US2702785A - Process of producing hard chromium platings on light metals - Google Patents

Process of producing hard chromium platings on light metals Download PDF

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US2702785A
US2702785A US225065A US22506551A US2702785A US 2702785 A US2702785 A US 2702785A US 225065 A US225065 A US 225065A US 22506551 A US22506551 A US 22506551A US 2702785 A US2702785 A US 2702785A
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chromium plating
plating bath
chromium
metal
layer
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US225065A
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Eyerund Paul
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GEA Group AG
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Metallgesellschaft AG
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/34—Pretreatment of metallic surfaces to be electroplated
    • C25D5/42—Pretreatment of metallic surfaces to be electroplated of light metals

Definitions

  • This invention relates to a process of producing hard chromium platings on light metals, such as, aluminum, :lluminum base alloys, magnesium and magnesium base oys.
  • Aluminium and aluminium alloys have hitherto been hard-chromium plated by first pickling the aluminimn or aluminium alloy. Subsequently an interlayer was applied, in a variety of ways, which, in the case of some processes, was again dissolved away in a separate operation before entering the metal into the chromium plating bath, or in other processes served as a bonding layer for the hard-chromium layer.
  • an electrolytic flash precipitate was applied in a preliminary bath as a bonding layer, on to which the desired metal layer was applied in the electro-plating bath proper (c. f. Germany patent specification No. 242,142).
  • a metallic interlayer was applied by cathodic sputtering, on which interlayer the hard metal layer, of for example, chromium, nickel or the like, was produced by electrolysis (c. f. German patent specification No. 703,588).
  • the hard chromium layer can be very intensively bonded to the base metal, i. e. light metal or light metal alloy, especially aluminium or aluminium alloy, if a preliminary metallic layer is ap plied electrolytically in such thickness that it is at least almost completely dissolved in the chromium-plating bath itself before a. hard chromium layer has been formed.
  • This can, for example, be effected by a short reversal of the polarity before the chromium plating operation.
  • preliminary metallic layers enable the prevention of oxidation before immersion in the chromium plating bath.
  • Brass, nickel, iron and copper, for example, are suitable for such layers, especially when a complete removal, advantageously by means of a short change of polarity of the cathode, lasting from 1 to 2 seconds, is produced before the first surge of plating current of the hard chromium plating process.
  • This complete removal of the preliminary layer is obtained with preliminary metal layers of a thickness of preferably 1 mu within 1 to 2 seconds.
  • the hard chromium layers obtained in accordance with the present invention are distinguished by a particularly intense bonding to the base material and do not peel ofi even when strongly deformed.
  • Example 1 The surface of an aluminium or aluminium alloy workpiece is first pickled in accordance with a normal pre-treating process before the preliminary metallic layer is applied to the surface to be chromium plated.
  • This pre-treatment can, for example be effected by using a known pickling solution containing ferrous or ferric chloride or boron-fiuorine-nickel chloride.
  • the Workpiece to be plated is then immersed, for example in a brass plating bath under current, and is galvauically treated until an electrolytic layer of brass of a thickness of about 1 mu is formed.
  • the workpiece After rinsing with Water for a short time, the workpiece is immersed in a chromium plating bath and treated anodically for about 2 seconds until the preliminary layer has been dissolved away, whereupon the polarity is reversed. The workpiece is then hard chromium plated under normal conditions using a current density of about 60 amps. per sq. decimetre.
  • a method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin metal layer of a metal selected from the group consisting of brass, nickel, iron and copper, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.
  • a method of applying a strongly adherent hard chromium plating upon an article having a surface of aluminum base metal which comprises pickling the aluminurn base metal surface to remove oxides, plating the thus cleaned surface with a thin metal layer of a metal selected from the group consisting of brass, nickel, iron and copper, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said aluminum base metal surface while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.
  • a method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin metal layer of a metal selected from the group consisting of brass, nickel, iron and copper about l mu thick, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface while immersed in said chromium plating bath and then immediately electroplating the surface with 11313.31] chromium while still in said chromium plating 4.
  • a method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin layer of brass, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.
  • a method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin metal layer of a metal selected from the group consisting of brass, nickel, iron and copper, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface anodically while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.
  • a method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin metal layer of a metal selected from the group consisting of brass, nickel, iron and copper about l mu thick, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface anodically while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.
  • a method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin layer of brass, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface anodically while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium While still in said chromium plating bath.
  • a method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin layer of brass about l mu thick, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface anodically While immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.

