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WO2011127473A1 - Traitement de passivation de revêtements à base de zinc - Google Patents

Traitement de passivation de revêtements à base de zinc Download PDF

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Publication number
WO2011127473A1
WO2011127473A1 PCT/US2011/031958 US2011031958W WO2011127473A1 WO 2011127473 A1 WO2011127473 A1 WO 2011127473A1 US 2011031958 W US2011031958 W US 2011031958W WO 2011127473 A1 WO2011127473 A1 WO 2011127473A1
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Prior art keywords
ions
source
zinc
composition
based layer
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PCT/US2011/031958
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English (en)
Inventor
Anthony Fiore
Joseph A. Abys
Theodore Antonellis
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MacDermid Enthone Inc
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Enthone Inc
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    • 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
    • C23C22/05—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 using aqueous solutions
    • C23C22/06—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 using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/46—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing oxalates
    • C23C22/47—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing oxalates containing also phosphates
    • 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
    • C23C2222/00—Aspects relating to chemical surface treatment of metallic material by reaction of the surface with a reactive medium
    • C23C2222/10—Use of solutions containing trivalent chromium but free of hexavalent chromium

Definitions

  • the present invention generally relates to the deposition of passivating coatings that protect zinc and zinc alloys from corrosion, and more specifically to the deposition of passivating chromium conversion coatings on zinc and zinc alloys .
  • Zinc or zinc alloy electroplating and/or galvanizing is known to enhance the corrosion resistance of metallic substrates, most usefully, iron-based substrates, such as steel. However, sufficient corrosion protection may not be achieved by the zinc-based coating alone.
  • the industry has developed a further treatment of the zinc-based layer comprising exposing the surface of the zinc-based layer to a composition comprising chromic acid containing hexavalent chromium.
  • Hexavalent chromium is toxic to the human body and the
  • Such passivating solutions can be controlled to impart a yellow, blue-bright, or even a dark black coating to the surface.
  • the present invention is directed to a method for depositing a passivating coating on a surface of a zinc-based layer.
  • the method comprises exposing the surface of the zinc- based layer to a composition for imparting certain properties.
  • the composition comprises (i) a source of Cr 3+ ions; (ii) in currently preferred embodiments a source of Co 2+ ions; (iii) a source of N0 3 ⁇ ions; and (iv) a source of fluoride ions.
  • the initial concentrations of the source of Cr 3+ ions and the source of N0 3 ⁇ ions are such that an initial molar ratio of N0 3 ⁇ ions to Cr 3+ ions is at least about 10:1.
  • the composition has a pH between 1.9 and about 4.0. Exposure of the surface of the zinc- based layer to the composition deposits the passivating coating having a thickness of at least about 20 nm and a resistivity of less than about 100 mQ per square.
  • the present invention is further directed to an article prepared by this method.
  • the invention is further directed to a composition for depositing a passivating coating on a surface of a zinc- based layer.
  • the composition comprises (i) a source of Cr 3+ ions; (ii) in currently preferred embodiments a source of Co 2+ ions; (iii) a source of N03 ⁇ ions; and (iv) a source of fluoride ions.
  • the initial concentrations of the source of Cr 3+ ions and the source of N0 3 ⁇ ions are such that an initial molar ratio of N0 3 ⁇ ions to Cr 3+ ions is at least about 10:1.
  • the composition has a pH between 1.9 and about 4.0.
  • the invention is still further directed to an article comprising a steel substrate; a zinc alloy layer on a surface of the steel substrate; and a passivating coating on a surface of the zinc alloy, wherein the passivating coating comprises a chromium conversion coating and has a thickness of at least about 20 nm and a resistivity of less than about 100 ⁇ per square.
  • FIGS. 1A and IB are photographs of zinc-nickel coated steel coupons after 24 hours (FIG. 1A) and 48 hours (FIG. IB) of neutral salt spray testing.
  • FIGS. 2A, 2B, 2C, and 2D are photographs of zinc- nickel coated steel coupons further coated with a conductive chromium conversion according to the method of the present invention after 48 hours of neutral salt spray testing.
  • FIG. 3A is a graph depicting the shielding
  • FIG. 3B is a graph depicting the shielding
  • One aspect of the present invention is directed to a method for depositing a protective, passivating coating on a surface of a zinc-based layer, such as a zinc alloy.
