Classifications

• • 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
  • C23C22/07—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 phosphates
  • C23C22/08—Orthophosphates
  • C23C22/12—Orthophosphates containing zinc cations
  • C23C22/13—Orthophosphates containing zinc cations containing also nitrate or nitrite anions
• • 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
  • C23C22/07—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 phosphates
  • C23C22/08—Orthophosphates
  • C23C22/12—Orthophosphates containing zinc cations
• • 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
  • C23C22/07—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 phosphates
  • C23C22/08—Orthophosphates
  • C23C22/18—Orthophosphates containing manganese cations
  • C23C22/182—Orthophosphates containing manganese cations containing also zinc cations
• • 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
  • C23C22/07—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 phosphates
  • C23C22/08—Orthophosphates
  • C23C22/22—Orthophosphates containing alkaline earth metal cations
• • 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
  • C23C22/78—Pretreatment of the material to be coated

Definitions

• the present invention relates to a method for forming phosphate coatings on the surfaces of metals that lack iron at the surface, e.g., galvanized steel sheet, magnesium alloys, and aluminum, wherein the phosphate coating is strongly adherent to films applied by painting and exhibits an excellent post- painting corrosion resistance.
• a phosphate coating is formed on the surface of metal that will be painted prior to its final use. This is done, for example, with the metal used for car bodies.
• the phosphate coating is applied in order to increase adherence of the paint film and improve the post-painting corrosion resistance.
• the phosphate coating is typically formed on a ferrous surface by immersion in a phosphate treatment bath containing zinc ion and phosphate ion.
• ion as used throughout is intended to encompass a plurality of ions.
• Galvanized steel sheet has recently become the most prominent metal stock for uses requiring subsequent painting, for example, in making car bodies.
• the phosphate coating is formed on the surface of a zinc plating layer.
• the use of the prior-art phosphate treatment baths containing zinc ion and phosphate ion on galvanized steel sheet has resulted in an unsatisfactory paint film adherence and an inadequate post-painting corrosion resistance.
• the addition of nickel ion and manganese ion to phosphate treatment baths enables the formation of high-quality phosphate coatings even on the surface of the zinc plating layer. This technology is being widely practiced at the present time.
• Japanese Laid Open (Kohyo or Unexamined) Patent Application (PCT) Number Hei 7-505445 teaches a nickel ion-free phosphate treatment bath that contains 0.2 to 2 g/L zinc ion, 0.5 to 25 mg/L copper ion, and 5 to 30 g/L phosphate ion. This phosphate treatment bath suffers from difficulties in managing the copper ion concentration due to the low copper ion content and the narrow range of the permissible copper ion content.
• This patent teaches that the bath can also be used for zinc-plated material and teaches that 0.001 to 0.5 weight% ferrous ion may additionally be present in the bath.
• This patent does not teach using a ferrous ion-containing treatment bath on zinc-plated material.
• this patent teaches that in the case of zinc-plated materials, the phosphate coating product contains plate-shaped crystals and not the desired spherical or columnar crystals.
• the present invention was developed in order to address the problems described above in the prior art. More specifically, the present invention addresses the problem of providing a method that can form a highly paint adherent, highly post-painting corrosion-resistant phosphate coating on the surfaces of metals that lack iron at the surface (e.g., galvanized steel sheet, aluminum, magnesium alloys) and that can do so using a phosphate treatment bath that does not contain the nickel ion or the copper ion with its narrow permissible content range.
• a phosphate treatment bath that does not contain the nickel ion or the copper ion with its narrow permissible content range.
• the present invention comprises (1) a method for forming phosphate coatings on nonferrous metals and plated steel sheets.
• the method is characterized by forming a phosphate coating that contains at least 50% phosphophyllite (Zn2Fe(PO4)2-4H2O) in terms of the P ratio (phosphophyllite ratio, vide infra) on nonferrous metal or plated steel sheet by effecting contact between nonferrous metal or plated steel sheet and a phosphate treatment bath that contains zinc ion, phosphate ion, and hydroxylammonium ion and at least 17 weight parts ferrous ion for each 100 weight parts zinc ion.
• Zn2Fe(PO4)2-4H2O phosphophyllite ratio
• the present invention also comprises (2) a method for forming phosphate coatings on nonferrous metals and plated steel sheets.
• the method is characterized by effecting contact between nonferrous metal or plated steel sheet and a surface conditioning bath that contains at least one selection from divalent and trivalent metal phosphate particles having a particle size no greater than 5 ⁇ m, and thereafter forming a phosphate coating that contains at least 50% phosphophyllite
• Zn2Fe(PO4)2-4H2O in terms of the P ratio (phosphophyllite ratio) on the nonferrous metal or plated steel sheet by effecting contact between the nonferrous metal or plated steel sheet and a phosphate treatment bath that contains zinc ion, phosphate ion, and hydroxylammonium ion and at least 17 weight parts ferrous ion for each 100 weight parts zinc ion.
