JP2007297692A - Method for producing surface treated steel sheet, and surface treated steel sheet - Google Patents
Method for producing surface treated steel sheet, and surface treated steel sheet Download PDFInfo
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本発明は、自動車、家電、建材用途に最適な表面処理鋼板の製造方法および表面処理鋼板に関し、詳細には、人体、環境に有害な６価クロムを全く含まない環境適応型表面処理鋼板の製造方法および環境適応型表面処理鋼板に関するものである。 TECHNICAL FIELD The present invention relates to a method for producing a surface-treated steel sheet and a surface-treated steel sheet that are most suitable for use in automobiles, home appliances, and building materials. The present invention relates to a method and an environment-adaptive surface-treated steel sheet.
家電、建材、自動車用鋼板としては、従来から、亜鉛系めっき鋼板の表面に、耐食性を向上させる目的で、クロム酸、重クロム酸またはその塩類を主要成分とした処理液によるクロメート処理が施された鋼板が幅広く用いられている。クロメート皮膜は主として難溶性のクロム水酸化物により耐食性や密着性等を発現させたものであり、その皮膜の形成方法としては、電解処理を伴わない塗布法や電解処理法などが挙げられる。 Conventionally, steel sheets for home appliances, building materials, and automobiles have been subjected to chromate treatment on the surface of galvanized steel sheets with a treatment liquid containing chromic acid, dichromic acid or salts thereof as the main component for the purpose of improving corrosion resistance. Steel plates are widely used. The chromate film is one in which corrosion resistance, adhesion, etc. are expressed mainly by a hardly soluble chromium hydroxide, and examples of the method of forming the film include a coating method without electrolytic treatment and an electrolytic treatment method.
また、クロメート処理は公害規制物質である６価クロムを使用しているが、６価クロムはいずれの皮膜形成方法においてクローズドシステムで処理されること、さらには、塗布法ではその上層に形成する有機皮膜によるシーリング作用により、電解法ではカソード電解による６価クロムから３価クロムへの還元反応により、クロメート皮膜中からのクロム溶出はほぼゼロにできること等、実質的には６価クロムによって人体や環境が汚染されることはない。 In addition, the chromate treatment uses hexavalent chromium, which is a pollution-controlling substance. However, hexavalent chromium can be treated with a closed system in any film forming method, and further, an organic layer formed on the upper layer in the coating method. Due to the sealing action of the film, the electrolysis method can reduce the elution of chromium from the chromate film by reducing the hexavalent chromium to trivalent chromium by cathodic electrolysis. Will not be contaminated.
一方で、近年の地球環境問題に対する高まりと共に、従来の作業環境や排水処理を重視した法規制だけではなく環境負荷や環境調和を重視した法規制も制定されつつある。また、製造者を環境貢献度で評価する時代背景もある。このような中で、６価クロムの使用を削減しようとする動きが高まりつつある。 On the other hand, along with the recent increase in global environmental problems, not only conventional laws and regulations that emphasize work environment and wastewater treatment, but also laws and regulations that emphasize environmental load and environmental harmony are being enacted. In addition, there is an era background in which manufacturers are evaluated for their degree of environmental contribution. Under these circumstances, there is a growing trend to reduce the use of hexavalent chromium.
以上のような背景を元に、６価クロムを用いない亜鉛系めっき鋼板の耐食性向上技術として、クロメートフリー技術が数多く提案されている。クロメートフリー皮膜でもクロメート皮膜と同様に難溶性化合物形成が性能発現に必須であり、以下に述べる各種プロセスにおいてもクロメートフリー皮膜形成技術が提案されている。 Based on the above background, many chromate-free techniques have been proposed as techniques for improving the corrosion resistance of galvanized steel sheets that do not use hexavalent chromium. In the case of chromate-free coatings, formation of poorly soluble compounds is essential for performance, as with chromate coatings, and chromate-free coating formation techniques have also been proposed in various processes described below.