  • Another aspect of the present invention is directed to a composition for depositing a protective, passivating layer on the surface of the zinc-based layer, such as a zinc alloy.
  • the protective, passivating coating on the surface of a zinc-based layer is a chromium conversion layer.
  • the passivating chromium conversion coating maintains a high level of electrical conductivity while also providing a high level of EMI shielding.
  • the passivating chromium conversion layer is deposited on the surface of the zinc-based layer by exposing the zinc-based layer surface to a composition comprising chromium ions in their 3+ valence state.
  • the passivating coating deposited thereby maintains the surface appearance of the underlying zinc-based layer surface. That is, the zinc surface comprising the passivating coating thereon has a uniform silvery-white metallic appearance typical of zinc-based layers. The uniform white metallic appearance of the underlying zinc-based layer is maintained essentially because the passivating coating is thin and clear. Additionally, the surface with the passivating coating thereon maintains that appearance after standard procedures designed to test the corrosion resistance of a deposited material, e.g., humidity and salt spray tests.
  • the passivating coating of the present invention possesses sufficient ductility so as not to negatively impact the ductility of the underlying zinc-based layer. Accordingly, a zinc-based layer having a passivating coating of the present invention thereon exhibits no cracking when the zinc-based layer having the passivating coating thereon is bent by as much as 30° .
  • the passivating coating of the present invention is also amenable to receive a paint after deposition. Accordingly, the passivating coating passes ASTM Spec. D3359-02, which is a standard test for paint adhesion.
  • the passivating coating deposited according to the method of the present invention generally has a thickness of at least about 15 nm, more preferably at least about 20 nm, and a resistivity of less than about 100 mQ per square.
  • the passivating coating of the present invention generally has a thickness no greater than about 100 nm, preferably no greater than about 50 nm.
  • the passivating coating is between about 15 nm and about 100 nm thick, preferably between about 20 nm and about 50 nm thick.
  • the thickness of the passivating coating is at least about 25 nm. Even more preferably, the thickness of the passivating coating is between about 25 nm and about 30 nm.
  • the resistivity of the passivating coating is preferably less than about 100 mQ per square, more preferably less than about 50 mQ per square, even more preferably less than about 25 mQ per square, less than about 20 mQ per square, or even less than about 15 mQ per square, such as less than about 10 mQ per square.
  • Surface resistivity is the resistance to leakage current along the material surface. ASTM D257 explains that the resistivity is the quotient of the potential gradient and the current per unit of electrode length, where resistance is measured between two parallel electrodes in contact with the surface separated by a distance equal to the contact length of the electrodes. The potential gradient is in V/m and the current per unit of electrode length is in A/m. The length units cancel and resistivity is reported in ohms or ohms per square. A square is formed by the four ends of the electrodes.
  • the passivating coating is deposited onto the surface of a zinc- based layer, such as a zinc alloy coating, i.e., the zinc-based layer is itself a coating over an underlying substrate.
  • the zinc-based layer may comprise a zinc alloy comprise alloying metals selected from among nickel, copper, tin, aluminum, magnesium, silver, and titanium, cobalt, tungsten among others, and combinations thereof, such as zinc-tin-nickel, zinc-cobalt- tungsten.
  • the zinc-based layer comprises between 5 and 25 wt . % alloying metal, the balance zinc.
  • the alloy metal comprises nickel.
  • the zinc-based layer coating comprises zinc-nickel alloy comprising between 5 and 25 wt . % nickel, balance zinc. More preferably, the zinc-nickel alloy comprises between 10 and 20 wt . % nickel, balance zinc. Even more
  • the zinc-nickel alloy comprises between 10 and 15 wt . % nickel, balance zinc.
  • the zinc-based layer is a coating over an underlying substrate.
  • the underlying substrate is an iron-based substrate, preferably a steel substrate, e.g., cold rolled steel, stainless steel, etc. In some preferred
  • the underlying substrate is an aluminum-based substrate.
  • the zinc- based layer is a coating over a steel housing adapted to house a networking device.
  • the steel housing that is adapted to house a networking device is a router box.
