EP1544322A1 - CORROSION-RESISTANT Al-BASED STRUCTURAL MEMBER AND METHOD FOR MANUFACTURE THEREOF - Google Patents

CORROSION-RESISTANT Al-BASED STRUCTURAL MEMBER AND METHOD FOR MANUFACTURE THEREOF Download PDF

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Publication number
EP1544322A1
EP1544322A1 EP03795217A EP03795217A EP1544322A1 EP 1544322 A1 EP1544322 A1 EP 1544322A1 EP 03795217 A EP03795217 A EP 03795217A EP 03795217 A EP03795217 A EP 03795217A EP 1544322 A1 EP1544322 A1 EP 1544322A1
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Prior art keywords
corrosion
base layer
structural member
treatment
based structural
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EP03795217A
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German (de)
French (fr)
Inventor
Junichi Kakuda 1st Plant of Keihin Corp. SATO
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Astemo Ltd
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Keihin Corp
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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
    • C23C22/48—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 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
    • C23C22/53—Treatment of zinc or alloys based thereon
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
    • C23C28/322—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only
    • C23C28/3225—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only with at least one zinc-based layer
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
    • C23C28/345—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
    • Y10T428/12611—Oxide-containing component

Definitions

  • the present invention relates to a corrosion-resistant Al-based structural member and a production process therefor.
  • the Al-based structural member includes both a structural member made of pure Al and a structural member made of an Al alloy.
  • the coating contains hexavalent Cr.
  • hexavalent Cr is an element that is harmful to the human body, and it is therefore desirable for the corrosion-inhibiting coating to contain no hexavalent Cr from the viewpoint of preventing pollution.
  • a corrosion-resistant Al-based structural member that includes a base layer adhered to the surface of an Al-based structural member, and a corrosion-inhibiting coating adhered to the surface of the base layer, the base layer being made of Zn, and the corrosion-inhibiting coating being made of a trivalent Cr-containing chromate coating for Zn.
  • This corrosion-inhibiting coating has excellent corrosion resistance and is useful in terms of preventing pollution since it contains no hexavalent Cr, which is harmful to the human body. Furthermore, although the trivalent Cr-containing chromate coating for Zn cannot adhere directly to the surface of the Al-based structural member, the coating exhibits sufficient adhesion to the base layer made of Zn, that is, the surface of the Zn base layer. Moreover, it is easy to form a Zn base layer adhering to the surface of the Al-based structural member by employing a known zincate treatment, etc.
  • a process for producing a corrosion-resistant Al-based structural member including a step of forming a base layer made of Zn, that is, a Zn base layer, on the surface of an Al-based structural member by a zincate treatment, and a step of forming a corrosion-inhibiting coating made of a trivalent Cr-containing chromate coating for Zn on the surface of the Zn base layer by a chromate treatment using a trivalent chromate agent.
  • the corrosion-resistant Al-based structural member having the above-mentioned arrangement can be obtained easily and reliably. Furthermore, the zincate treatment and the chromate treatment are both carried out by employing a dip method, and the two treatments may be carried out as an in-line process, thereby improving the productivity.
  • a treatment time t 1 required for the zincate treatment is set at a value, for example t 1 ⁇ 30 s, that enables the amount of Zn deposited on the surface of the Al-based structural member to be increased to give a Zn base layer having a required thickness.
  • a treatment time t 2 required for the chromate treatment is set at a value, for example t 2 ⁇ 15 s, that enables the trivalent Cr-containing chromate coating for Zn to be reliably formed on the surface of the Zn base layer while ensuring the thickness of the Zn base layer, despite the Zn base layer being dissolved by the chromate treatment.
  • the treatment time t 1 for the zincate treatment is less than 30 s, the thickness of the Zn base layer is insufficient for the chromate treatment, whereas when the treatment time t 2 for the chromate treatment is more than 15 s, dissolution of the Zn base layer proceeds, thus giving rise to a possibility that the surface of the Al-based structural member might be exposed.
  • FIG. 1 shows a corrosion-resistant carburetor main body 1 made of an Al alloy, which corresponds to the corrosion-resistant Al-based structural member.