• the present invention additionally comprises (3) a method in accordance with the aforementioned (1) or (2) for forming phosphate coatings on nonferrous metals and plated steel sheet, wherein the method is characterized in that the hydroxylammonium ion concentration is 0.2 to 5 g/L.
• the present invention further comprises (4) a method in accordance with the aforementioned (1), (2), or (3) for forming phosphate coatings on nonferrous metals and plated steel sheet, wherein the method is characterized in that the phosphate ion concentration is 5.0 to 30 g/L, the zinc ion concentration is 0.5 to 5.0 g/L, and the ferrous ion concentration is 0.2 to 5.0 g/L.
• the present invention employs a phosphate treatment bath that contains zinc ion, phosphate ion, hydroxylammonium ion, and ferrous ion.
• Phosphate coatings are typically formed on metals having iron at the surface, e.g., steel sheet, using a phosphate treatment bath that differs from the one employed in the present invention by containing zinc ion and phosphate ion but neither the hydroxylammonium ion nor the ferrous ion.
• the phosphate coating obtained under these conditions will contain both hopeite (Zn3(PO_ ⁇ )2-4H2 ⁇ ) and phosphophyllite
• the present invention is directed to the formation of phosphate coatings on plated steel sheets and nonferrous metals that lack iron at the surface.
• a conventional phosphate treatment bath that is, a bath that contains zinc ion and phosphate ion but which lacks both hydroxylammonium ion and ferrous ion
• the surface of the metal workpiece again is dissolved by the phosphate treatment bath, but in this case without the
• the present inventors carried out the addition of ferrous ion to a prior-art phosphate treatment bath containing zinc ion and phosphate ion in order to prepare a phosphate treatment bath that did not contain hydroxylammonium ion and carried out immersion of galvanized steel sheet in this phosphate treatment bath. While this phosphate treatment bath did contain ferrous ion, the phosphate coating formed on the surface of the surface iron-free metal workpiece had hopeite (Zn3(PO4)2-4H2O) as its main component, while phosphophyllite
• the inventors also carried out immersion of galvanized steel sheet in a phosphate treatment bath prepared by the addition of both ferrous ion and hydroxylammonium ion to a prior-art phosphate treatment bath containing zinc ion and phosphate ion. Under these conditions, a large amount of phosphophyllite
• the inventors prepared phosphate treatment baths having different ferrous ion concentrations by adding different amounts of ferrous ion to solutions containing zinc ion, phosphate ion, and hydroxylammonium ion.
• Galvanized steel sheet was immersed in each bath to give a series of galvanized steel sheets bearing phosphate coatings having different phosphophyllite contents. These sheets were painted and the adherence of the paint films and post-painting corrosion resistance were evaluated. The results of these evaluations showed that the paint film adherence and post-painting corrosion resistance were inadequate at low phosphophyllite contents in the phosphate coating.
• phosphophyllite + hopeite phosphate coatings containing at least 50% phosphophyllite were found to exhibit a substantially improved paint film adherence and post-painting corrosion resistance.
• a phosphate treatment bath that has a relatively low content of ferrous ion relative to zinc ion is essentially unable to form a phosphate coating that contains at least 50% phosphophyllite. Rather, a phosphate coating containing at least 50% phosphophyllite is obtained when the bath contains at least 17 weight parts ferrous ion per 100 weight parts zinc ion.
• the present invention comprises the addition of hydroxylammonium ion to the prior-art phosphate treatment bath, but also requires the presence therein of ferrous ion in a specific amount (at least 17 weight parts ferrous ion for each 100 weight parts zinc ion).
• Use of the inventive phosphate treatment bath enables the formation, even on nonferrous metals and plated steel sheets, of a phosphate coating having a remarkably good paint film adherence and corrosion resistance.
• the phosphate treatment bath used in the present invention is an acidic aqueous solution that contains zinc ion, phosphate ion, ferrous ion, and hydroxylammonium ion as essential components.
• the zinc ion concentration in this treatment bath is preferably in the range of 0.5 to 5.0 g/L.
• a zinc ion concentration below 0.5 g/L causes an inadequate post-painting corrosion resistance due to failure to form a coating in adequate amounts and a low coating weight by the phosphate crystals that are formed.
• a zinc ion concentration in excess of 5.0 g/L results in a coarsening of the coating crystals and in particular in a decline in the post-painting adherence.
• the phosphate ion concentration in the phosphate treatment bath used by this invention is preferably in the range of 5.0 to 30 g/L. It becomes quite difficult to form a regular phosphate coating at a phosphate ion concentration below 5.0 g/L, while exceeding 30 g/L is uneconomical since no additional effects are obtained beyond 30 g/L.