例えば、塗布法に関する技術としては、亜鉛系めっき皮膜上に難溶性化合物皮膜を形成させるため、バナジウムを含有した処理液を塗布乾燥する方法が提案されている。特許文献１や特許文献２や特許文献３には、２〜４価のバナジウムとＺｒ、Ｔｉ、Ｍｏ，Ｗ、Ｍｎ、Ｃｅから選ばれる少なくとも１種の金属を含む金属化合物を含有した表面処理剤およびそれを金属材料上で加熱乾燥して形成された皮膜を有する金属材料が提案されている。また、特許文献４には、Ｚｒ化合物とバナジウム化合物とリン酸化合物と樹脂を含有した表面処理剤をＡｌめっき鋼板上で加熱乾燥して形成された皮膜を有するＡｌめっき鋼板が提案されている。 For example, as a technique related to the coating method, a method of applying and drying a treatment solution containing vanadium has been proposed in order to form a poorly soluble compound film on a zinc-based plating film. Patent Document 1, Patent Document 2, and Patent Document 3 include a surface treatment agent containing a metal compound containing divalent to tetravalent vanadium and at least one metal selected from Zr, Ti, Mo, W, Mn, and Ce. A metal material having a film formed by heating and drying it on a metal material has been proposed. Patent Document 4 proposes an Al-plated steel sheet having a film formed by heating and drying a surface treatment agent containing a Zr compound, a vanadium compound, a phosphate compound, and a resin on an Al-plated steel sheet.
例えば、電解法に関する技術としては、特許文献５および特許文献６に、４価のバナジウム化合物の一種以上とｐＨ調整剤としてリン酸化合物を含有した水溶液中で鋼板を電解処理する表面処理鋼板の製造方法が開示されている。
しかしながら、上記従来技術には、以下の問題点がある。
塗布法によるクロメートフリー皮膜形成技術では、電解法では困難な有機樹脂皮膜層の形成やシリカ等の防錆添加剤やワックスの皮膜中への導入が容易であり、潤滑性等の特殊な機能性付与の観点からはメリットがある。しかし、その反面、ロールコーターや乾燥炉、冷却設備を必要とし、設備コストアップは避けられない。
電解法によるクロメートフリー皮膜形成技術では、塗布法にくらべ乾燥温度が低いため、設備コストは低廉化が可能である。しかし、潤滑性等の特殊な機能性付与は困難である。また、酸性溶液との接触あるいはカソード電解によって、亜鉛めっき皮膜表面の酸化物を溶解あるいは還元するため、めっき表面が活性化されてしまい、その表面にクロメートフリー皮膜を形成しても湿潤環境下等でめっき皮膜が酸化され、外観が黒化する現象（黒変現象）が避けられない。例えば、前述の特許文献５および特許文献６に開示されている方法では、亜鉛系めっき皮膜のエッチング効果が著しく高いリン酸化合物をｐＨ調整液として添加しており、電解法（カソード電解）により得られる皮膜では、皮膜形成過程においてめっき皮膜が活性化され、耐黒変性は使用上許容できないレベルにある。すなわち、従来手法での電解法で形成したクロメートフリー皮膜で、耐食性と耐黒変性を両立することは困難であった。
However, the above prior art has the following problems.
With the chromate-free film formation technology by coating method, it is easy to form an organic resin film layer, which is difficult with the electrolytic method, and to introduce antirust additives such as silica and wax into the film, and special functions such as lubricity There is merit from the viewpoint of grant. However, on the other hand, a roll coater, a drying furnace, and cooling equipment are required, and the equipment cost is unavoidable.
In the chromate-free film formation technology by the electrolytic method, the drying temperature is lower than that of the coating method, so that the equipment cost can be reduced. However, it is difficult to impart special functionality such as lubricity. In addition, since the oxide on the surface of the galvanized film is dissolved or reduced by contact with an acidic solution or by cathodic electrolysis, the plated surface is activated, and even if a chromate-free film is formed on the surface, in a wet environment, etc. In this case, the phenomenon that the plating film is oxidized and the appearance turns black (blackening phenomenon) is inevitable. For example, in the methods disclosed in Patent Document 5 and Patent Document 6 described above, a phosphoric acid compound having a remarkably high etching effect on a zinc-based plating film is added as a pH adjusting solution, and obtained by an electrolytic method (cathodic electrolysis). In the obtained film, the plating film is activated in the film formation process, and the blackening resistance is at an unacceptable level in use. That is, it has been difficult to achieve both corrosion resistance and blackening resistance with a chromate-free coating formed by the conventional electrolytic method.
本発明はかかる事情に鑑みてなされたもので、人体、環境に有害な６価クロムを全く含まず、耐食性と耐黒変性を両立した環境適応型表面処理鋼板を製造する方法および環境適応型表面処理鋼板を提供することを目的とする。 The present invention has been made in view of such circumstances, and a method for producing an environment-adaptive surface-treated steel sheet that does not contain any hexavalent chromium harmful to the human body and the environment and has both corrosion resistance and blackening resistance, and an environment-adaptive surface. It aims at providing a treated steel plate.