  • passivating coating of the present invention maintains the conductivity of the underlying zinc-based layer and is itself conductive, as described above, i.e., less than or equal to 1000 mQ per square, 50 mQ per square, 25 mQ per square, 20 mQ per square, or even less than 15 mQ per square or 10 mQ per square.
  • the passivating coating of the present invention is less resistive than conventional passivation coatings used to passivate a zinc layer.
  • the passivating coating may be applied to a substrate in the shape of a gasket, such as steel gaskets, CuBe (copper-beryllium) gaskets, ECE (electrically conductive elastomer) gaskets, and FOF (foam over fabric) gaskets .
  • a gasket such as steel gaskets, CuBe (copper-beryllium) gaskets, ECE (electrically conductive elastomer) gaskets, and FOF (foam over fabric) gaskets .
  • a primary function of the passivating chromium coating here is to enhance the corrosion resistance of the zinc- based layer and steel substrate, thereby enabling corrosion protection particularly during transport through hot, humid conditions. Protected substrates that are transported overseas, in air loaded with salt, are better protected against oxidation and rust when coated with the passivating coating of the present invention .
  • a further primary function of the passivating coating deposited on a zinc-based layer on a steel housing useful for housing a network device is to provide shielding from electromagnetic interferences in the ranges up to 40 GHz, such as from 10 kHz to 40 GHz, or from 1 to 5 GHz.
  • the passivating coating provides at least about 60 db EMI shielding, more preferably, the passivating coating provides between about 80 db to 120 db shielding, such as between 85 db and 100 db shielding.
  • a high degree of shielding is required over a larger frequency range due to higher frequency transmission devices.
  • the substrate preferably an iron-based substrate, such as a steel substrate, may be pre-treated prior to
  • an iron-based substrate such as steel may be acid activated and rinsed prior to deposition of the zinc-based layer.
  • the activation solution may be a strongly acidic composition comprising, e.g., sulfuric acid, phosphoric acid, hydrochloric acid, preferably a 3 to 6 M hydrochloric acid solution.
  • the optionally pre-treated steel substrate is then coated with a zinc-based layer.
  • the zinc- based layer may be deposited by electrolytic deposition, i.e., by immersing the substrate in a composition suitable for electrolytic deposition of a zinc-based layer and applying an external voltage.
  • the composition suitable for the electrolytic deposition of a zinc-based layer comprises a source of zinc ions, optionally a source of alloying metal ions, and suitable additives for electrolytic zinc deposition. Any commercially available electrolytic zinc composition may be suitable.
  • the zinc-based layer is deposited to a thickness between about 2 micrometers and about 30 micrometers, preferably between about 5 micrometers and about 20 micrometers, more preferably to a thickness between about 7 micrometers and about 15 micrometers.
  • the substrate having the zinc-based layer thereon is then rinsed and exposed to a composition for depositing the passivating coating according to the process of the present invention.
  • the present invention is further directed to a composition for depositing the present invention.
  • the composition for depositing the passivating coating comprises a source of Cr 3+ ions, a source of Co 2+ ions in
  • a source of NC>3 ⁇ ions, and a source of fluoride ions optionally further comprises an organic acid, such as a carboxylic acid. Without being bound by a particular theory, it is thought that the carboxylic acid may act as a chelating agent for zinc ions.
  • the initial concentrations of the source of Cr 3+ ions and the source of NC>3 ⁇ ions are such that an initial molar ratio of NC>3 ⁇ ions to Cr 3+ ions is at least about 10:1, preferably at least about 12:1, even more preferably at least about 14:1.
  • the composition has a pH between 1.9 and about 4.0, more preferably between about 3.0 and 3.5, such as between about 3.0 and about 3.2.
  • the composition for depositing the passivating coating on the zinc alloy comprises a source of Cr 3+ ions.
