JP2004338236A

JP2004338236A - Surface treated weather-resistant steel material, surface treating agent for weather-resistant steel material and manufacturing method of surface treated weather-resistant steel material

Info

Publication number: JP2004338236A
Application number: JP2003137730A
Authority: JP
Inventors: Tomoyoshi Konishi; 知義小西; Toshiyuki Kitamura; 俊行北村; Yoshiyuki Harada; 佳幸原田; Akihiro Miyasaka; 明博宮坂
Original assignee: Nihon Parkerizing Co Ltd; Nippon Steel Corp
Current assignee: Nihon Parkerizing Co Ltd; Nippon Steel Corp
Priority date: 2003-05-15
Filing date: 2003-05-15
Publication date: 2004-12-02

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treated weather-resistant steel material having a resin coat which facilitates formation of protective rust on the surface of weather-resistant steel used outdoors, while suppressing occurrence of flow rust till the protective rust is formed, a surface treating agent therefor and a manufacturing method thereof. <P>SOLUTION: The surface treating agent containing a resin, a phosphoric acid compound and a pigment is applied at normal temperatures on at least one surface of a base constituted of a weather-resistant steel material and it is dried at normal temperatures or by heating at an ambient temperature up to 200°C and formed into the resin coat. The total content of the phosphoric acid compound and the pigment in this coat is controlled to be 40-95 mass%, the content of the phosphoric acid compound to be 3-40 mass%, the thickness to be 2-100 μm and the water vapor permeability at 20°C to be 1,000-5,000 g/m<SP>2</SP>24h. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、耐候性鋼材からなる基体の表面に、防食保護層となる保護性錆の形成を促進し、かつ長期に渡って流れ錆を抑制する樹脂系皮膜を具備していることを特徴とする景観に優れる表面処理耐候性鋼材、耐候性鋼材用表面処理剤、および表面処理耐候性鋼材の製造方法に関するものである。
【０００２】
【従来の技術】
Ｐ，Ｃｕ，Ｃｒ，Ｎｉ，Ｓｉ，Ｍｏ，Ｍｎ等の中から選ばれた一種、または二種以上の元素を合金用元素としてを少量含む鋼材は、大気中における腐食が少なく、耐候性鋼として知られている。すなわち、この耐候性鋼材は、大気中に暴露されると、表面に緻密で保護性のある錆（以下、保護性錆）層が形成され、鋼材自体の腐食が抑制される。
【０００３】
