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
  • C25D5/10—Electroplating with more than one layer of the same or of different metals
  • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
  • C25D5/14—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium two or more layers being of nickel or chromium, e.g. duplex or triplex layers
• • 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
  • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
  • C25D3/14—Electroplating: Baths therefor from solutions of nickel or cobalt from baths containing acetylenic or heterocyclic compounds
  • C25D3/18—Heterocyclic compounds
• • 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
  • C25D5/60—Electroplating characterised by the structure or texture of the layers
  • C25D5/605—Surface topography of the layers, e.g. rough, dendritic or nodular layers
  • C25D5/611—Smooth layers
• • 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
  • C25D5/60—Electroplating characterised by the structure or texture of the layers
  • C25D5/625—Discontinuous layers, e.g. microcracked layers
• • 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
  • C25D5/627—Electroplating characterised by the visual appearance of the layers, e.g. colour, brightness or mat appearance
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/922—Static electricity metal bleed-off metallic stock
  • Y10S428/9335—Product by special process
  • Y10S428/934—Electrical process
  • Y10S428/935—Electroplating
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12479—Porous [e.g., foamed, spongy, cracked, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12861—Group VIII or IB metal-base component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12861—Group VIII or IB metal-base component
  • Y10T428/12944—Ni-base component

Definitions

• This invention comprises a composite or laminated metallic coating, and a process for making such coating, comprising a first layer of nickel and an overlying layer of chromium, the laminate being cracked in a craze pattern in the range of 300 to 3000 cracks per lineal inch prepared by electrodepositing on a metal substrate a stressed layer of nickel and thereafter electrodepositing on this stressed layer of nickel a stressed layer of chromium adherent to the stressed layer of nickel and heating the resultant laminate.
• the stressing in the respective layers may be effected by means of an additive in the electroplating solution from which it is produced.
• the resultant crazing gives an improved protection against corrosion.
• This invention relates to composite, metallic coatings or laminated coatings comprising a first layer of nickel and an overlying layer of chromium. More specifically, the present invention relates to the discovery that when both layers of a two-layer nickel-chromium laminate are suitably stressed, the composite can be caused to become microcracked in a fine pattern and the resulting microcracked laminate has superior properties, especially in regard to protection against corrosion.
• a nickel deposit having a high tensile stress is used, which, when combined with a suitable chromium overlying layer, produces coatings of improved corrosion resistance.
• Nickel deposits according to the in vention are stressed and, when combined with the chro mium deposit, which is also stressed, the stresses reinforce each other and the composite exhibits a microscopic crazing or cracking in a craze pattern which is made up of fine lines, from about 300 to 3000 cracks per lineal inch. Although still finer crack patterns are acceptable, it is preferred to produce 700 to 2000 cracks per inch.
• the deposits having patterns in the preferred range tend to give the best protection against corrosion.
• the nickel layer may be applied to a thickness from 0.03 mil to 0.5 mil, preferably 0.05 to 0.25 mil, and the thickness of the chromium layer being preferably from 10 millionths of an inch to 50 millionths of an inch.
• a selenium compound e.g. sodium selenate
• a concentration of the order of 0.015 gram per liter is added to a chromium plating bath
• the resulting chromium deposit when plated over nickel to a thickness of, for example, 30 millionths of an inch will produce microcracking when the plated object is suitably heated, as, for example, by immersion in hot water.
• Said seleniumcontaining bath does not have good throwing power and the deposit from such a bath has little or no chromium deposited in the low current density areas of the object being plated.
• chromium In order to provide better coverage by the chromium and still retain the improved corrosion resistance of the microcracked chromium, it is customary to deposit in the order of 10 millionths of an inch thickness of chromium from a standard chromium bath (containing no selenium) and follow this with a deposit from the selenium-containing chromium bath of the order of 15 millionths or more in thickness. In addition to the reduced throwing power of the chromium bath containing the customary amount of selenium compound, the chromium deposits from such selenium-containing bath tends to have a bluish color which is undesirable.
