US3424660A - Process for chemical plating - Google Patents

Process for chemical plating Download PDF

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US3424660A
US3424660A US424264A US42426465A US3424660A US 3424660 A US3424660 A US 3424660A US 424264 A US424264 A US 424264A US 42426465 A US42426465 A US 42426465A US 3424660 A US3424660 A US 3424660A
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plating
potential
nickel
bath
metal
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US424264A
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Heinz-Gunter Klein
Konrad Lang
Edith-Luise Schmeling
Helmut Weissbach
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Bayer AG
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Bayer AG
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
    • C23F13/005—Anodic protection
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/1601—Process or apparatus
    • C23C18/1619—Apparatus for electroless plating
    • C23C18/1621—Protection of inner surfaces of the apparatus
    • C23C18/1623—Protection of inner surfaces of the apparatus through electrochemical processes

Definitions

  • PROCESS FOR CHEMICAL PLATING Filed Jan. 8, 1965 Sheet g of 5 5 +200 +000 0' b +1000 mV 10' A/cm 10"; q ID INVENTORS HE/NZ GUNTHEP KLEIN, KONRAD LANG, EDITH LU/SE SCHMEL/NG, HELMUT WEISSBACH.
  • PROCESS FOR CHEMICAL PLATING Filed Jan. 8, 1965 Sheet 3 of5 l n I l l l FlG 6 INVENTORS HE/NZ GUNTHEP KL E/N, KONPAD LANG, EDITH LU/SE SCHMELING, HELMUT WEISSBACH.
  • the metallic surfaces to be protected are connected in an electric circuit which contains additionally the plating bath as electrolyte, which bath contains a chemical reducing agent such as alkali metal borohydride, sodium hypophosphite, a borazane or a borazole, as well as at least one counterelectrode and at least one voltage source of direct current, such that (b) An electric potential isapplied to the metallic surfaces to be protected as the anode and to the counterelectrode as the cathode, which potential corresponds to the protection potential region lying between the mottling potential and the transpassivity on the current density/ potential curve (or which corresponds to the rest potential on such curve), and
  • the present invention relates to an improved process for chemical plating, and more particularly to an improvement in a chemical plating process by which specific metal surfaces, which are in contact with the chemical plating bath but are not intended to be plated, may be protected against plating while other metal or metallic or non-metal or non-metallic surfaces which are intended to be plated may be plated by such bath.
  • Metals such as nickel, cobalt and/or iron can be deposited on catalytically active surfaces by reducing agents such as sodium hypophosphite, sodium borohydride, borazanes or other boron hydride compounds.
  • This so called chemical plating is performed very easily on metal surfaces but non'metallic surfaces such as glass, ceramic, graphite or synthetic resins can also be coated with metal by chemical processes after activation by easily reducible metal salts. Surfaces without any catalytic activity are very often so activated by prolonged exposure to the action of plating baths. It is in this connection that the present process is of significance as the same more precisely relates to an improved process for the protection of particular metal surfaces which are in contact with chemical plating baths.
  • Tanks made of glass a material which is in itself practically inactive, can only be manufactured up to a certain, relativelysmall size; and moreover, glass tanks have the known disadvantages, as they are too sensi tive to mechanical and temperature stresses.
  • Graphite, synthetic resins and rubberized surfaces tend to undergo autocatalytic plating.
  • plating apparatus of stainless Cr-Ni steels rendered chemically passive achieves only a soon terminated success, as the passive layer before long is destroyed by the strongly reducing bath, whereupon deposition of metal on the walls of the container occurs after a comparatively short time.
  • the apparatus must then be treated with nitric acid or mixtures of nitric acid and hydrofluoric acid to remove the deposited metal and to render the surface of the apparatus passive again, as described in the literature.
  • the process is very complicated and uneconomic due to servicing and prolonged times of standstill.