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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 Methods And Accessories (AREA)

Description

United States Patent PROCESS OF PRODUCING HARD CHROMIUNI PLATINGS 0N LIGHT METALS Paul Eyerund, Stuttgart-Weilimdorf, Germany, assignor to Metallgesellschaft Aktiengesellschaft, Frankfurt am Main, Germany, a corporation of Germany No Drawing. Application May 7, 1951, Serial No. 225,065
Claims priority, application Germany June 16, 1950 8 Claims. (Cl. 204-33) This invention relates to a process of producing hard chromium platings on light metals, such as, aluminum, :lluminum base alloys, magnesium and magnesium base oys.
Aluminium and aluminium alloys have hitherto been hard-chromium plated by first pickling the aluminimn or aluminium alloy. Subsequently an interlayer was applied, in a variety of ways, which, in the case of some processes, was again dissolved away in a separate operation before entering the metal into the chromium plating bath, or in other processes served as a bonding layer for the hard-chromium layer.
For example, in the production of electro-plated metals, an electrolytic flash precipitate was applied in a preliminary bath as a bonding layer, on to which the desired metal layer was applied in the electro-plating bath proper (c. f. Germany patent specification No. 242,142). Alternately a metallic interlayer was applied by cathodic sputtering, on which interlayer the hard metal layer, of for example, chromium, nickel or the like, was produced by electrolysis (c. f. German patent specification No. 703,588).
In other processes, a layer of copper was precipitated on aluminium-magnesium alloys in a bath of copper chloride solution, which layer was then dissolved by nitric acid so as to roughen the surface of the alloy (c. f. German patent specification No. 762,716). It is also known to produce a finely divided heavy metal covering layer on aluminium alloys which covering, after treatment with an acid metallic salt solution is then removed with the aid of nitric acid, so that the surface of the alloy is exposed (c. f. German patent specification No. 760,230).
It has also been suggested to produce thick deposits of hard chromium on aluminium or aluminium alloys by first pre-treating said aluminium or aluminium alloy in an alkaline solution containing iron and zinc, then removing the resultant layer by means of nitric acid or a mixture of sulphuric acid and hydrogen peroxide, subsequently applying a copper layer of at the most mu by electrolysis in an alkaline copper plating bath and finally carrying out the chromium plating in a normal chromium plating bath in accordance with known processes.
These known processes have the disadvantage that they are generally applicable only to certain groups of alloys and that hard chromium layers electrolytically applied according to these processes are insufliciently bonded to the base metal especially when subjected to simultaneous thermal and mechanical stresses. The metallic layer applied before chromium plating is either removed in a separate process before immersion of the metal into the chromium plating bath, so that the aluminium surface is not protected from oxidation up to the time of application of the hard chromium layer, or the preliminarily applied layers are intended to serve as bonding layers and are preserved as interlayers m such cases.
It was now found that the hard chromium layer can be very intensively bonded to the base metal, i. e. light metal or light metal alloy, especially aluminium or aluminium alloy, if a preliminary metallic layer is ap plied electrolytically in such thickness that it is at least almost completely dissolved in the chromium-plating bath itself before a. hard chromium layer has been formed. This can, for example, be effected by a short reversal of the polarity before the chromium plating operation.
These preliminary metallic layers enable the prevention of oxidation before immersion in the chromium plating bath. Brass, nickel, iron and copper, for example, are suitable for such layers, especially when a complete removal, advantageously by means of a short change of polarity of the cathode, lasting from 1 to 2 seconds, is produced before the first surge of plating current of the hard chromium plating process. This complete removal of the preliminary layer is obtained with preliminary metal layers of a thickness of preferably 1 mu within 1 to 2 seconds.
The hard chromium layers obtained in accordance with the present invention, are distinguished by a particularly intense bonding to the base material and do not peel ofi even when strongly deformed.
The invention will be illustrated by the following nonlimitative example:
Example The surface of an aluminium or aluminium alloy workpiece is first pickled in accordance with a normal pre-treating process before the preliminary metallic layer is applied to the surface to be chromium plated. This pre-treatment can, for example be effected by using a known pickling solution containing ferrous or ferric chloride or boron-fiuorine-nickel chloride. The Workpiece to be plated is then immersed, for example in a brass plating bath under current, and is galvauically treated until an electrolytic layer of brass of a thickness of about 1 mu is formed. After rinsing with Water for a short time, the workpiece is immersed in a chromium plating bath and treated anodically for about 2 seconds until the preliminary layer has been dissolved away, whereupon the polarity is reversed. The workpiece is then hard chromium plated under normal conditions using a current density of about 60 amps. per sq. decimetre.
What I claim is:
1. A method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin metal layer of a metal selected from the group consisting of brass, nickel, iron and copper, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.
2. A method of applying a strongly adherent hard chromium plating upon an article having a surface of aluminum base metal which comprises pickling the aluminurn base metal surface to remove oxides, plating the thus cleaned surface with a thin metal layer of a metal selected from the group consisting of brass, nickel, iron and copper, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said aluminum base metal surface while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.
3. A method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin metal layer of a metal selected from the group consisting of brass, nickel, iron and copper about l mu thick, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface while immersed in said chromium plating bath and then immediately electroplating the surface with 11313.31] chromium while still in said chromium plating 4. A method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin layer of brass, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.
5. A method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin metal layer of a metal selected from the group consisting of brass, nickel, iron and copper, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface anodically while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.
6. A method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin metal layer of a metal selected from the group consisting of brass, nickel, iron and copper about l mu thick, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface anodically while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.
7. A method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin layer of brass, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface anodically while immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium While still in said chromium plating bath.
8. A method of applying a strongly adherent hard chromium plating upon an article having a surface of a light metal selected from the group consisting of aluminum, aluminum base alloys, magnesium and magnesium base alloys which comprises pickling the light metal surface to remove oxides, plating the thus cleaned surface with a thin layer of brass about l mu thick, immersing the plated metal surface into a chromium plating bath, substantially completely dissolving said metal layer from said light metal surface anodically While immersed in said chromium plating bath and then immediately electroplating the surface with hard chromium while still in said chromium plating bath.
References Cited in the file of this patent UNITED STATES PATENTS 2,091,386 Viers Aug. 31, 1937 2,327,676 Spence Aug. 24, 1943 FOREIGN PATENTS 258,724 Great Britain Sept. 30, 1926 476,720 Great Britain Dec. 14, 1937 OTHER REFERENCES Metal Finishing, February 1949, pages 51 to 53.

