JP4579714B2 - Chemically treated steel sheet with excellent film adhesion after forming - Google Patents
Chemically treated steel sheet with excellent film adhesion after forming Download PDFInfo
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- 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
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- C—CHEMISTRY; METALLURGY
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- 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
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- 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
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- 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
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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
- 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
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Description
本発明は、環境に有害な六価クロムを含まず優れた耐食性，塗装性を呈し、外装材，内装材，表装材，車両用鋼板等として有用な化成処理鋼板に関する。 The present invention relates to a chemically treated steel sheet that does not contain hexavalent chromium harmful to the environment, exhibits excellent corrosion resistance and paintability, and is useful as an exterior material, an interior material, a surface material, a vehicle steel sheet, and the like.
亜鉛めっき鋼板，亜鉛合金めっき鋼板等は、海塩粒子飛散雰囲気や高温多湿雰囲気で使用すると、外観劣化の原因となる白錆が鋼板表面に発生し、めっき層の犠牲防食作用も損なわれる。白錆の発生は、クロメート処理，リン酸塩処理等によって防止できる。しかし、クロメート処理は、生成した皮膜からの六価クロムの溶出が避けられない。リン酸塩処理でも、リン酸塩処理後にクロメート処理を通常必要とすることから、六価クロム溶出の問題は未解決である。 When a galvanized steel sheet, a zinc alloy plated steel sheet, etc. are used in a sea salt particle scattering atmosphere or a high-temperature and high-humidity atmosphere, white rust that causes the appearance deterioration is generated on the surface of the steel sheet, and the sacrificial anticorrosive action of the plating layer is also impaired. Generation of white rust can be prevented by chromate treatment, phosphate treatment, and the like. However, in chromate treatment, elution of hexavalent chromium from the formed film is inevitable. Even in the phosphate treatment, the chromate treatment is usually required after the phosphate treatment, so the problem of hexavalent chromium elution has not been solved.
環境に有害な六価クロムを含まない化成皮膜を形成するため、リン酸塩処理の改良が検討されている。たとえば、特許文献１は、ヒドラジン誘導体，シリカ微粒子，金属表面に対してエッチング作用のある酸を含む処理液でリン酸塩皮膜を後処理することを紹介している。特許文献２では、リン酸塩処理皮膜を介しチオカルボニル基含有化合物を含む有機樹脂皮膜を亜鉛系めっき鋼板に設けることを紹介している。
化成処理鋼板は、通常、鉄鋼メーカ側でリン酸塩処理され、ユーザ側で製品形状に成形加工されている。成形加工に際し、従来のリン酸塩皮膜では皮膜構成成分である無機質のリン酸塩が硬質で延性がないため、亀裂，剥離等の皮膜欠陥が導入されやすい。皮膜欠陥は腐食発生の起点となり、化成皮膜の耐食性改善作用や塗膜密着性が極端に低下する。めっき層／リン酸塩皮膜の密着性を改善するため、リン酸塩処理した亜鉛めっき鋼板の表面粗さを調整する方法（特許文献３），表面粗さに加えてリン酸塩皮膜の膜厚を調整する方法（特許文献４）等が提案されているが、依然としてユーザ側での加工性，加工後密着性を十分に満足させるに至っていない。
本発明は、高耐食性を呈するＺｎ-Ａｌ-Ｍｇ合金めっき鋼板を基材に選択し、リン酸塩系の化成処理がめっき層表面に及ぼす影響を調査・検討した結果得られた知見をベースとし、めっき層にリン酸塩結晶が食い込んだリン酸塩皮膜を形成することにより、成形加工による亀裂，剥離が抑制され、優れた皮膜密着性を維持する化成処理鋼板を提供することを目的とする。 The present invention is based on the knowledge obtained as a result of investigating and examining the influence of phosphate-based chemical conversion treatment on the surface of the plating layer by selecting Zn-Al-Mg alloy-plated steel sheet exhibiting high corrosion resistance as the base material. An object of the present invention is to provide a chemical conversion treated steel sheet that is formed by forming a phosphate film in which a phosphate crystal penetrates into a plating layer, thereby suppressing cracking and peeling due to forming and maintaining excellent film adhesion. .
本発明の化成処理鋼板は、めっき層最表面に占める〔Ａｌ／Ｚｎ／Ｚｎ2Ｍｇの三元共晶組織〕の割合が６０面積％以上である溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板を基材とし、基材のめっき層表面をリン酸塩皮膜，析出層，化成皮膜で覆っている。析出層は、付着量：０.０５〜５.０ｍｇ／ｍ2でＮｉ，Ｃｏ，Ｆｅから選ばれた少なくとも一種を析出させた層及び／又は０.０５〜３０ｍｇ／ｍ2でＭｎを析出させた層である。リン酸塩皮膜は、基部がめっき層に食い込んでめっき層から起立する平均粒径：０.５〜５.０μｍのリン酸塩結晶からなる。化成皮膜は、バルブメタルの酸化物又は水酸化物とバルブメタルのフッ化物とを含み、リン酸塩結晶の間で露出しためっき層又は析出層の上に形成されている。 The chemical conversion treated steel sheet of the present invention is based on a molten Zn—Al—Mg alloy plated steel sheet in which the ratio of [Al / Zn / Zn 2 Mg ternary eutectic structure] to the outermost surface of the plating layer is 60 area% or more. The surface of the plating layer of the substrate is covered with a phosphate film, a deposited layer, and a chemical conversion film. The deposited layer is a layer in which at least one selected from Ni, Co, and Fe is deposited at an adhesion amount of 0.05 to 5.0 mg / m 2 and / or Mn is deposited at 0.05 to 30 mg / m 2. Layer. The phosphate film is composed of phosphate crystals having an average particle size of 0.5 to 5.0 μm whose base portion bites into the plating layer and stands up from the plating layer. The chemical conversion film contains a valve metal oxide or hydroxide and a valve metal fluoride, and is formed on a plating layer or a deposited layer exposed between phosphate crystals.
リン酸塩処理による塗膜密着性やフィルム密着性を改善する上で、めっき層最表面に占めるリン酸塩結晶の割合を５０面積％以上、めっき層に食い込むリン酸塩結晶の平均深さを０.０５μｍ以上にすることが好ましい。化成皮膜のバルブメタルには、Ｔｉ，Ｚｒ，Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｍｏ，Ｗ等が使用される。化成皮膜は、０.００１μｍ以上でリン酸塩皮膜の膜厚の１０％以下に膜厚を規制することが好ましい。 In improving coating film adhesion and film adhesion by phosphate treatment, the proportion of phosphate crystals occupying the outermost surface of the plating layer is 50 area% or more, and the average depth of phosphate crystals that bite into the plating layer The thickness is preferably 0.05 μm or more. Ti, Zr, Hf, V, Nb, Ta, Mo, W, etc. are used for the valve metal of a chemical conversion film. The film thickness of the chemical conversion film is preferably 0.001 μm or more and 10% or less of the film thickness of the phosphate film.
Ｎｉ，Ｃｏ，Ｆｅ，Ｍｎ等を含むリン酸処理液で溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板をリン酸塩処理すると、めっき層の表層に食い込んだ状態でリン酸塩結晶が生成する。そのため、めっき層に対するリン酸塩皮膜は、従来の亜鉛系めっき鋼板をリン酸塩処理した場合に得られるリン酸塩皮膜に比較して格段に優れた密着性を呈し、成形加工後にも健全な状態に維持される。
めっき層に対するリン酸塩結晶の食込みは、次のメカニズムによるものと推察され、溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板とＮｉ，Ｃｏ，Ｆｅ，Ｍｎ等を含むリン酸処理液との組合せによって初めて生じる現象である（図１）。以下の説明ではＮｉを例に置換析出元素としているが、Ｃｏ，Ｆｅ及び／又はＭｎを含むリン酸処理液を使用した場合でも同様にめっき層に食い込んだリン酸塩結晶が生成する。
When the molten Zn—Al—Mg alloy-plated steel sheet is subjected to a phosphate treatment with a phosphoric acid treatment solution containing Ni, Co, Fe, Mn, etc., phosphate crystals are generated in a state of being bitten into the surface layer of the plating layer. Therefore, the phosphate film on the plating layer exhibits much better adhesion than the phosphate film obtained when the conventional zinc-based plated steel sheet is subjected to phosphate treatment, and is sound even after forming. Maintained in a state.
