Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/565—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of zinc

Definitions

• the present invention relates to a zinc-based alloy electroplated film excellent in corrosion resistance and a plated metal material using the same, which can be utilized in a wide range of fields such as automobiles, home electric appliances, and building materials.
• zinc-based alloy metal materials where iron-based materials are coated with zinc or a zinc-based alloy plated film.
• Various kinds of methods for coating iron-based materials with zinc are present.
• hot dip galvanization where a plated film is formed by dipping a base metal in molten zinc or zinc alloy
• electrogalvanization where a plated film is formed by precipitating metallic zinc dissolved in an aqueous solution through electrolysis have been known.
• baths for the electrogalvanization is classified into an acidic bath and an alkaline bath according to the nature of the plating solution.
• Examples of the acid bath include a sulfate bath, an ammonium chloride bath, a potassium chloride bath, an ammonium chloride and potassium chloride mixed bath, and the like.
• Examples of the alkaline bath include a cyan bath, a zincate bath, and the like. They have been used properly according to individual characteristics. However, with regard to the metal materials used in automobiles, home electric appliances, building materials, and the like and exposed under severe conditions, even when these plated metal materials are utilized, a sufficient corrosion resistance cannot be obtained in some cases and thus further improvement of corrosion resistance has been required. Under such circumstances, zinc-based alloy plated metal materials such as Zn-Fe, Zn-Ni, and Zn-Cr have been developed. Of these, it is disclosed that a Zn-Cr alloy plated film has a high corrosion resistance (For example, see Patent Literatures 1, 2, and 3).
• the Zn-Cr alloy plated film is practically excellent but it contains a problem of hexavalent chromium mist generated at plating and hence environmental problems of disturbing plating worker's health and inducing air pollution have been closed up.
• development and practical application of a highly corrosion-resistant alternative metal material giving a less environmental load have been an urgent necessity.
• An object of the invention is to provide a zinc-based alloy electroplated film having a high corrosion resistance comparable to Zn-Cr alloy plating without containing chromium which gives a heavy environmental load, and a plated metal material using the same.
• the invention relates to a zinc-based alloy electroplated film containing:
• the invention relates to a plated metal material which has the above-described zinc-based alloy electroplated film.
• the zinc-based alloy electroplated film of the invention contains zinc (A), an iron-group metal (B), and tungsten (C) as essential components.
• composition of the plated film falls within the following range of each component in view of corrosion resistance: 30 to 96% by weight, preferably 50 to 90% by weight of zinc (A), 2 to 20% by weight, preferably 5 to 15% by weight of an iron-group metal (B), and 2 to 50% by weight, 3 to 20% by weight of tungsten (C).
• the iron-group element (B) herein means nickel, cobalt, or iron.
• a plated film of an alloy of zinc and iron-group metal is generally known but corrosion resistance of the resulting alloy plated film is remarkably improved by further combining tungsten therewith.
• corrosion resistance is also good in the system where iron is combined with cobalt and/or nickel.
• the zinc-based alloy electroplated film of the invention is formed by subjecting primary molded articles such as steel strip in coil to continuous electroplating and by subjecting small parts such as bolts and secondary molded articles including press molded articles to electroplating with placing them in rotatable perforated vessels such as barrels or cages.
• the Zn ion as component (a) of the plating solution constitutes a main component of the plated layer.
• the Zn ion is added to the plating bath in the form of chloride, sulfate, fluoride, cyanide, oxide, an organic acid salt, a phosphate salt, or elementary metal.
• the iron-group-metal ion as component (b) of the above-described plating solution is selected from an Ni ion, a Co ion, and an Fe ion.
• the iron-group-element ion (b) is added to the plating bath in the form of chloride, sulfate, fluoride, cyanide, oxide, an organic acid salt, a phosphate salt, or elementary metal.
• the W ion as component (c) of the above-described plating solution is added to the plating bath in the form of tungstic acid-based compound.
• tungstic acid-based compound examples include tungstic acid, tungstate salts, phosphotungustic acid, and phosphotungstate salts.
