US3775193A - Method for passivating a zinc surface - Google Patents

Method for passivating a zinc surface Download PDF

Info

Publication number
US3775193A
US3775193A US00187649A US3775193DA US3775193A US 3775193 A US3775193 A US 3775193A US 00187649 A US00187649 A US 00187649A US 3775193D A US3775193D A US 3775193DA US 3775193 A US3775193 A US 3775193A
Authority
US
United States
Prior art keywords
passivating
liquid
coating
vacuum chamber
substrate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00187649A
Other languages
English (en)
Inventor
P Costelloe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
British Steel Corp
Original Assignee
British Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by British Steel Corp filed Critical British Steel Corp
Application granted granted Critical
Publication of US3775193A publication Critical patent/US3775193A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/08—Plant for applying liquids or other fluent materials to objects
    • B05B5/14—Plant for applying liquids or other fluent materials to objects specially adapted for coating continuously moving elongated bodies, e.g. wires, strips, pipes
    • 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
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
    • 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
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
    • C23C22/76—Applying the liquid by spraying

Definitions

  • ABSTRACT [52 us. c1. 148/6.2, 148/6.15, 118/634, A method of passivating a metallic smface to improve 117/934 117/119 the subsequent adhesion of paint thereto comprising [51] Int. C1.
  • the painting of a galvanised ferrous substrate affords substantial protection to the substrate additional to that provided by the zinc coating thereof, but necessitates the prior passivation of the zinc coating.
  • This passivation is necessary because, if this is not done, the adhesion of the paint to the zinc coating is poor, while a chemical reaction which occurs between the zinc coating, the constituents of the paint, and moisture which penetrates the paint, can lead to blistering and flaking of the paint during service.
  • the passivating treatment moreover, which is also known as conversion coating, not only assists paint adhesion, but also prevents the final product from white rusting during storage.
  • a method of passivating a metallic surface to improve the subsequent adhesion of paint thereto comprising directing a passivating liquid through an electrostatic field and onto the metallic surface, the electrostatic field atomising the passivating liquid.
  • the passivating liquid is preferably so directed through a liquid outlet aperture of a container for the passivating liquid, the container being provided with an electrode which extends through said aperture, and a high intensity electric discharge being created between the said electrode and the metallic surface.
  • the passivating liquid may be directed through the said outlet aperture by subjecting the passivating liquid in the container to a gas pressure which exceeds that prevailing externally of the container.
  • the passivating liquid may be a phosphating solution, but is preferably a chromating solution such, for example, as that marketed under the Trade Name Accomet C.
  • the said metallic surface is preferably that of a zinc coating on a ferrous substrate.
  • a metal substrate may be provided with a metallic coating, which provides the said surface, while the substrate is disposed within a vacuum chamber, molten coating metal being evaporated under the reduced pressure in the vacuum chamber, and the vapour of the coating metal being condensed onto the substrate.
  • the metal substrate is preferably a steel strip which is moved continuously through the vacuum chamber, the coating metal being zinc.
  • the passivating liquid is preferably directed onto the surface of the coating metal while the latter is in the vacuum chamber, the passivating liquid being an aqueous solution containing a low freezing point liquid whose freezing point is such that the passivating liquid is in the liquid state when it contacts the surface of the coating metal.
  • the said low freezing point liquid ensures that the passivating liquid is in the liquid state when it contacts the surface of the zinc coating metal, the water in the passivating liquid is able to perform its required chemical function in effecting passivation.
  • the passivating liquid preferably contains at least 20 percent, and may contain at least 30 percent, by volume of water.
  • the low freezing point liquid is preferably a glycol, e.g. diethylene glycol.
  • the pressure in the vacuum chamber preferably does not exceed 10 Torr and may, for example, not exceed 10 Torr.
  • the passivating liquid preferably reaches the surface of the coating metal in the form of droplets whose average diameter does not exceed 200 microns.
  • the passivated surface is first painted with a radiation curable, non solvent based paint, and the paint is then radiation cured.
  • the paint may be applied to the passivated surface by roller coating, and the paint so applied may be cured by the Videcolor electron bombardment process of the British Iron and Steel Research Association.
  • the invention also comprises a substrate when treated by the method set forth above.
  • the invention comprises apparatus for use in the said method comprising a container for a passivating liquid, the said container having a liquid outlet aperture through which extends an electrode; means for supporting a metallic substrate adjacent to said electrode; means for creating a high intensity electric discharge between the electrode and the metallic substrate whereby to produce an electrostatic field in which the passivating liquid is atomised; and means for forcing the passivating liquid to pass through the outlet aperture and through the electrostatic field onto the metallic substrate.
  • the said apparatus may be disposed within a vacuum chamber, there also being provided within the said vacuum chamber means for coating the substrate with a metal prior to the application of the passivating liquid, and means for painting the passivated metallic coating.
  • a vacuum chamber l the pressure within which may be of the order of 10* Torr.
  • Molten zinc in the zinc applicator 114 is evaporated under the reduced pressure in the vacuum chamber 1 and is condensed onto the surface 4 so as to provide the latter with a zinc coating (not shown).
  • the surface 3 of the strip 2 whilst in the said second horizontal run, passes adjacent to and above a zinc applicator from which it receives a zinc coating (not shown).