It is presumed that the phosphate crystal bites into the plating layer due to the following mechanism, and it occurs for the first time by a combination of a hot-dip Zn-Al-Mg alloy-plated steel sheet and a phosphating solution containing Ni, Co, Fe, Mn, etc. This is a phenomenon (FIG. 1). In the following description, Ni is used as an example of the substitutional precipitation element. However, even when a phosphating solution containing Co, Fe and / or Mn is used, phosphate crystals that have penetrated into the plating layer are generated.
溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板は、めっき層の大部分が〔Ａｌ／Ｚｎ／Ｚｎ2Ｍｇの三元共晶組織〕の微細組織になっている。Ｎｉ含有処理液でめっき層をリン酸塩処理すると、三元共晶組織のなかで表面電位が最も低いＺｎ2Ｍｇ相で優先的にＮｉの置換析出反応が生じる。貴な金属であるＮｉがＺｎ2Ｍｇ相の表面に析出すると、Ｚｎ2Ｍｇ相，析出ＮｉとＺｎ相との間に腐食電流が流れ、Ｚｎ相が優先的に溶解する。Ｚｎ相の溶解は、エッチングされ難いＡｌ相がめっき層に存在するため深さ方向に進行する。Ｚｎ相の溶解に伴ってリン酸塩結晶が析出するので、Ｚｎ相が深くエッチングされた個所では根の深いリン酸塩結晶となる。 In the molten Zn—Al—Mg alloy-plated steel sheet, most of the plating layer has a microstructure of [Al / Zn / Zn 2 Mg ternary eutectic structure]. When the plating layer is phosphate-treated with a Ni-containing treatment solution, a substitutional precipitation reaction of Ni occurs preferentially in the Zn 2 Mg phase having the lowest surface potential in the ternary eutectic structure. When a noble metal Ni is deposited on the surface of the Zn 2 Mg phase, Zn 2 Mg phase, the corrosion current flows between the deposition Ni and Zn phase, Zn phase is preferentially dissolved. The dissolution of the Zn phase proceeds in the depth direction because an Al phase that is difficult to etch exists in the plating layer. Since phosphate crystals are precipitated as the Zn phase dissolves, the phosphate crystals are deeply rooted where the Zn phase is deeply etched.
これに対し、めっき層がほぼ単一な組織を呈する電気亜鉛めっき鋼板や溶融亜鉛めっき鋼板をＮｉ含有処理液でリン酸塩処理すると、めっき層のほぼ全面にＮｉが置換析出する。析出Ｎｉのないめっき層が深さ方向及び水平方向に溶解し、リン酸塩結晶が析出する。しかし、深さ方向に沿った溶解が進行しがたいため、析出したリン酸塩結晶がめっき層に僅かに食い込むだけであり、水平方向に成長した比較的大粒径の結晶となる。 On the other hand, when an electrogalvanized steel sheet or a hot dip galvanized steel sheet in which the plated layer has a substantially single structure is subjected to phosphate treatment with a Ni-containing treatment solution, Ni is substituted and deposited on almost the entire surface of the plated layer. The plating layer without precipitated Ni is dissolved in the depth direction and the horizontal direction, and phosphate crystals are precipitated. However, since dissolution along the depth direction is difficult to proceed, the precipitated phosphate crystal slightly bites into the plating layer, resulting in a crystal having a relatively large grain size grown in the horizontal direction.
リン酸塩結晶２は、根深くめっき層１に食い込んだ状態でめっき層１から起立する方向に成長する。リン酸塩結晶２の間ではめっき層１が露出し、或いはＮｉ析出層３が形成されている。バルブメタルのフッ化物を含むクロムフリー化成処理液でリン酸塩処理後のめっき層１を処理すると、処理液のエッチング作用によりリン酸塩結晶２の一部が溶解し、溶解したリン酸塩成分が処理液成分と共にめっき層１の露出表面と反応し、クロムフリーの化成皮膜４が生成する（図２）。めっき層１の露出表面が化成皮膜４で覆われ、環境から遮断される。めっき層１から起立しているリン酸塩結晶２の表面にも粒状の反応生成物５が沈積する。
The phosphate crystal 2 grows in a direction to stand up from the plating layer 1 in a state of being deeply rooted in the plating layer 1. Between the phosphate crystals 2, the plating layer 1 is exposed or the
クロムフリー化成皮膜４には、バルブメタルの酸化物又は水酸化物及びバルブメタルのフッ化物が共存している。バルブメタルの酸化物又は水酸化物は、優れた環境遮断能を呈し、腐食性雰囲気からめっき層１を保護する。バルブメタルのフッ化物は、腐食性雰囲気に曝されると溶出し、難溶性の酸化物又は水酸化物となって再析出する過程でリン酸塩皮膜，化成皮膜４の欠陥部を自己修復する。
In the chromium-free
クロムフリー化成皮膜４は、隣接リン酸塩結晶２の間で露出しているめっき層１の表面に形成されるため、未処理のめっき層１やＮｉ析出層３に形成される化成皮膜に比べ成長が促進され、環境遮断能，自己修復作用が格段に向上する。環境遮断能，自己修復作用は膜厚０.００１μｍ以上の化成皮膜４でみられるが、化成皮膜４が厚く成長しすぎると塗料や接着剤の密着性に及ぼすリン酸塩結晶２の効果が損なわれるので、めっき層１の表面から起立するリン酸塩結晶２の平均高さの１０％以下に化成皮膜４の膜厚を制御することが好ましい。化成皮膜４の膜厚は、クロムフリー化成処理液の濃度や処理時間等で制御できる。リン酸塩結晶２の突出高さは１〜２μｍの微細サイズから５〜２０μｍの通常サイズまであるので、該突出高さに応じて化成皮膜４の膜厚を選定する。
Since the chromium-free
化成皮膜４は、無機質で延性のない皮膜ではあるが、リン酸塩結晶２で分断されているため、めっき層１に対する密着性低下も軽減される。リン酸塩結晶２の表面に析出している粒状反応生成物５も、自己修復作用を呈するフッ化物の供給源となる。更に、硬質で延性のないリン酸塩結晶２のシャープな角部がクロムフリー化成処理液のエッチング作用で消失するので、プレス成形等の加工時に亀裂や剥離がリン酸塩皮膜３に生じにくくなる。
Although the
化成処理原板に使用される溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板は、Ａｌ：２.５〜１５質量％，Ｍｇ：２.０〜４.０質量％を含み残部が実質的にＺｎの合金めっき浴を用いた溶融めっき法で製造される。合金めっき浴の組成は、必要とする形態のリン酸塩結晶の形成に有効な〔Ａｌ／Ｚｎ／Ｚｎ2Ｍｇの三元共晶組織〕の微細組織を主とするめっき層が鋼板表面に形成されるように所定組成に調整される。リン酸塩処理の反応性を確保する上で、〔Ａｌ／Ｚｎ／Ｚｎ2Ｍｇの三元共晶組織〕を６０面積％以上（好ましくは、８０面積％以上）にしている。 The hot-dip Zn—Al—Mg alloy-plated steel sheet used for the chemical conversion raw plate contains Al: 2.5-15 mass%, Mg: 2.0-4.0 mass%, and the balance is substantially Zn alloy plating. Manufactured by hot dipping using a bath. The composition of the alloy plating bath is such that a plating layer mainly composed of a microstructure of [Al / Zn / Zn 2 Mg ternary eutectic structure] effective on the formation of phosphate crystals in the required form is formed on the surface of the steel sheet. To a predetermined composition. In order to ensure the reactivity of phosphating, the [Al / Zn / Zn 2 Mg ternary eutectic structure] is set to 60 area% or more (preferably 80 area% or more).
めっき層の金属組織を〔Ａｌ／Ｚｎ／Ｚｎ2Ｍｇの三元共晶組織〕とする場合、外観及び耐食性に悪影響を与えるＺｎ11Ｍｇ2相の生成・成長を抑制するためＴｉ，Ｂ，Ｔｉ-Ｂ合金又はＴｉ，Ｂ含有化合物をめっき浴に添加することが有益である。めっき浴に対する添加量は、Ｔｉ：０.００１〜０.１質量％，Ｂ：０.００１〜０.０４５質量％の範囲で定めることが好ましい。過剰なＴｉ，Ｂの添加はめっき層に析出物が成長させる原因であり、却ってリン酸塩処理性を阻害することがある。
更に、加工時のめっき密着性を向上させるため、めっき層と素地鋼との界面におけるＡｌ-Ｆｅ合金層の成長を抑制する作用のあるＳｉを０.００５〜０.５質量％の範囲で添加することもできる。
When the metal structure of the plating layer is [Al / Zn / Zn 2 Mg ternary eutectic structure], Ti, B, Ti are used to suppress the formation and growth of the Zn 11 Mg 2 phase which adversely affects the appearance and corrosion resistance. It is beneficial to add a B alloy or a Ti, B containing compound to the plating bath. The addition amount to the plating bath is preferably determined in the range of Ti: 0.001 to 0.1% by mass and B: 0.001 to 0.045% by mass. Excessive addition of Ti and B causes the precipitate to grow on the plating layer, and on the other hand, the phosphate processability may be hindered.