しかし、保護性錆層が形成されるまでの初期段階、通常、大気中に暴露された直後から３年間程度の期間内には、鋼材表面に赤錆や黄錆などの浮錆や流れ錆が生成することがあり、これは外観上好ましくないことである。このような浮錆や流れ錆を防止するために、従来から各種の技術が提案されている。例えば、特公昭５３−２２５３０号公報（特許文献１）には、Ｆｅ_３Ｏ_４＋Ｆｅ_２Ｏ_３が５〜５０％、りん酸が０．０１〜５％、Ｐｂ，Ｎｉ，Ｃｕ，Ｐ，Ｚｎ，Ｃｒ等の単体もしくは化合物を０．０１〜１０％、ブチラール樹脂、およびブチラール樹脂と相溶性を有する樹脂３〜３０％、残部溶剤よりなる混合処理液を、鋼材表面に塗布する技術が提案されている。また特公昭５６−３３９９１号公報（特許文献２）には、前記保護膜層の上に、さらに耐候性を有する皮膜を形成する処理液を塗布する技術が提案されている。上記技術は、保護性錆層が形成されるまでの初期段階における赤錆や黄錆などの浮錆や流れ錆の発生を防止しながら、上記混合処理液又は処理液を塗布していない裸の鋼材に比較して、保護性錆層を非常にゆっくりと形成する技術である。
【０００４】
これに対し保護性錆層の形成を促進する方法としては、例えば下記の技術が提案されている。すなわち、特許２６６６６７３号公報（特許文献３）には、硫酸クロムおよび硫酸銅のうちの少なくとも一方を、合計量で１〜６５質量％含む有機樹脂塗料により、５〜１５０μｍの乾燥厚をもって被覆されていることを特徴とする耐候性に優れる表面処理鋼材が提案されている。上記公報の詳細な説明によれば、上記技術により、鉄イオンの流出を防止し、かつ鉄イオンのα−ＦｅＯＯＨへの変換を促進し、以後の大気腐食環境中で形成される保護性錆層の形成、およびすでに形成されている錆層の保護性錆層への変換を、早期に、しかも流れ錆等を発生させることなく促進し得るとしている。しかしながら、この表面処理鋼材においては処理皮膜の風化による斑や、さらには添加される溶出性の硫酸塩により外観斑を生ずる可能性があり、美観の点で改善の余地がある。
【０００５】
上記のものとは別の保護性錆の形成を促進する方法として、特開２００１−８１５７１号公報（特許文献４）には、鉄イオンに対し捕捉沈着作用を有するアニオンと対カチオンからなる、少なくとも１種以上の塩、およびマイナスの固定電荷を有する樹脂組成物の硬化皮膜が表面に形成された鋼材であって、更にその硬化皮膜の４０℃における水蒸気透過率が１０〜１０００ｇ／ｍ^２・ｄａｙであることを特徴とする錆安定化処理鋼材が提案されている。しかしこの処理技術は、外観上における皮膜のフクレや剥離が改善されているが、処理皮膜が風化損耗するまで鋼材表面に存在するために、時間の経過に伴い色相変化が大きく外観斑も存在する。
【０００６】
本発明者らは、特開２００２−１２９３５５号公報において、保護性錆の形成を促進する方法として、耐候性鋼材からなる基体と、この基体の少なくとも１表面上に形成され、樹脂、りん酸化合物及び顔料を含み、かつ２〜１００μｍの厚さを有する樹脂皮膜とを含み、前記樹脂がカルボキシル基を有する重合体を含み、かつその乾燥皮膜の赤外吸収スペクトルが１５００〜１８００ｃｍ^−１の範囲内に少なくとも１個の吸収ピークを有することを特徴とする表面処理耐候性鋼を開示した。この技術は、保護性錆が形成されるまでの初期段階における流れ錆の発生を抑制し、保護性錆の形成を促進するが、外観斑抑制を十分に考慮した皮膜設計とはなっておらず、暴露環境によっては経時で外観斑を発生する場合があった。
上記のように、耐候性鋼の保護性錆の形成を促進するタイプの従来の錆安定化処理では、様々な要因によって生じる外観斑を少なくするという点において、必ずしも十分ではない。
【０００７】
【特許文献１】
特公昭５３−２２５３０号公報、第１頁請求項１，２及び第３〜４頁
実施例
【特許文献２】
特公昭５６−３３９９１号公報、第１頁請求項１，２及び第３〜４頁
実施例
【特許文献３】
特許第２６６６６７３号公報、第１頁請求項１，２及び第３〜７頁実
施例
【特許文献４】
特開２００１−８１５７１号公報、第２頁請求項１〜５及び第５〜８
頁実施例
【０００８】
【発明が解決しようとする課題】
本発明は、耐候性鋼表面に保護性錆が形成されるまでの流れ錆の発生を少なくし、かつ保護性錆の形成を促進するとともに、外観斑を少なくして景観にも優れた表面処理耐候性鋼材、並びにこの耐候性鋼材を得るための表面処理剤、及び表面処理耐候性鋼材の製造方法を提供することを目的とするものである。
【０００９】
【課題を解決するための手段】
本発明の表面処理耐候性鋼材は、耐候性鋼材からなる基材と、その少なくとも１面上に形成され、樹脂と、りん酸化合物と、顔料とを含む樹脂系皮膜とを含み、
前記樹脂系皮膜の総合計質量に対し、前記りん酸化合物と顔料との合計含有量が４０〜９５質量％であり、かつ前記りん酸化合物の含有量が３〜４０質量％であり、かつ、
前記樹脂系皮膜の厚さが、２〜１００μｍであって、その２０℃における水蒸気透過率が１０００〜５０００ｇ／ｍ^２・２４ｈである
ことを特徴とするものである。