  • the electrolytically produced polarization imparts a permanent protection against chemical plating in spite of the fact that one would expect the strong reducing agents contained in the plating bath to have a depolarizing effect. Furthermore it has been found that by a suitable selection of material the current density is very low so that no marked corrosion of the parts of the apparatus such as tanks for the bath, pumps, heat exchangers, storage and buffer vessels, purification apparatus etc. occurs. This latter effect increases the economy of the process considerably.
  • FIGS. 1 to 4 illustrate graphically' current density/potential curves for plating baths contemplated in accordance with the present invention
  • FIGS. 5 and 6 illustrate electrode arrangements usable in plating bath environments contemplated by the present invention.
  • a current density/ potential curve is plotted in known manner by the potentiostatic, potentiokinetic or galvanostatic method, as indicated schematically in FIGURE 1.
  • the current density increases in a characteristic manner with increasing potential. In the cathodic region, it first follows Tafels straight line (T in FIGURE 1) in which hydrogen and metal may be deposited. At GR it passes through the so called rest potential where the external polarization is zero. As the negativity of the potential is decreased, the anodic part of the curve begins at ER, as does the anodic polarization region in its wider sense.
  • the current density I referred to hereinafter as the protective current density, which is in many cases very low, is almost independent of the potential. Protection against chemical plating can most easily and reliably be carried out in the above defined protective potential region S since the region S is usually very wide and fluctuation in potential do not have any adverse efiects. Hence, working in this region is very reliable.
  • the increase in current as the potential increases still further after the region S, an increase defined as transpassivity Tr indicates the dissolution of the metal in its highest state of oxidation. If relatively large quantities of chloride ions are contained in the electrolyte an increase in current frequently occurs before the potential corresponding to transpassivity is reached. This increase is also known as branched pitting corrosion L which indicates the formation of pitted corrosion.
  • the work is carried out at a potential or potential region lying in the range between the mottling potential and the transpassivity.
  • the position of the range of protective potential S and the magnitude of the polarization current density I is characteristic for individual materials and also depends on the type, concentration and temperature of the plating baths used as electrolytes. It can be determined by the generally known method for determining the current density/potential curve.
  • the protective current density I should be below about a./cm. so that the anodic dissolution of the metal can be kept within tolerable limits. In the case of iron, this corresponds to a removal of metal of 28.5 g./(m. .day). According to Todts Korrosion and Korrosionsschutz, page 1227, a heavy metal which undergoes dissolution at the rate of about 21 g./(m. .day) can still be regarded as sufficiently stable.
  • Th current density/potential curve for 18/8 Cr-Ni steel in a plating bath of composition 30 g./l. of nickel chloride, 40 g./l. of sodium hydroxide, 60 g./l. of ethylene diamine of concentration 98%, 3 g./l. of sodium fluoride and 0.6 g./l, of sodium borohydride at 90 C. is shown in FIGURE 2.
  • the current density/potential curve for 18/8 Cr-Ni steel in a bath of the composition 30 g./l. of nickel chloride, 10 g./l. of sodium citrate, 10 g./l. of trimethyl borazane at 65 C. and pH 5.3 is shown in FIGURE 3.
  • the abscissae denote the voltages in (mv.) millivolt referred to thalamide electrodes and the ordinates denote the current density in a./cm.
  • Table I shows the characteristic values of the rest potential ER, protective potential region S, maximum current density at mottling potential, i.e., Flade potential 5 and protective current density I obtained for various chemical plating baths from the potentiokinetically determined (change in potential: 200 mv./ h.) current density/ 4 potential curves for 18/ 8 Cr-Ni steel, 18/ 10/2 Cr-Ni-Mo steel, 18/18/2/2 Cr-Ni-Mo'Cu steel, an 18% Cr steel and a nickel-boron alloy (about 94% Ni, 6% B); deposited in a plating bath based on sodium borohydride of the composition shown in Table I.
  • the metals and alloys which can be subjected to the process according to the invention are by no means limited to the materials shown in Table I and mentioned in the examples; in fact, any anodically polarizable metals and metal alloys can be used whose protective current density I lies in the region of about 10- a./cm. or below. Whereas the limitation described above applies to the choice of materials used for the containers etc., the composition, concentration and temperature of the plating baths used are not critical for carrying out the process of the invention.