  • the trivalent chromium ions can be introduced in the form of any bath soluble and compatible salt such as chromium ( III ) sulfate, [Cr 2 (S0 4 )3] and hydrates thereof, e.g., chromium (III) sulfate hydrate, [Cr 2 (S0 4 ) 3 ⁇ 2 0] , chromium (III) alum [KCr(S0 4 ) 2 ] and hydrates thereof, e.g., chromium (III) alum dodecahydrate
  • chromium(III) chloride [CrCl 3 ] and hydrates thereof e.g., chromium (III ) chloride hexahydrate [CrCl 3 ⁇ 6H 2 0] , chromium (III ) bromide [CrBr 3 ] and hydrates thereof, e.g., chromium (III ) bromide hexahydrate [ CrCl 3 ⁇ 6H 2 0] , chromium (III ) fluoride [CrF 3 ] and hydrates thereof, e.g., chromium (III) fluoride tetrahydrate [CrCl 3 ⁇ 4H 2 0] , chromium (III) nitrate
  • Cr(NC>3)3 and hydrates thereof e.g., chromium (III) nitrate nonahydrate [Cr (NO 3 ) 3 ⁇ 9H 2 0] , chromium (III) phosphate [CrP0 4 ] and hydrates thereof, e.g., chromium (III) phosphate hydrate
  • the trivalent chromium ions can also be introduced by a reduction of a solution containing hexavalent chromium ions preferably using sulfur dioxide or bisulfite providing a mixture of trivalent chromium ions and sulfate compounds .
  • a preferred source of Cr 3+ ions comprises chromium (III) nitrate Cr(NC>3)3 and hydrates thereof, e.g., chromium (III) nitrate nonahydrate [Cr (NO 3 ) 3 ⁇ 9H 2 0] .
  • the concentration of the trivalent chromium ions in the treating solution may be at least about 0.05 g/L and less than about 4 g/L, with concentrations of about 0.2 to about 2 g/L being preferred, and concentrations between 0.4 g/L and 1.2 g/L being more preferred.
  • the composition for depositing the passivating coating on the zinc alloy comprises a source of NC>3 ⁇ ions.
  • the source of NC>3 ⁇ ions may be selected from among nitric acid, alkali metal nitrate salts, e.g., sodium nitrate, potassium nitrate, and hydrates of each, and alkaline earth metal salts, e.g., calcium nitrate, barium nitrate, magnesium nitrate, amine nitrates, such as tetramethylammonium nitrate, and additional sources, such as cobalt nitrate and hydrates thereof, which provides the additional bath component, Co 2+ ions.
  • the concentration of nitrate ions initially added relative to the concentration of chromium ions is such that the initial molar ratio of N0 3 ⁇ ions to Cr 3+ ions is at least about 10:1.
  • the concentration of nitrate ions initially added relative to the concentration of chromium ions is such that the initial molar ratio of NC>3 ⁇ ions to Cr 3+ ions is at least about 12:1. More preferably, the initial concentrations of the source of Cr 3+ ions and the source of NC>3 ⁇ ions are such that the initial molar ratio of NC>3 ⁇ ions to Cr 3+ ions is at least about 14:1.
  • the composition may be periodically
  • the various sources of nitrate are added to ensure an initial concentration of NC>3 ⁇ ions of at least about 10 g/L, preferably at least about 12 g/L, even more preferably at least about 13.5 g/L.
  • the composition for depositing the passivating coating on the zinc alloy may also comprise a transition metal cation, such as a source of iron ions, cobalt ions, nickel ions, molybdenum ions, manganese ions, or aluminum ions.
  • a transition metal cation such as a source of iron ions, cobalt ions, nickel ions, molybdenum ions, manganese ions, or aluminum ions.
  • composition for depositing the passivating coating on the zinc alloy in preferred embodiments may also comprise a source of Co 2+ ions.
  • the Co 2+ ions can be introduced in the form of any bath soluble and compatible salt such as cobalt (II) sulfate, [CoS0 4 ] and hydrates thereof, e.g., cobalt (II) sulfate hydrate,
  • a preferred source of Co 2+ ions comprises cobalt (II) nitrate Co(NC>3) 2 and hydrates thereof, e.g., cobalt (II) nitrate hexahydrate [Co (N0 3 ) 2 ⁇ 6H 2 0] .
  • the concentration of the transition metal ions, preferably Co 2+ ions in preferred embodiments, in the treating solution may be at least about 0.2 g/L and less than about 6 g/L, with concentrations of about 0.8 to about 4 g/L being preferred, and concentrations between 1.2 g/L and 2.8 g/L being more preferred.