  • this corrosion-resistant carburetor main body 1 is obtained by providing an unprotected surface of a carburetor main body 1 0 , obtained by die-casting using JIS ADC12, with a base layer 2, which is adhered thereto, and a corrosion-inhibiting coating 3, which is adhered to the surface of the base layer 2.
  • the base layer 2 is made of Zn
  • the corrosion-inhibiting coating 3 is made of a trivalent Cr-containing chromate coating for Zn.
  • This corrosion-inhibiting coating 3 has excellent corrosion resistance and is useful in terms of prevention of pollution since it does not contain hexavalent Cr, which is harmful to the human body. Furthermore, the trivalent Cr-containing chromate coating for Zn cannot directly adhere to the surface of the carburetor main body 1 0 , which is made of an Al alloy, but exhibits sufficient adhesion to the surface of the base layer made of Zn, that is, the Zn base layer 2. Moreover, it is easy to form the Zn base layer 2 adhering to the surface of the carburetor main body 1 0 made of an Al alloy by employing a known zincate treatment, etc.
  • the die-cast carburetor main body 1 0 is first subjected to a known pretreatment, that is, sequentially washing with hot water, degreasing, washing with water, activating, washing with water, and washing with hot water.
  • a step of forming the Zn base layer 2 on the surface of the pretreated carburetor main body 1 0 by a zincate treatment, a water washing step, a step of forming the corrosion-inhibiting coating 3, which is made of a trivalent Cr-containing chromate coating for Zn, on the surface of the Zn base layer 2 by a chromate treatment employing a trivalent chromate agent, a water washing step, and a drying step are carried out in sequence.
  • the corrosion-resistant carburetor main body 1 having the above-mentioned arrangement can be obtained easily and reliably. Furthermore, since the zincate treatment and the chromate treatment are both carried out by employing a dip method, the two treatments may be carried out as an in-line process, thus improving the productivity.
  • a treatment time t 1 required for the zincate treatment is set at a value, for example t 1 ⁇ 30 s, that enables the amount of Zn deposited on the surface of the carburetor main body 1 0 to be increased to give the Zn base layer 2 having a required thickness.
  • a treatment time t 2 required for the chromate treatment is set at a value, for example t 2 ⁇ 15 s, that enables the trivalent Cr-containing chromate coating for Zn to be reliably formed on the surface of the Zn base layer 2 while ensuring the thickness of the Zn base layer 2, despite the Zn base layer 2 being dissolved by the chromate treatment.
  • a Zn substitution liquid (product name: K-102, manufactured by Japan Kanigen Co., Ltd.) was selected.
  • This zinc substitution liquid contains 18.6 wt % of NaOH, 3.1 wt % of ZnO, 7.8 wt % of an organic acid, and a trace amount of an additive. The concentration of this liquid was adjusted to 220 mL/L to give a zincate treatment liquid.
  • a trivalent chromate agent (product name: Dipsol ZT-444A, liquid form, manufactured by Dipsol Chemicals Co., Ltd.) was selected.
  • This trivalent chromate agent contains 14 to 16 wt % (Cr 3+ : 4) of chromium nitrate [Cr(NO 3 ) 3 ⁇ 9H 2 O], 2 to 4 wt % of cobalt nitrate [Co(NO 3 ) 2 ], with the balance being normal materials, and they are existing chemical substances.
  • the concentration of this liquid was adjusted to 60 mL/L to give a chromate treatment liquid.
  • a plurality of the Al alloy carburetor main bodies (JIS ADC12, die-cast) 1 0 as described above were prepared, and they were subjected to the pretreatment described above. Subsequently, various types of corrosion-resistant carburetor main bodies 1 were obtained by carrying out, in sequence, formation of the Zr base layer 2 using the zincate treatment liquid at 30°C for various treatment times t 1 , washing with water, formation of the corrosion-inhibiting coating 3 using the chromate treatment liquid at 30°C for various treatment times t 2 , washing with water, and drying.
  • Corrosion-resistant carburetor main body Treatment time of zincate treatment t 1 (s) Treatment time of chromate treatment t 2 (s) Percentage area of white product A (%) Example 1 50 15 1 Example 2 30 15 3 Example 3 15 15 10 Example 4 15 30 30 Example 5 15 50 70
  • the Al-based structural member is not limited to the Al alloy carburetor main body, and includes a throttle body, a solenoid valve main body, a compressor housing, etc. made of an Al alloy, and further includes a structural member made of pure Al.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)

Abstract

A corrosion-resistant Al-based structural member (1) is provided that has a base layer (2) adhered to the surface of an Al-based structural member (10), and a corrosion-inhibiting coating (3) adhered to the surface of the base layer (2). The base layer (2) is made of Zn, and the corrosion-inhibiting coating (3) is made of a trivalent Cr-containing chromate coating for Zn. It is thereby possible to provide a corrosion-resistant Al-based structural member equipped with a nonpolluting corrosion-inhibiting coating containing no hexavalent chromium.