  • any of the plating baths known in the literature using sodium hypophosphite, alkali metal borohydrides, boron hydrides and/ or boron hydride compounds such as borazanes and borazoles as reducing agents, may be used. Since protection against plating is imparted over a relatively wide range of potentials, the fluctuations in concentration occurring during the plating process, especially in intermittent operations, are of no importance.
  • a counter electrode of pure nickel is installed centrally in a cylindrical vessel of 18/ 8 Cr-Ni steel having an (inner) surface of about 0.1 m wetted with electrolyte (plating liquid) and a standard electrode of the same material as the counter electrode is installed near the wall of the vessel.
  • a Wenking potentiostat is used as source of direct current voltage and as control instrument. Owing to the good conductivity (about 0.3 ohmcm? at C.) of the plating bath used as electrolyte, which has a composition of 30 g./l. of nickel chloride, 40 g./l. of sodium hydroxide, 6O g./l. of ethylene diamine, 30 g./l.
  • the distance of the electrodes from the wall of the vessel is of no significance in a plating vessel of such small dimensions.
  • a drop in potential would be noticed only at distances of about 1 m. by means of the potentiostat, a potential of +600 mv. against the nickel standard electrode is imparted to the wall of the vessel, this potential having been determined previously by current density/ potential measurements.
  • the current density which becomes established in the process is about 50 ma./ m.
  • Plating was carried out continuously for 3 days in this vessel. No deposition of nickel occurred on the walls of the vessel. No loss in weight of the material of the vessel could be determined. No pitting corrosion occurred in spite of the relatively high chloride concentration.
  • One advantage for the technical application of the process of the invention is that the system can be adjusted to the desired range of passivity with relatively weak electric currents, on an average about 0.05 a./m.
  • standard electrodes are used which are made of nickel or of a nickelboron or nickel-phosphorus alloy which corresponds to the composition of the nickel alloy chemically deposited from the bath. It is immaterial whether the standard electrode is made from a molten nickel alloy or from a nickel alloy applied by chemical plating on a metal or nonmetallic material. Thus, for example, it is possible to use standard electrodes made of copper, brass, iron, silicon carbide, graphite, porcelain, glass or synthetic resins such as polystyrene, which materials have been plated with a chemically non-porous layer of nickel about 50 mg thick.
  • counter-electrodes it is preferable to use metals or alloys which correspond substantially to the metal etc. to be deposited.
  • metals or alloys which correspond substantially to the metal etc. to be deposited.
  • counter-electrodes of pure nickel it is suit-able to use counter-electrodes of pure nickel.
  • the above mentioned electrodes may, surprisingly, be used not only in plating baths which have a constant metal content but also in intermittently operated chemical plating baths, i.e. in baths in which wide fluctuations in the concentration of metal salts occurs.
  • the potential varies by only about 20 mv. in transition from a freshly prepared plating bath (30 g./l. nickel chloride) to a bath which has been exhausted to a considerable extent by plating (7.2 g./l. nickel chloride). This fluctuation has no adverse effect on the process in practice in view of the great width of the protective potential region S.
  • Polarization shows no harmful effect on the reducing agents used in chemical plating. In plating processes carried out for the sake of comparison in polarized V2A vessels, no greater consumption of reducing agents was found to take place than in the case of plating carried out in glass containers.
  • the process of the invention provides a technical advance in that easily accessible and inexpensive metals and alloys can be used for the manufacture of all the containers, pumps, filters, heat exchangers, conductors, valves etc. used for the chemical plating, and the repeated interruption of the operation for removal of the metal deposits and renewed passivation of the material of the container is dispensed with. Losses due to deposition of metal on parts of the plating apparatus no longer occur, with the result that the plating yield and the reliability of the process are considerably increased. Further it is possible for the first time, without the use of covering lacquers, to plate parts of metal surfaces on the one hand and to protect other parts of the metal surfaces against plating on the other hand, provided that these parts of metal surfaces are electrically insulated from each other.
