• the coercivity of the deposited ferromagnetic coat ing may not only be controlled but predicted by controlling the amount of phosphorus that is added to the electrolyte and particularly phosphorus in the form of a hypophosphite ion. To this end, it has been found that the coercivity of the deposited ferromagnetic coating increases as the amount of hypophosphite ion in the electrolyte is increased. In coatings having the minimum coercivities, the remanence is 13,000 to 15,000 gausses.
• hypophosphite ions to the electrolyte, it has been found that with an increase in the coercivity to 300 oersteds the remanence decreases to 8,500 to 10,000 gausses and then stays approximately constant as the coercivity is further increased.
• the coercivity of the deposited coating can be controlled to achieve preselected values in the range of to 800 oersteds for cobalt nickel alloy deposits and in the range of 60 to 700 oersteds for cobalt coatings.
• the deposited ferromagnetic coating assumes the composition of the essential elements in the electrolyte but, in the case of cobalt-nickel alloys, not in the same proportions as these elements are present in the electrolyte. Accordingly, the ferromagnetic coatings produced by the present invention may comprise essentially cobalt or cobalt-nickel alloys as these elements are present in the electrolyte and small amounts of phosphorus.
• hypophosphite ion in the electrolyte of the present invention to thereby cause the coating to exhibit an increased coercivity.
• the amount of hypophosphite ion and thereby the coercivity may be increased. 1
• Hypophosphite ions as the source of phosphorus in the process of the present invention, are felt to be important in producing the high density magnetic recording films.
• composition of an electrolyte utilizing a combination of hypophosphite ions and phosphite ions in accordance with the improved form of the present invention is as follows:
• Cobalt-Nickel-Phosphorus Alloy Deposition Ranges of Composition Cobaltous Ions, CO", as Cobaltous sulfate, CoSO 10-50 g./l. Nickelous ions, Ni, as Nickelous sulfate, NiSO, 10-50 g.l
• H,PO Phosphite Ions
• H,PO Phosphite Ions
• H,P0,' Hypophosphite lons
• H,P0,' Hypophosphite lons
• H,P0,' as the salt of Na, K, Ca, NH, or as H ,PO, 0-2.0 g./1.
• Cobalt-Phosphorus Alloy Deposition Ranges of Composition Cohaltous Ions, CO", as Cobaltous sulfate, CnSO, 20-80 g./l. Additional Sulfate Ions, 80,, as the salt of Na, K, Ca, or NH, -12 g./l. Formate Ions, COOH, as HCOOH or as the salt of Na, K, Ca, NH, or Ni 0-20 gJl. Boric Acid, H ,BO, 0-40 g./l. Phosphitc Ions, H,PO,, as the salt ofNa, K, Ca. NH, or as H,PO, 0-12 g./l, Hypophosphite Ions, H,PO ⁇ or as the salt of Na, K. Ca, NH, or as H PO, 0-4.0 g./l.
• Co Cobalt-Nickel Phosphorus Alloy Deposition Ranges of Composition Cobaltous Ions, Co", as Cobaltous sulfate CoSO, 20-50 gJl.
• Nickelous Ions, Ni as Nickelous sulfate, M80, 20-50 g./l.
• Phosphitc Ions, H,PO ⁇ as the salt of Na, K, Ca, NH, or as H,PO 7.5-12 g./l.
• Hypophosphite Ions, H,PO ⁇ as the salt ofNa, K, Ca, NH or as H PO, 0-l.10 g./l. 5
• Cobalt-Phosphorus Alloy Deposition The aforementioned electrolytes must have a pH in the range of 3.2 to 5.0 or preferably a pH of 3.8 maintained by addition of nickel, potassium, or sodium carbonate or sulfuric acid, as required to maintain the chosen value.
• the cathode current density should be maintained in the range of 10-120 amperes per square foot with a temperature in the range of 90-140bL F. Preferably the temperature is maintained in the range of 100 to 110 F.
• the bath is preferably agitated adjacent to the surface being plated for high density recording films.
• hypophosphite ions to phosphite ions is less than 1 to 7 for cobalt-nickel-phosphorus films and less than 2 to 7 for cobalt-phosphorus films.
• the change in hypophosphite ions due to oxidation does not appreciably change the phosphorus and hence the coercivity in the resulting film. This is due to the much greater contribution to phosphorus by the phosphite ions.
• Cobalt-Nickel-Phosphorus Alloy Deposition Ranges of Composition Cobaltous Ions, Co", as cobultous sulfate, C050 25 g./l.
• Nickelous Ions, Ni as nickelous sulfate, NiSO, 28 gJI.
• Hypophosphite Ions, H,PO,' as NaH,PO 1.05 g./I.
• Cobalt-Phosphorus Alloy Deposition Ranges of Composition Cobaltous Ions, Co, as Cobaltous sulfate, C050. 50 g./l. Additional Sulfate Ions, S0,", as Na,S0, 8.0 g./l. Formate Ions, COOH', as NaCOOH 20 g./l. Boric Acid, H ,B0, 30 g./l. Phosphite Ions, H,PO, as NaH P0, 12 71. Hypophosphitt: Ions, H,PO, as NaH,PO, 1.7 g./l.