• the salts include ammonium salts, potassium salts, calcium salts, sodium salts, and the like. Of these, sodium tungstate and ammonium tungstate are particularly preferred in view of corrosion resistance.
• Ions of metals other than the above-described (a), (b), and (c), e.g., Mg, Mn, Ti, Pb, Al, P, or the like may be added to the above-described plating solution.
• the complexing agent can be selected from the group consisting of oxycarboxylate salts such as citrate salts, tartrate salts, and gluconate salts, aminoalcohols such as monoethanolamine, diethanolamine, and triethanolamine, polyamines such as ethylenediamine (EDA), diethylenetriamine, and triethylenetetramine, aminocarboxylate salts such as ethylenediamine tetraacetate salts and nitroacetate salts, polyhydric alcohols such as sorbit and pentaerythritol, and mixtures thereof.
• oxycarboxylate salts such as citrate salts, tartrate salts, and gluconate salts
• aminoalcohols such as monoethanolamine, diethanolamine, and triethanolamine
• polyamines such as ethylenediamine (EDA), diethylenetriamine, and triethylenetetramine
• aminocarboxylate salts such as ethylenediamine tetraacetate salts and nitroacetate salts
• functions of high corrosion resistance, coating adhesiveness, and the like can be imparted by combining a corrosion-inhibiting pigment and/or ceramic particles capable of being precipitated as discontinuous particles from the electroplating solution.
• corrosion-inhibiting pigment generally known one can be used and preferred examples thereof include phosphate salts, molybdate salts, metaborate salts, silicate salts, and the like.
• examples of the ceramic particles include particles of oxides such as Al 2 O 3 , SiO 2 , TiO 2 , ZrO 2 , Y 2 O 2 , ThO 2 , CeO 2 , and Fe 2 O 3 ; carbides such as B 4 C, SiC, WC, ZrC, TiC, graphite, and graphite fluoride; nitrides such as BN, Si 3 N 4 , and TiN; borates such as Cr 3 B 2 , and ZrB 2 ; silicate salts such as 2MgO ⁇ SiO 2 , MgO ⁇ SiO 2 , and ZrO 2 ⁇ SiO 2 , and the like.
• oxides such as Al 2 O 3 , SiO 2 , TiO 2 , ZrO 2 , Y 2 O 2 , ThO 2 , CeO 2 , and Fe 2 O 3
• carbides such as B 4 C, SiC, WC, ZrC, TiC, graphite, and graphite
• the blending amount of the corrosion-inhibiting pigment and/or ceramic particles into the plating bath is desirably within the range of 5 to 500 g per liter. Further, the smaller the particle size is, the more excellent dispersion stability is. Therefore, ultrafine particles having a size of 1 ⁇ m or less are preferred. Furthermore, it is desirable to control co-precipitated amount in the plating matrix to the range of 1 to 30% by weight, particularly 1 to 10% by weight per total precipitated amount. When the co-precipitated amount is small, an effect of improving corrosion resistance is not exhibited and, when it exceeds 30% by weight, the plated film becomes brittle and also adhesiveness with the base material decreases, so that the cases are problematic.
• a corrosion-inhibiting organic compound may be further added to the plating bath.
• preferable corrosion-inhibiting organic compound include alkynes, alkynols, amines or salts thereof, thio compounds, aromatic carboxylic acid compounds or salts thereof, and heterocyclic compounds, and the like.
• alkynes mean organic compounds containing a carbon-carbon triple bond and examples thereof include pentyne, hexyne, heptyne, octyne, and the like.
• the alkynols mean organic compounds having one or more hydroxyl groups in the alkynes and examples thereof include propargyl alcohol, 1-hexyn-3-ol, 1-heptyn-3-ol, and the like.
• the amines mean organic compounds containing one or more nitrogen atoms in the molecule, which include any of aliphatic or aromatic compounds. Examples of such amines include octylamine, nonylamine, decylamine, laurylamine, tridecylamine, cetylamine, and the like.