• the amount of selenium can be reduced or selenium can be omitted, as will be shown later, with increased throwing power as a result; also, the undesirable bluish color is reduced.
• the nickel deposit must be prestressed in order to get these good results.
• Microcracking also has been produced in two-layer chromium systems by variations in the character of the separate chromium deposits due to differences in operating conditions or by variations in compositions of the plating baths (US. Pat. 3,157,585).
• the present invention dilfers from the earlier methods of producing microcracking in that the two-layer composite responsible for the mircrocracking comprises a thin layer of nickel of special character, prestressed, and
• a smaller than usual concentration of the selenium compound in the chromium bath can be used to produce the corrosion resistant coating. This is accomplished by plating first a stressed nickel deposit and then a layer of chromium from the chromium bath containing less than the usual concentrations of selenate. The first coating (nickel) is stressed but not cracked and the chromium layer from the selenium-containing bath is then laid down, thereby producing enough stress to crack the chromium when, for example, the deposit is heated as by dipping the coated substrate in hot water, e.g. boiling water or water at F. Certain selenium-free chromium plating solutions may be employed.
• the usual chromium plating solution produces a moderately stressed deposit and adding the selenium reduces throwing power. Adding less selenium gives better results as indicated above.
• the highly stressed nickel deposit makes possible omission of some or all the selenium without substantial loss in throwing power, still getting the improved throwing power as if selenium had not been used.
• the smaller than customary amount of selenium in the chromium bath does not result in the very large loss of throwing power caused by the normal amount of selenium. Further, the objectionable blue color of the chromium deposit from the usual selenium-containing bath is avoided or reduced.
• a single additive (other than an antipitter which may be used if desired) to the Watts type nickel bath may be used to provide a stressed nickel of improved lustre.
• Small concentrations of certain additives yield a high degree of tensile stress in nickel deposits when sulfooxygen control agents are absent.
• concentration of the selenium compound in the bath used for deposition of chromium over the stressed nickel the lesser amount of selenium results in a laminate which will crack in a desirable fine pattern and good corrosion resistance will result.
• the stress in both the nickel deposit and the chromium deposit be such that microcracking of the laminate occurs. Microcracking may occur spontaneously toward the end of or after electrodeposition of the chromium, or by immersion in hot water, or during outside exposure, or during accelerated corrosion testing.
• microcracking show a pattern of the order of 300 to 3000 or more cracks per lineal inch, preferably from 700 to 2000 cracks per lineal inch.
• the crack pattern is controlled by the degree of prestressing. Numerous methods can be used to prestress the nickel deposits. Examples are hereinbelow stated.
• the Dubpernell test in which the composite electroplate including a top layer of chromium is made cathodic in an acid copper sulfate solution at low current density. Copper is deposited only at the microcracks and not on the uncracked area where it is believed the chromium is covered by an oxide film.
• nickel includes cobalt and nickel-cobalt codeposits, but nickel is preferred.
• the hereindescribed laminates of stressed nickel and chromium may be applied over a variety of substrates, including a usual bright nickel substrate or a semibright nickel substrate, said bright or semibright nickel substrates being electrodeposited over metallic surfaces generally, for example, iron or steel.
• the stressed nickel may be applied upon metals or conductive surfaces quite generally; for example, cobalt, nickel, copper, brass, or other metals, and alloys of two or more thereof.
• a two-layer deposit according to the invention may be laid down by depositing a layer of stressed nickel on any of the substrates indicated above. On the stressed nickel layer there may be deposited a layer of stressed chromium.
• the nickel layer may be stressed by means of an additive to the solution.
• the chromium layer likewise, may be stressed by an additive to the solution in which it is produced.
• the stressed nickel producing solutions may be produced, for example, by using as an additive an amine borane compound, or a pyridinium compound, or a quinolinium, or isoquinolinium compound.
• These additives in the nickel bath, and selenium compounds, for example, in the chromium bath cooperate to make a deposit plate more uniformly over the work be more free from objectionable bluish color.