  • the electrolytic polarization is not only more effective but can also be carried out more elegantly and with less risk of accident than chemical passivation with strong acids and it does not require a specially trained staff.
  • Example 1 In a cylindrical vessel of 18/8 Cr-Ni steel having a diameter of 15 cm., a height of 20 cm. and an inner surface of about 0.1 m? wetted with electrolyte, a circular road of pure nickel (diameter mm., length 30 cm.) was arranged concentrically as the counter-electrode, and a standard electrode of the same material and some dimensions was arranged in an insulated manner near the wall of the vessel. The counter-electrode was connected as the cathode, the wall of the vessel as the anode to the corresponding current outputs, and the standard electrode was connected to the socket a of a Wenking potentiostat (FIGURES 5 and 6).
  • a potential of +600 mv. compared with the standard electrode was imparted to the vessel, this potential being derived from the current density/potential curve.
  • 3 liters of a chemical plating solution of the composition 30 g./l. of nickel chloride, 40 g./1. of sodium hydroxide, 60 g./l. of ethylene diamine, 3 g./l. of sodium fluoride, 0.6 g./l. of sodium borohydride and 0.01 g./l. of lead acetate was heated to 90 C. in the vessel.
  • the electrolyte has a specific conductivity of about 0.3 ohm .cm"
  • Two iron plates each having a surface of 10 cm. 10 cm.
  • the surfaces of the plates covered with Ni-B had a silvery shiny appearance.
  • the current required for protecting the plating vessel was in the region of 2 marl-1 ma.
  • the vessel used for the experiment was completely unaltered after an experimental time of 10 hours and in particular it showed no covering with nickel.
  • Example 2 In a cylindrical container of 18/8 Cr-Ni steel of the dimensions given in Example 1, having a surface of 0.1 m? wetted with plating bath, a counter-electrode of pure nickel was placed concentrically and a standard electrode of Ni-B alloy was placed near the wall of the vessel.
  • the standard electrode consisted of an earthenware pipe closed at the bottom (diameter 12 mm., length 250 mm.) on which a non-porous coating, 50,41. in thickness, of Ni-B alloy had been deposited by chemical plating. The two electrodes were connected to the potentiostat in the manner described in Example 1. A potential of+ 600 mv. compared with the standard electrode was imparted to the vessel.
  • Example 2 3 liters of the plating bath mentioned in Example 1 were placed in the vessel and heated to C. By plating the iron plates suspended in the bath, the nickel was removed from the bath down to a residual content of 6.8 g./l. of nickel chloride.
  • the polarization current had an average value of 5 to 8 ma. and did not alter significantly during the time of the experiment in spite of the loss in concentration of the Ni salt. Nickel plating of the Wall of the container did not take place.
  • Example 3 A pipe of 18/ 8 Cr-Ni steel, 2 m. in length, was provided with 5 inlet connecting tubes, as shown schematically in FIGURE 5, in which the three standard electrodes 1, 2 and 3 and two counter-electrodes 4 and 5, all made of nickel, were inserted in an insulated fashion and connected with potentiostat A.
  • Plating solution was constantly pumped through the pipe by means of a glass circulating pump from a 10 1.
  • glass beaker which contained a plating bath solution of the composition given in Example 1 heated to 90 C. in which sheet irons were continuously nickel plated.
  • the inner surface of the pipe was about 0.25 m? and it was polarized potentiostatically to +800 mv.
  • the current intensity became established at about 3 ma. After an operating time of 5 days no nickel was deposited on the surface of the pipe.
  • Example 4 instead of the cylindrical vessel described in Example 1, a plating bath vat of dimensions 2 m. 1 m. 0.4 m. was used. As shown schematically in FIGURE 6, two counterelectrodes 1 and 2 and two standard electrodes 3 and 4, all made of nickel, were arranged therein, in an insulated manner. The polarization potential compared with the standard electrode was +600 m'v. The current intensity had an average value of 200 ma. The bath was used continuously over a period of 2 weeks without deposition of nickel occurring on the wall of the container.