• the thio compounds mean organic compounds containing one or more sulfur atoms in the molecule and examples of such thio compounds include decyl mercaptan, cetyl mercaptan, thiourea, and the like.
• the heterocyclic compounds mean organic compounds containing atom(s) other than a carbon atom as ring-constituting atoms in a cyclic molecule and examples of such heterocyclic compounds include pyridine, benzothiazole, benzotriazole, quinoline, indole, and the like.
• aromatic carboxylic acid compounds include benzoic acid, salicylic acid, toluic acid, naphthalenecarboxylic acid, and the like.
• Salts that can be used include, for the case of amines, acid addition salts such as sulfates and hydrochlorides, and for the case of the aromatic carboxylic acid compounds, metal salts such as alkali metal salts and zinc salts, and ammonium salts.
• the amount of the corrosion-inhibiting organic compound to be added to the plating bath is desirably regulated to 0.1 to 10% by weight in the case of the alkynes or alkynols, 3 to 10% by weight in the case of the amines or salts thereof, 0.2 to 5% by weight in the case of the thio compounds, 1 to 10% by weight in the case of the heterocyclic compounds, and 3 to 8% by weight in the case of the aromatic carboxylic acid compounds or salts thereof.
• a plated film having a co-precipitated amount in terms of C (carbon) content of 0.001 to 10% by weight can be formed on the metal material by using a plating bath to which such a corrosion-inhibiting organic compound. It is possible to determine the carbon content in the plated film according to a combustion method, for example, by measurement on a "C-S analyzing apparatus" where an organic substance is burned and absorbance in an infrared absorption band of CO 2 formed is measured.
• additive(s) usually used for the purpose of improving burnt deposit at a high current density or throwing power at a low current density examples thereof include a reaction product of an amine with an epihalohydrin, a polyethylenepolyamine, the other quaternary amine polymer, urea, thiourea, gelatin, polyvinyl alcohol, an aldehyde, and the like.
• the above-described plating bath composition can form a plated film excellent in corrosion resistance and coated film adhesiveness by electroplating in a similar manner to a conventional method.
• pH is about 1 to 3 and a bath temperature is about 30 to 80°C in the case that the plating bath is a sulfate bath, pH is about 4 to 7 and a bath temperature is about 10 to 50°C in the case that the plating bath is a chloride bath, and pH is 12 or higher and a bath temperature is about 10 to 50°C in the case that the plating bath is an alkaline bath, and the thickness of the plated film is suitably from about 0.5 to 10 ⁇ m in all cases.
• the electroplated metal material of the present invention is obtained by electroplating a metal raw material using the above-described electroplating solution composition to form a plated film.
• the metal raw material includes materials mainly comprising iron, e.g., materials for automobiles, home electric appliances, and building materials, processed into a shape of a plate, tube, joint, clamp, bolt, nut or the like.
• the electroplating conditions are as described above.
• the advantages of the invention can be further enhanced by post-treatment with an acidic aqueous solution of a compound containing at least one element selected from the group consisting of cobalt, nickel, titanium and zirconium, after the formation of the electroplated film.
• a compound containing at least one element selected from the group consisting of cobalt, nickel, titanium and zirconium usable examples include oxides, hydroxides, fluorides, complex fluorides, chlorides, nitrates, sulfates, carbonates, etc. of these metals.
• preferred examples thereof include cobalt nitrate, zirconium oxynitrate, titanium hydrofluoride, zirconium hydrofluoride, ammonium titanium hydrofluoride, and ammonium zirconium hydrofluoride.
• the acidic aqueous solutions of the compounds containing these metal elements preferably has a pH falling within the range of from 1 to less than 7, preferably from 3 to 6.
• the pH can be adjusted by an acid such as hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid, or a base such as sodium hydroxide, potassium hydroxide and amines.
• a complexing agent, silica particles, etc. may be added to the acidic aqueous solution as needed.