Further, in order to improve plating adhesion during processing, Si having an action of suppressing the growth of the Al—Fe alloy layer at the interface between the plating layer and the base steel is added in the range of 0.005 to 0.5 mass%. You can also
リン酸塩処理液は、リン酸イオン濃度を０.０３〜０.５モル／ｌ，金属イオン濃度を０.０１〜０.５モル／ｌの範囲に調整することが好ましい。硝酸イオンを含ませる場合には、硝酸イオン濃度を０.０１〜１.０モル／ｌの範囲に調整する。リン酸イオン濃度：０.０３モル／ｌ未満では短時間処理でリン酸塩結晶が充分に析出せず、逆に０.５モル／ｌを超えるとリン酸塩処理液の安定性が低下し、スラッジが発生し易くなる。金属イオン濃度：０.０１〜０.５モル／ｌは各種金属イオンを合計した値であり、０.０１モル／ｌ未満では短時間処理でリン酸塩結晶を充分に析出させることができず、逆に０.５モル／ｌを超えるとリン酸塩処理液の安定性が低下する。硝酸イオンによる反応促進効果は０.０１モル／ｌ以上でみられるが、１.０モル／ｌを超える過剰量の硝酸イオンが含まれると酸化作用によりめっき層の表面が不活性化し、却って反応性が低下する。 In the phosphating solution, it is preferable to adjust the phosphate ion concentration to a range of 0.03 to 0.5 mol / l and the metal ion concentration to a range of 0.01 to 0.5 mol / l. When nitrate ions are included, the nitrate ion concentration is adjusted to a range of 0.01 to 1.0 mol / l. When the phosphate ion concentration is less than 0.03 mol / l, phosphate crystals are not sufficiently precipitated in a short time treatment. Conversely, when the concentration exceeds 0.5 mol / l, the stability of the phosphate treatment solution decreases. Sludge is likely to occur. Metal ion concentration: 0.01 to 0.5 mol / l is a total value of various metal ions. If it is less than 0.01 mol / l, phosphate crystals cannot be sufficiently precipitated in a short time treatment. On the other hand, if it exceeds 0.5 mol / l, the stability of the phosphating solution is lowered. The reaction promoting effect by nitrate ions is observed at 0.01 mol / l or more, but if an excessive amount of nitrate ions exceeding 1.0 mol / l is included, the surface of the plating layer is inactivated by the oxidation action and reacts instead. Sex is reduced.
リン酸処理液にはＺｎ，Ｍｎ，Ｍｇ，Ｃａ，Ｎｉ，Ｃｏ，Ｆｅ等の金属イオンがリン酸イオンの他に必要に応じて添加されているが、本発明ではＮｉ，Ｃｏ、Ｆｅ，Ｍｎの金属イオンを少なくとも一種を含んだ水溶液を使用する。Ｎｉ，Ｃｏ，Ｆｅ，Ｍｎは、溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板の〔Ａｌ／Ｚｎ／Ｚｎ2Ｍｇの三元共晶組織〕の中で表面電位が最も低いＺｎ2Ｍｇ相に優先的に置換析出し、貴な金属であるＮｉ，Ｃｏ，Ｆｅ又はＭｎ化合物がＺｎ2Ｍｇ相に析出することで近傍のＺｎ相が優先的に溶解する。Ｚｎ相の溶解は深さ方向に進行し、Ｚｎ相の溶解に伴ってリン酸塩結晶が析出するため根の深いリン酸塩結晶となる。しかも、〔Ａｌ／Ｚｎ／Ｚｎ2Ｍｇの三元共晶組織〕が微細組織であるため、リン酸塩結晶も微細且つ緻密な状態で形成されやすくなる。 Metal ions such as Zn, Mn, Mg, Ca, Ni, Co, and Fe are added to the phosphoric acid treatment liquid as needed in addition to phosphate ions. In the present invention, Ni, Co, Fe, and Mn are added. An aqueous solution containing at least one of the above metal ions is used. Ni, Co, Fe, and Mn are preferential to the Zn 2 Mg phase having the lowest surface potential in the [Al / Zn / Zn 2 Mg ternary eutectic structure] of the molten Zn—Al—Mg alloy-plated steel sheet. The substitutional precipitation causes Ni, Co, Fe, or Mn compounds, which are noble metals, to precipitate in the Zn 2 Mg phase, so that the nearby Zn phase is preferentially dissolved. The dissolution of the Zn phase proceeds in the depth direction, and a phosphate crystal is precipitated as the Zn phase dissolves, so that the phosphate crystal has a deep root. Moreover, since [Al / Zn / Zn 2 Mg ternary eutectic structure] is a fine structure, phosphate crystals are also easily formed in a fine and dense state.
リン酸処理液に含まれるＮｉ，Ｃｏ，Ｆｅ，Ｍｎの含有量が０.００１モル／ｌ以上になると、Ｚｎ相の優先溶解が十分に進行し、根が深く密着性の良好なリン酸塩結晶が生成しやすくなる。しかし、０.１モル／ｌを超える過剰量のＮｉ，Ｃｏ，Ｆｅ，Ｍｎが含まれると、貴な金属又は化合物の置換析出量が多くなりすぎリン酸塩皮膜の耐食性が低下する傾向が伺われる。
溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板をリン酸塩処理するので、めっき層から溶出したＡｌがリン酸塩反応を阻害することが懸念されるが、リン酸塩処理液にフッ化物を添加することにより溶出Ａｌの悪影響を抑制できる。フッ化物としてはフッ化ナトリウム、フッ化カリウム、フッ化水素ナトリウム等があり、フリーのフッ素イオン濃度が３０ｐｐｍ以上でフッ化物の添加効果が顕著になる。連続的な操業を可能とする上では、一定量のフッ化物を連続的にリン酸塩処理液に添加し、フッ素イオン濃度を３０ｐｐｍ以上に維持することが好ましい。
When the content of Ni, Co, Fe, Mn contained in the phosphating solution is 0.001 mol / l or more, the preferential dissolution of the Zn phase proceeds sufficiently, the roots are deep and the adhesiveness is good. Crystals are easily formed. However, if excessive amounts of Ni, Co, Fe, and Mn exceeding 0.1 mol / l are included, the amount of substitutional precipitation of noble metals or compounds increases so that the corrosion resistance of the phosphate film tends to decrease. Is called.
Since the molten Zn-Al-Mg alloy-plated steel sheet is subjected to phosphate treatment, there is a concern that Al eluted from the plating layer may inhibit the phosphate reaction, but adding fluoride to the phosphate treatment solution Thus, the adverse effect of eluted Al can be suppressed. Fluoride includes sodium fluoride, potassium fluoride, sodium hydrogen fluoride and the like, and the effect of adding fluoride becomes remarkable when the free fluorine ion concentration is 30 ppm or more. In order to enable continuous operation, it is preferable that a certain amount of fluoride is continuously added to the phosphating solution to maintain the fluorine ion concentration at 30 ppm or more.
リン酸塩処理は、好ましくは液温４０〜８０℃の範囲で実施される。液温が４０℃に達しない場合、短時間処理ではリン酸塩結晶の析出が不充分となる。逆に、８０℃を超える液温ではリン酸塩処理液の安定性が低下し、スラッジの発生や水分の蒸発が多くなり連続操業での濃度管理が難しくなる。液温が４０〜８０℃のリン酸塩処理液を使用する限り、スプレー処理であれば２〜６秒程度、浸漬処理であれば３〜９秒程度で必要とするリン酸塩皮膜が形成される。処理時間を長く設定しても、リン酸塩の析出が飽和状態になり外観に変化は無く問題は無い。また、めっき層表面に常に新液を供給し、リン酸塩結晶析出時に界面のｐＨ上昇を抑制するとき、処理液の反応性が向上し、根の深いリン酸塩結晶が生成する。 Phosphate treatment is preferably carried out at a liquid temperature in the range of 40 to 80 ° C. When the liquid temperature does not reach 40 ° C., phosphate crystals are not sufficiently precipitated by short-time treatment. On the other hand, when the liquid temperature exceeds 80 ° C., the stability of the phosphating solution decreases, and sludge generation and water evaporation increase, making it difficult to manage the concentration in continuous operation. As long as a phosphating solution having a liquid temperature of 40 to 80 ° C. is used, the necessary phosphate film is formed in about 2 to 6 seconds for spraying and about 3 to 9 seconds for immersion. The Even if the treatment time is set long, there is no problem because the precipitation of phosphate becomes saturated and the appearance does not change. Further, when a new solution is constantly supplied to the surface of the plating layer to suppress an increase in pH at the interface during precipitation of phosphate crystals, the reactivity of the treatment solution is improved, and deeply rooted phosphate crystals are generated.