本発明者らはクロメート処理を施した表面処理鋼板に替わる耐食性と耐黒変性に優れた表面処理鋼板を得るべく研究を重ねた。そして、陰極電解処理時の処理液に着目し検討を進めた。その結果、処理液中に硝酸あるいは硝酸塩を含有させることによって亜鉛系めっき皮膜表面を酸化、不活性化させ、また、４価の価数を有する１種又は２種以上のバナジウム化合物を含有させることによってバナジウム化合物を主成分とするバリア性皮膜を鋼板表面に形成することが可能となることを見出した。
本発明は、このような知見に基づきなされたもので、その特徴は以下のとおりである。
［１］４価の価数を有する１種又は２種以上のバナジウム化合物と、硝酸または硝酸塩を含有する処理液で亜鉛系めっき鋼板を陰極電解処理することを特徴とする表面処理鋼板の製造方法。
［２］前記［１］において、前記処理液には、さらに、Y、Ｌａから選ばれる金属を含む金属化合物を含有することを特徴とする表面処理鋼板の製造方法。
［３］前記［１］または［２］において、前記処理液には前記バナジウム化合物が０．０１〜１．０mol／ｌ、前記硝酸または前記硝酸塩が０．０１〜１．０mol／ｌ含有することを特徴とする表面処理鋼板の製造方法。
［４］前記［２］または［３］において、前記処理液には、Y、Ｌａから選ばれる金属を含む前記金属化合物が０．００１〜０．１mol／ｌ含有することを特徴とする表面処理鋼板の製造方法。
［５］前記［１］〜［４］のいずれかにおいて、ｐＨが１．０〜３．０の処理液で、１〜５０Ａ／ｄｍ２の電流密度、０．５〜１０秒の処理時間で亜鉛系めっき鋼板を陰極電解処理することを特徴とする表面処理鋼板の製造方法。
［６］前記［１］〜［５］のいずれかの方法により製造され、鋼板表面の皮膜付着量が金属バナジウム換算で30〜500mg/m2である表面処理鋼板。
The inventors of the present invention have made researches to obtain a surface-treated steel sheet excellent in corrosion resistance and blackening resistance in place of the surface-treated steel sheet subjected to chromate treatment. Then, the investigation proceeded with attention paid to the treatment liquid during the cathodic electrolysis treatment. As a result, the surface of the zinc plating film is oxidized and inactivated by containing nitric acid or nitrate in the treatment solution, and one or more vanadium compounds having a tetravalent valence are contained. Thus, it was found that a barrier film mainly composed of a vanadium compound can be formed on the surface of a steel sheet.
The present invention has been made based on such findings, and the features thereof are as follows.
[1] A method for producing a surface-treated steel sheet, comprising subjecting a zinc-based plated steel sheet to a cathodic electrolytic treatment with a treatment liquid containing one or more vanadium compounds having a valence of four and nitric acid or nitrate. .
[2] The method for producing a surface-treated steel sheet according to [1], wherein the treatment liquid further contains a metal compound containing a metal selected from Y and La.
[3] In the above [1] or [2], the treatment liquid contains 0.01 to 1.0 mol / l of the vanadium compound and 0.01 to 1.0 mol / l of the nitric acid or the nitrate. A method for producing a surface-treated steel sheet characterized by the following.
[4] In the above [2] or [3], the treatment liquid contains 0.001 to 0.1 mol / l of the metal compound containing a metal selected from Y and La. A method of manufacturing a steel sheet.
[5] In any one of the above [1] to [4], with a treatment liquid having a pH of 1.0 to 3.0, with a current density of 1 to 50 A / dm 2 and a treatment time of 0.5 to 10 seconds. A method for producing a surface-treated steel sheet, comprising subjecting a zinc-based plated steel sheet to cathodic electrolysis.
[6] A surface-treated steel sheet produced by the method of any one of [1] to [5], wherein the coating amount on the steel sheet surface is 30 to 500 mg / m 2 in terms of metal vanadium.
本発明によれば、耐食性と耐黒変性に優れた表面処理鋼板が得られる。また、人体、環境に有害な６価クロムを全く含んでいないため、作業環境の保全性にもすぐれ、優れた性能を有する環境適応型表面処理鋼板を提供することが可能となる。 According to the present invention, a surface-treated steel sheet excellent in corrosion resistance and blackening resistance can be obtained. In addition, since it contains no hexavalent chromium harmful to the human body and the environment, it is possible to provide an environment-adaptive surface-treated steel sheet having excellent performance and excellent work environment maintenance.