Claims (1)

1. A METHOD OF APPLYING A STRONGLY ADHERENT HARD CHROMIUM PLATING UPON AN ARTICLE HAVING A SURFACE OF A LIGHT METAL SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, ALUMINUM BASE ALLOYS, MAGNESIUM AND MAGNESIUM BASE ALLOYS WHICH COMPRISES PICKLING AND LIGHT METAL SURFACE TO REMOVE OXIDES, PLATING THE THUS CLEANED SURFACE WITH A THIN METAL LAYER OF A METAL SELECTED FROM THE GROUP CONSISTING OF BRASS, NICKEL, IRON AND COPPER, IMMERSING THE PLATED METAL SURFACE INTO A CHROMIUM PLATING BATH, SUBSTANTIALLY COMPLETELY DIS SOLVING SAID METAL LAYER FROM SAID LIGHT METAL SURFACE WHILE IMMERSED IN SAID CHROMIUM PLATING BATH AND THEN IMMEDIATELY ELECTROPLATING THE SURFACE WITH HARD CHROMIUM WHILE STILL IN SAID CHROMIUM PLATING BATH.
US225065A 1950-06-16 1951-05-07 Process of producing hard chromium platings on light metals Expired - Lifetime US2702785A (en)

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DEM4242A DE873478C (en) 1950-06-16 1950-06-16 Process for applying hard chrome layers to light metal

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2873154A (en) * 1954-01-04 1959-02-10 Harold F Marker Piston packing rings and method of producing same
US3634207A (en) * 1969-09-04 1972-01-11 Us Navy Nickel etching and plating bath
US4157941A (en) * 1977-06-03 1979-06-12 Ford Motor Company Method of adherency of electrodeposits on light weight metals
US4159229A (en) * 1977-06-03 1979-06-26 Ford Motor Company Method of plating light weight metal to enhance lateral corrosion resistance
US5456818A (en) * 1993-11-03 1995-10-10 Ingersoll-Rand Company Method for preventing fretting and galling in a polygon coupling

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB258724A (en) * 1925-09-04 1926-09-30 Clement Loftus Long Improved process for the electro-deposition of chromium
US2091386A (en) * 1935-08-01 1937-08-31 Eaton Detroit Metal Company Electroplating
GB476720A (en) * 1936-04-07 1937-12-14 Finckh G M B H Improvements in or relating to the chromium plating of aluminium and aluminium alloys
US2327676A (en) * 1940-01-09 1943-08-24 Repel Corp Du Plating process

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB258724A (en) * 1925-09-04 1926-09-30 Clement Loftus Long Improved process for the electro-deposition of chromium
US2091386A (en) * 1935-08-01 1937-08-31 Eaton Detroit Metal Company Electroplating
GB476720A (en) * 1936-04-07 1937-12-14 Finckh G M B H Improvements in or relating to the chromium plating of aluminium and aluminium alloys
US2327676A (en) * 1940-01-09 1943-08-24 Repel Corp Du Plating process

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2873154A (en) * 1954-01-04 1959-02-10 Harold F Marker Piston packing rings and method of producing same
US3634207A (en) * 1969-09-04 1972-01-11 Us Navy Nickel etching and plating bath
US4157941A (en) * 1977-06-03 1979-06-12 Ford Motor Company Method of adherency of electrodeposits on light weight metals
US4159229A (en) * 1977-06-03 1979-06-26 Ford Motor Company Method of plating light weight metal to enhance lateral corrosion resistance
US5456818A (en) * 1993-11-03 1995-10-10 Ingersoll-Rand Company Method for preventing fretting and galling in a polygon coupling
US5482437A (en) * 1993-11-03 1996-01-09 Ingersoll-Rand Company Method for preventing fretting and galling in a polygon coupling

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Publication number Publication date
FR1042768A (en) 1953-11-03
DE873478C (en) 1953-04-13
GB684456A (en) 1952-12-17

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