４０℃以上に加温したリン酸処理液を用いて溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板を処理すると、反応性が高いためめっき層表面にリン酸塩の結晶核が形成されやすくなる。結晶核が多数生成するほど結晶の析出起点が増加し、微細なリン酸塩結晶が析出する。
リン酸処理液を攪拌しながらめっき層に接触させることも、微細なリン酸塩結晶を析出させる有効な方法である。攪拌によりめっき層表面に常に新液が供給され、めっき層の成分が溶解することによるｐＨ上昇が抑えられ、反応性が高位に維持される。また、スプレー方式でリン酸処理液をめっき層表面に供給することによっても、微細なリン酸塩結晶が析出する。
When a molten Zn—Al—Mg alloy-plated steel sheet is treated with a phosphoric acid treatment solution heated to 40 ° C. or higher, phosphate crystal nuclei are easily formed on the surface of the plating layer because of high reactivity. As the number of crystal nuclei is increased, the crystal starting point increases and fine phosphate crystals are precipitated.
Bringing the phosphoric acid treatment solution into contact with the plating layer while stirring is also an effective method for precipitating fine phosphate crystals. By stirring, a new solution is always supplied to the surface of the plating layer, the increase in pH due to dissolution of the components of the plating layer is suppressed, and the reactivity is maintained at a high level. Further, fine phosphate crystals are also deposited by supplying a phosphating solution to the surface of the plating layer by spraying.
リン酸処理液の温度や攪拌強度は、リン酸塩結晶の平均粒径が０.５〜５.０μｍ，平均食込み深さが０.０５μｍ以上となるように調整される。食込み深さは、クロム酸二アンモニウム水溶液を用いてリン酸塩結晶のみを溶解した後、リン酸塩結晶の痕跡を走査型レーザ顕微鏡を用いた観察により測定できる。食込み深さが平均で０.０５μｍ以上になると成形加工時にリン酸塩結晶が十分な密着性を呈するが、５.０μｍを超える食込み深さではめっき層の溶解量が多すぎ処理液の安定性が低下する。 The temperature and stirring strength of the phosphoric acid treatment solution are adjusted so that the average particle diameter of the phosphate crystals is 0.5 to 5.0 μm and the average bite depth is 0.05 μm or more. The biting depth can be measured by observing a trace of the phosphate crystal using a scanning laser microscope after dissolving only the phosphate crystal using an aqueous diammonium chromate solution. When the average penetration depth is 0.05 μm or more, phosphate crystals exhibit sufficient adhesion during molding, but when the penetration depth exceeds 5.0 μm, the amount of dissolution of the plating layer is too high and the stability of the treatment solution Decreases.
リン酸塩結晶は、平均粒径０.５μｍ未満では塗装後の密着性や耐食性に与える影響が小さく、５.０μｍを超える粒径では成形加工時の応力による脆性破壊が懸念される。結晶粒径を調整するため、有機酸，多糖類等の反応抑制剤をリン酸処理液に添加することも可能である。リン酸塩処理時、Ｎｉ，Ｃｏ，Ｆｅ，Ｍｎの析出量をＮｉ，Ｃｏ，Ｆｅで０.０５〜５.０ｍｇ／ｍ2、Ｍｎで０.０５〜３０ｍｇ／ｍ2の範囲に調整している。反応性を高め根の深いリン酸塩結晶を析出させる上で０.０５ｍｇ／ｍ2以上の析出量が好ましいが、Ｎｉ，Ｃｏ，Ｆｅで５.０ｍｇ／ｍ2を超える過剰析出量、Ｍｎで３０ｍｇ／ｍ2を超える過剰析出量は貴な金属又は化合物の多量残存，ひいては耐食性低下の原因となる。 Phosphate crystals have a small effect on adhesion and corrosion resistance after coating when the average particle size is less than 0.5 μm, and brittle fracture due to stress during molding is feared when the particle size exceeds 5.0 μm. In order to adjust the crystal grain size, reaction inhibitors such as organic acids and polysaccharides can be added to the phosphating solution. At the time of phosphating, the precipitation amount of Ni, Co, Fe, and Mn is adjusted to the range of 0.05 to 5.0 mg / m 2 for Ni, Co, and Fe and 0.05 to 30 mg / m 2 for Mn. Yes. A precipitation amount of 0.05 mg / m 2 or more is preferable for increasing the reactivity and precipitating deep-rooted phosphate crystals, but an excessive precipitation amount exceeding 5.0 mg / m 2 for Ni, Co and Fe, and Mn An excessive amount of precipitation exceeding 30 mg / m 2 causes a large amount of noble metal or compound to remain, and thus causes a decrease in corrosion resistance.
リン酸塩皮膜は、めっき層最表面の被覆率が５０面積％以上となるように形成することが好ましい。リン酸塩皮膜３の被覆率は膜厚やリン酸塩結晶２のサイズに影響されるが、５０面積％以上でリン酸塩皮膜３を設けることにより十分な塗膜密着性，塗装後耐食性が得られる。
リン酸塩皮膜３を形成した後、クロムフリー化成処理液で亜鉛系めっき鋼板を処理する。クロムフリー化成処理液自体は、本発明者等が特許第3305703号で紹介した処理液を使用でき、可溶性ハロゲン化物又は酸素酸塩をバルブメタルのソースとして含んでいる。バルブメタルには、Ｔｉ，Ｚｒ，Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｍｏ，Ｗから選ばれた１種又は２種以上の金属がある。たとえば、Ｔｉのフッ化物はＴｉソース，Ｆソースとしても有効であるが、(ＮＨ4)Ｆ等の可溶性フッ化物をクロムフリー化成処理液に別途添加しても良い。Ｔｉ以外のバルブメタルについても同様であるが、以下ではＴｉを例にとって説明する。
The phosphate film is preferably formed so that the coverage of the outermost surface of the plating layer is 50 area% or more. The coverage of the
After forming the
Ｔｉソースとしては、ＫnＴｉＦ6（Ｋ：アルカリ金属又はアルカリ土類金属，ｎ：１又は２），Ｋ2[ＴｉＯ(ＣＯＯ)2]，(ＮＨ4)2ＴｉＦ6，ＴｉＣｌ4，ＴｉＯＳＯ4，Ｔｉ(ＳＯ4)2，Ｔｉ(ＯＨ)4等がある。Ｔｉソースは、化成処理液を塗布した後で乾燥・焼付けするときに所定組成の酸化物又は水酸化物とフッ化物からなる化成皮膜が形成されるように各成分の配合比率が選定される。
The Ti source, K n TiF 6 (K: an alkali metal or alkaline earth metal, n: 1 or 2), K 2 [TiO ( COO) 2], (NH 4) 2 TiF 6,
Ｔｉソースを化成処理液中にイオンとして安定的に維持する上で、キレート作用のある有機酸を添加することが好ましい。有機酸を添加する場合、金属イオンをキレート化して化成処理液を安定させることから、有機酸／金属イオンのモル比が０.０２以上となる添加量に定められる。有機酸としては、酒石酸，タンニン酸，クエン酸，蓚酸，マロン酸，乳酸，酢酸等が挙げられる。なかでも、酒石酸等のオキシカルボン酸やタンニン酸等の多価フェノール類は、処理液を安定化させると共に、フッ化物の自己修復作用を補完する作用も呈し、塗膜密着性の向上にも有効である。
任意成分としての可溶性又は難溶性金属リン酸塩又は複合リン酸塩を化成皮膜に含ませるため、各種金属のオルソリン酸塩やポリリン酸塩を添加してもよい。
In order to stably maintain the Ti source as ions in the chemical conversion solution, it is preferable to add an organic acid having a chelating action. In the case of adding an organic acid, metal ions are chelated to stabilize the chemical conversion solution, so that the organic acid / metal ion molar ratio is set to 0.02 or more. Examples of the organic acid include tartaric acid, tannic acid, citric acid, succinic acid, malonic acid, lactic acid, acetic acid and the like. Among them, polyphenols such as tartaric acid and other oxycarboxylic acids and tannic acid stabilize the treatment liquid and also complement the self-healing action of fluoride, which is also effective in improving coating film adhesion. It is.