本発明は、４価の価数を有する１種又は２種以上のバナジウム化合物と、硝酸または硝酸塩を、またはさらにY、Ｌａから選ばれる金属を含む金属化合物を含有する処理液で亜鉛系めっき鋼板を陰極電解処理することにより、亜鉛系めっき皮膜表面を酸化して不活性化しつつ、バナジウム化合物を主成分とするバリア性皮膜を形成するものである。その結果、耐食性と耐黒変性を両立するクロメートフリー皮膜が鋼板表面に形成され、耐食性と耐黒変性に優れた表面処理鋼板が得られることになる。
以下、本発明の詳細を説明する。
まず、本発明で下地鋼板となる亜鉛系めっき鋼板について説明する。
The present invention relates to a galvanized steel sheet with a treatment liquid containing one or more vanadium compounds having a tetravalent valence and nitric acid or nitrate, or a metal compound further containing a metal selected from Y and La. Is subjected to cathodic electrolysis to form a barrier film mainly composed of a vanadium compound while oxidizing and inactivating the surface of the zinc-based plating film. As a result, a chromate-free film having both corrosion resistance and blackening resistance is formed on the surface of the steel sheet, and a surface-treated steel sheet excellent in corrosion resistance and blackening resistance is obtained.
Details of the present invention will be described below.
First, the zinc-based plated steel sheet that is the base steel sheet in the present invention will be described.
本発明で対象とする亜鉛系めっき鋼板としては、亜鉛めっき鋼板、Ｚｎ−Ｎｉ合金めっき鋼板、Ｚｎ−Ｆｅ合金めっき鋼板（電気めっきおよび合金化溶融亜鉛めっき鋼板）、Ｚｎ−Ｃｒ合金めっき鋼板、Ｚｎ−Ｍｎ合金めっき鋼板、Ｚｎ−Ｃｏ合金めっき鋼板、Ｚｎ−Ｃｏ−Ｃｒ合金めっき鋼板、Ｚｎ−Ｃｒ−Ｎｉ合金めっき鋼板、Ｚｎ−Ｃｒ−Ｆｅ合金めっき鋼板、Ｚｎ−Ａｌ合金めっき鋼板（例えば、Ｚｎ−５％Ａｌ合金めっき鋼板、Ｚｎ−５５％Ａｌ合金めっき鋼板）、Ｚｎ−Ｍｇ合金めっき鋼板、Ｚｎ−Ａｌ−Ｍｇ合金めっき鋼板、さらにはこれらのめっき皮膜中に金属酸化物、ポリマーなどを分散した亜鉛系複合めっき鋼板（例えば、Ｚｎ−ＳｉＯ2分散めっき鋼板）などである。また、上記のようなめっきのうち、同種または異種のものを２層以上めっきした複層めっき鋼板も用いることができる。また、めっき鋼板としては、鋼板面にあらかじめＮｉなどの薄目付けのめっきを施し、その上に上記のような各種めっきを施したものであってもよい。
また、めっきの方法としては、電解法（水溶液中での電解または非水溶媒中での電解）、溶融法、気相法のうち、実施可能ないずれの方法も採用することができる。また、後述するような二層皮膜をめっき皮膜表面に形成した際に皮膜欠陥やムラが生じないようにするために、必要に応じて、あらかじめめっき皮膜表面にアルカリ脱脂、溶剤脱脂、表面調整処理（アルカリ性の表面調整処理、酸性の表面調整処理）等の処理を施しておくことができる。また、使用環境下での黒変（めっき表面の酸化現象の一種）を防止する目的で、必要に応じてあらかじめめっき表面に鉄族金属イオン（Ｎｉイオン，Ｃｏイオン，Ｆｅイオン）を含む酸性またはアルカリ性水溶液による表面調整処理を施しておくこともできる。また電気亜鉛めっき鋼板を下地鋼板として用いる場合には、黒変を防止する目的で電気めっき浴に鉄族金属イオン（Ｎｉイオン，Ｃｏイオン，Ｆｅイオン）を添加し、めっき皮膜中にこれらの金属を１ｐｐｍ以上含有させておくことができる。この場合、めっき皮膜中の鉄族金属濃度の上限については特に限定はしない。
Examples of the zinc-based plated steel sheet to be used in the present invention include a zinc-plated steel sheet, a Zn-Ni alloy-plated steel sheet, a Zn-Fe alloy-plated steel sheet (electroplating and galvannealed steel sheet), a Zn-Cr alloy-plated steel sheet, and Zn. -Mn alloy plated steel sheet, Zn-Co alloy plated steel sheet, Zn-Co-Cr alloy plated steel sheet, Zn-Cr-Ni alloy plated steel sheet, Zn-Cr-Fe alloy plated steel sheet, Zn-Al alloy plated steel sheet (for example, Zn -5% Al alloy-plated steel sheet, Zn-55% Al alloy-plated steel sheet), Zn-Mg alloy-plated steel sheet, Zn-Al-Mg alloy-plated steel sheet, and metal oxides, polymers, etc. dispersed in these plating films Zinc-based composite plated steel sheet (for example, Zn—SiO 2 dispersion plated steel sheet). In addition, among the above-described plating, a multilayer plated steel sheet in which two or more layers of the same kind or different kinds are plated can be used. Moreover, as a plated steel plate, the steel plate surface may be pre-plated with light-weight plating such as Ni and the above-described various plating may be performed thereon.