• the selenium may be partly or completely omitted from certain chromium solutions while retaining many of the benefits of the invention. It is preferred, however, to incorporate a limited concentration of selenium into the chromium plating solution
• the process for producing the desirable laminates is critical in three respects.
• the chromium solution either with or without selenium must yield a stressed deposit, sufliciently stressed to cooperate with the nickel deposit to yield a microcracked laminate.
• the stressed composite must yield a double stressed laminate capable of cracking in a fine pattern of from about 300 to 3000, or more, cracks per lineal inch.
• the nickel deposit from the nickel plating solution must yield deposits which will be stressed such that the desirable crack pattern of from about 300 to 3000 or more cracks per lineal inch is obtained.
• Any additive to the nickel solution can be used to produce a nickel deposit which can be used in connection with a chromium deposit taken from a chrome solution comprising chromic acid and sulfate ion, provided the deposit is sufficiently stressed.
• the nickel deposit should be stressed prior to cracking to the extent of at least about 30,000 pounds per square inch (rigid strip method). The stressing of the deposits can be varied by adjusting the amount of additive in the solutions or as hereafter described.
• Sulfo-oxygen carriers such as benzene sulfonate and saccharin, are undesirable in the solution used to produce stressed nickel of the present invention since they lower the tensile stress. If used in the bath, the concentration of the carrier should be lower than customary in a bright nickel bath and should not exceed 0.1 gram per liter.
• the Watts type of nickel plating solution is preferred when stress-inducing agents are used. It may, for the purposes of this invention, consist of nickel sulfate in high concentration, nickel chloride in lesser concentration, and boric acid also in lesser concentration. Sodium lauryl alcohol sulfate may also be included but is not essential since the bath will function more or less well without it. In addition to the Watts bath, other baths ranging from all sulfate to all chloride solutions may be used. Baths containing sulfamates may be used. Alkaline solutions may be used as well as nickel fiuoborate, and many more as basic nickel plating solutions.
• the invention contemplates preferably the two-layer laminate coatings, both layers together under stress high enough to allow microcracking and the process of producing the said laminates with suitable stress, and cracking such laminates so stressed. Further, more specific and preferred features of the invention are:
• the thickness of the deposits and the temperatures of electrodeposition are important although considerable and numerous variations can be utilized.
• the nickel deposit should be plated to a thickness of from 0.03 to 0.52, preferably 0.05 to 0.25 mil at a temperature in the range of 60 F. to 160 F.
• the layer of chromium should be of a thickness from to 50 millionths of an inch applied in the temperature range of from 90 F. to 150 F.
• the laminate preferably should be heated to a temperature in the range from 180 F. to 450 F. in a period of time from 5 to 120 seconds. It may be desirable to alternately chill and heat the composite.
• Benzimidazole diborane The concentrations of the compounds listed in Table II hereof should be maintained in solution in the plating bath to the extent of from 0.01 to 1.0 gram per liter, the amount used for preferred results depending on the type of compound employed.
• Nitrates in low concentrations may actually docrense tensile stress. Higher concentrations increase Ithe stress.
• NiSO -6H O 75 to 225, preferably to 200 grams.
• NiCl -6H O 50 to 150, preferably 75 to 150 grams.
• Boric acid 0 to 50, preferably 15 to 40 grams.
• the basic chromium solution may be a water solution of chromic acid with sulfate ion to the extent of about 0.6 to 1.5 percent of the chromic acid. To this may be added, to produce microcracking in combination with a stressed nickel, a selenium compound, such as Na SeO or an organic compound, such as AS203.
• the following chromium solution (See Table V) produces a good microcrack with prestressed nickel but not with unstressed nickel.
• the stress in the nickel deposit was obtained by use of a bis-pyridinium compound additive in the Watts bath.
• the bis-pyridinium compound may be used at a concentration of preferably from 0.1 to 1.0 gram per liter.