In order to include a soluble or poorly soluble metal phosphate or composite phosphate as an optional component in the chemical conversion film, orthophosphates and polyphosphates of various metals may be added.
可溶性金属リン酸塩又は複合リン酸塩は、化成皮膜から溶出して皮膜欠陥部に溶出し、めっき層１と反応して不溶性リン酸塩を析出することによって、チタンフッ化物の自己修復作用を補完する。また、可溶性リン酸塩が解離する際に雰囲気が若干酸性化するため、チタンフッ化物の加水分解、ひいては難溶性チタン酸化物又は水酸化物の生成が促進される。可溶性リン酸塩又は複合リン酸塩を生成する金属にはアルカリ金属，アルカリ土類金属，Ｍｎ等があり、各種金属リン酸塩又は各種金属塩とリン酸，ポリリン酸，リン酸塩として化成処理液に添加される。 Soluble metal phosphate or composite phosphate is eluted from the chemical conversion film and eluted in the film defect, and reacts with the plating layer 1 to precipitate insoluble phosphate, thereby complementing the self-healing action of titanium fluoride. To do. Further, since the atmosphere is slightly acidified when the soluble phosphate is dissociated, the hydrolysis of titanium fluoride, and hence the generation of hardly soluble titanium oxide or hydroxide, is promoted. Metals that produce soluble phosphates or composite phosphates include alkali metals, alkaline earth metals, Mn, etc., various metal phosphates or various metal salts and chemical conversion treatment as phosphoric acid, polyphosphoric acid, phosphate Added to the liquid.
難溶性の金属リン酸塩又は複合リン酸塩は、化成皮膜に分散し、皮膜欠陥を解消すると共に皮膜強度を向上させる。難溶性リン酸塩又は複合リン酸塩を形成する金属にはＡｌ，Ｔｉ，Ｚｒ，Ｈｆ，Ｚｎ等があり、各種金属リン酸塩又は各種金属塩とリン酸，ポリリン酸，リン酸塩として化成処理液に添加される。フッ化物，リン酸塩の自己修復作用だけでは不充分な場合、Ｍｏ，Ｗの可溶性六価酸素酸塩を皮膜中に多量存在させることにより、六価クロムと同様の作用を発現させてめっき層のクラックを補修し、耐食性を向上させることができる。 The hardly soluble metal phosphate or composite phosphate is dispersed in the chemical conversion film to eliminate film defects and improve the film strength. There are Al, Ti, Zr, Hf, Zn, etc. as metals that form poorly soluble phosphates or composite phosphates. Various metal phosphates or various metal salts and phosphoric acid, polyphosphoric acid, and phosphate Added to the treatment solution. When the self-healing action of fluoride and phosphate is not sufficient, the presence of a large amount of Mo and W soluble hexavalent oxyacid salt in the film causes the same action as that of hexavalent chromium to form a plating layer. The cracks can be repaired and the corrosion resistance can be improved.
Ｚｎ，Ｍｎ，Ｍｇ，Ｃａ等の酸化物，水酸化物，リン酸塩，フッ化物，炭酸塩，有機酸塩を添加したリン酸塩処理液を使用すると、処理液中からＺｎ，Ｍｎ，Ｍｇ，Ｃａ等の金属がリン酸塩結晶に取り込まれる。Ｍｎ，Ｍｇ，Ｃａ等の金属成分を含まないリン酸塩処理液で形成されたリン酸塩結晶がリン酸亜鉛単独のホパイト〔Ｚｎ3(ＰＯ4)・4Ｈ2Ｏ〕であるのに対し、Ｍｎ，Ｍｇ，Ｃａ等を取り込んだリン酸塩結晶はめっき層に対する密着性，耐水性に優れた複合リン酸塩となり、耐食性の向上に有効なリン酸塩皮膜を形成する。 When a phosphate treatment liquid to which oxides, hydroxides, phosphates, fluorides, carbonates, organic acid salts such as Zn, Mn, Mg, and Ca are added is used, Zn, Mn, Mg is added from the treatment liquid. , Ca and other metals are incorporated into the phosphate crystals. Whereas the phosphate crystals formed with a phosphate treatment solution that does not contain metal components such as Mn, Mg, and Ca are zinc phosphate alone [Zn 3 (PO 4 ) · 4H 2 O], The phosphate crystal incorporating Mn, Mg, Ca, etc. becomes a composite phosphate having excellent adhesion and water resistance to the plating layer, and forms a phosphate film effective for improving corrosion resistance.
以上のように、ハロゲン化物や酸素酸塩からなるＴｉソース化合物含む処理液をベースとし、必要に応じてイオン安定化作用のある有機酸や、チタンフッ化物の自己修復作用を補完し耐食性を向上させる作用のあるリン酸塩を配合する。
調製された処理液をリン酸塩処理された溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板に塗布すると、フッ素イオンとめっき層１又はＴｉと反応したクロムフリー化成皮膜４がリン酸塩結晶２の間にあるめっき層１の露出表面に優先的に形成される。クロムフリー化成皮膜４は、リン酸塩結晶２のないめっき層１に析出する場合に比較して成長が促進され、自己修復作用のあるフッ化チタンを十分な量含む皮膜になる。
As described above, based on a treatment liquid containing a Ti source compound composed of a halide or an oxyacid salt, if necessary, an organic acid having an ion stabilizing action and a self-repairing action of titanium fluoride are complemented to improve the corrosion resistance. Formulate phosphate with action.
When the prepared treatment liquid is applied to a phosphate-treated hot-dip Zn—Al—Mg alloy-plated steel sheet, the chromium-free
化成皮膜４の膜厚は、クロムフリー化成処理液の濃度で制御できる。ロールコート法でクロムフリー化成処理液を塗布する場合、ロールの表面粗さ，硬さ，塗布時のロール表面のウエット量を調整することによっても膜厚制御可能である。
生成したクロムフリー化成皮膜は、リン酸塩結晶で分断されているので、加工時等に加えられる応力を分散させる作用を呈し、めっき層に対する密着性も低下しない。しかも、めっき層から突出しているリン酸塩結晶の大半が化成皮膜で覆われていないので、その上に設けられる塗膜や接着剤層の密着性，塗装後耐食性等が格段に向上する。
The film thickness of the
Since the produced | generated chromium free chemical conversion film is parted by the phosphate crystal | crystallization, the effect | action which disperse | distributes the stress added at the time of a process, etc. is exhibited, and the adhesiveness with respect to a plating layer does not fall. In addition, since most of the phosphate crystals protruding from the plating layer are not covered with the chemical conversion film, the adhesion of the coating film or adhesive layer provided thereon, the corrosion resistance after coating, and the like are significantly improved.
リン酸塩結晶，クロムフリー化成皮膜でめっき層が被覆された溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板は、クロムフリー化成皮膜で皮膜欠陥が自己修復されるため環境遮断能が高く、溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき本来の高耐食性と相俟って鋼板塗膜密着性，塗装後耐食性が格段に向上している。
クロムフリー化成処理液の塗布量は、十分な耐食性を確保するため０.１ｍｇ／ｍ2以上のチタン付着量となるように調整することが好ましい。
The molten Zn-Al-Mg alloy-plated steel sheet coated with a phosphate crystal and a chromium-free chemical conversion film has a high environmental barrier because the film defects are self-repaired with the chromium-free chemical conversion film, and the molten Zn-Al -Combined with the high corrosion resistance inherent in Mg alloy plating, the steel film coating adhesion and post-coating corrosion resistance are significantly improved.
It is preferable to adjust the coating amount of the chromium-free chemical conversion treatment liquid so that the titanium adhesion amount is 0.1 mg / m 2 or more in order to ensure sufficient corrosion resistance.