In addition, as a plating method, any feasible method among an electrolytic method (electrolysis in an aqueous solution or electrolysis in a non-aqueous solvent), a melting method, and a gas phase method can be employed. In addition, in order to prevent film defects and unevenness when a two-layer film as described later is formed on the surface of the plating film, alkali degreasing, solvent degreasing, and surface conditioning treatment are performed on the surface of the plating film as necessary. (Alkaline surface conditioning treatment, acidic surface conditioning treatment) or the like can be performed. In addition, for the purpose of preventing blackening (a kind of oxidation phenomenon on the plating surface) under the usage environment, an acidic or iron group metal ion (Ni ion, Co ion, Fe ion) is previously contained on the plating surface as necessary. Surface adjustment treatment with an alkaline aqueous solution can also be performed. When electrogalvanized steel sheet is used as the base steel sheet, iron group metal ions (Ni ions, Co ions, Fe ions) are added to the electroplating bath for the purpose of preventing blackening, and these metals are included in the plating film. Can be contained in an amount of 1 ppm or more. In this case, the upper limit of the iron group metal concentration in the plating film is not particularly limited.
以上の亜鉛系めっき鋼板を本発明では陰極電解処理する。この時の処理液は４価の価数を有する１種又は２種以上のバナジウム化合物と、硝酸または硝酸塩を含有するものとする。さらには、Y、Ｌａから選ばれる金属を含む金属化合物を含有することが好ましい。これは本発明の最も重要な要件である。 In the present invention, the above zinc-based plated steel sheet is subjected to cathodic electrolytic treatment. The treatment solution at this time contains one or more vanadium compounds having a tetravalent valence and nitric acid or nitrate. Furthermore, it is preferable to contain a metal compound containing a metal selected from Y and La. This is the most important requirement of the present invention.
次に前記処理液について、説明する。
４価の価数を有する１種又は２種以上のバナジウム化合物としては、バナジウムの酸化物、水酸化物、硫化物、硫酸物、炭酸物、ハロゲン化物、窒化物、フッ化物、炭化物、シアン化物およびこれらの塩などが挙げられる。また、５価のバナジウム化合物にメタノール等のアルコール類、ホルムアルデヒド等のアルデヒド化合物、酒石酸等の有機酸、グルコース等の単糖類、ショ糖等の多糖類などを添加して還元した４価のバナジウム化合物も本発明では用いることができる。このようにバナジウムの供給源は特別な制約はなく、これらの内１種または２種以上を混合して用いる事ができる。中でも、酸化硫酸バナジウムや５酸化バナジウムの還元物は耐食性と耐黒変性の両立が容易であり、また水に易溶であるため好ましい。以上のような４価の価数を有する１種又は２種以上のバナジウム化合物を含有する処理液を亜鉛系めっき鋼板に接触させたり、亜鉛系めっき鋼板を電解処理させると、亜鉛系めっき鋼板の界面ｐＨが上昇し、バリア性の高い４価のバナジウム化合物を主成分とする皮膜が形成され、高度の耐食性が発揮されることになる。
Next, the processing liquid will be described.
Examples of one or more vanadium compounds having a tetravalent valence include vanadium oxides, hydroxides, sulfides, sulfates, carbonates, halides, nitrides, fluorides, carbides, and cyanides. And salts thereof. A tetravalent vanadium compound reduced by adding an alcohol such as methanol, an aldehyde compound such as formaldehyde, an organic acid such as tartaric acid, a monosaccharide such as glucose, a polysaccharide such as sucrose to the pentavalent vanadium compound. Can also be used in the present invention. Thus, the supply source of vanadium is not particularly limited, and one or more of these can be mixed and used. Among these, a reduced product of vanadium oxide sulfate or vanadium pentoxide is preferable because it is easy to achieve both corrosion resistance and blackening resistance and is easily soluble in water. When a treatment liquid containing one or more vanadium compounds having a tetravalent valence as described above is brought into contact with a zinc-based plated steel sheet or an electrolytic treatment of a zinc-based plated steel sheet, The interface pH is increased, and a film mainly composed of a tetravalent vanadium compound having a high barrier property is formed, and a high degree of corrosion resistance is exhibited.