本発明の表面処理耐候性鋼材において、前記樹脂が、アクリル系樹脂、アルキッド系樹脂、エポキシ系樹脂、ウレタン系樹脂、ポリエステル系樹脂、エポキシポリエステル系樹脂、酢酸ビニル系樹脂、スチレン−ブタジエン共重合体系樹脂、及びアクリル変性エポキシ系樹脂から選ばれることが好ましい。
本発明の表面処理耐候性鋼材において、前記りん酸化合物が、りん酸亜鉛、りん酸カルシウム、りん酸マグネシウム、縮合りん酸塩から選ばれることが好ましい。
本発明の表面処理耐候性鋼材において、前記顔料が、酸化鉄、カーボンブラック、有機顔料、二酸化チタン、タルク、沈降性硫酸バリウム、カオリンクレー、炭酸カルシウム、アルミナ、シリカ粉、石膏粉、バナジウム化合物、モリブデン化合物、硝酸化合物、及びマンガン化合物から選ばれることが好ましい。
本発明の表面処理耐候性鋼材において、屋外において使用されたとき、前記樹脂系皮膜の上下に錆が生成し、この錆と、前記樹脂系皮膜が、複合一体化して、前記鋼材基体表面に錆−樹脂系皮膜複合一体化層が形成被覆されていることが好ましい。
本発明の耐候性鋼材用表面処理剤は、樹脂と、りん酸化合物と、顔料とを含む表面処理剤であって、この表面処理剤の乾燥総合計質量に対し、前記りん酸化合物と顔料との合計含有量比率が４０〜９５質量％であり、かつ前記りん酸化合物の含有量比率が３〜４０質量％であることを特徴とするものである。
本発明の表面処理耐候性鋼材の製造方法は、耐候性鋼材からなる基材の少なくとも一表面上に、請求項６に記載の表面処理剤を含む塗工液を、乾燥膜厚が２〜１００μｍになるように常温で塗布し、これを常温において、或は２００℃以下の雰囲気温度において加熱乾燥して、１０００〜５０００ｇ／ｍ^２・２４ｈの水蒸気透過度を有する樹脂系皮膜を形成することを特徴とするものである。
【００１０】
【発明の実施の形態】
本発明の表面処理耐候性鋼材において、その基体上に形成される樹脂系皮膜の目的は、（１）鋼材上に保護性錆の生成を促進すること、（２）流れ錆の生成を抑制すること、および（３）外観斑の無い均一な錆外観を呈する表面処理耐候性鋼材を得ること、の３要求を同時に満足する事にある。以下、これら３要求を同時に解決するに至った本発明の皮膜設計について、各項ごとに説明する。
【００１１】
要求（１）〜（３）を達成するために、耐候性鋼の表面に樹脂とりん酸化合物と顔料とを含む樹脂系皮膜を形成しながら、錆の生成を阻害しないように、水蒸気透過度の大きな皮膜構造とする。要求される皮膜の性質としては、厚さが２〜１００μｍであり、かつ、ＪＩＳＫ−５４００に記載の手法に従って、温度２０±０．５℃の相対湿度９０±２％に保たれた空気中で測定された水蒸気透過度が１０００〜５０００ｇ／ｍ^２・２４ｈであることであり、より好ましくは、１５００〜４０００ｇ／ｍ^２・２４ｈである。水蒸気透過率が１０００ｇ／ｍ^２・２４ｈ未満の場合には、樹脂系皮膜の水及び酸素の透過性が過小になり、鋼素地からの腐食による鉄イオンの溶出が遅くなるため、保護性錆形成速度が十分ではない。また水蒸気透過率が５０００ｇ／ｍ^２・２４ｈを超える場合は、樹脂系皮膜に空隙が大きく、かつ多数になり、水及び酸素の透過性が過大となって腐食反応の進行が速くなりすぎ、このため流れ錆の流出が目立ち易くなる。樹脂系皮膜の厚さが２μｍ未満では、欠陥の無い樹脂系皮膜を得ることが実質的に困難であり、また、樹脂系皮膜の厚さが１００μｍを上回ると、水蒸気透過率が１０００ｇ／ｍ^２・２４ｈを超える皮膜を得る事が困難になる。樹脂系皮膜の厚さが５〜６０μｍで、水蒸気透過度を１０００〜５０００ｇ／ｍ^２・２４ｈとするのがより好ましい。樹脂系皮膜の膜厚および水蒸気透過率を、上記の範囲内に制御することによって、錆層が成長する際に、時間の経過により樹脂系皮膜が錆層に取り込まれこれらが複合一体化するようになる。
【００１２】
本発明用樹脂系皮膜を形成する樹脂としては、アクリル系樹脂、アルキッド系樹脂、エポキシ系樹脂、ウレタン系樹脂、ポリエステル系樹脂、エポキシポリエステル樹脂、酢酸ビニル樹脂、及びスチレンブタジエン樹脂等が使用できる。樹脂系皮膜を親水性にすると、特に高い水蒸気透過率が得られるようになるので、親水性樹脂系皮膜を形成するために、水溶性樹脂及び／又は水性エマルション樹脂から皮膜を形成することが好ましい。また、皮膜を形成するときに、ＶＯＣ（Ｖｏｌａｔｉｌｅｏｒｇａｎｉｃｃｏｍｐｏｕｎｄ、揮発性有機物質）の発生を少なくするためには上記親水性樹脂の水性液を用いることが好ましい。本発明用樹脂系皮膜の形成に際し、その樹脂に好ましい性能は、（ａ）顔料比率の高い皮膜を得るために、接着性に優れていること、また、（ｂ）経時的に発生する外観斑を少なくするために、耐候性が良好であることなどである。そのため、高い水蒸気透過率が得られ、かつ密着性と耐候性の両者を、バランス良く確保するために、それぞれの役割を分担させたアクリル変性エポキシ樹脂等を用いることが好適である。アクリル変性エポキシ樹脂としては、樹脂分子中にビスフェノール系エポキシ樹脂構造が、１０〜９０質量％の含有率で含有されている樹脂骨格を有するものが好ましい。
