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
  • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
• • 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
  • C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
  • C23D3/00—Chemical treatment of the metal surfaces prior to coating

Definitions

• ABSTRACT A method of electrochemically pretreating articles, especially bands and sheets of steel, for a later onelayer enameling process according to which the article to be pretreated is degreased and, if necessary, pickled and in an electrolytic nickel and/or cobalt bath containing a nitrate ion is provided with a nickel and/or cobalt layer.
• the present invention relates to a method of electrochemically pretreating bands and sheets of steel and articles made therefrom for the one-layer enameling process according to which the bands and sheets are degreased, if desired pickled, and in an electrolytic nickel and/or cobalt bath are provided with a nickel and/or cobalt layer.
• the metal sheet to be enameled is first electrolytically degreased and after washing in water is pickled chemically or electrolytically in sulfuric acid or in a mixture of formic acid and nitric acid, and subsequently is rinsed again.
• the sheet metal is plated electrolytically with nickel in a nickel bath and subsequently is enameled. If the enameling process is not carried out shortly after the nickel plating step, the metal sheet to be nickel plated is electrolytically coated with a zinc layer which is removed prior to the enameling process. A sufficient adherence between the steel metal sheet and the enamel coat is, however, not obtained by this method.
• the metal sheet is likewise cleaned, washed and briefly treated with an acid.
• a nickel and/or cobalt layer is deposited upon the metal sheet, whereupon the sheet is rinsed, is heated in an oxidizing atmosphere, and zinc is deposited upon the nickel and/or cobalt layer which zinc is again removed by the user or in the enameling plant.
• the drawback of this known method similar to the before mentioned method, consists in the necessary oxidizing annealing, on the one hand, and, on the other hand, in the fact that the baths to be employed are as to their composition rather unstable.
• an object of the present invention to provide a method of the above described general character by means of which it will be possible in a very simple manner to pretreat bands or sheets to be enameled in a continuous way, while at the same time the method according to the present invention will be such that it can be practiced and controlled in a simple manner so that also the required installations for carrying out the method can be kept simple.
• the nickel and/or cobalt bath there are added to the nickel and/or cobalt bath from 0.5 to 110 gr, preferably from 25 to gr, of nitrate ions per liter of electrolyte liquid, and a nickel and/or cobalt layer is at room temperature deposited on the band or sheet in a time period of from 50 to seconds at a current density of from 5 to 15 amperes/dm at a pH-value of the electrolyte of from 1 to 5.
• the electrolytic bath for carrying out the method according to the invention consists of from 20 to gr/liter of nickel, 0.6 to gr/liter of ammonium nitrate, from 15 to 40 gr of boric acid in sulfuric acid or hydrochloric acid solution.
• the bath expediently consists of from 20 to 100 gr/liter of cobalt, of 0.6 to 135 g/liter of ammonium nitrate, of from 15 to 40 gr/liter of boric acid in sulfuric acid solution.
• an adhesive layer consisting of nickel and cobalt is required for the subsequent enameling step, a corresponding mixed bath is employed in conformity with the above referred to bath compositions.
• the nickel and/or cobalt layer is in a time period of from 5 to 60 seconds deposited at a current density of from 5 to 50 A/dm in the bath having a temperature of from room temperature to boiling temperature.
• a considerably widened range of the bath temperature and, more specifically, from room temperature or slightly above room temperature to boiling temperature of the bath is available and a further reduced time range of from 5 to 15 or 14 seconds, and furthermore a likewise widened range of the current density of from 15 or 16 to 50 A/dm is available in an advantageous manner for carrying out the method according to the invention.
• EXAMPLE 1 a. Electrolytic degreasing in alkaline lye at 80C for 6 seconds. b. Rinsing for 5 seconds.
• Nickel plating in an electrolyte having the following composition: 135 gr/liter of nickel sulfate 35 gr/liter of ammonium nitrate 25 gr/liter of boric acid in a sulfuric acid solution at a pH-value of 3.5 and at room temperature, a current density of A/dm in 28 seconds.
• EXAMPLE 2 The method is carried out in the same manner as set forth in Example 1 without the method step cpickling while the method step b-rinsing is replaced by a spray rinsing step with longer duration of the spraying.
• Example 3 The method steps a) to d) and f) and g) of Example 1 are likewise used in this Example.