• the amount of the compound containing the metal element to be added is preferably from 0.001 to 5 mol/liter, and particularly preferably about 0.01 to 1 mol/liter.
• the post-treatment with the acidic aqueous solution can be carried out by bringing the electroplated film into contact with the processing solution, for example by immersing the metal material into the processing solution of a bath temperature of 20 to 80°C, preferably 30 to 60°C, for 5 seconds or longer, preferably about 20 to 90 seconds.
• the electroplated metal material thus obtained is usually subjected to surface treatment and, if necessary, a coating material is further applied thereto.
• the surface treatment is usually conducted with a chromate-based surface treating agent or phosphate salt-based surface treating agent.
• a chromate-based surface treating agent or phosphate salt-based surface treating agent is usually conducted with a chromate-based surface treating agent or phosphate salt-based surface treating agent.
• the electroplated metal material of the invention is excellent in corrosion resistance, an excellent corrosion resistance is also exhibited even when it is combined with a chromium-free environment-responsive surface-treating agent. In order to reduce an environmental load, it is preferred to combine the material with a chromium-free environment-responsive surface-treating agent.
• the coating material in the case of coating the electroplated metal material of the invention is not particularly limited, any curing mode such as roomtemperature drying, hot curing, or active energy ray-curing can be employed, and any kind of coating materials such as solvent-type coating materials, water-based coating materials, and powdered coating materials may be used.
• any curing mode such as roomtemperature drying, hot curing, or active energy ray-curing
• any kind of coating materials such as solvent-type coating materials, water-based coating materials, and powdered coating materials may be used.
• an electrodeposition paint, an intermediate coat, and a top coat are sequentially applied on the plated film and then baked after phosphate salt treatment is applied on the plated film.
• a cold-rolled steel plate having a plate thickness of 0.8 mm and a size of 70 mm x 150 mm was subjected to alkaline degreasing and washed with water, and then it was plated in an acidic plating bath containing predetermined metal ions, corrosion-inhibiting pigment, corrosion-inhibiting organic compound, and ceramic particles using an electroplating experimental apparatus.
• the composition of the film was regulated by changing the concentration ratio of the metal ions in the plating bath, current density, and bath temperature and the thickness of the plated film was controlled by suitably choosing a plating time.
• the film composition (wt%) and film thickness of each plated layer are shown in Table 1 below. In this connection, the film composition and film thickness of the plated layer were measured on a fluorescent X-ray analyzer SEA5200 (manufactured by Seiko Instruments Inc.).
• Respective metal ions used in the test are supplied from the following compounds.
• Metal Composition (% by weight) Corrosion-inhibiting pigment Ceramic particles Corrosion-inhibiting organic compound Film thickness ( ⁇ m) Zn Fe Co Ni W A1(*1) A2(*2) B1(*3) B2(*4) C1(*5) C2(*6)
• Example 1 94 3 3 3 2 92 3 5 5 3 90 5 5 3 4 85 5 10 5 5 80 10 10 3 6 75 15 10 5 7 80 10 10 3 8 80 10 10 3 9 70 15 15 3 10 65 20 15 5 11 65 15 20 3 12 60 20 20 5 13 85 5 10 3 3 14 85 5 10 5 3 15 85 5 10 0.5 3 16 85 5 10 0.5 3 17 85 5 10 5 3 18 85 5 10
• A1 K-WHITE 840E, manufactured by Tayca Corporation, condensed aluminum phosphate-based one.
• A2 LF Bousei ZP-DL, Kikuchi Color & Chemicals Corporation, zinc phosphate-based one.
• B1 Silica fine particles, average particle diameter of about 0.02 ⁇ m.
• B2 Alumina fine particles, average particle diameter of about 0.01 ⁇ m.
• C1 3-Amino-1,2,4-triazole.
• C2 Thiourea.