• Recording films were deposited from the aforementioned two electrolytes at a pH of 3.8, a temperature of F. and a current density of 45 amperes per square foot.
• the control described herein is achieved by analysis of the electrolyte using conventional techniques to determine the concentrations of hypophosphite ions and phosphite ions.
• the control also involves adjusting the concentrations of hypophosphite ions and phosphite ions so that a predetermined desired coercivity is achieved.
• a predetermined desired coercivity is achieved.
• the phosphite ion concentration by addition of phosphorous acid, it is preferred to neutralize the phosphorus acid to the pH of the rest of the electrolyte before addition to the bath.
• the predetermined coercivity is preferably a single value but may be a relatively small range of coercivities within the tolerances of the magnetic recording and reading heads and the associated electronic circuitry to be used therewith. This range of permissible coercivities is smaller at higher recording densities than at lower recording densities.
• the adjustment of the hypophosphite ions may be accomplished by adding hypophosphite ions to the electrolyte from time to time as needed, as the hypophosphite ions oxidize.
• the adjustment of the phosphite ions may be accomplished by diluting the electrolyte from time to time as needed to maintain the concentration of phosphite ions, in proportion to the hypophosphite ions, at a level where the predetermined coercivity is obtained.
• the phosphite ions may be removed to reduce the concentration.
• adjustment may also include addition of hypophosphite ions to the electrolyte from time to time as required to maintain a prefixed concentration thereof and allowing the phosphite ions to build up from an initial value to a maximum value at which time the electrolyte is replaced.
• hypophosphite ions and phosphite ions start with 0, it will be understood that this value is given as a limit and that there must be some phosphite ions or hypophosphite ions present as the case may be.
• the method for the deposition of a ferromagnetic recording film on an electrically conductive carrier comprising subjecting the carrier as cathode to a current density of between l and 120 amperes per square foot in an aqueous electrolyte having a pH of 3.2 to 5.0 wherein the aqueous electrolyte consists essentially of:
• the source of phosphorus comprising at least some hypophosphite ions up to 2.75 grams per liter, derived from sodium hypophosphite; the bath being maintained at a temperature in the range of 100 F.
• aqueous electrolyte comprising cobaltous ions in the range of 20 to 80 grams per liter and a source of phosphorus, the source of phosphorus comprising at least some hypophosphite ions up to 4 grams per liter and phosphite ions in the range of from 7.5 to 12 grams per liter 7
• maintaining the pH of the electrolyte at a value of from c. maintaining the temperature of the electrolyte in the range of from 90 to 140 F.;
• cobaltous ions are derived from cobaltous sulfate and wherein the hypophosphite ions are derived from hypophosphorus acid or the sodium, potassium, calcium, or ammonium salt thereof.
• cobaltous ions are derived from cobaltous sulfate and wherein the hypophosphite ions are derived from hypophosphorous acid or the sodium, potassium, or calcium salt thereof and the phosphite ions are derived from phosphorous acid or the sodium, potassium, or calcium salt thereof.
• the method for the deposition of a ferromagnetic recording film on an electrically conductive carrier comprising subjecting the carrier as cathode to a current density of between 10 and 120 amperes per square foot in an aqueous electrolyte having a pH of from 3.2 to 5.0 and consisting essentially of: cobaltous ions in the range of 20 to 80 grams per liter, at least some hypophosphite ions and phosphite ions; and controlling the hypophosphite ions in the range up to 4 grams per liter and the phosphite ions in the range of 7.5 to 12 grams per liter to obtain a recording film having a predetermined coercivity, the phosphite ions reducing the concentration of hypophosphite ions required for the predetermined coercivity.
• phosphite ions are derived from phosphorus acid or the sodium, potassium, calcium or ammonium salt thereof.
• hypophosphite ions are derived from hypophosphorus acid or the sodium, potassiumcalcium or ammonium salt thereof.
• the method for deposition of a ferromagnetic recording film on an electrically conductive carrier comprising subjecting the carrier as cathode to a current density of between 10 and l20 amperes per square foot in an aqueous electrolyte having a pH of from 3.2 to 5.0, a temperature in the range of 20 to 25 g./l. (0.6790.848N) 20 to 25 gJl.
• hypophosphite ions (0.68l0.852N) from about to l40 F., and consisting essentially of: cobaltous ions in the range of l0 to 50 grams per liter, nickelous ions in the range of 10 to 50 grams per liter, and at least some hypophosphite ions and phosphite ions; and controlling the hypophosphite ions in the range up to 2 grams per liter and the phosphite ions in the range of 7.5 to 12 grams per liter to obtain a recording film having a predetermined coercivity, the phosphite ions reducing the concentration of hypophosphite ions required for the predetermined coercivity.
• phosphite ions are derived from phosphorus acid or the sodium, potassium calcium or ammonium salt thereof.
• hypophosphite ions are derived from hypophosphorus acid or the sodium, potassium, calcium, or ammonium salt thereof.