• the phosphate ion can be supplied to the treatment bath by the addition thereto of phosphoric acid or an aqueous solution thereof, or can be supplied by dissolution in the treatment bath of a phosphate salt, e.g., the sodium, magnesium, or zinc salt.
• the ferrous ion concentration in the phosphate treatment bath used by this invention will vary depending on the zinc ion concentration, but preferably is in the range of 0.2 to 5 g/L. More preferably, the concentration of ferrous ion in the phosphate bath is in an amount so that the phosphate bath contains at least 17 weight parts ferrous ion for each 100 weight parts zinc ion, even more preferably at least 25 weight parts, and even more preferably at least 75 weight parts. In other preferred baths, at least 100 weight parts ferrous ion for each 100 weight parts zinc ion is present, more preferably at least 150 weight parts ferrous ion, even more preferably at last 200 weight parts ferrous ion, and most preferably at least 275 weight parts ferrous ion.
• This ferrous ion is a crucial source component for forming phosphophyllite crystals on the surface of nonferrous metals since a nonferrous metal workpiece is unable to supply iron ion.
• Ferrous ion can be supplied by dissolving, for example, ferrous sulfate, ferrous nitrate, ferrous hydroxide, or ferrous halide, in the treatment bath.
• Ferrous ion is readily oxidized by atmospheric oxygen to ferric ion.
• the ferric ion cannot form a stable solution in phosphate treatment baths and produces an insoluble iron phosphate (sludge) with the phosphate ion; this results in the generation of large amounts of sludge in the phosphate treatment bath.
• This problem when it must be addressed — can be addressed by the addition of a weak reducing agent, such as L-ascorbic acid, to the bath.
• the concentration of the reducing agent in the phosphate treatment bath is preferably in the range of 10 to
• ferrous ion alone to the phosphate treatment bath is essentially insufficient to produce phosphate crystals with a high phosphophyllite ratio on the surface of a metal workpiece that cannot function as an iron source.
• hydroxylammonium ion An important consideration for producing high phosphophyllite ratio phosphate crystals is also how to maintain a high ferrous ion concentration at the interface with the metal workpiece. This function is fulfilled by the hydroxylammonium ion, and the ferrous ion and the hydroxylammonium ion are essential and indispensable components in the present invention. The hydroxylammonium ion is believed to exercise a stabilizing function on the ferrous ion at the interface with the metal workpiece and also to accelerate the reactions that form the phosphate coating of this invention.
• the hydroxylammonium ion concentration in the phosphate treatment bath used in this invention is preferably in the range of 0.2 to 5 g/L.
• a concentration of hydroxylammonium ion below 0.2 g/L results in inadequate conversion reactions and also strongly impairs the ability to produce a phosphate coating that has a high phosphophyllite ratio. Concentrations in excess of 5 g/L are uneconomical because no additional effects occur beyond 5 g/L.
• the hydroxylammonium ion can be supplied by dissolving, for example, hydroxylamine sulfate, hydroxylamine phosphate, or hydroxylamine hydrochloride, in the treatment bath.
• An etchant may be added to the phosphate treatment bath used in this invention in order to induce a uniform etch of the surface of the metal workpiece.
• this etchant are the fluoride ion and complex fluoride ions such as the fluosilicate ion. These ions can be obtained from such fluorine compounds as, for example, hydrofluoric acid and fluosilicic acid and their metal salts, e.g., the sodium and potassium salts.
• the phosphate treatment bath of this invention may also contain one or more metal ions selected from the manganese ion, magnesium ion, cobalt ion, and calcium ion. These ions can be furnished to the treatment bath by dissolution therein of, for example, the oxide, hydroxide, carbonate, sulfate, nitrate, or phosphate of the particular metal.
• concentration of the added metal ion in the phosphate treatment bath is preferably in the range of 0.1 to 2 g/L.
• the inventive method for forming phosphate coatings requires that the metal surface be clean prior to its contact with the phosphate treatment bath.
• the metal can be brought into contact with the treatment bath without an intervening cleaning step when the surface of the metal is already clean.
• the contaminants adhering on the surface must first be removed in a cleaning step using, for example, a water-based alkaline degreaser, an emulsified degreaser, or a solvent degreaser.
• a water-based cleaner it will be preferable to carry out a water rinse step after cleaning in order to thoroughly remove cleaner adhering on the metal surface.
• a typical treatment sequence for the inventive method for forming phosphate coatings comprises alkaline degreasing — water rinse — > contact with the phosphate treatment bath — > water rinse.
• the alkaline degreasing and water rinses may be run either as single-stage processes or as multistage processes, while the final water rinse is preferably carried out using deionized water.