  • the passivating liquid applicator 16 comprises a glass container having a tubular portion 20 which is adapted to receive an aqueous passivating solution.
  • the latter may be constituted by a chromating solution containing 35 percent by volume of water, 60 percent by volume of diethylene glycol, and 5 percent by volume of Accomet C.
  • the bottom of the tubular portion 20 is provided with a liquid outlet aperture 21 which is disposed at a distance of not more than one half an inch from the adjacent surface 4 of the strip 2.
  • a wire electrode 22 which carries a high voltage and which extends through the outlet aperture 21, the passivating liquid applicator 16 being so sized that the tubular portion 20 and wire electrode 22 collectively resemble a hypodermic needle.
  • the wire electrode 22 and the strip 2 are electrically connected (by means not shown) in a circuit such that a high intensity electric discharge is created between the wire electrode 22 and the zinc coated surface 4 so as to produce an electrostatic field in which the passivating solution is atomised.
  • the passivating liquid applicator 16 is provided at its upper end with an enlarged diameter portion 23 which is supplied (by means not shown) with air which is at atmospheric pressure and which is thus at a pressure exceeding that prevailing externally of the passivating liquid applicator 16. Due to the pressure differential between the pressure of this air and the pressure prevailing in the vacuum chamber 1, the solution in the passivating liquid applicator 16 is forced through the outlet aperture 21 and through the said electrostatic field so as to be deposited on the zinc surface 4. As will be appreciated, the amount of passivating solution applied to the surface 4 can be varied and controlled by controlling the said pressure differential, e.g. by altering the pressure in the enlarged diameter portion 23.
  • the electrostatic field atomises the passivating solution so that the average diameter of the droplets of passivating solution reaching the surface 4 does not exceed 200 microns, the outlet aperture 21 being so disposed that the droplets take a period not exceeding 0.05 seconds to reach the surface 4.
  • the presence of the diethylene glycol in the passivating solution ensures that the latter does not freeze during this period and thus contacts the zinc coating in the liquid state, this being necessary for the solution to effect its passivating function.
  • the small period of time for the travel of the droplets from the outlet aperture 21 to the strip 2 is such that the droplets will merely be subcooled, i.e.
  • the final temperature of the droplets on reaching the strip 2 may be of the order of -70C and may nevertheless remain in the liquid state, notwithstanding the fact that their freezing point may be of the order of 47C.
  • the high intensity electrical discharge has the effect of causing dissociation of the passivating solution so as to cause the latter to become very reactive.
  • hypodermic needle-like passivating liquid applicator l6 enables very small amounts of the passivating solution to be applied to the surface 4. This is extremely important since, for example, if the passivating solution were to be applied to the strip by roller coating, it would be very difficult to apply a thin liquid film thereto, and great expertise on the part of the operator would be required to control the coating thickness.
  • the control of the coating thickness is, however, very important when applying a passivating film, since the latter tends to be friable and, if too much is applied, subsequent paint adhesion can be poor.
  • the surface 4 which has been both zinc coated and passivated is lowermost while the surface 3 is uppermost.
  • both of the opposite surfaces 3, 4 of the strip 2 are provided with passivated zinc coatings.
  • the strip 2- then passes sequentially through a paint applicator 25 and an electron beam curing apparatus 26.
  • the paint applicator 25 the strip passes between rollers 30, 31 which apply paint to the passivated zinc coatings 12, 13.
  • the paint applied is a radiation curable, non-solvent based paint such as an alkyd, epoxy, or polyester paint which is applied in the form of a hot melt.
  • this paint is cured by electron bombardment.
  • the strip After leaving the electron beam cun'ng apparatus 26, the strip passes over the rollers 11, 12 and so passes out of the vacuum chamber 1 through the exit seal 6.
  • the invention has been described above primarily with reference to the passivation of a zinc surface, the invention is also applicable to the passivation of surfaces of aluminium, copper, tin plate, steel, alloys such as aluminium/zinc alloys, and substrates coated with metallic oxides such as alumina or silica. Accordingly, the term metallic as used in this specification is to be understood to include both alloys and compounds of metals.
  • vacuum coating technique is described above with reference to a zinc coating, the vacuum coating technique may also be used for the coating of large numbers of metals, e.g. aluminium, titanium, copper, or any alloys thereof.
  • a method of passivating a metallic surface to improve the subsequent adhesion of paint thereto comprising atomizing an aqueous passivating solution and increasing its reactivity by passing it through an electrostatic field located within a vacuum chamber and directing the atmoized solution onto a metallic surface in said vacuum chamber, the passivating solution containing a low freezing point liquid which ensures that the droplets of the passivating solution are in the liquid state when they contact and react with the metallic surface.
  • a method as claimed in claim 1 in which the passivating liquid is directed through a liquid outlet aperture of a container for the passivating liquid, the container being provided with an electrode which extends through said aperture and about which the passivating liquid flows, and a high intensity electric discharge is created between the said electrode and the metallic surface.
  • a method as claimed in claim 1 in which a metal substrate is provided with a metallic coating, which constitutes the said metallic surface, while the substrate is disposed within the vacuum chamber, molten coating metal being evaporated under the reduced pressure in the vacuum chamber, and the vapour of the coating metal being condensed onto the substrate.
  • the metal substrate is a steel strip which is moved continuously through the vacuum chamber, the coating metal being zinc.
  • a method as claimed in claim l in which, while the substrate is disposed in the vacuum chamber, the passivated surface is first painted with a radiation curable, non solvent based paint, and the paint is then radiation cured.