  • Example 5 The cylindrcal container of 18/ 8 Cr-Ni steel described in Example 1 was filled with a plating bath solution of the composition 30 g./l. of nickel chloride, 10 g./l. of sodium citrate and 10 g./l. of N-trimethylborazane (pH 5 to 6). A potential of +750 mv. measured against a thallamide electrode, was imparted to the vessel, and the plating bath was then heated to the plating temperature of 65 C. A current of 3 ma. was established.
  • Plating was carried out in known manner with hostaphane foils (i.e., cellulose acetate or cellulose butyrate foils) superficially activated with SnCl /PdCl In this case again there was no deposition of nickel on the walls of the plating vessel.
  • hostaphane foils i.e., cellulose acetate or cellulose butyrate foils
  • Example 6 3 liters of plating bath of composition 30 g./l. of nickel chloride, 10 g./l. of sodium citrate and 10 g./l. of sodium hypophosphite (-made up to the full volume with water) were placed in the cylindrical container of 18/8 Cr-Ni steel described in Example 1.
  • the Wall of the container was polarized to a potential of +412 mv. against the nickel standard electrode by means of a potentiostat as described in Example 1.
  • the plating bath was heated to the plating temperature of 93 C., a current of 8 to 9 ma. becoming established.
  • Example 7 Using the apparatus described in Example 1, iron sheets were nickel plated chemically in a bath of composition 45 g./l. of nickel chloride, 100 g./l. of sodium citrate, 50 g./l. of ammonium chloride, 11 g./l. of sodium hypophosphite (pH 8 to at a temperature of 93 C. in the manner described in Example 6.
  • nickel chloride 100 g./l. of sodium citrate
  • 50 g./l. of ammonium chloride 11 g./l. of sodium hypophosphite (pH 8 to at a temperature of 93 C. in the manner described in Example 6.
  • a current of 1 ma. was established.
  • the wall of the plating vessel was not nickel plated.
  • the standard electrode is made of a material selected from the group consisting of nickel, cobalt, iron, copper, boron containing and phosphorus-containing alloys thereof, and non-conductive materials coated with a layer of one of said metals and alloys.
  • the counter-electrode is made of a material selected from the group consisting of nickel, cobalt, iron, copper, boron containing and phosphorus-containing alloys thereof, and non-conductive materials coated with a layer of one of said metals and alloys.
  • the improvement which comprises protecting particular metallic surfaces in contact with such chemical reducing agent bath against chemical plating thereby by (a) connecting said metallic surfaces into an electric circuit, which circuit contains additionally the plating bath as electrolyte, said bath containing as chemical reducing agent a member selected from the group consisting of an alkali metal borohydride, sodium group consisting of nickel, cobalt, iron, copper, and boron containing and phosphorus-containing alloys thereof.
  • the metallic surfaces are made of metals having a protective current density of a value of not more than about 10 a./cm.
  • the improvement which comprises protecting particular metallic surfaces in contact with such chemical reducing agent bath against chemical plating thereby by (a) connecting said metallic surfaces into an electric circuit, which circuit contains additionally the plating bath as electrolyte, said bath containing as chemical reducing agent a member selected from the group consisting of an alkali metal borohydride, sodium hypophosphite, a borazane and a borazole, at least one counter-electrode and at least one voltage source of direct current,
  • the standard electrode is made of a material selected from the group consisting of nickel, cobalt, iron, copper, boron containing and phosphorus-containing alloys thereof, and non-conductive materials coated with a layer of one of said metals and alloys.
  • the counter-electrode is made of a material selected from the group consisting of nickel, cobalt, iron, copper, boron containing and phosphorus-containing alloys thereof, and non-conductive materials coated with a layer of one of said metals and alloys.
  • the metals deposited by the plating are selected from the group consisting of nickel, cobalt, iron, copper, boron containing and phosphorus-containing alloys thereof.
  • the metallic surfaces are made of metals having a protective current density of a value of not more than about 10 a./cm.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
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US424264A 1964-01-14 1965-01-08 Process for chemical plating Expired - Lifetime US3424660A (en)