本発明では処理液中に４価のバナジウム化合物に加え、硝酸または硝酸塩を含有する。処理液に硝酸または硝酸塩を添加して亜鉛系めっき鋼板を電解処理する事により、めっき皮膜表面が酸化し、耐黒変性が著しく改善し向上する。特に電解法では水素発生反応（２Ｈ＋＋２ｅ− → Ｈ２）だけでなく、硝酸イオンの還元反応（ＮＯ３ −＋Ｈ２Ｏ＋２ｅ− → ＮＯ２ −＋２ＯＨ−）も起こり、効果的に亜鉛系めっき鋼板の界面ｐＨを上昇させ、硝酸あるいは硝酸塩が無添加の場合に比べ同一電気量で緻密かつ高付着量の皮膜を得ることが可能となる。
硝酸塩としては、特に限定しない。水溶性であり、かつ、耐食性や耐黒変性を著しく劣化させるものでなければよい。例えば、硝酸Ｍｇ、硝酸Ｍｎ、硝酸Ａｌ、硝酸Ｃａなどが挙げられる。
In the present invention, the treatment liquid contains nitric acid or nitrate in addition to the tetravalent vanadium compound. By adding nitric acid or nitrate to the treatment solution and subjecting the zinc-based plated steel sheet to electrolytic treatment, the surface of the plating film is oxidized, and the blackening resistance is remarkably improved and improved. In particular, in the electrolytic method, not only hydrogen generation reaction (2H + + 2e − → H 2 ) but also nitrate ion reduction reaction (NO 3 − + H 2 O + 2e − → NO 2 − + 2OH − ) occurs, and the galvanized steel sheet is effectively obtained. It is possible to obtain a dense and highly adhered film with the same amount of electricity compared to when no nitric acid or nitrate is added.
The nitrate is not particularly limited. It does not have to be water-soluble and does not significantly deteriorate the corrosion resistance and blackening resistance. Examples thereof include Mg nitrate, Mn nitrate, Al nitrate, and Ca nitrate.
さらに、本発明では、上記４価のバナジウム化合物、硝酸または硝酸塩に加え、Y、Ｌａから選ばれる金属を含む金属化合物を含有することが好ましい。Y、Ｌａから選ばれる金属を含む金属化合物を含有する事により、耐黒変性が一層向上する。この耐黒変性向上メカニズムは明確では無いが、ＹあるいはＬａは酸素親和力が高いため、４価のバナジウム化合物との共析時に容易に安定な酸化物を形成し、湿潤環境下での亜鉛めっき皮膜の酸化を抑制すると考えられる。
Y、Ｌａから選ばれる金属を含む金属化合物としては、水溶性であれば特に限定しない。中でも、前述の理由から硝酸塩が特に好ましい。
Furthermore, in this invention, it is preferable to contain the metal compound containing the metal chosen from Y and La in addition to the said tetravalent vanadium compound, nitric acid, or nitrate. By containing a metal compound containing a metal selected from Y and La, blackening resistance is further improved. Although the mechanism for improving blackening resistance is not clear, Y or La has a high oxygen affinity, so it easily forms a stable oxide when co-deposited with a tetravalent vanadium compound, and galvanized film in a humid environment. It is thought to suppress the oxidation of.
The metal compound containing a metal selected from Y and La is not particularly limited as long as it is water-soluble. Among them, nitrate is particularly preferable for the above-described reason.
また、必要に応じて防錆添加剤、酸化物ゾルを添加することもできる。また、反応性制御の観点から、酸性物質としてフッ酸等の無機酸及びその塩やカルボン酸等の有機酸及びその塩、アルカリ性物質としてアンモニア水、水酸化ナトリウムなどの添加も可能である。また、密着性改善の観点からシランカップリング剤などの添加は支障がない限り可能であり、これらの添加を全て否定するものではない。 Moreover, an antirust additive and oxide sol can also be added as needed. From the viewpoint of reactivity control, inorganic acids such as hydrofluoric acid and salts thereof, organic acids such as carboxylic acids and salts thereof as acidic substances, and aqueous ammonia and sodium hydroxide can be added as alkaline substances. Moreover, addition of a silane coupling agent etc. is possible from a viewpoint of adhesive improvement, as long as there is no hindrance, and all these additions are not denied.