• Sodium selenate for example, may be used in the above solution. It may be added in concentration from no selenium to about 0.10 gram per liter: preferbaly, about 0.0025 to 0.0075 gram per liter should be used. (Note: sodium selenate of the order of 0.015 gram per liter should be used to produce microcracking over ordinary bright nickel.)
• Groups of additives have been set forth by way of examples as to how to produce the stressed nickel deposits of the invention.
• One of these groups is the amine boranes; another group is the bis-pyridiniums, bis-quinoliniums, and bis-isoquinoliniums.
• the plating conditions have been stated suificiently to enable the chemist skilled in the art to produce the stressed deposits.
• the nickel is first deposited having requisite stress, after which there is applied a coating of chromium having the requisite stress.
• the chromium solution may contain selenium as above stated.
• the composite will microcrack during the chromium plating step, shortly thereafter on mild heating, or on corrosion testing, such as the Corrodkote test, or on outdoor exposure (which may take an undesirably long time.) Heating with hot water apparently is the most practical cracking step.
• the values obtained for stress of electrodeposits are affected by nonreproducibility of calculated stress values when measured by different methods, the nature of the substrate, the thickness of the deposit, and the cracking of the deposit during the plating process which relieves the apparent stress.
• the rigid strip method of measuring stress will give values of 12,000 to 17,000 p.s.i.; the helical contractometer method for the same solution gives values of 20,000 to 27,000 p.s.i.
• the helical contractometer method for the same solution gives values of 20,000 to 27,000 p.s.i.
• the following values may be obtained:
• the stress of a deposit will depend on its thickness primarily because of the effect the substrate structure has on the deposit structure. This eflect may disappear after 500 angstroms or still be present at thicknesses of .1 to .2 mil. In most cases (see C. Williams, Met. Finishing J. 8 (85) (1962)) for nickel or chromium on their normal substrates (Fe, Cu, Ni), the tensile stress will decrease with increase in thickness. It is possible, however, for the reverse effect to occur (see 11. Watkins, J. Electrochem Soc., November 1961.)
• the stressed nickel fiash is best described operationally as one which will effect microcracking when a higher than normal stressed chromium deposit is applied over it and will not give microcracking when standard chromium is applied over it.
• the stressed chromium deposit is described operationally as one which will give microcracking when applied over a higher than normal stressed nickel depcsit but will not give microcracking when applied over a normal nickel deposit such as that from a Watts bath at pH 3.5 or such as that from a bright nickel solution containing a sulfo-oxygen control agent.
• the stressed nickel deposit should not be too thick; if greater than 0.15 to 0.2 mil, it may tend to crack before chromium plating and give undesirable macrocracking visible to the naked eye. Provided the nickel flash is under enough stress, finer microcracking is obtained, after chromium plating, for thin nickel deposits. Stressed nickel deposits in the order of 0.1 mil or less are preferred. The stress of the nickel deposit when measured by the rigid strip method and at 0.2 mil should be at least 30,000 p.s.i.
• Addition agents are not always needed in order to obtain high tensile stresses in the nickel deposit.
• the stress in the nickel deposit increases with increase in chloride content of the solution, with decrease in temperature, and with increase in current density.
• the pH should be either high (greater than 5.0) or low (less I than 2.0).
• the acid solutions should not be too highly buffered.
• Alkaline nickel solutions such as described in U.S. 2,773,818, US. 2,069,566, British 512,484, and British 880,786 may be used, although simple solutions containing only nickel citrate or tartrate are as effective as some of those solutions proposed for heavier nickel deposits.
• acetylenic type brighteners such as butynediol to alkaline solutions, further increases the tensile stress in the nickel flash and excellent corrosion results have been obtained.
• NiSQ -6-H O 100 grams per liter. Na citrate 200 grams per liter. pH 6.5. Temperature 50C.
• the microcracked composite coating may be applied directly to a basis metal, such as steel, copper, etc., we believe it will find its greatest use when applied over a substrate of bright or semibright nickel coatings, or combinations of semibright and bright nickel electrodeposits.