【００１３】
本発明において、高い水蒸気透過性を有する樹脂系皮膜を形成するには、りん酸化合物と顔料とを乾燥樹脂系皮膜中に含有させることが好ましい。樹脂系皮膜中におけるりん酸化合物と顔料との合計含有量は、樹脂系皮膜の厚さに関係して定められるが、４０〜９５質量％である。乾燥皮膜中のりん酸化合物と顔料との合計含有量は、６０〜８５質量％であることが好ましく、さらに好ましくは７０〜８０質量％である。この配合量が４０質量％未満の場合には、実用的な膜厚において、樹脂系皮膜の水蒸気透過率を１０００ｇ／ｍ^２・２４ｈ以上にすることが困難であり、このため保護性錆の形成速度が不十分になる。またその配合量が９５質量％を超える場合は、得られる樹脂皮膜層に形成される空隙が大きくかつ多くなり、このため実用的な膜厚において、樹脂系皮膜の水蒸気透過率が５０００ｇ／ｍ^２・２４ｈを超えてしまい、水、酸素の透過性が過大になって腐食反応の進行が速く、流れ錆が流出しやすくなる。さらに、この場合には得られる樹脂系皮膜の機械的強度が実用上不十分になることがある。
【００１４】
樹脂系皮膜中に含有されるりん酸化合物は、固形物として樹脂系皮膜に添加される。りん酸化合物は、具体的には、りん酸亜鉛、りん酸カルシウム、りん酸マグネシウム、などのようにりん酸根を有する金属化合物から適宜に選択し使用できる。また縮合りん酸塩など亜りん酸系の金属化合物も使用できる。りん酸化合物は、樹脂系皮膜中に同時に含有されている他の顔料と同様に水蒸気透過度を制御する作用を有するが、その他に、保護性錆の生成促進作用、及び流れ錆抑制作用も有する。樹脂系皮膜中のりん酸化合物が徐々に溶解することにより樹脂系皮膜中に供給されるりん酸根は、耐候性鋼材の保護性錆の生成を促進する。さらに、樹脂系皮膜中に添加されるりん酸化合物は皮膜をカチオン透過性にするために、保護性錆化する際の阻害因子であるＣｌ⁻を効果的に遮断する効果を示し、それとともに、鋼面から流出するＦｅ^２＋を、Ｆｅ^３＋のりん酸化合物として皮膜中に固定化する効果を示す。
【００１５】
本発明において樹脂系皮膜中のりん酸化合物の配合量は、水蒸気透過度の調節以外の作用を考慮すると、乾燥皮膜質量の３〜４０質量％であることが好ましく、より好ましくは５〜３０質量％であり、さらに好ましくは１０〜２０質量％である。その配合量が３質量％未満の場合には、樹脂系皮膜中へのりん酸イオンの供給が少なく、りん酸化合物の上記効果が十分に発揮されないことがある。また配合量が４０質量％を超える場合はその効果が飽和し、特に樹脂系皮膜の形成に水系の樹脂を用いた場合には、りん酸化合物が水系樹脂中に溶出し、そのために、水系樹脂含有処理剤の貯蔵安定性が不良になることがある。
【００１６】
本発明において、樹脂系皮膜に含まれる顔料として、各種着色顔料、各種体質顔料が用いられることが好ましい。着色顔料としては、樹脂系皮膜を錆類似色に着色するために、Ｆｅ_２Ｏ_３、Ｆｅ_３Ｏ_４、及びＦｅＯＯＨなどの各種酸化鉄、カーボンブラック及び、有機色素などを使用できる。また体質顔料として、二酸化チタン、タルク、沈降性硫酸バリウム、カオリンクレー、炭酸カルシウム、アルミナ、シリカ粉及び、石膏粉などを使用できる。これらの顔料は、０．１〜１μｍの平均粒径を有することが好ましい。また上記の他の顔料として、バナジウム化合物、モリブデン化合物、硝酸化合物、マンガン化合物などのように酸化作用を有する顔料が包含される。このような酸化作用を有する顔料を樹脂系皮膜中に含有させることにより、次に説明するように、樹脂系皮膜が錆層中に取り込まれ、これと複合され一体化される作用をより顕著に発揮させることが可能になる。
【００１７】
本発明において、樹脂系皮膜は、その大気中暴露の早期から、鋼材に生成した錆層に取り込まれ、またその後、長期にわたり錆層中に、これと複合一体化した状態で存在する。従来の錆安定化処理においては、経時とともに処理皮膜下に錆層が成長し、処理皮膜自身は表層部から徐々に消失して外観斑を生じやすい。すなわち、この経時による外観斑は、処理皮膜が風化消失して錆層が剥き出しになった部分と、残存する処理皮膜部分との色調差違が主な要因である。これに対し、本発明の樹脂系皮膜は、鋼材上に生成した連続錆層中に、連続した状態で取り込まれるから、屋外で使用されたとき、その初期から長期間にわたり均一な錆外観を呈するという特徴を有する。すなわち、本発明の表面処理耐候性鋼材は、屋外での使用において経時とともに、耐候性鋼素地から流出した鉄イオンは樹脂系皮膜下で緻密な錆を形成し、この錆の一部は、樹脂系皮膜を通って皮膜表面に現れ、固着することにより均一な錆外観を呈する。このような過程において、樹脂系皮膜が錆層中に取り込まれる。これは２〜１００μｍの厚さで被覆された樹脂系皮膜の、２０℃における水蒸気透過度を、１０００〜５０００ｇ／ｍ^２・２４ｈにコントロールする事によって発現する現象であり、それが１０００ｇ／ｍ^２・２４ｈ以下である場合には、樹脂系皮膜の表面が錆に覆われまでに長時間を要し、経時とともに樹脂系皮膜の風化による斑が目立つようになる。また水蒸気透過度が５０００ｇ／ｍ^２・２４ｈを上回ると、樹脂系皮膜は錆層と複合化するけれども、流れ錆の生成が過剰となり、外観斑が顕著になる。