  • the composition for depositing the conductive layer on the zinc alloy comprises an organic acid, such as a carboxylic acid.
  • an organic acid such as a carboxylic acid
  • the organic acid comprises a carboxylic acid or carboxylate salt. Even more preferably, the organic acid comprises a dicarboxylic acid or dicarboxylate salt.
  • Suitable organic acids include sources of acetate ions, sources of malate ions, sources of lactate ions, sources of oxalate ions, sources of malonate ions, sources of maleate ion, sources of succinate ion, sources of glutarate ions, sources of adipate ions, sources of gluconate ion, sources of tartrate ions, sources of citrate ion, sources of isocitrate ion, sources of aconitate ion, and the like.
  • Preferred sources include the carboxylic acids, alkali metal salts, e.g., sodium and potassium, water soluble and bath compatible alkaline earth metal salts, and water soluble and bath compatible amine salts.
  • a preferred source of dicarboxylate ions comprises a source of oxalate ions, such as oxalic acid or sodium oxalate.
  • the composition generally comprises between about 0.1 and about 4 g/L of the carboxylate ion, preferably between about 0.2 and about 2 g/L of the carboxylate ion.
  • the composition for depositing the conductive layer on the zinc alloy comprises a source of fluoride ions.
  • Sources of fluoride ion include hydrofluoric acid, alkali metal salts of fluoride such as sodium fluoride and potassium fluoride, and alkaline earth metal salts of fluoride, among other sources of fluoride, such as amine fluoride sources.
  • the fluoride ion may be present in the composition in a concentration between about 0.1 and about 4 g/L, such as between about 0.2 and about 2 g/L.
  • the fluoride ion acts as a film builder, which enhances the passivating coating's corrosion resistance and therefore enables deposition of a thinner conversion coating than is
  • chloride ion may be present in the composition in a concentration between about 0.2 and about 8 g/L, such as between about 0.4 and about 4 g/L, from sources such as sodium chloride, potassium chloride, and the like.
  • the composition preferably has a pH between 1.9 and about 4.0, more preferably between about 3.0 and about 3.5, such as between about 3.0 and about 3.2.
  • a pH between 1.9 and about 4.0, more preferably between about 3.0 and about 3.5, such as between about 3.0 and about 3.2.
  • alkaline sources e.g., preferably sodium hydroxide, potassium hydroxide, and the like. If salts of these components are used to introduce the components into solution, the
  • composition may require acidic adjustment using, for example, carboxylic acids of the type described above, nitric acid, hydrochloric acid and the like.
  • the pH is generally within the above described range in order to maintain a uniform metallic zinc appearance and inhibit darkening of the film, which is associated with lower conductivity.
  • composition comprising Cr 3+ ions, NC>3 ⁇ ions, fluoride ions, optionally, transition metals, such as Co 2+ ions in currently preferred embodiments, and optionally an organic acid oxidizes the surface of a zinc-based layer and forms a passivating chromium conversion coating layer over the surface of the zinc-based layer, the passivating conversion coating comprising chromium, cobalt, and chelated zinc.
  • the passivating layer may be deposited on the surface of the zinc-based layer by exposing the surface of the zinc-based layer to the composition. Such exposure may comprise immersion, spray, cascade, or the like for a period of time sufficient to form the desired conductive coating thereon.
  • the treating solution can be applied at a temperature ranging from about 20°C up to about 80°C with temperatures ranging from about 25°C to about 40°C being preferred.
  • the contact time of the solution with the substrate can vary from as little as about 1 second to as long as 180 seconds or longer, with the duration of about 60 seconds being sufficient for most applications.
  • the contact times in which the zinc-based layer is immersed in the composition can range from about 10 seconds up to about 1 minute in consideration of the thickness and conductivity of the film required .
  • a composition suitable for electrolytic deposition of a zinc-nickel alloy was prepared by combining a source of zinc ions, a source of nickel ions, a source of chloride ions, and boric acid and additional bath additives:
  • Nickel ions 27 g/L (nickel chloride)
  • the pH of the electrolytic zinc-nickel composition was 5.4.
  • the acid activated steel substrates were then immersed in the above-described composition suitable for the electrolytic deposition of zinc-nickel alloy.