Description

    FIELD OF THE INVENTION
  • The present invention relates to a corrosion-resistant Al-based structural member and a production process therefor. Here, the Al-based structural member includes both a structural member made of pure Al and a structural member made of an Al alloy.
    • BACKGROUND ART
  • Conventionally, as this type of Al-based structural member, an arrangement in which a corrosion-inhibiting coating made of a chromate coating is provided is known (e.g., Japanese Patent Publication No. 60-35432).
  • However, since the conventional chromate coating is formed using a treatment liquid containing CrO3 as an essential component, the coating contains hexavalent Cr. As is well known, hexavalent Cr is an element that is harmful to the human body, and it is therefore desirable for the corrosion-inhibiting coating to contain no hexavalent Cr from the viewpoint of preventing pollution.
    • DISCLOSURE OF INVENTION
  • It is an object of the present invention to provide a corrosion-resistant Al-based structural member that includes a nonpolluting corrosion-inhibiting coating containing no hexavalent chromium.
  • In order to attain this object, in accordance with the present invention, there is provided a corrosion-resistant Al-based structural member that includes a base layer adhered to the surface of an Al-based structural member, and a corrosion-inhibiting coating adhered to the surface of the base layer, the base layer being made of Zn, and the corrosion-inhibiting coating being made of a trivalent Cr-containing chromate coating for Zn.
  • This corrosion-inhibiting coating has excellent corrosion resistance and is useful in terms of preventing pollution since it contains no hexavalent Cr, which is harmful to the human body. Furthermore, although the trivalent Cr-containing chromate coating for Zn cannot adhere directly to the surface of the Al-based structural member, the coating exhibits sufficient adhesion to the base layer made of Zn, that is, the surface of the Zn base layer. Moreover, it is easy to form a Zn base layer adhering to the surface of the Al-based structural member by employing a known zincate treatment, etc.
  • It is another object of the present invention to provide a production process that enables the corrosion-resistant Al-based structural member having this arrangement to be mass produced.
  • In order to attain this object, in accordance with the present invention, there is provided a process for producing a corrosion-resistant Al-based structural member, the process including a step of forming a base layer made of Zn, that is, a Zn base layer, on the surface of an Al-based structural member by a zincate treatment, and a step of forming a corrosion-inhibiting coating made of a trivalent Cr-containing chromate coating for Zn on the surface of the Zn base layer by a chromate treatment using a trivalent chromate agent.
  • In accordance with this production process, the corrosion-resistant Al-based structural member having the above-mentioned arrangement can be obtained easily and reliably. Furthermore, the zincate treatment and the chromate treatment are both carried out by employing a dip method, and the two treatments may be carried out as an in-line process, thereby improving the productivity.
  • A treatment time t1 required for the zincate treatment is set at a value, for example t1 ≥ 30 s, that enables the amount of Zn deposited on the surface of the Al-based structural member to be increased to give a Zn base layer having a required thickness. On the other hand, a treatment time t2 required for the chromate treatment is set at a value, for example t2 ≤ 15 s, that enables the trivalent Cr-containing chromate coating for Zn to be reliably formed on the surface of the Zn base layer while ensuring the thickness of the Zn base layer, despite the Zn base layer being dissolved by the chromate treatment. When the treatment time t1 for the zincate treatment is less than 30 s, the thickness of the Zn base layer is insufficient for the chromate treatment, whereas when the treatment time t2 for the chromate treatment is more than 15 s, dissolution of the Zn base layer proceeds, thus giving rise to a possibility that the surface of the Al-based structural member might be exposed.
    • BRIEF DESCRIPTION OF DRAWINGS
  • FIG. 1 is a front view of a carburetor main body made of a corrosion-resistant Al alloy, and FIG. 2 is an enlarged sectional view of an essential part of the carburetor main body made of the corrosion-resistant Al alloy.
    • BEST MODE FOR CARRYING OUT THE INVENTION
  • FIG. 1 shows a corrosion-resistant carburetor main body 1 made of an Al alloy, which corresponds to the corrosion-resistant Al-based structural member. As shown in FIG. 2, this corrosion-resistant carburetor main body 1 is obtained by providing an unprotected surface of a carburetor main body 10, obtained by die-casting using JIS ADC12, with a base layer 2, which is adhered thereto, and a corrosion-inhibiting coating 3, which is adhered to the surface of the base layer 2. The base layer 2 is made of Zn, whereas the corrosion-inhibiting coating 3 is made of a trivalent Cr-containing chromate coating for Zn.