【００１８】
本発明の表面処理耐候性鋼材が、その表面に水蒸気透過度の高い皮膜が形成されているにもかかわらず、流れさびの生成を効果的に抑制し得る理由は、下記のように考えられる。前述したように、本発明における樹脂系皮膜のイオン透過性は、基体樹脂と、必要により添加されたりん酸化合物によって発現され、顕著なカチオン透過性を有する。この樹脂系皮膜は、カチオン透過性を示すけれども、流れ錆中に、その成分として含まれるＦｅ^２＋をはじめとする多価陽イオンに対しては、極めて高い遮断能力を示し、すなわち流れ錆の抑制能力が高いものである。この特性の発現の原因は、樹脂系皮膜中の各種イオンが透過する経路の大きさが、大きなイオン半径を有する多価陽イオンを透過させない程度に制御されていることにあると考えられる。流れ錆抑制能は、りん酸化合物より徐々に溶出するりん酸によるりん酸鉄生成や、金属カチオンと塩を作りやすい樹脂中のカルボキシル基によっても発現する。さらに、樹脂系皮膜の構造を上記のように構成することにより、鋼材表面から鉄イオンが生成する生成速度、鉄イオンが樹脂系皮膜を透過する量および速度、及び鉄イオンが樹脂系皮膜表面に固定される速度などをバランス良く制御することが可能となり、その結果、全面にわたり均一な錆外観を早期に呈し、外観斑を生ずることのない表面処理耐候性鋼材の提供が可能となる。
【００１９】
本発明において耐候性鋼材基体上に形成された樹脂系皮膜は、暴露長期間にわたり鋼材基体上に形成された錆層中に複合一体化した状態で存在するため、樹脂系皮膜のカチオン透過性による塩素イオンの侵入抑制効果が、鋼材基体上に保護性錆層が生成されるまでの長期間にわたり継続作用する。また、樹脂系皮膜の流れ錆抑制能も、同様に長期間にわたり作用を持続する。
【００２０】
本発明の表面処理剤は、樹脂とりん酸化合物と顔料を含むものであって、この表面処理剤を塗布後に乾燥して得られる樹脂系皮膜中のりん酸化合物と顔料との合計含有量は、表面処理剤の総合計乾燥質量に対して４０〜９５質量％であり、この表面処理剤により厚さ２〜１００μｍの乾燥皮膜を形成したとき、その２０℃における水蒸気透過度が１０００〜５０００ｇ／ｍ^２・２４ｈとなるものである。本発明の表面処理剤に用いられる樹脂としては、アクリル系樹脂、アルキッド系樹脂、エポキシ系樹脂、ウレタン系樹脂、ポリエステル系樹脂、エポキシポリエステル樹脂、酢酸ビニル樹脂、スチレン−ブタジエン共重合体樹脂等が使用できるが、水系アクリル変性エポキシ系樹脂からなるものが特に好ましい。本発明の処理剤は、前述の皮膜構成要素である樹脂、りん酸化合物および顔料から構成されるが、レベリング剤、消泡剤、防腐・防かび剤、増粘剤、乾燥剤などの１種以上を含有することもできる。
【００２１】
本発明の表面処理耐候性鋼材の製造方法において、耐候性鋼材からなる基体の少なくとも一表面上に、前記本発明の表面処理剤を含む塗工液を、乾燥膜厚が２〜１００μｍになるように常温で塗布し、常温において乾燥して、もしくは２００℃以下の雰囲気温度において加熱乾燥して、１０００〜５０００ｇ／ｍ^２・２４ｈの水蒸気透過度を有する樹脂系皮膜を形成する。
【００２２】
本発明の表面処理剤の塗工液の固形分濃度は、その塗装作業性を勘案して定められるが、２０〜８０質量％であることが好ましく、より好ましくは３０〜６０質量％である。塗工液の塗布時には、各成分が混合された一液剤として使用される。本発明の表面処理剤は貯蔵時の安定性を考慮して、複数の成分薬剤に小分けしておき、使用時にこれらを混合して塗工液を調製し、これを塗布する方法をとることもできる。
【００２３】
本発明において耐候性鋼材からなる基体は、通常、表面処理剤塗工液の塗布に先立ってブラスト処理に供される。表面処理剤塗工液は、耐候性鋼材基材の表面に、乾燥膜厚が２〜１００μｍになるように塗布され好ましくは５〜６０μｍである。膜厚が２μｍ未満の場合は、ブラスト処理により粗面化された耐候性鋼材基材の表面を均一に被覆することができず、裸の素地が一部露出して流れ錆を抑制する効果が十分に発揮されないようになる。また膜厚が１００μｍを超える場合は、得られる樹脂系皮膜の水、酸素の透過性が小さく、保護性錆形成の促進効果が発揮されない。