形成された化成皮膜を蛍光Ｘ線，ＥＳＣＡ等で元素分析すると、化成皮膜に含まれているＯ及びＦ濃度が測定される。測定値から算出した濃度比Ｆ／Ｏ（原子比率）と耐食性との関係を調査したところ、濃度比Ｆ／Ｏ（原子比率）１／１００以上で皮膜欠陥部を起点とする腐食の発生が大幅に減少した。これは、自己修復作用のあるチタンフッ化物が十分な量で化成皮膜中に含まれていることによるものと推察される。
クロムフリー化成皮膜は、５〜３００ｎｍ程度の厚みをもっていることが好ましい。クロムフリー化成皮膜は、膜厚５ｎｍ以上で十分な環境遮断能を、１０ｎｍ以上で良好な防食能を発現するが、３００ｎｍを超える厚膜に成長すると成形加工時に加わる応力によってクラックが発生しやすくなり、却って耐食性を低下させる。なお、クロムフリー化成皮膜や化成皮膜の厚みは、ＡＥＳやＧＤＳによる深さ方向の元素分析，ＴＥＭ観察等によって測定できる。
When the formed chemical conversion film is subjected to elemental analysis by fluorescent X-ray, ESCA, etc., the O and F concentrations contained in the chemical conversion film are measured. When the relationship between the concentration ratio F / O (atomic ratio) calculated from the measured values and the corrosion resistance was investigated, the occurrence of corrosion starting from the film defects was significantly observed at a concentration ratio F / O (atomic ratio) of 1/100 or more. Decreased. This is presumably due to the fact that a sufficient amount of titanium fluoride having a self-repairing action is contained in the chemical conversion film.
The chromium-free chemical conversion film preferably has a thickness of about 5 to 300 nm. A chromium-free chemical conversion film exhibits sufficient environmental barrier ability at a film thickness of 5 nm or more and good anticorrosion ability at a film thickness of 10 nm or more, but when it grows to a thick film exceeding 300 nm, cracks are likely to occur due to stress applied during molding processing. On the contrary, it reduces the corrosion resistance. The thickness of the chromium-free chemical conversion film or chemical conversion film can be measured by elemental analysis in the depth direction by AES or GDS, TEM observation, or the like.
溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板に塗布したクロムフリー化成処理液を常温で乾燥することもできるが、連続操業を考慮すると８０℃以上に保持して乾燥時間を短縮することが好ましい。ただし、３００℃を超える乾燥温度では、クロムフリー化成皮膜４が厚膜の場合に凝集破壊が生じ耐食性が損なわれる虞がある。
化成皮膜を形成した後、更に耐食性に優れた有機皮膜を形成することもできる。この種の皮膜として、たとえばウレタン系樹脂，エポキシ樹脂，ポリエチレン、ポリプロピレン，エチレン−アクリル酸共重合体等のオレフィン系樹脂，ポリスチレン等のスチレン系樹脂，ポリエステル，或いはこれらの共重合物又は変性物，アクリル系樹脂等の樹脂皮膜を膜厚０.１〜５μｍで化成皮膜の上に設けると、クロメート皮膜を凌駕する高耐食性が得られる。或いは、導電性に優れた樹脂皮膜を化成皮膜の上に設けることにより、潤滑性が改善され、溶接性も付与される。この種の樹脂皮膜としては、たとえば有機樹脂エマルジョンを静電霧化して塗布する方法で形成できる。
Although the chromium-free chemical conversion treatment solution applied to the molten Zn—Al—Mg alloy-plated steel sheet can be dried at room temperature, it is preferable to keep the temperature at 80 ° C. or higher to shorten the drying time in consideration of continuous operation. However, at a drying temperature exceeding 300 ° C., when the chromium-free
After forming the chemical conversion film, an organic film having further excellent corrosion resistance can be formed. As this type of film, for example, urethane resin, epoxy resin, polyethylene, polypropylene, olefin resin such as ethylene-acrylic acid copolymer, styrene resin such as polystyrene, polyester, or a copolymer or modified product thereof, When a resin film such as an acrylic resin is provided on the chemical film with a film thickness of 0.1 to 5 μm, high corrosion resistance surpassing that of the chromate film can be obtained. Alternatively, by providing a resin film having excellent conductivity on the chemical conversion film, lubricity is improved and weldability is also imparted. This type of resin film can be formed by, for example, applying an organic resin emulsion by electrostatic atomization.
原板として、Ａｌ：６.１質量％，Ｍｇ：３.１質量％，Ｚｎ：残部の合金めっき層が片面当り付着量：９２ｇ／ｍ2で形成された板厚：０.８ｍｍの溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板を使用した。合金めっき層を顕微鏡観察すると、微細な〔Ａｌ／Ｚｎ／Ｚｎ2Ｍｇの三元共晶組織〕が７０面積％以上の割合で観察された。 As the original plate, Al: 6.1% by mass, Mg: 3.1% by mass, Zn: the remaining alloy plating layer formed with an adhesion amount per side: 92 g / m 2 : Plate thickness: 0.8 mm Molten Zn— An Al—Mg alloy plated steel sheet was used. When the alloy plating layer was observed with a microscope, fine [Al / Zn / Zn 2 Mg ternary eutectic structure] was observed at a ratio of 70 area% or more.
リン酸塩処理液（表１）を用いて各めっき鋼板をリン酸塩処理した後、クロムフリー化成処理液（表２）を塗布し乾燥することによりリン酸塩皮膜をクロムフリー化成皮膜でシーリングした。リン酸塩処理とクロムフリー化成処理の組合せを表３に、亜鉛系めっき鋼板の表面に形成されたリン酸塩皮膜，クロムフリー化成皮膜を表４に示す。表４中、リン酸塩皮膜の食込み深さは、リン酸塩処理後にクロム酸二アンモニウム水溶液でリン酸塩結晶のみを溶解除去し，リン酸塩結晶の痕跡部を走査型レーザ顕微鏡を用いて観察し、痕跡の深さを２０回繰り返し測定して平均化した値で示す。 After each galvanized steel sheet is phosphated using a phosphating solution (Table 1), the chrome-free conversion coating solution (Table 2) is applied and dried to seal the phosphate coating with a chrome-free conversion coating. did. Table 3 shows combinations of phosphate treatment and chromium-free chemical conversion treatment, and Table 4 shows phosphate coatings and chromium-free chemical conversion coatings formed on the surface of galvanized steel sheets. In Table 4, the depth of penetration of the phosphate film is determined by dissolving and removing only phosphate crystals with a diammonium chromate aqueous solution after phosphate treatment, and using a scanning laser microscope to trace the phosphate crystals. Observed, the depth of the trace is measured 20 times and is shown as an average value.
クロムフリー処理後の亜鉛系めっき鋼板から試験片を切り出し、各種腐食試験に供した。
〔平坦部腐食試験〕
試験片の端面をシールし、JIS Z2371に準拠して３５℃の５％ＮａＣｌ水溶液を試験片表面に噴霧した。塩水噴霧を７２時間又は２４０時間継続した後、試験片表面を観察し白錆発生状況を調査した。試験片表面に占める白錆の面積占有率が５面積％未満を◎，５〜１０面積％を○，１０〜３０面積％を△，３０〜５０面積％を▲，５０面積％以上を×として平坦部耐食性を評価した。
Test pieces were cut out from the zinc-based plated steel sheet after the chromium-free treatment and subjected to various corrosion tests.
[Flat corrosion test]
The end face of the test piece was sealed, and a 5% NaCl aqueous solution at 35 ° C. was sprayed on the test piece surface in accordance with JIS Z2371. After spraying salt water for 72 hours or 240 hours, the surface of the test piece was observed to investigate the occurrence of white rust. The area occupancy ratio of white rust on the surface of the test piece is less than 5 area%, ◎, 5-10 area% is ◯, 10-30 area% is △, 30-50 area% is ▲, and 50 area% or more is x. The flat part corrosion resistance was evaluated.
〔加工部腐食試験〕
リン酸塩皮膜が部分的に損傷を受ける１８０度曲げ加工を施した試験片について，平坦部腐食試験と同じ塩水噴霧を２４時間，１２０時間継続し、加工部に発生した白錆の面積占有率を求めた。面積占有率が５面積％未満を◎，５〜１０面積％を○，１０〜３０面積％を△，３０〜５０面積％を▲，５０面積％以上を×として加工部耐食性を評価した。
[Processed part corrosion test]
The test piece subjected to 180-degree bending work that partially damaged the phosphate coating was subjected to the same salt spray as the flat part corrosion test for 24 hours and 120 hours, and the area occupancy rate of white rust generated in the processed part Asked. The area occupancy was evaluated as corrosion resistance of a processed part, where 占有 is less than 5%, ５〜 is 5-10%, △ is 10-30%, ▲ is 30-50%, and x is 50% or more.