• Each of the electroplated steel plates obtained in the above-shown Table 1 was treated with a phosphate salt by subjecting it to washing with hot water, degreasing (spraying at 43°C for 120 seconds using an alkali degreasing agent "FINE L-4460" manufactured by Nihon Parkerizing Co., Ltd.), washing with water, surface adjustment (spraying at ordinary temperature for 30 seconds using a titanium colloid-based surface adjusting agent "PREPALEN ZN” manufactured by Nihon Parkerizing Co., Ltd.), zinc phosphate-based chemical conversion (spraying at 43°C for 120 seconds using a zinc phosphate chemical conversion agent "Palbond L-3020" manufactured by Nihon Parkerizing Co., Ltd.), washing with water, and drying with draining.
• degreasing spraying at 43°C for 120 seconds using an alkali degreasing agent "FINE L-4460" manufactured by Nihon Parkerizing Co., Ltd.
• surface adjustment spraying at ordinary temperature for 30 seconds using
• a cation-type electrodeposition coating "ELECRON GT-10" (manufactured by Kansai Paint Co., Ltd., an epoxypolyester resin-based cation-type electrodeposition coating material) was applied by electrodeposition coating and baked at 170°C for 30 minutes to obtain an electrodeposition plate having a dry film thickness of 20 ⁇ m.
• An intermediate coat “AMILAC TP-65 gray” (manufactured by Kansai Paint Co., Ltd., an aminoalkyd resin-based intermediate coat) was applied to the electrodeposition surface using a spray so that a dry film thickness became 30 ⁇ m, and baked at 140°C for 30 minutes.
• a top coat "NEO AMILAC #6000 white” (manufactured by Kansai Paint Co., Ltd., an aminoalkyd resin-based top coat) was applied using a spray so that a dry film thickness became 30 ⁇ m, and baked at 140°C for 20 minutes to obtain each test coated plate.
• a titanium-based base-treating agent prepared according to the following formulation was applied thereon by a bar coater so that a dry film thickness became 0.5 ⁇ m and the resulting plate was heated for 10 seconds under conditions so that PMT (maximum reaching temperature of steel plate) became 100°C to manufacture a base-treated plate.
• KP color 8000 primer manufactured by Kansai Paint Co., Ltd., a modified epoxy resin-based coating material
• a bar coater so that a dry film thickness became 5 ⁇ m
• the resulting plate was heated for 20 seconds under conditions so that PMT became 210°C to form a coated film.
• KP color 1580 white manufactured by Kansai Paint Co., Ltd., a polyester resin-based coating material
• a mixture of 10 parts of tetra(iso-propoxy)titanium and 10 parts of iso-propanol was added dropwise into a mixture of 10 parts of a 30% hydrogen peroxide solution and 100 parts of deionized water at 20°C under stirring over a period of 1 hour and then the whole was aged at 25°C for 2 hours to obtain a 2% titanium compound aqueous solution.
• Five parts of 20% zircon hydrofluoric acid and 45 parts of deionized water were blended with 50 parts of the resulting 2% titanium compound aqueous solution to obtain a titanium-based base-treating agent.
• a steel bolt was subjected to alkali degreasing and washed with water and then it was dipped in a 1% sulfuric acid solution at room temperature for 30 seconds to effect activation treatment. Thereafter, using a batch-type barrel plating apparatus, plating was conducted in an alkaline plating bath containing predetermined metal ions, corrosion-inhibiting pigment, corrosion-inhibiting organic compound, and ceramic particles shown in Table 7.
• the composition of the film was regulated by changing the concentration ratio of the metal ions in the plating bath, current density, and bath temperature and the thickness of the plated film was controlled by suitably choosing a plating time.
• the zinc-based alloy electroplated film of the invention comprises specific amounts of an iron-group metal and tungsten relative to zinc and has remarkably improved corrosion resistance as compared with the conventional zinc or zinc alloy plated films.
• the plated metal material having the zinc-based alloy electroplated film is useful as a metal member particularly for automobiles.

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• 2004
  • 2004-12-07 US US10/596,307 patent/US20080028976A1/en not_active Abandoned
  • 2004-12-07 EP EP04801681A patent/EP1719825A4/fr not_active Withdrawn
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