【００２４】
表面処理剤の塗工液は通常スプレー塗装されるが、塗装環境等に応じてローラー塗装、はけ塗り、あるいはディッピング塗装（浸漬塗り）等が可能である。通常、表面処理剤塗工液は一工程で塗布されるが、数回に分けて塗り重ねてもよい。表面処理剤塗工液の粘度は、塗装作業性を勘案して定められるが、通常は、フォードカップ＃４試験で１０秒〜６０秒であることが好ましい。
【００２５】
塗布された表面処理剤塗工液層は、常温において、もしくは２００℃までの温度における加熱によって乾燥され、成膜される。特に常温で乾燥する際には、雰囲気の相対湿度にも依存するが、概ね１〜３時間ほどで乾燥し、皮膜を形成するから、現場塗布が可能である。なお、本発明の表面処理方法は、鋼板段階で施されてもよく、鋼板を製品形状・寸法に切断・加工・組立された段階で施されてもよく、製品を最終設置場所に設置した後にこれに施されてもよく、処理段階は、コスト、施工性等を考慮して選択すればよい。
【００２６】
本発明に基材として用いられる耐候性鋼材としては、Ｃｕ、Ｎｉ、Ｃｒ、Ｐ、Ｍｏ等を含む低合金鋼材が好ましく用いられるが、その種類に特に限定はない。また、本発明の処理方法に基づいて耐候性鋼材に、表面処理を施すに際しても、鋼板段階で表面処理してもよく、鋼板を製品形状・寸法に切断・加工・組立した段階で表面処理してもよく、あるいは製品を最終設置場所に設置した後に表面処理してもよく、施工段階はコスト、施工性等を考慮して選択すればよい。
【００２７】
【実施例】
本発明を下記実施例によりさらに説明する。
【００２８】
実施例１〜５及び比較例１〜５
実施例１〜５及び比較例１〜５の各々において、下記の操作を行った。
（１）表面処理剤塗工液の調製
表１に記載の水系樹脂液に、りん酸化合物、顔料及び添加剤を混合し、卓上サンドミルを用いて、粒度が２０μｍ以下になるまで分散して水系表面処理剤塗工液を調製した。表１に水系表面処理剤塗工液（表中Ａ１〜Ａ７）の組成を示す。但し、塗工液Ａ４は、溶剤（キシロール）を用いて調製した。
【００２９】
【表１】

【００３０】
〔表１の註〕
＜１＞表１中各成分の含有量の値は質量％であり、またそれらの合計量は１００質量％である。また、各樹脂の含有量については便宜上、不揮発分含有量をもって表示した。
＜２＞水系アクリル変性エポキシ樹脂１は、分子中にビスフェノール系エポキシ樹脂構造を７０質量％含有するものであり、分子中のカルボキシル基をトリエチルアミンで中和することにより水系化したものであった。
水系アクリル変性エポキシ樹脂２、及び溶剤系アクリル変性エポキシ樹脂１の樹脂骨格は、水系アクリル変性エポキシ樹脂１とほぼ同じであり、水系アクリル変性エポキシ樹脂２は、界面活性剤を用いて水系エマルション化したものであった。
＜３＞各処理剤成分比較の内訳は下記の通り。
Ａ１：標準
Ａ１対Ａ２：酸化剤の有無
Ａ１対Ａ３：樹脂の水性化手段の影響
Ａ１対Ａ４：処理剤が水系か溶剤系かの違いによる影響
Ａ１対Ａ５：りん酸化合物の含有量
Ａ１対Ａ６：りん酸化合物と顔料の合計含有量が過少である場合の影響
Ａ１対Ａ７：りん酸化合物と顔料の合計含有量が過多である場合の影響
＜４＞りん酸化合物：ＺｎＰＯ_４、（商標：ＺＰ−ＤＬ、キクチカラー（株）製）
＜５＞顔料：硫酸バリウム（商標：沈降性硫酸バリウム３００、堺化学工業（株）製）、赤酸化鉄（商標：トダカラー赤１９０ＥＤ、戸田工業（株）製）、黒酸化鉄（商標：トダカラー黒ＫＮ−３２０、戸田工業（株）製）、の３種の顔料を、硫酸バリウム：赤酸化鉄：黒酸化鉄＝５８：１９：２３、の質量比率で予め混合したもの
＜６＞酸化剤Ｍｏ：（ＮＨ_４）_６Ｍｏ_７Ｏ_２４・４Ｈ_２Ｏ、（商標：無し、和光純薬工業（株）製）
＜７＞溶剤：キシロール
【００３１】
（２）鋼板試験片の調製
まず、表２の組成を有し、寸法：７０ｍｍ×１５０ｍｍ、厚さ３．２ｍｍを有する耐候性鋼板（Ｂ１、Ｂ２）にショットブラスト処理を施した後、エアーブローにより、その表面に付着した鉄粉を除去した。
【００３２】
【表２】

【００３３】
（３）表面処理
前記鋼板試験片の１表面上に、前記表面処理剤塗工液を、エアースプレー方法により種々の膜厚で塗布したのち、２３℃の室内にて静置・乾燥して表面処理鋼板試験片を作製した。また、流れ錆の目視観察のために、表面処理試験片の樹脂系皮膜層の乾燥塗装面の下部４ｃｍ幅に、白色塗料（２液型アクリルウレタン塗料）を重ね塗りした。表３に、実施例１〜５及び比較例１〜５の各々に用いられた耐候性鋼材の種類、表面処理剤の種類、樹脂系皮膜の厚さ及び水蒸気透過度を示す。
【００３４】
【表３】

【００３５】
（４）試験