〔塗装後腐食試験〕
化成処理した亜鉛系めっき鋼板をメラミンアルキッド塗装し、膜厚３０μｍの塗膜を形成した。塗膜にクロスカットを入れ、１０００時間の塩水噴霧に供した後、クロスカット部に接着テープを貼り付け瞬時に引き剥がすテープ剥離試験し、塗膜が剥離した幅を腐食幅として測定した。腐食幅が２ｍｍ未満を◎，５ｍｍ未満を○，１０ｍｍ未満を△，１０ｍｍを超える腐食幅を×として塗装後耐食性を評価した。
[Corrosion test after painting]
The galvanized steel sheet subjected to chemical conversion treatment was coated with melamine alkyd to form a coating film having a thickness of 30 μm. After the crosscut was put into the coating film and subjected to salt water spraying for 1000 hours, a tape peeling test was performed in which an adhesive tape was applied to the crosscut portion and peeled off instantaneously, and the width at which the coating film was peeled was measured as the corrosion width. Corrosion resistance after coating was evaluated with ◎ when the corrosion width was less than 2 mm, ◯ when it was less than 5 mm, Δ when it was less than 10 mm, and x when the corrosion width was more than 10 mm.
表５の腐食試験結果にみられるように、リン酸塩処理後にクロムフリー化成処理した溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板は、平坦部耐食性，加工部耐食性，塗装後耐食性の何れにも優れた特性を示した。なかでも、被覆率の高いリン酸塩皮膜とクロムフリー化成皮膜とを組み合わせた場合、加工部耐食性が格段と改善されており、クロムフリー化成皮膜の自己修復作用が発現していることが窺われる。 As can be seen from the corrosion test results in Table 5, the hot-dip Zn-Al-Mg alloy-plated steel sheet that was chromium-free conversion treated after phosphate treatment was excellent in all of the flat part corrosion resistance, processed part corrosion resistance, and post-coating corrosion resistance. The characteristics are shown. In particular, when a phosphate coating with a high coating rate and a chromium-free chemical coating are combined, the corrosion resistance of the processed parts is remarkably improved, and the self-healing action of the chromium-free chemical coating is expressed. .
他方、リン酸塩処理せずにクロムフリー化成皮膜を設けた試験Ｎo.１３，１４や、Ｔｉ（バルブメタル）を含まない試験Ｎo.１５，１６では、平坦部耐食性，塗装後耐食性に劣り、塩水噴霧が長期になるほど平坦部，加工部共に白錆発生が助長された。バルブメタルのフッ化物を含まないクロムフリー化成皮膜を形成した試験Ｎo.１７，１８でも、塩水噴霧が長期になると平坦部に多量の白錆が発生した。リン酸塩処理をクロメート処理でシーリングする従来の化成処理を施した試験Ｎo.１９，２０では、短時間の塩水噴霧によっても加工部に白錆が発生し、平坦部耐食性，塗装後耐食性も十分でなかった。 On the other hand, in tests No. 13 and 14 in which a chromium-free chemical conversion film was provided without phosphating, and in test Nos. 15 and 16 that did not contain Ti (valve metal), the flat portion corrosion resistance and post-coating corrosion resistance were poor. The longer the salt spray, the more the white rust was generated in the flat and processed parts. Even in Test Nos. 17 and 18 in which a chromium-free chemical conversion film containing no fluoride of valve metal was formed, a large amount of white rust was generated on the flat portion when the salt spray was prolonged. In the test No. 19 and 20 where the conventional chemical conversion treatment was applied to seal the phosphate treatment with chromate treatment, white rust was generated in the processed part even with a short salt water spray, and the flat part corrosion resistance and post-coating corrosion resistance were sufficient. It was not.
更に、リン酸塩皮膜，クロムフリー化成皮膜を設けた溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板にエポキシ系接着剤を用いて膜厚：３００μｍのPETフィルムを貼り合わせた。
得られたラミネート鋼板について、ドロービード変形試験（荷重：２００ｋｇｆ）後の引張試験によりフィルムの剥離強度を測定した。めっき層に対するリン酸塩結晶の食込み深さで測定結果を整理したところ、リン酸塩結晶の平均食込み深さが０.０５μｍ以上になると８０Ｎ／２０ｍｍを超える高い剥離強度を示した（図３）。リン酸塩結晶の結晶サイズと剥離強度との関係では、リン酸塩結晶の平均粒径を５.０μｍ以下にすることにより、高い剥離強度でPETフィルムが貼り合わされていることが確認された（図４）。図３，４の結果から、リン酸塩結晶の平均粒径を０.５〜５.０μｍの範囲に、平均食込み深さを０.０５μｍ以上にすることが有効であることが理解できる。
メラミンアルキッド塗料を用い、膜厚：２５μｍの塗膜を加工後の化成処理鋼板に設けた場合でも、同様に平均粒径：０.５〜５.０μｍ，平均食込み深さ：０.０５μｍ以上のリン酸塩結晶が形成されているので、密着性に優れた塗膜が形成された。
Furthermore, a PET film having a film thickness of 300 μm was bonded to a molten Zn—Al—Mg alloy-plated steel sheet provided with a phosphate film and a chromium-free chemical conversion film using an epoxy adhesive.
About the obtained laminated steel plate, the peel strength of the film was measured by a tensile test after a draw bead deformation test (load: 200 kgf). When the measurement results were arranged by the penetration depth of the phosphate crystals with respect to the plating layer, when the average penetration depth of the phosphate crystals was 0.05 μm or more, a high peel strength exceeding 80 N / 20 mm was shown (FIG. 3). . Regarding the relationship between the crystal size of the phosphate crystals and the peel strength, it was confirmed that the PET film was bonded with a high peel strength by setting the average particle size of the phosphate crystals to 5.0 μm or less ( FIG. 4). From the results of FIGS. 3 and 4, it can be understood that it is effective to set the average grain size of phosphate crystals in the range of 0.5 to 5.0 μm and the average bite depth to 0.05 μm or more.
Even when a melamine alkyd paint is used and a coating film having a film thickness of 25 μm is provided on the chemically treated steel sheet after processing, the average particle diameter is similarly 0.5 to 5.0 μm, and the average biting depth is 0.05 μm or more. Since phosphate crystals were formed, a coating film having excellent adhesion was formed.
実施例１と同じ溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき鋼板を原板に用い、表１のＮo.１処理液でリン酸塩処理した。本実施例では、リン酸塩処理に先立つ表面調整やリン酸塩処理時の液温，処理時間等を調整することにより、平均高さを０.５〜５μｍの範囲で変化させたリン酸塩結晶を生成させた。クロムフリー処理には、Ｎo.３の処理液を用い、希釈率，ロールコート条件等を変えることによってリン酸塩皮膜の上に膜厚を変化させたクロムフリー化成皮膜を形成した。 The same molten Zn—Al—Mg alloy-plated steel plate as in Example 1 was used as the original plate, and was phosphated with the No. 1 treatment solution shown in Table 1. In this example, the average height was changed in the range of 0.5 to 5 μm by adjusting the surface adjustment prior to the phosphate treatment, the liquid temperature during the phosphate treatment, the treatment time, and the like. Crystals were formed. In the chromium-free treatment, a treatment solution of No. 3 was used, and a chromium-free chemical conversion film having a changed film thickness was formed on the phosphate film by changing the dilution rate, roll coating conditions, and the like.
作製した化成処理鋼板から試験片を切り出し、次の試験でフィルム接着性を調査した。エポキシ系接着剤を用いてPETフィルムを試験片にラミネートした後、荷重２００kgfのドロービード摺動変形試験後にフィルムの先端を強制的に剥がす引張試験によって剥離強度を測定した。試験結果を図５に示すが、何れのリン酸塩結晶高さにおいても化成皮膜が厚膜化するほど剥離強度が低下する傾向が伺われ、起立するリン酸塩結晶の平均高さに対して１０％以下の厚みで化成皮膜を形成した場合に良好な剥離強度を維持できた。 A test piece was cut out from the produced chemical conversion treated steel sheet, and the film adhesion was investigated by the following test. After laminating a PET film on a test piece using an epoxy adhesive, the peel strength was measured by a tensile test in which the film tip was forcibly peeled after a draw bead sliding deformation test with a load of 200 kgf. Although the test results are shown in FIG. 5, it is observed that the peel strength tends to decrease as the chemical conversion film becomes thicker at any phosphate crystal height, and the average height of the standing phosphate crystals is When the chemical conversion film was formed with a thickness of 10% or less, good peel strength could be maintained.