Landscapes

  • Chemical & Material Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Chemical Treatment Of Metals (AREA)
US00187649A 1970-10-13 1971-10-08 Method for passivating a zinc surface Expired - Lifetime US3775193A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB4858370 1970-10-13

Publications (1)

Publication Number Publication Date
US3775193A true US3775193A (en) 1973-11-27

Family

ID=10449130

Family Applications (1)

Application Number Title Priority Date Filing Date
US00187649A Expired - Lifetime US3775193A (en) 1970-10-13 1971-10-08 Method for passivating a zinc surface

Country Status (8)

Country Link
US (1) US3775193A (xx)
AU (1) AU3456371A (xx)
BE (1) BE773766A (xx)
DE (1) DE2151046A1 (xx)
FR (1) FR2110402B1 (xx)
GB (1) GB1339565A (xx)
IT (1) IT942672B (xx)
NL (1) NL7114054A (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20010004557A1 (en) * 1999-12-15 2001-06-21 Wolfgang Scheideler Flat conductor ribbon cable
ITUD20090008A1 (it) * 2009-01-14 2010-07-15 Giovanni Defant Macchina da inserire in una linea di processo di zincatura continua della lamiera che applica alla lamiera zincata la sostanza passivante o antiossidante o protettiva dello zinco con metodo elettrostatico