• the phosphate coating of the invention When the phosphate coating of the invention is to be used as an underpaint coating, it will be desirable to produce a thin, fine, and dense phosphate
• the workpiece prior to its contact with the phosphate treatment bath the workpiece is preferably brought into contact with a suitable surface conditioning bath.
• the surface conditioning bath used in such cases preferably contains at least 1 divalent or trivalent metal phosphate powder having a particle size no greater than 5 ⁇ m.
• Said divalent or trivalent metal in said metal phosphate powder is preferably at least 1 selection from the group consisting of zinc, manganese, cobalt, iron, calcium, aluminum, and magnesium.
• Dipping, spraying, or a combination thereof can be used to effect contact with the phosphate treatment bath used by the inventive method for forming phosphate coatings.
• the treatment time can be approximately 1 to 5 minutes; this treatment duration can produce a phosphate coating that is entirely satisfactory from a practical standpoint.
• the temperature of the phosphate treatment bath is preferably in the range of 30 to 60°C.
• the inventive method for forming phosphate coatings is directed to the precipitation in large amounts of chemically stable phosphophyllite crystals on the surface of metals that lack iron at the surface.
• Metals suitable for the practice of the invention therefore include plated steel sheet, such as galvanized steel sheet and zinc alloy-plated steel sheet, and nonferrous metals such as aluminum alloys and magnesium alloys.
• the inventive method for forming phosphate coatings can also be applied in an entirely unproblematic manner to metals that have iron at the surface, for example, steel sheet such as cold-rolled steel sheet. Application of the inventive method to such metals is not associated with any reduction whatever in the post-painting adherence or post-painting corrosion resistance.
• This feature enables treatment of the usual types of steel sheet on the same line as used for nonferrous materials and plated steel sheet.
• the presence of nickel in the phosphate treatment bath used by this invention again causes no decline whatever in the paint film adherence or post-painting corrosion resistance.
• EG electrogalvanized steel sheet (sheet thickness: 0.8 mm, plating add-on: 20 g/m )
• GA hot-dip zinc alloy-plated steel sheet (sheet thickness: 0.8 mm, plating add- on: 45 g/m 2 )
• Degreasing used FINECLEANER L4460, an alkaline degreaser from Nihon Parkerizing Co., Ltd.
• Drying was carried out for 120 seconds using a hot wind at
• P ratio phosphophyllite ratio in %: The intensity of the phosphophyllite (100) plane in the phosphate coating and the intensity of the hopeite (020) plane in the phosphate coating were measured using an x-ray diffractometer (Cu tube). The P ratio was calculated using the following formula.
• This process formed a paint film with an overall
• Salt-spray resistance An electrocoating with a thickness of 20 ⁇ m was
• Table 1 covers the working examples of the inventive phosphate treatment bath. All of the phosphate treatment baths in Table 1 contained the hydroxylammonium ion (NH3OH ) and each bath contained at least 17 weight
• Table 2 covers the phosphate treatment baths of the comparative examples.
• the bath in Comparative Example 1 contained the hydroxylammonium
• This bath contained neither the hydroxylammonium ion nor the Fe ion.
• This bath contained the Ni ion and was a phosphate treatment bath as used in the prior art on galvanized steel sheet. While the phosphate coating afforded by this phosphate treatment bath did have an excellent paint film adherence and post-painting corrosion resistance, as noted above such a bath is undesirable from an environmental standpoint due to admixture of Ni ion into the wastewater during formation of the phosphate coating.
• the prior art has employed the addition of nickel ion to phosphate treatment baths in order to bring about the formation of highly paint film-adherent phosphate coatings with an excellent post-painting corrosion resistance on nonferrous metals and plated steel sheet.
• the present invention enables the formation, without the addition of nickel ion, on nonferrous metals and plated steel sheets of phosphate coatings whose paint film adherence and post-painting corrosion resistance are equal to those obtained by nickel-modified phosphate treatment. Due to their nickel ion content, the prior-art phosphate treatment baths cause problems from an environmental standpoint due to entry of the Ni ion into the wastewater.
• the inventive phosphate treatment bath does not contain components that would cause these environmental problems.
• This invention therefore enables the formation of highly paint film-adherent, highly post-painting corrosion-resistant phosphate coatings on nonferrous metals and plated steel sheet and does so without causing environmental problems.

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• 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)
• Chemical Treatment Of Metals (AREA)

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• 2000
  • 2000-04-10 JP JP2000107436A patent/JP2001295063A/ja active Pending
• 2001
  • 2001-04-06 WO PCT/US2001/011248 patent/WO2001077411A1/en not_active Application Discontinuation
  • 2001-04-06 AU AU2001255239A patent/AU2001255239A1/en not_active Abandoned
  • 2001-04-06 EP EP01928375A patent/EP1290244A4/en not_active Withdrawn

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