なお、処理液中の上記４価のバナジウム化合物、硝酸または硝酸塩の濃度は、各々0.01〜1.0mol／ｌが好ましい。また、Y、Ｌａから選ばれる金属は、塩等の化合物として、0.001〜0.1mol／ｌが好ましい。いずれの成分も下限値未満では、十分な付着量を得ることが出来ない。一方、上限値超では、亜鉛めっき鋼板上に付着して系外に持ち出されてしまう液量がコスト的に無視できなくなり、経済性の点から好ましくない。
また、処理液のｐＨとしては処理液安定性の理由から1.0〜3.0が好ましい。
The concentration of the tetravalent vanadium compound, nitric acid or nitrate in the treatment liquid is preferably 0.01 to 1.0 mol / l. The metal selected from Y and La is preferably 0.001 to 0.1 mol / l as a compound such as a salt. If any component is less than the lower limit, a sufficient amount of adhesion cannot be obtained. On the other hand, if it exceeds the upper limit, the amount of liquid that adheres to the galvanized steel sheet and is taken out of the system cannot be ignored in terms of cost, which is not preferable from the viewpoint of economy.
Further, the pH of the treatment liquid is preferably 1.0 to 3.0 for reasons of treatment liquid stability.
以上の処理液を用いて、亜鉛系めっき鋼板を陰極電解処理する。電解処理では電流密度は１〜５０Ａ／ｄｍ２とすることが好ましい。１Ａ／ｄｍ２未満では皮膜形成時間に時間を要し、短時間での製造には不利である。一方、５０Ａ／ｄｍ２超では、外観異常を招く。
処理時間は0.5〜10秒が好ましい。0.5秒未満では所定の皮膜付着量を得るために高電流密度での電解となり外観異常を招く。一方、10秒超えでは、形成した皮膜の溶解も平行して起こり不経済である。
Using the above treatment liquid, the galvanized steel sheet is subjected to cathodic electrolytic treatment. The current density in the electrolytic process is preferably set to 1~50A / dm 2. If it is less than 1 A / dm 2, it takes time to form the film, which is disadvantageous for production in a short time. On the other hand, if it exceeds 50 A / dm 2 , an appearance abnormality will be caused.
The treatment time is preferably 0.5 to 10 seconds. If the time is less than 0.5 seconds, electrolysis is performed at a high current density in order to obtain a predetermined coating amount, resulting in an appearance abnormality. On the other hand, if it exceeds 10 seconds, dissolution of the formed film occurs in parallel and is uneconomical.
電解処理後、水洗して電解液を除去後、乾燥することにより皮膜を得る。
本発明によって得られる皮膜は優れた耐食性と耐黒変性を付与するものであり、皮膜付着量が金属バナジウム換算で30〜500mg/m2が好ましい。30mg/m2未満では十分な耐食性が得られない。一方、500mg/m2超えでは、外観異常や皮膜密着性の低下を招く。
また、さらなる性能向上や潤滑性等の機能性付与の観点から、上層に有機樹脂皮膜を形成してもよい。有機樹脂としては、特に限定はなく、アクリル樹脂、ウレタン樹脂、エポキシ樹脂、フェノール樹脂が挙げられ、防錆添加剤、酸化物ゾル、潤滑剤を混合してもよい。有機樹脂皮膜の塗布方法としては、連続的かつ均一な付着が可能な方法を適用する。このような方法として、スプレー塗布を行い、ロール絞りあるいは気体絞りにより付着量を調整する方法、あるいはロールコーターにより塗布する方法がある。塗布後の乾燥方法については、目標温度、加熱時間等を考慮し選択すればよく、熱風炉、誘導加熱炉等の加熱方法が挙げられる。乾燥炉にて加熱塗布方法については特に規定するものではなく、本発明の効果を満足できる範囲で均一な塗布が行える方法であればよい。
After the electrolytic treatment, the membrane is washed with water to remove the electrolytic solution and then dried to obtain a film.
The film obtained by the present invention imparts excellent corrosion resistance and blackening resistance, and the film adhesion amount is preferably 30 to 500 mg / m 2 in terms of metal vanadium. If it is less than 30 mg / m 2 , sufficient corrosion resistance cannot be obtained. On the other hand, if it exceeds 500 mg / m 2 , an appearance abnormality and a decrease in film adhesion will be caused.