前記試験片の各々を、神奈川県平塚市（海岸より内陸部へ約１０ｋｍ入った住居地域）において屋外暴露し、暴露１ヶ月後、６ヶ月後および２４ヶ月後に、流れ錆の発生状況と試験片の外観変化を観察した。なお試験片は、白色塗料塗布面が下になるよう南面９０度（地面と垂直）に設置し、その南面側を評価面とした。
【００３６】
（５）流れ錆評価方法
白色塗料上の流れ錆の発生状況について、以下の基準で評価した。
×：流れ錆が白色塗料面の３０％以上の面に付着していた。
△：流れ錆が白色塗料面の５〜３０％の面に付着していた。
○：流れ錆が白色塗料面の５％未満の面に付着していた。
【００３７】
（６）外観評価方法
試験片の表面外観の変化状況について、以下の基準で評価した。
−：初期と全く変化なく樹脂系皮膜のみの外観であった。
×：処理剤塗布面の１０％以上に黄錆が発生し、黄錆、黒錆と樹脂系皮膜との外観斑が発生していた。
△：黄錆の発生は１０％未満であるが、表面の所々に黒錆と樹脂系皮膜との外観斑が発生していた。
○：黄錆の発生は１０％未満で、表面には目立った外観斑は無く、均一な黒錆色を呈していた。
【００３８】
（７）断面状態の評価
試験片の一部を切断採取した後に樹脂に埋め込み、その断面の錆形態や樹脂系皮膜の状況を偏光金属顕微鏡およびＥＰＭＡで観察した。
−：樹脂系皮膜はほとんど変化せず、錆もほとんど発生していなかった。
△：樹脂系皮膜下に錆層が生成しているが、表層部は樹脂のみで覆われていた。
○：樹脂系皮膜と錆層が複合一体化していた。
【００３９】
表４に試験結果を示す。
【表４】

【００４０】
表４の試験結果から明らかなように、本発明の表面処理を施した耐候性鋼材の実施例１〜５は、ほぼ６ヶ月の短期間で皆良好な外観を呈し、さらに、流れ錆の発生も抑制された。また、６ヶ月後で既に樹脂系皮膜と錆層とが複合一体化し、樹脂系皮膜下には保護性錆が密着良く形成されていた。これに対して、本発明の範囲外である比較例１〜５では、初期における流れ錆の発生が目立ったり、特に２４ヶ月経過後でも良好な外観と流れ錆抑制との両者をバランス良く満足しているものが無いことが確認された。
【００４１】
【発明の効果】
本発明は、耐候性鋼材の表面に保護性錆が形成されるまで、流れ錆の発生を抑制し、かつ保護性錆の形成を促進するとともに、外観斑を少なくして外観にも優れた表面処理耐候性鋼材、それを製造するための耐候性鋼材用表面処理剤及び表面処理耐候性鋼材の製造方法を提供でき、これらはきわめて工業価値の高いものである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is characterized in that on the surface of a base made of a weather-resistant steel material, a resin-based coating that promotes the formation of protective rust as a corrosion protection layer and suppresses flow rust over a long period of time is provided. Field of the Invention The present invention relates to a surface-treated weather-resistant steel material having an excellent landscape, a surface-treating agent for a weather-resistant steel material, and a method for producing a surface-treated weather-resistant steel material.
[0002]
[Prior art]
A steel material containing a small amount of one or two or more elements selected from P, Cu, Cr, Ni, Si, Mo, Mn, etc. as an alloying element has low corrosion in the atmosphere and is a weather-resistant steel. Are known. That is, when this weathering steel is exposed to the air, a dense and protective rust (hereinafter, protective rust) layer is formed on the surface, and the corrosion of the steel itself is suppressed.