  • This corrosion-inhibiting coating 3 has excellent corrosion resistance and is useful in terms of prevention of pollution since it does not contain hexavalent Cr, which is harmful to the human body. Furthermore, the trivalent Cr-containing chromate coating for Zn cannot directly adhere to the surface of the carburetor main body 10, which is made of an Al alloy, but exhibits sufficient adhesion to the surface of the base layer made of Zn, that is, the Zn base layer 2. Moreover, it is easy to form the Zn base layer 2 adhering to the surface of the carburetor main body 10 made of an Al alloy by employing a known zincate treatment, etc.
  • When producing the corrosion-resistant carburetor main body 1, the die-cast carburetor main body 10 is first subjected to a known pretreatment, that is, sequentially washing with hot water, degreasing, washing with water, activating, washing with water, and washing with hot water. Subsequently, a step of forming the Zn base layer 2 on the surface of the pretreated carburetor main body 10 by a zincate treatment, a water washing step, a step of forming the corrosion-inhibiting coating 3, which is made of a trivalent Cr-containing chromate coating for Zn, on the surface of the Zn base layer 2 by a chromate treatment employing a trivalent chromate agent, a water washing step, and a drying step are carried out in sequence.
  • In accordance with this production process, the corrosion-resistant carburetor main body 1 having the above-mentioned arrangement can be obtained easily and reliably. Furthermore, since the zincate treatment and the chromate treatment are both carried out by employing a dip method, the two treatments may be carried out as an in-line process, thus improving the productivity.
  • A treatment time t1 required for the zincate treatment is set at a value, for example t1 ≥ 30 s, that enables the amount of Zn deposited on the surface of the carburetor main body 10 to be increased to give the Zn base layer 2 having a required thickness. On the other hand, a treatment time t2 required for the chromate treatment is set at a value, for example t2 ≤ 15 s, that enables the trivalent Cr-containing chromate coating for Zn to be reliably formed on the surface of the Zn base layer 2 while ensuring the thickness of the Zn base layer 2, despite the Zn base layer 2 being dissolved by the chromate treatment.
    • [Embodiment]
  • As a main component of a zincate treatment liquid, a Zn substitution liquid (product name: K-102, manufactured by Japan Kanigen Co., Ltd.) was selected. This zinc substitution liquid contains 18.6 wt % of NaOH, 3.1 wt % of ZnO, 7.8 wt % of an organic acid, and a trace amount of an additive. The concentration of this liquid was adjusted to 220 mL/L to give a zincate treatment liquid.
  • As a main component of a chromate treatment liquid, a trivalent chromate agent (product name: Dipsol ZT-444A, liquid form, manufactured by Dipsol Chemicals Co., Ltd.) was selected. This trivalent chromate agent contains 14 to 16 wt % (Cr3+: 4) of chromium nitrate [Cr(NO3)3·9H2O], 2 to 4 wt % of cobalt nitrate [Co(NO3)2], with the balance being normal materials, and they are existing chemical substances. The concentration of this liquid was adjusted to 60 mL/L to give a chromate treatment liquid.
  • A plurality of the Al alloy carburetor main bodies (JIS ADC12, die-cast) 10 as described above were prepared, and they were subjected to the pretreatment described above. Subsequently, various types of corrosion-resistant carburetor main bodies 1 were obtained by carrying out, in sequence, formation of the Zr base layer 2 using the zincate treatment liquid at 30°C for various treatment times t1, washing with water, formation of the corrosion-inhibiting coating 3 using the chromate treatment liquid at 30°C for various treatment times t2, washing with water, and drying.
  • These corrosion-resistant carburetor main bodies 1 were subjected to a brine spray test, and the percentage area A of white product (product due to corrosion of Al alloy) 48 hours after starting the test, that is, A = (area of white product / total surface area of carburetor main body) x 100 (%), was determined. Table 1 shows the treatment time t1 of the zincate treatment, the treatment time t2 of the chromate treatment, and the percentage area A of the white product related to Examples 1 to 6 of the corrosion-resistant carburetor main bodies 1.
    Corrosion-resistant carburetor main body Treatment time of zincate treatment t1 (s) Treatment time of chromate treatment t2 (s) Percentage area of white product A (%)
    Example 1 50 15 1
    Example 2 30 15 3
    Example 3 15 15 10
    Example 4 15 30 30
    Example 5 15 50 70
  • As is clear from Table 1, if the treatment time t1 of the zincate treatment is set at t1 ≥ 30 s and the treatment time t2 of the chromate treatment is set at t2 ≤ 15 s, as in Examples 1 and 2, an Al alloy carburetor main body 1 having excellent corrosion resistance can be obtained. In the case of Examples 3 to 5, since the treatment time t1 of the zincate treatment was 15 s, the Zn base layer 2 was relatively thin, but since the treatment time t2 of the chromate treatment was t2 = 15 s < t2 = 30 s < t2 = 50 s, the amount of the surface of the carburetor main body 10 exposed increased in the order Example 3, Example 4, Example 5, and the corrosion resistance also deteriorated in this order.
  • The Al-based structural member is not limited to the Al alloy carburetor main body, and includes a throttle body, a solenoid valve main body, a compressor housing, etc. made of an Al alloy, and further includes a structural member made of pure Al.