• the composite coating of the invention may be deposited over a bright nickel electroplate, such as deposited according to U.S. Pat. 2,712,522, or preferably over a duplex nickel deposit comprising a semibright electroplate according to, for example, U.S. Pat. 2,635,076, followed by a bright electrodeposit according to, for example, U.S. Pat. 2,978,391.
• the composite according to the present invention may also be used with a triplate nickel coating according to U.S. Pat. 3,090,733.
• EXAMPLE I Over a 1 mil thick electrodeposit of bright nickel on steel, an additional electrodeposit of stressed nickel was laid down (to a thickness of 0.1 mil.) This stressed nickel was deposited from an aqueous solution made up as follows:
• Example II Over a bright nickel deposit on steel, as cited in Example I, we electroplated a 0.1 mil deposit of stressed nickel from a bath as cited in Example I except that the amine borane was replaced by 0.4 gram per liter of N,N-trimethylene-bis-pyridinium bromide. Over the stressed nickel was then deposited chromium as cited in Example I. Results were similar to those reported for Example I.
• a good microcracked pattern was secured on dipping for one minute in water at 200 F.
• the resulting composite gave a good microcrack pattern after dipping for 2 minutes in water at 200 F.
• EXAMPLE V EXAMPLE VI Using the composite nickel electrodeposit on steel, including the stressed nickel layer of Example II, chromium was deposited to a thickness of 30 millionths of an inch in the following bath:
• microcracking was secured. When the stressed nickel layer was omitted, microcracking did not occur.
• EXAMPLE VII Steel plated with 1 mil bright nickel was further plated with 0.1 mil of stressed nickel at 40 a.s.f. and 140 F. from a Watts bath (pH containing 0.015 gram per liter of 2-oxydiethylene-bis-isoquinolinium chloride. When a 30 millionth of an inch deposit of chromium was applied from the bath cited in Example I, microcracking was produced by the hot water treatment and good corrosion resistance was secured.
• EXAMPLE XIII Onto a bright nickel deposit on steel, an 0.1 mil deposit of stressed nickel was electroplated from a Watts bath containing 0.5 gram per liter of N,N'-methyl-N'-piperazino-l hydroxy butene, at 140 F. and 40 a.s.f. After further electroplating 20 millionths of an inch of chromium from the bath of Example I, and heating the deposit at 190 F. when microcracking occurred.
• a method of depositing a corrosion resistant microcracked duplex coating on a substrate said duplex coating consisting of chromium over nickel which comprises electrodepositing a smooth continuous nickel layer having high internal stress on a substrate and thereafter electrodepositing a chromium layer on said smooth continuous nickel layer, said chromium layer being sufiiciently stressed so that it interacts with said smooth continuous nickel layer to cause both said nickel and chromium layers to crack into a micro-cracked pattern during or subsequent to the electrodeposition of said chromium layer.
• a method of depositing a corrosion resistant microcracked coating on a substrate which comprises electrodepositing nickel on said substrate from an aqueous acidic bath and thereafter electrodepositing chromium on said nickel, said nickel being deposited with a high internal stress level, said stress level being sufiicient to produce micro-cracks therein during the deposition of the chromium layer which in turn produces a micro-crack pattern in the chromium layer.

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• 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)
• Laminated Bodies (AREA)
• Electroplating Methods And Accessories (AREA)

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Cited By (7)

• 0
  • NL NL128956D patent/NL128956C/xx active
• 1965
  • 1965-04-26 US US451028A patent/US3563864A/en not_active Expired - Lifetime
• 1966
  • 1966-04-01 GB GB14658/66A patent/GB1148433A/en not_active Expired
  • 1966-04-05 ES ES0325133A patent/ES325133A1/es not_active Expired
  • 1966-04-26 NL NL6605580A patent/NL6605580A/xx unknown
  • 1966-04-26 DE DE19661496829 patent/DE1496829A1/de active Pending

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