Moreover, you may form an organic resin film in an upper layer from a viewpoint of functional addition, such as the further performance improvement and lubricity. There is no limitation in particular as organic resin, An acrylic resin, a urethane resin, an epoxy resin, and a phenol resin are mentioned, You may mix an antirust additive, oxide sol, and a lubrication agent. As a method for applying the organic resin film, a method capable of continuous and uniform adhesion is applied. As such a method, there is a method of performing spray coating and adjusting the amount of adhesion by roll squeezing or gas squeezing, or a method of coating by a roll coater. About the drying method after application | coating, what is necessary is just to select in consideration of target temperature, heating time, etc. Heating methods, such as a hot air furnace and an induction heating furnace, are mentioned. The method for heat application in the drying furnace is not particularly defined as long as it is a method capable of performing uniform application within a range in which the effects of the present invention can be satisfied.
評価材（表面処理鋼板）の作製
電気亜鉛めっき鋼板（片面当たりの亜鉛付着量20g/m2）を表１に示す電解液組成、電解条件にて陰極電解し、評価材を作製した。なお、電解液温度は５０℃に制御し、アノードには酸化イリジウム電極を使用した。
以上から得られた評価材に対し、下記に示す方法にて耐食性および耐黒変性を測定し評価を行った。得られた結果を、電解条件と併せて表1に示す。
（１）耐食性
端部と裏面をテープシールした供試材をＪＩＳ Ｚ ２３７１の塩水噴霧試験を行った後、表面を目視観察し白錆発生面積率が５％となる試験時間を測定した。評価基準は以下の通りである。
○ ： ７２時間以上
△ ： ２４時間以上７２時間未満
× ： ２４時間未満
（２）耐黒変性
供試材を温度８０℃、相対湿度９５％ＲＨ雰囲気制御された恒温恒湿機に２４時間静置し、白色度（Ｌ値）変化をΔＬ（試験前のＬ値−試験後のＬ値）で算出した。評価基準は以下の通りである。なお、Ｌ値はＪＩＳ Ｚ ８７３０色差表示方法のハンターの色素式における明度指数を用いた。
◎ ： ΔＬ≧−２．０
○ ： −２．０＞ΔＬ≧−４.０
△ ： −４．０＞ΔＬ≧−１０.０
× ： −１０．０＞ΔＬ
Preparation of Evaluation Material (Surface-treated Steel Sheet) An electrogalvanized steel sheet (zinc adhesion amount per side of 20 g / m 2 ) was cathodic electrolyzed with the electrolytic solution composition and electrolysis conditions shown in Table 1 to prepare an evaluation material. The electrolyte temperature was controlled at 50 ° C., and an iridium oxide electrode was used for the anode.
The evaluation materials obtained as described above were evaluated by measuring corrosion resistance and blackening resistance by the following methods. The obtained results are shown in Table 1 together with the electrolysis conditions.
(1) After performing the salt spray test of JIS Z 2371 for the test material having the corrosion-resistant end portion and the back surface tape-sealed, the surface was visually observed to measure the test time when the white rust generation area ratio was 5%. The evaluation criteria are as follows.
○: 72 hours or more Δ: 24 hours or more and less than 72 hours ×: Less than 24 hours (2) The black-denatured specimen was left in a constant temperature and humidity chamber controlled at a temperature of 80 ° C. and a relative humidity of 95% RH for 24 hours. The change in whiteness (L value) was calculated by ΔL (L value before test-L value after test). The evaluation criteria are as follows. In addition, the L value used the brightness index in Hunter's pigment formula of JIS Z 8730 color difference display method.
A: ΔL ≧ −2.0
○: −2.0> ΔL ≧ −4.0
Δ: −4.0> ΔL ≧ −10.0
×: −10.0> ΔL
表１より、本発明例においては、耐食性、耐黒変性のいずれも優れていることがわかる。特に、Y、Ｌａから選ばれる金属を含む金属化合物を処理液に含有する本発明例では、一層優れた耐黒変性を有している。
一方、処理液中に硝酸または硝酸塩を含有しない比較例では、耐食性、耐黒変性のいずれも劣り、特に耐食性が劣っている。
Table 1 shows that both the corrosion resistance and blackening resistance are excellent in the examples of the present invention. In particular, the examples of the present invention in which a metal compound containing a metal selected from Y and La is contained in the treatment liquid have further excellent blackening resistance.
On the other hand, in the comparative example in which the treatment liquid does not contain nitric acid or nitrate, both the corrosion resistance and blackening resistance are inferior, and particularly the corrosion resistance is inferior.
本発明の表面処理鋼板は耐食性、耐黒変性に優れ、また、６価クロムを全く含まずに製造される。そのため家電製品、自動車、建材等の広範な用途での使用が可能となる。 The surface-treated steel sheet of the present invention is excellent in corrosion resistance and blackening resistance, and is produced without any hexavalent chromium. Therefore, it can be used in a wide range of applications such as home appliances, automobiles, and building materials.
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