• method step e) there will be carried out a coating or plating with cobalt in an electrolyte composed of 135 gr/liter of cobalt sulfate 35 gr/liter of ammonium nitrate 30 gr/liter of boric acid, and this is carried out in a sulfuric acid solution at a pH- value of 3.5 and at room temperature, and a current density of 10 A/cm in 28 seconds.
• Method step c) may also in this Example be replaced in the same manner as described in connection with Example 2.
• EXAMPLE 4 a. Electrolytic degreasing in alkaline lye at 80C for 6 seconds. b. Rinsing for 5 seconds. c. Pickling at room temperature in a 10% by weight sulfuric acid for 2 seconds. (1. Rinsing for 5 seconds. e. Nickel plating in an electrolyte having the following composition: 135 gr/liter of nickel sulfate 35 gr/liter of ammonium nitrate 25 gr/liter of boric acid at a pH-value of 4.5, a temperature of from 40 to 60 C, and a current density of 20 A/dm in 28 seconds.
• Example 5 The method steps a) to d) and f) and g) of Example 4 are applied to this Example.
• the nickel plating according to method step e) in Example 4 is carried out with the same electrolyte but at a pH-value of 5.0, a temperature of from 10 to 25C, and a current density of 30 A/dm for 20 seconds.
• EXAMPLE 6 This Example follows the same method steps a) to d) and f) and g) as in Example 4.
• the nickel plating according to method step e) is carried out with the same electrolyte but at a pH-value of 4.0, a temperature of from 80 to 90C, and a current density of A/dm for 45 seconds.
• Example 7 The method steps a) to d) and f) and g) of Example 4 also apply to this Example.
• the nickel plating according to the method step e) of Example 4 is carried out with the same electrolyte as in Example 4 but at a pH- value of 4.5, a temperature of from to C, and a current density of 40 A/dm for 10 seconds.
• the advantages of the method according to the present invention in addition to avoiding oxidizing annealing steps and an acid treatment of relatively long duration, consist primarily in the simple way of carrying out and controlling the course of the method according to the invention.
• correspondingly simple installations for carrying out the method are obtained which method can also be practiced in installations already in existence. lnasmuch as in conformity with the method of the invention the heretofore required acid treatment of the metal sheets and bands is no longer necessary, the method according to the invention also avoids the problems of waste water refining which problems occur to an ever increasing extent.
• the method according to the invention also improves the interengagement of the enamel coat with the supporting or base material, the bands. sheets or individual articles of steel is improved so that an excellent adherence is obtained.
• a method of pretreating a steel article for an enameling process which includes the steps of preparing an electrolyte bath containing at least one element selected from the group consisting of nickel and cobalt, adding non-substituted nitrate ions from inorganic substance to said electrolyte in the amount of 0.5 to l 10 gr./liter of the electrolyte fluid, and depositing upon the steel article a layer containing at least one of said elements from the electrolyte bath upon the article to be pretreated at a bath temperature of from room temperature to boiling temperature at a current density of from 5 to 50 A/dm for a period of from 5 to 60 secends.
• a method in combination according to claim l which includes the step of pickling the article to be' gr/liter of nickel, from 0.6 to 135 gr/liter of ammonium nitrate and from 15 to 40 gr/liter of boric acid in a solution selected from the group consisting of sulfuric acid solution and hydrochloric acid solution.
• the electrolytic bath contains from 20 to gr/liter of cobalt, from 0.6 to gr/liter of ammonium nitrate and from 15 to 40 gr/liter of boric acid in sulfuric acid solution.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Electrochemistry (AREA)
• Electroplating Methods And Accessories (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Electroplating And Plating Baths Therefor (AREA)

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Cited By (4)

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Citations (4)

• 0
  • BE BE789793D patent/BE789793A/xx unknown
• 1971
  • 1971-10-06 DE DE2149808A patent/DE2149808C2/de not_active Expired
• 1972
  • 1972-09-04 AT AT7592A patent/AT324070B/de not_active IP Right Cessation
  • 1972-09-28 GB GB4481572A patent/GB1389609A/en not_active Expired
  • 1972-10-02 ES ES407226A patent/ES407226A1/es not_active Expired
  • 1972-10-03 IT IT53144/72A patent/IT966172B/it active
  • 1972-10-04 US US295010A patent/US3880727A/en not_active Expired - Lifetime
  • 1972-10-05 NL NL7213459A patent/NL7213459A/xx not_active Application Discontinuation
  • 1972-10-05 CA CA153,322A patent/CA1022875A/en not_active Expired
  • 1972-10-05 CH CH1453672A patent/CH572986A5/xx not_active IP Right Cessation
  • 1972-10-05 NO NO3574/72A patent/NO131350C/no unknown
  • 1972-10-06 JP JP47099950A patent/JPS4845531A/ja active Pending
  • 1972-10-06 FR FR7235584A patent/FR2156155B1/fr not_active Expired

Patent Citations (4)

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