片面当り付着量が９０ｇ／ｍ2一定でめっき層の組成が異なる複数のＺｎ-Ａｌ-Ｍｇ合金めっき鋼板（板厚：０.８ｍｍ一定）を用意した。合金めっき層を顕微鏡観察すると、何れも微細な〔Ａｌ／Ｚｎ／Ｚｎ2Ｍｇの三元共晶組織〕が８０面積％以上の割合で観察された。
表６のリン酸塩処理液を用いて各めっき鋼板を液温：６０℃，接触時間：５秒でリン酸塩処理した後、表２のNo.４化成処理液を塗布し乾燥することにより、Ｔｉ付着量：５ｍｇ／ｍ2のクロムフリー化成皮膜でリン酸塩皮膜をシーリングした。
A plurality of Zn—Al—Mg alloy-plated steel sheets (plate thickness: constant 0.8 mm) having a constant adhesion amount per side of 90 g / m 2 and different coating layer compositions were prepared. When the alloy plating layer was observed with a microscope, a fine [Al / Zn / Zn 2 Mg ternary eutectic structure] was observed at a ratio of 80 area% or more.
By subjecting each plated steel sheet to phosphate treatment at a liquid temperature of 60 ° C. and a contact time of 5 seconds using the phosphate treatment liquid of Table 6, the No. 4 chemical conversion treatment liquid of Table 2 is applied and dried. The phosphate coating was sealed with a chromium-free chemical conversion coating with a Ti adhesion amount of 5 mg / m 2 .
めっき層の組成及びめっき層表面に形成したリン酸塩皮膜の組合せを表７に示す。
表７中、置換金属析出量は、次の手順で求めた。リン酸塩処理後のめっき鋼板から切り出した１０ｃｍ×１０ｃｍの試験片を室温の二クロム酸アンモニウム水溶液（二クロム酸アンモニウム：２０ｇ／ｌ，濃アンモニウム：４８０ｇ／ｌ）に１５分浸漬してリン酸塩結晶を溶解させた後、試験片を室温の１０％ＨＣｌ水溶液に浸漬してめっき層ごと溶解し、溶解液のＩＣＰ分析結果から置換金属析出量を算出した。また、リン酸塩結晶の食込み深さは、実施例１と同じ方法で測定した。
Table 7 shows the composition of the plating layer and the combination of the phosphate film formed on the surface of the plating layer.
In Table 7, the amount of substitutional metal precipitation was determined by the following procedure. A test piece of 10 cm × 10 cm cut out from the plated steel sheet after the phosphate treatment was immersed in an aqueous solution of ammonium dichromate (ammonium dichromate: 20 g / l, concentrated ammonium: 480 g / l) at room temperature for 15 minutes. After the salt crystals were dissolved, the test piece was immersed in a 10% aqueous HCl solution at room temperature to dissolve the entire plating layer, and the amount of displacement metal deposited was calculated from the ICP analysis result of the solution. Further, the penetration depth of the phosphate crystals was measured by the same method as in Example 1.
クロムフリー処理後のめっき鋼板から試験片を切り出し、実施例１と同じ各種腐食試験に供した。
表８の腐食試験結果にみられるように、各種組成のＺｎ-Ａｌ-Ｍｇ合金めっき鋼板に本発明に従ったリン酸塩処理後、クロムフリー化成処理を施すと、平坦部耐食性，加工部耐食性，塗装後耐食性の何れにも優れた特性を示す塗装鋼板となることが確認される。
A test piece was cut out from the plated steel sheet after the chromium-free treatment and subjected to the same various corrosion tests as in Example 1.
As can be seen from the corrosion test results in Table 8, when the Zn-Al-Mg alloy-plated steel sheet of various compositions is subjected to the phosphate treatment according to the present invention and then subjected to chromium-free chemical conversion treatment, the flat part corrosion resistance and the processed part corrosion resistance are obtained. Thus, it is confirmed that the coated steel sheet exhibits excellent characteristics in both corrosion resistance after coating.
以上に説明したように、めっき層に基部が食い込んでめっき層から起立するリン酸塩結晶をリン酸塩処理で形成した後、自己修復作用のあるクロムフリー化成皮膜でシーリングするとき、加工後においてもリン酸塩皮膜が良好な密着状態を維持する化成処理鋼板が得られる。このリン酸塩皮膜を介して塗膜やラミネートフィルムが設けられるので塗膜密着性，フィルム密着性にも優れ、溶融Ｚｎ-Ａｌ-Ｍｇ合金めっき本来の高耐食性も活かされる。そのため、ユーザ側で製品形状に成形加工して塗装やラミネートする用途に適した鋼材として、外装材，内装材，表装材，車両用鋼板等として使用される。 As explained above, after forming the phosphate crystal rising from the plating layer with the base biting into the plating layer by phosphating, sealing with a self-repairing chromium-free conversion coating, after processing Moreover, the chemical conversion treatment steel plate with which a phosphate membrane | film | coat maintains a favorable contact state is obtained. Since a coating film or a laminate film is provided via this phosphate film, the coating film adhesion and film adhesion are excellent, and the high corrosion resistance inherent to the molten Zn—Al—Mg alloy plating is also utilized. Therefore, it is used as an exterior material, an interior material, a cover material, a steel plate for vehicles, and the like as a steel material suitable for use in painting and laminating by processing into a product shape on the user side.
１：めっき層 ２：リン酸塩結晶 ３：Ｎｉ析出層 ４：クロムフリー化成皮膜 ５：粒状反応生成物 1: Plating layer 2: Phosphate crystal 3: Ni precipitation layer 4: Chromium-free chemical conversion film 5: Granular reaction product
Claims (5)
Ｎｉ，Ｃｏ，Ｆｅ，Ｍｎから選ばれた少なくとも一種を含み、Ｎｉ，Ｃｏ，Ｆｅの合計付着量が０.０５〜５.０ｍｇ／ｍ２ の範囲であり，Ｍｎの付着量が０.０５〜３０ｍｇ／ｍ２ の範囲である析出層，平均粒径：０.５〜５.０μｍのリン酸塩結晶からなるリン酸塩皮膜，バルブメタルの酸化物又は水酸化物とバルブメタルのフッ化物が共存している化成皮膜でめっき層表面が覆われ、
リン酸塩結晶は基部がめっき層に食い込んでめっき層から起立しており、化成皮膜はリン酸塩結晶の間で露出しためっき層又は析出層の上に形成されていることを特徴とする、成形加工後の皮膜密着性に優れた化成処理鋼板。 The base material is a molten Zn—Al—Mg alloy-plated steel sheet in which the ratio of [Al / Zn / Zn 2 Mg ternary eutectic structure] to the outermost surface of the plating layer is 60 area% or more,
It contains at least one selected from Ni, Co, Fe, and Mn, the total adhesion amount of Ni, Co, and Fe is in the range of 0.05 to 5.0 mg / m 2 , and the adhesion amount of Mn is 0.05 to deposit is in the range of 30 mg / m 2, average particle diameter: phosphate coating consisting of phosphate crystals of 0.5 to 5.0 .mu.m, a fluoride of an oxide or hydroxide and a valve metal valve metal is The plating layer surface is covered with the coexisting chemical film,
The phosphate crystal is characterized in that the base part stands up from the plating layer by biting into the plating layer, and the chemical conversion film is formed on the plating layer or the precipitation layer exposed between the phosphate crystals . Chemically treated steel sheet with excellent film adhesion after forming.
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| JP4579715B2 (en) * | 2004-03-08 | 2010-11-10 | 日新製鋼株式会社 | Chemically treated steel sheet with excellent corrosion resistance, coating adhesion, and adhesion |
| JP4753721B2 (en) * | 2006-01-05 | 2011-08-24 | 日新製鋼株式会社 | Galvanized steel sheet with excellent water-resistant adhesion of coating film |
| JP4986538B2 (en) * | 2006-08-21 | 2012-07-25 | 日新製鋼株式会社 | Chemically treated steel plate with excellent corrosion resistance and blackening resistance |
| WO2009145183A1 (en) * | 2008-05-27 | 2009-12-03 | ユケン工業株式会社 | Finishing agent and member having overcoat formed from the finishing agent |
| WO2013160566A1 (en) | 2012-04-25 | 2013-10-31 | Arcelormittal Investigacion Y Desarrollo, S.L. | Method for producing a metal sheet having oiled zn-al-mg coatings, and corresponding metal sheet |
| JP6576689B2 (en) * | 2015-05-27 | 2019-09-18 | Ntn株式会社 | Fastening band for constant velocity universal joint boots |
| JP6964406B2 (en) * | 2016-12-12 | 2021-11-10 | 日本パーカライジング株式会社 | Oxide film remover, oxide film removal method, surface treatment method and manufacturing method of metal material from which the oxide film has been removed |
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