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102007052770A1 (de) 2007-11-02 2009-05-07 Hydro Aluminium Deutschland Gmbh Verfahren und Vorrichtung zum Erzeugen einer Konversionsschicht

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2768104A (en) * 1952-03-25 1956-10-23 Heintz Mfg Co Method for coating iron
US2826451A (en) * 1954-11-01 1958-03-11 Sedlacsik John Spray device for electrostatic deposition of a fluid
US3576207A (en) * 1968-04-23 1971-04-27 Steel Co Of Wales Ltd Formation of steel strip
US3594214A (en) * 1969-04-04 1971-07-20 United States Steel Corp Method of applying a zinc coating to a sheet-steel base
US3595687A (en) * 1969-08-04 1971-07-27 Ford Motor Co Divinyl compounds from monoepoxides and painting process

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2768104A (en) * 1952-03-25 1956-10-23 Heintz Mfg Co Method for coating iron
US2826451A (en) * 1954-11-01 1958-03-11 Sedlacsik John Spray device for electrostatic deposition of a fluid
US3576207A (en) * 1968-04-23 1971-04-27 Steel Co Of Wales Ltd Formation of steel strip
US3594214A (en) * 1969-04-04 1971-07-20 United States Steel Corp Method of applying a zinc coating to a sheet-steel base
US3595687A (en) * 1969-08-04 1971-07-27 Ford Motor Co Divinyl compounds from monoepoxides and painting process

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20010004557A1 (en) * 1999-12-15 2001-06-21 Wolfgang Scheideler Flat conductor ribbon cable
ITUD20090008A1 (it) * 2009-01-14 2010-07-15 Giovanni Defant Macchina da inserire in una linea di processo di zincatura continua della lamiera che applica alla lamiera zincata la sostanza passivante o antiossidante o protettiva dello zinco con metodo elettrostatico

Also Published As

Publication number Publication date
BE773766A (fr) 1972-01-31
AU3456371A (en) 1973-04-19
NL7114054A (xx) 1972-04-17
FR2110402A1 (xx) 1972-06-02
GB1339565A (en) 1973-12-05
FR2110402B1 (xx) 1975-02-07
DE2151046A1 (de) 1972-04-20
IT942672B (it) 1973-04-02

Similar Documents

Publication Publication Date Title
US4992337A (en) Electric arc spraying of reactive metals
CA1153255A (en) Metallizing of a corrodible metal with a protective metal
US4657787A (en) Flow coating of metals
US11319631B2 (en) Metal sheet treatment method and metal sheet treated with this method
US3438754A (en) Zinc-coated steel with vapor-deposited aluminum overlay and method of producing same
EP0756022A2 (de) Korrosionsgeschütztes Stahlfeinblech und Verfahren zu seiner Herstellung
US4587135A (en) Process for producing metallic coatings
GB1471977A (en) Organic coating of metallic substrates
US3775193A (en) Method for passivating a zinc surface
US20200299844A1 (en) Metal sheet treatment method and metal sheet treated with this method
US3382085A (en) Cladding of strip material
AU6939581A (en) Wiping hot dip metallic coatings
US3594214A (en) Method of applying a zinc coating to a sheet-steel base
DE4438608C2 (de) Verfahren zum Beschichten eines Aluminiumsubstrates
US3718509A (en) Coated metal and method
US2876176A (en) Marking or dulling of tin plate
US3730783A (en) Process for treating a coating of aluminium deposited on a metal support,more particularly,sheet metal
US2354109A (en) Method of forming selenium coatings
JPH08176804A (ja) 金属部材の表面処理方法
US3834933A (en) Method of making a metal coated article with a protective film
US2993804A (en) Surface treatment for metal coated objects
US3758349A (en) Method of producing chemical conversion coatings on metal surfaces
US2245226A (en) Method of coating metal
JP6740888B2 (ja) 表面処理金属板およびその製造方法
DE3035000A1 (de) Vorrichtung zum kontinuierlichen verzinken von kaltgewalztem stahlband