• hypophosphite ions are derived from hypophosphorous acid or the sodium, potassium, or calcium salt thereof.
• phosphite ions are derived from phosphorous acid or the sodium, potassium, or calcium salt thereof.
• the method for the deposition of a magnetic recording film on an electrically conductive carrier comprising subjecting the carrier as cathode to a current density of between 10 and amperes per square foot in an aqueous electrolyte having a pH of from 3.2 to 5.0 and consisting essentially of: cobaltous ions in the range of 20 to 80 grams per liter, at least some hypophosphite ions and phosphite ions; and controlling the hypophosphite ions in the range up to 2 grams per liter and the phosphite ions in the range of 7.5 to 12 grams per liter to obtain a recording film having a predetermined coercivity, the phosphite ions reducing the concentration of hypophosphite ions required for the predetermined coercivity.
• hypophosphite ions are derived from hypophosphorus acid or the sodium, potassium, calcium, or ammonium salt thereof.
• the method for the electrolytic deposition of a ferromagnetic recording film on an electrically conductive carrier comprising subjecting the carrier as cathode to a current density of between 10 and 120 amperes per square foot in an aqueous sulfate electrolyte having a pH of from 3.2 to 5.0, a temperature in the range of from about 90 to F., and consisting essentially of: cobaltous ions in the range of 10 to 50 grams per liter, nickelous ions in the range of l0 to 50 grams per liter, and at least some hypophosphite ions and phosphite ions; and controlling the hypophosphite ions in the range up to 1.10 grams per liter and the phosphite ions in the range of 7.5 to 12 grams per liter to obtain a recording film having a predetermined coercivity, the phosphite ions reducing the concentration of hypophosphite ions required for the predetermined coercivity.
• hypophosphite ions are derived from hypophosphorus acid or the sodium, potassium, calcium, or ammonium salt thereof.
• electrolyte includes at least some formate ions derived from the sodium, potassium, or calcium salt of formic acid in the range up to 20 grams/liter.
• hypophosphite ions are derived from hypophosphorous acid or the sodium, potassium, or calcium salt thereof.
• the method for the deposition of a ferromagnetic recording film on an electrically conductive carrier comprising subjecting the carrier as cathode to a current density of between 10 and 120 amperes per square foot in an aqueous electrolyte having a pH in the range of 3.2 to 5.0 and consisting essentially of:
• Cobaltous ions derived from cobaltous sulfate 20 to 80 g./l. Additional sulfate ions as the sodium, potassium,
• hypophosphite ions derived from hypophosphorous acid or the sodium, potassium, calcium or ammonium salt thereof and phosphite ions derived from phosphorous acid or the sodium, potassium, calcium, or ammonium salt thereof and absent sufficient ammonium ions to cause chemical deposition and controlling the hypophosphite ions within the range up to 4.0 grams per liter and the phosphite ions within the range of 7.5 to 12 grams per liter to obtain a recording film having a predetermined coercivity, the phosphite ions reducing the concentration of hypophosphite ions required for the predetermined coercivity.
• hypophosphite ions derived from hypophosphorous acid or the sodium, potassium, calcium or ammonium salt thereof, and phosphite ions derived from phosphorus acid or the sodium, potassium, calcium or ammonium salt thereof and absent sufficient ammonium ions to cause chemical deposition; and controlling the hypophosphite ions within the range up to 2.0 grams per liter and the phosphite ions within the range of 7.5 to 12 grams per liter to obtain a recording film having a predetermined coercivity, the phosphite ions reducing the concentration of hypophosphite ions required for the predetermined coercivity.
• the method for the electrolytic deposition of a ferromagnetic recording film on an electrically conductive carrier comprising subjecting the carrier as cathode to a current density of between 10 and amperes per square foot in an aqueous electrolyte having a pH of 3.2 to 5.0, a temperature in the range of from 90 to F., and consisting essentially of:
• potassium or calcium, salt of sulfuric acid 0 to l2 gJl. Formate ions as the sodium, potassium, or
• hypophosphite ions derived from hypophosphorous acid, or the sodium, potassium, or calcium salt thereof and phosphite ions derived from phosphorous acid or the sodium potassium, or calcium salt thereof, and absent sufficient ammonium ions to cause chemical deposition and controlling the hypophosphite ions within the range up to 2.0 grams/liter and the phosphite ions within the range of from 7.5 to 12 grams/liter to obtain a recording film having a predetermined coercivity, the phosphite ions reducing the concentration of hypophosphite ions required for the predetennined coercivity.
• hypophosphite ions are maintained in the range up to 1.10 grams/liter.

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• 1969
  • 1969-01-29 US US795054*A patent/US3637471A/en not_active Expired - Lifetime
  • 1969-03-10 BE BE729665D patent/BE729665A/xx unknown
  • 1969-03-27 GB GB06230/69A patent/GB1244681A/en not_active Expired
  • 1969-04-22 DE DE1920221A patent/DE1920221C3/de not_active Expired
  • 1969-05-21 FR FR6916510A patent/FR2029599A6/fr not_active Expired

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