Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D13/00—Electrophoretic coating characterised by the process
  • C25D13/20—Pretreatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
  • B22F7/02—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite layers
  • B22F7/04—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite layers with one or more layers not made from powder, e.g. made from solid metal
• • 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
  • C23C24/00—Coating starting from inorganic powder
• • 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
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D13/00—Electrophoretic coating characterised by the process

Definitions

• ABSTRACT OF THE DISCLOSURE This specification describes a method of coating elongated steel substrates, e.g., strip, with a powdered coating material, in which a gelatinous, colloidal metal hydroxide is used as a binder.
• Suitable metal hydroxides include those of aluminium, zinc, nickel, iron, chromium, magnesium and manganese. After deposition of the coating material, the coated substrate is heated to render the coating adherent.
• This invention is concerned with a method of coating metal substrates, more particularly metal substrates which can be subjected to rolling, such as sheet, strip, Wire or rod, which types of material are hereinafter referred to generally as substrates in elongated form.
• a method of coating metal substrates in elongated form which comprises coating the substrate with a colloidal. solution of a suitable metal hydroxide, applying a uniform layer of the desired coating material in powder form to the metal hydroxide coating, drying the coated substrate, rolling the substrate to compact the coating, and then heating the coated substrate to an elevated temperature to obtain a tightly adherent coating.
• This process is particularly applicable to the formation of metal coatings, for example coatings of aluminium, tin, nickel, brass, zinc, iron and steel and mixtures or alloys of two or more of these or other metals, but can also be used to form coatings of other types, for example coatings of metal oxides such as alumina.
• a preformed powdered alloy may be used or alternatively the individual constituents of the alloy, in powdered form, may be mixed and the powder mixture applied to the substrate, alloying by inter-diffusion of the constituents taking place during the final heat treatment.
• Suitable metal hydroxides for this purpose are those which l) are gelatinous when suitably hydrated and can, in the presence of water, form a colloidal solution, (2) when applied to a metal substrate in the form of such a colloidal solution, are capable of adhering the subsequently applied powder to the substrate sufficiently well, both before and after the drying operation, that the powder is not dislodged to a significant extent by the normal vibrations of a processing line and a roll ing mill, and (3) are not deleterious to the rolling and heat treatment and, after the rolling and heat treatment, are not significantly deleterious to the corrosion resistance, formability or appearance of the coated substrate.
• ICC Metal hydroxides which have proved successful include Al(OH) Zn(OH) Ni(OH)2; Fe(OH) Cr(OH) Mg(OH) and Mn(OH) of which Al(OH) and Ni(OH) are preferred.
• a colloidal solution of the desired metal hydroxide is prepared and applied to the substrate by any suitable coating procedure, such as dipping, roller coating or spraying.
• the colloidal solution of metal hydroxide may be prepared electrolytically by electrolysing a dilute aqueous solution of a soluble salt of the metal, the hydroxide of which it is desired to use; the anode should be formed of the same metal. Suitable concentrations of the soluble salt are from 1 to 5 millimoles/litre; nickel chloride can conveniently be used as the soluble nickel salt when it is desired to form a colloidal solution of nickel hydroxide and aluminium nitrate in the case of aluminium hydroxide.
• the solution is preferably agitated during the course of the electrolysis, for example by means of stirrers immersed in the solution or by continuously circulating the solution through the electrolysis tank.
• Electrolysis may be continued until the solution contains a quantity of the desired metal hydroxide appropriate to the particular coating procedure to be used or a more concentrated colloidal solution may be prepared and used as a stock solution, being diluted as required prior to use.
• a suitable concentration of the metal hydroxide is from 2 to 5 grams/litre.
• a coating of colloidal metal hydroxide can be formed directly on the substrate by making the latter the cathode in the abovedescribed electrolysis process.
• the formation of such coatings can be carried out batchwise or continuously; in the latter case, the substrate in elongated form is passed continuously over a conductor roll or guide and then through the electrolysis tank.
• the anode length, current density and rate of travel of the substrate should be adjusted so that sufiicient metal hydroxide is deposited on the substrate; for example where it is desired to form a nickel hydroxide coating on steel strip using an aqueous solution containing from 1 to 2 millimoles of nickel chloride per litre, a strip speed of 50 feet/minute, an anode length of 6 feet (the anode having the same width as the strip and being arranged parallel to the latter), a current density of from 5 to 10* amps/sq. ft. will give a suitable deposit of the hydroxide.
• metal hydroxide coating weight of from 0.5 X 10* to 5X10- grams per sq. cm. of substrate surface. It is preferred to use lower coating weights within this range in the case of nickel hydroxide, the preferred range for this hydroxide being from 0.6 10 to 0.9 1()- gms./sq. cm., and higher coating weights within the broad range in the case of aluminium hydroxide, the preferred range for the latter hydroxide being from 1.5 X 10 to 4X10 gms./sq. cm.