  • the composition was held at a temperature between 32°C and 40°C, and the zinc- nickel layer was electroplated at a cathodic current density of about 2.2 amps/dm 2 .
  • Zinc and nickel anodes were employed to replenish zinc and nickel ions.
  • the plating rate was about 0.5 micrometers per minute at this current density.
  • Plating continued for a duration sufficient to deposit a Zn-Ni coating having between 10 and 15 wt . % Ni and a plating thickness between about 8 and 15 micrometers.
  • the composition for depositing the passivating coating on the zinc-nickel layer is prepared by combining 3 wt . % (approximately 30 mL) of the CAP A composition and 3 wt . %
  • the zinc-nickel coated steel substrates were immersed in the composition suitable for deposition of the passivating chromium conversion coating for 60 seconds at a temperature of 30°C, which was sufficient to deposit a passivating chromium conversion coating having a thickness between about 25 nm and about 30 nm.
  • the coated coupons were then rinsed for 1 minute with room temperature distilled water and air dried.
  • the coated steel coupons were then baked at a temperature between about 80°C and about 200°C for 10 minutes.
  • the resistivity of the passivating coatings on each coupon that was coated with the passivating chromium conversion coating was less than 50 mQ per square.
  • the passivating coating was further resistant to tarnishing from fingerprints.
  • FIGS. 1A and IB are photographs of these zinc-nickel coated steel coupons after 24 hours (FIG. 1A) and 48 hours (FIG. IB) of testing.
  • FIGS. 2A, 2B, 2C, and 2D are photographs of these zinc-nickel coated steel coupons that were further treated to have a passivating coating thereon after 48 hours exposure to the salt spray. It is apparent from FIGS. 1A and IB and from FIGS. 2A, 2B, 2C, and 2D that the passivating chromium
  • conversion layer maintains the uniform metallic finish of the underlying zinc-nickel layer water after 48 hours of testing.
  • the passivating coatings on each coupon were measured for their resistivity. The resistivities were 44.07 mQ per square (coupon depicted in FIG. 2A) , 39.48 mQ per square (coupon depicted in FIG. 2B) , 42.31 ⁇ per square (coupon depicted in FIG. 2C) , and 35.58 mQ per square (coupon depicted in FIG. 2D) .
  • FIG. 3A is a graph depicting the shielding effectiveness of the steel coupons electroplated using the commercially available Perma Pass Immunox 3K.
  • FIG. 3B is a graph depicting the shielding effectiveness of coupons prepared according to the method described in Example 2. As is apparent, the shielding

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Abstract

L'invention porte sur un procédé et une composition pour le dépôt d'un revêtement de passivation sur une surface d'une couche à base de zinc. Le procédé comprend l'exposition de la surface de la couche à base de zinc à une composition appropriée pour le dépôt d'un revêtement de passivation sur la surface de la couche à base de zinc. La composition comprend une source d'ions Cr3+ ; une source d'ions NO3 - ; et une source d'ions fluorures. Les concentrations initiales de la source d'ions Cr3+ et de la source d'ions NO3 - sont telles que le rapport molaire initial des ions NO3 - aux ions Cr3+ est d'au moins environ 10:1. L'exposition de la surface de la couche à base de zinc à la composition dépose le revêtement de passivation ayant une épaisseur d'au moins environ 20 nm et une résistivité inférieure à environ 100 mΩ par carré.
PCT/US2011/031958 2010-04-09 2011-04-11 Traitement de passivation de revêtements à base de zinc Ceased WO2011127473A1 (fr)

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Cited By (4)

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Publication number Priority date Publication date Assignee Title
CN109487255A (zh) * 2018-11-30 2019-03-19 佛山市海明威生态科技股份有限公司 一种环保型镀锌板无铬本色钝化产品的配制
US10415148B2 (en) 2014-03-07 2019-09-17 Macdermid Acumen, Inc. Passivation of micro-discontinuous chromium deposited from a trivalent electrolyte
CN114107969A (zh) * 2021-11-26 2022-03-01 山西汾西重工有限责任公司 一种钝化液及蓝白钝化膜的制备方法
CN116426912A (zh) * 2023-04-06 2023-07-14 广东工业大学 一种锌基复合稀土钝化涂层及其制备方法和应用

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