Claims (4)

  1. A corrosion-resistant Al-based structural member comprising a base layer (2) adhered to the surface of an Al-based structural member (10), and a corrosion-inhibiting coating (3) adhered to the surface of the base layer (2), the base layer (2) comprising Zn, and the corrosion-inhibiting coating (3) comprising a trivalent Cr-containing chromate coating for Zn.
  2. A process for producing a corrosion-resistant Al-based structural member, the process comprising a step of forming a base layer (2) comprising Zn on the surface of an Al-based structural member (10) by a zincate treatment, and a step of forming a corrosion-inhibiting coating (3) comprising a trivalent Cr-containing chromate coating for Zn on the surface of the base layer (2) by a chromate treatment using a trivalent chromate agent.
  3. The process for producing a corrosion-resistant Al-based structural member according to Claim 2, wherein a treatment time t1 required for the zincate treatment is set at a value that enables the amount of Zn deposited on the surface of the Al-based structural member (10) to be increased to give the base layer (2) comprising Zn having a required thickness, and a treatment time t2 required for the chromate treatment is set at a value that enables the trivalent Cr-containing chromate coating for Zn to be reliably formed on the surface of the base layer (2) while ensuring the thickness of the base layer (2), despite the base layer (2) being dissolved by the chromate treatment.
  4. The process for producing a corrosion-resistant Al-based structural member according to Claim 3, wherein the treatment time t1 required for the zincate treatment is ≥ 30 s, and the treatment time t2 required for the chromate treatment is ≤ 15 s.
EP03795217A 2002-08-12 2003-08-11 CORROSION-RESISTANT Al-BASED STRUCTURAL MEMBER AND METHOD FOR MANUFACTURE THEREOF Withdrawn EP1544322A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2002234965 2002-08-12
JP2002234965A JP2004076041A (en) 2002-08-12 2002-08-12 Corrosion resistant Al-based structural member and method of manufacturing the same
PCT/JP2003/010225 WO2004024988A1 (en) 2002-08-12 2003-08-11 CORROSION-RESISTANT Al-BASED STRUCTURAL MEMBER AND METHOD FOR MANUFACTURE THEREOF

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EP3746580A1 (en) 2018-01-30 2020-12-09 PRC-Desoto International, Inc. Systems and methods for treating a metal substrate

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JPS6035432B2 (en) * 1977-06-27 1985-08-14 デイツプソ−ル株式会社 Method of forming a chromate conversion film on the surface of aluminum or aluminum alloy
JP3333611B2 (en) * 1993-11-09 2002-10-15 日本パーカライジング株式会社 Hexavalent chromium-free chemical conversion surface treatment agent for aluminum and aluminum alloys
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1879260A3 (en) * 2006-07-04 2008-05-21 ITT Manufacturing Enterprises, Inc. Electrically conductive housing part for electrical plug connectors
US7875364B2 (en) 2006-07-04 2011-01-25 Itt Manufacturing Enterprises, Inc. Electrically conductive connector housing part

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CN1675410A (en) 2005-09-28
US20060110619A1 (en) 2006-05-25
TWI249590B (en) 2006-02-21
AU2003254940A1 (en) 2004-04-30
JP2004076041A (en) 2004-03-11
WO2004024988A1 (en) 2004-03-25
TW200528579A (en) 2005-09-01

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