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DEF41743A DE1277642B (de) 1964-01-14 1964-01-14 Verfahren zum Schutz von metallischen Oberflaechen gegen Metallabscheidung in chemischen Metallisierungsbaedern

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BE (1) BE658219A (is")
CH (1) CH465995A (is")
DE (1) DE1277642B (is")
FR (1) FR1445478A (is")
GB (1) GB1093701A (is")

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3539390A (en) * 1966-08-26 1970-11-10 Bosch Gmbh Robert Process for making a semiconductor device
US3673064A (en) * 1970-10-29 1972-06-27 Us Army Method of eliminating copper contamination
US4391841A (en) * 1980-03-28 1983-07-05 Kollmorgen Technologies Corporation Passivation of metallic equipment surfaces in electroless copper deposition processes
DK151233B (da) * 1979-04-30 1987-11-16 Kollmorgen Tech Corp Fremgangsmaade til undgaaelse af uoenskede kobberaflejringer paa overflader af udstyr, der avendes i stroemloese pletteringsbade

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH613475A5 (en) * 1976-07-28 1979-09-28 Bbc Brown Boveri & Cie Appliance for the electroless metal coating of objects
FR2371523A1 (fr) * 1976-11-19 1978-06-16 Nikhaenko Jury Electrode de reference pour la protection anodique d'une cuve de nickelage chimique
DE3008434A1 (de) * 1980-03-03 1981-09-17 Schering Ag Berlin Und Bergkamen, 1000 Berlin Verfahren zur selektiven chemischen und/oder galvanischen abscheidung von metallueberzuegen, insbesondere zur herstellung von gedruckten schaltungen

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2642368A (en) * 1950-01-19 1953-06-16 Wallace De Yarman Coating metal articles by dipping in bath of dissimilar molten metal
US3208925A (en) * 1960-01-07 1965-09-28 Continental Oil Co Anodic protection against corrosion
US3216916A (en) * 1962-11-13 1965-11-09 Continental Oil Co Anodic passivation of wetted wall vessels
US3282819A (en) * 1962-12-05 1966-11-01 Leonard B Hovanic Treating of workpieces
US3303111A (en) * 1963-08-12 1967-02-07 Arthur L Peach Electro-electroless plating method
US3345278A (en) * 1963-03-25 1967-10-03 Hooker Chemical Corp Anodic passivation of metals
US3348969A (en) * 1963-11-06 1967-10-24 Gen Motors Corp Electroless nickel plating
US3350287A (en) * 1962-09-06 1967-10-31 M & T Chemicals Inc Method of preventing etch on cast iron in plating baths

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2642368A (en) * 1950-01-19 1953-06-16 Wallace De Yarman Coating metal articles by dipping in bath of dissimilar molten metal
US3208925A (en) * 1960-01-07 1965-09-28 Continental Oil Co Anodic protection against corrosion
US3350287A (en) * 1962-09-06 1967-10-31 M & T Chemicals Inc Method of preventing etch on cast iron in plating baths
US3216916A (en) * 1962-11-13 1965-11-09 Continental Oil Co Anodic passivation of wetted wall vessels
US3282819A (en) * 1962-12-05 1966-11-01 Leonard B Hovanic Treating of workpieces
US3345278A (en) * 1963-03-25 1967-10-03 Hooker Chemical Corp Anodic passivation of metals
US3303111A (en) * 1963-08-12 1967-02-07 Arthur L Peach Electro-electroless plating method
US3348969A (en) * 1963-11-06 1967-10-24 Gen Motors Corp Electroless nickel plating

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3539390A (en) * 1966-08-26 1970-11-10 Bosch Gmbh Robert Process for making a semiconductor device
US3673064A (en) * 1970-10-29 1972-06-27 Us Army Method of eliminating copper contamination
DK151233B (da) * 1979-04-30 1987-11-16 Kollmorgen Tech Corp Fremgangsmaade til undgaaelse af uoenskede kobberaflejringer paa overflader af udstyr, der avendes i stroemloese pletteringsbade
US4391841A (en) * 1980-03-28 1983-07-05 Kollmorgen Technologies Corporation Passivation of metallic equipment surfaces in electroless copper deposition processes

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FR1445478A (fr) 1966-07-15
DE1277642B (de) 1968-09-12
BE658219A (is") 1965-07-13
CH465995A (de) 1968-11-30
GB1093701A (en) 1967-12-06

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