• the preferred nickel hydroxide coating weight can be obtained, for example, by applying a colloidal solution containing from 2 to 3 gms./litre of nickel hydroxide to the substrate in such a way, for example by dipping followed by light squeegeeing, as to leave 30 ml./sq. metre of the solution on the substrate.
• the powder which is to form the coating can be applied to the substrate in any way which enables a substantially uniform rate of coating, in terms of weight of powder per unit area of substrate surface, to be obtained.
• One method of applying the powder to substrates in the form of sheet or strip involves the use of a rotating metering roll as described in British patent specification No. 1,035,256, the
• the powder can be varied by varying the speed of rotation Steel samples 22 cm. x cm. were cathodically deof the roll. Powder deposition may also be effected by greased in aqueous sodium hydroxide solution, dried and electrostatic deposition from a gaseous suspension of the weighed. The samples were then dipped into the colloidal powder particles.
• the coated substrate is powder deposited from a metering roll apparatus as shown dried and then rolled. Suitable temperatures for drying are, in FIGURE 2 of the aforementioned British patent specifor example, from 100 to 300 C. The rolling pressure fication No. 1,035,256. The coating was dried at 100 C., required to obtain adequate compaction will depend upon the sample weighed and then clamped at each end with such factors as the nature of the powder coating, the hardthe plane of the sample vertical in an apparatus which inness of the substrate and the diameter of the rolls.
• aluminium powder is used as the coating material, suitable It is considered that where not more than 25% of the heat treatments are, for example, 10-15 hours at 250 powder coating is removed by the test described above, C., minutes at 500 (3,, or a few o d t 600 65() c, the coating is sufficiently adherent to withstand the vibra- If the coating is liable to undergo undesirable oxidation at non of a Commerclal continuolls Coatlng 11116- the temperature of the heat treatment, it should be carried The p coated as described Wfife then compacled out in a Homoxidising atmosphere by passing them through compacting rolls which applied The process is well adapted for the continuous treat- 2 f 4 a i wlglth 1 i anoextfmslon of ment of substrates in continuous form, such as strip and a an were en gate or f In all cases, that is with all the coating weights of wire, since all the steps of the process can be carried out fa d1 and therefore in
• Example 2 a colloidal solution z gfiig ggg if g fi i2 without damage of aluminium hydroxide.
• coated samples were then compacted by passing them through compacting rolls which applied a load of 75 4 tons/inch width and caused an extension of 4% and,
• Steel sheets have also been coated with nickel and with zinc using a procedure as described in Example 1.
• suitable rolling loads were found to be from 12 to 15 tons/inch width and a suitable heat treatment, hours at 700 C. or 2 minutes at 1000 C.
• a suitable rolling load was found to be 4 tons/inch width and a suitable heat treatment, 30 minutes at 350 C.
• the coated sheet could be bent flat through 180 without damage or delamination of the coating taking place.
• a method of coating steel substrates in elongated form which comprises coating the substrate with a colloidal solution of a metal hydroxide selected from the group consisting of Al(OH);;, Zn( OH) Ni(OH) Fe(OH) C1"(OH) Mg(OH) and Mn(OH) applying a uniform layer of the desired coating material selected from the group consisting of aluminum, tin, nickel, brass, zinc, iron and steel mixtures of said metals, alloys of said metals and oxides of said metals in powder form to the metal hydroxide coating, drying the coated substrate, rolling the substrate to compact the coating, and then heating the coated substrate to an elevated temperature to obtain a tightly adherent coating, said coating materal being selected from the group consisting of metals, metal alloys, and metal oxides.
• a metal hydroxide selected from the group consisting of Al(OH);
• Zn( OH) Ni(OH) Fe(OH) C1"(OH) Mg(OH) and Mn(OH) applying a uniform layer of
• metal hydroxide is nickel hydroxide and the substrate is coated with from 0.6 x 10" to- 0.9 10- gm. of nickel hydroxide per square centimetre of substrate surface.
• metal hydroxide is aluminium hydroxide and the substrate is coated with from 1.5 10 to 4X10 gm. of aluminium hydroxide per square centimetre of substrate surface.
• a method according to claim 1 in which, after rolling, the coated substrate is coiled and the final heat treatment is effected in coil.
• ALFRED L. LEAVITT Primary Examiner.
• A. M. GRIMALDI Assistant Examiner.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Manufacturing & Machinery (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Chemically Coating (AREA)
• Paints Or Removers (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)

Applications Claiming Priority (1)

Publications (1)

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Cited By (8)

Citations (3)

• 0
  • NL NL137232D patent/NL137232C/xx active
• 1963
  • 1963-06-17 GB GB23989/63A patent/GB1035519A/en not_active Expired
• 1964
  • 1964-06-05 DE DE1521136A patent/DE1521136C3/de not_active Expired
  • 1964-06-10 FR FR977691A patent/FR1398354A/fr not_active Expired
  • 1964-06-11 LU LU46294A patent/LU46294A1/xx unknown
  • 1964-06-11 BE BE649157A patent/BE649157A/xx unknown
  • 1964-06-15 US US375289A patent/US3364057A/en not_active Expired - Lifetime
  • 1964-06-17 NL NL6406864A patent/NL6406864A/xx unknown

Patent Citations (3)

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