[0003]
However, in the initial stage until a protective rust layer is formed, usually within a period of about three years immediately after exposure to the atmosphere, floating rust and flowing rust such as red rust and yellow rust are formed on the steel surface. Which is undesirable in appearance. In order to prevent such floating rust and flowing rust, various techniques have been conventionally proposed. For example, Japanese Patent Publication No. 53-22530 (Patent Document 1) discloses that Fe₃O₄+ Fe₂O₃Is 5 to 50%, phosphoric acid is 0.01 to 5%, and Pb, Ni, Cu, P, Zn, Cr or the like is used in an amount of 0.01 to 10% for butyral resin and butyral resin. There has been proposed a technique for applying a mixed treatment liquid containing 3 to 30% of a resin having a balance of a solvent to a steel material surface. Japanese Patent Publication No. 56-33991 (Patent Document 2) proposes a technique of applying a treatment liquid for forming a weather-resistant film on the protective film layer. The above technique is to prevent the occurrence of floating rust and flowing rust such as red rust and yellow rust in the initial stage until the protective rust layer is formed, and to apply a bare steel material not coated with the mixed treatment liquid or the treatment liquid. This is a technique for forming a protective rust layer very slowly as compared with the conventional technique.
[0004]
On the other hand, as a method for promoting the formation of the protective rust layer, for example, the following technology has been proposed. That is, Japanese Patent No. 2666673 (Patent Literature 3) discloses an organic resin coating containing at least one of chromium sulfate and copper sulfate in a total amount of 1 to 65% by mass with a dry thickness of 5 to 150 μm. There has been proposed a surface-treated steel material having excellent weather resistance. According to the detailed description of the above publication, the above technique prevents the outflow of iron ions, promotes the conversion of iron ions to α-FeOOH, and forms a protective rust layer formed in a subsequent atmospheric corrosion environment. It is stated that the formation of the rust layer and the conversion of the already formed rust layer to the protective rust layer can be promoted at an early stage and without generation of flowing rust and the like. However, in this surface-treated steel material, there is a possibility that unevenness due to weathering of the treated film, and also unevenness in appearance due to added leachable sulfate, may leave room for improvement in terms of aesthetic appearance.
[0005]
As another method for promoting the formation of protective rust, which is different from the above, JP-A-2001-81571 (Patent Document 4) discloses at least an anion having a trapping and depositing action for iron ions and a counter cation. A steel material having a cured film of one or more salts and a resin composition having a negative fixed charge formed on a surface thereof, and further having a water vapor permeability at 40 ° C. of 10 to 1000 g / m.²-A rust stabilization treated steel material characterized by being "day" has been proposed. However, this processing technique has improved blistering and peeling of the film on the appearance, but since the treated film is present on the surface of the steel material until it is weathered and worn, there is a large change in hue with the passage of time and appearance irregularities. .
[0006]
The present inventors have disclosed in Japanese Patent Application Laid-Open No. 2002-129355 as a method for promoting the formation of protective rust, a base made of a weather-resistant steel, a resin formed on at least one surface of the base, a resin and a phosphate compound. And a resin film having a thickness of 2 to 100 μm, wherein the resin contains a polymer having a carboxyl group, and the infrared absorption spectrum of the dried film is 1500 to 1800 cm.^-1A surface-treated weatherable steel having at least one absorption peak in the range of. This technology suppresses the generation of flowing rust in the initial stage until the formation of protective rust, and promotes the formation of protective rust. Depending on the exposure environment, spots may appear over time.
As described above, the conventional rust stabilization treatment of the type that promotes the formation of protective rust of weathering steel is not always sufficient in terms of reducing appearance unevenness caused by various factors.
[0007]
[Patent Document 1]
JP-B-53-22530, page 1, claims 1, 2 and 3-4.
Example
[Patent Document 2]
JP-B-56-33991, page 1, claims 1, 2 and 3-4.
Example
[Patent Document 3]
Japanese Patent No. 2666673, page 1, claims 1, 2 and 3 to 7
Example
[Patent Document 4]
JP-A-2001-81571, page 2, claims 1 to 5 and 5 to 8
Page Examples
[0008]
[Problems to be solved by the invention]
The present invention is a surface treatment that reduces the occurrence of flowing rust until the protective rust is formed on the surface of the weathering steel, promotes the formation of the protective rust, and reduces the appearance unevenness and is excellent in the landscape. It is an object of the present invention to provide a weather-resistant steel material, a surface treatment agent for obtaining the weather-resistant steel material, and a method for producing the surface-treated weather-resistant steel material.
[0009]
[Means for Solving the Problems]
The surface-treated weather-resistant steel material of the present invention includes a base material made of a weather-resistant steel material, and a resin-based film including a resin, a phosphate compound, and a pigment formed on at least one surface thereof,
The total content of the phosphate compound and the pigment is 40 to 95% by mass, and the content of the phosphate compound is 3 to 40% by mass, based on the total mass of the resin-based coating; and
The thickness of the resin-based coating is 2 to 100 μm, and the water vapor permeability at 20 ° C. is 1000 to 5000 g / m 2.²・ 24h
It is characterized by the following.
In the surface-treated weatherable steel material of the present invention, the resin is an acrylic resin, an alkyd resin, an epoxy resin, a urethane resin, a polyester resin, an epoxy polyester resin, a vinyl acetate resin, a styrene-butadiene copolymer system. It is preferable to be selected from a resin and an acrylic-modified epoxy resin.
In the surface-treated weatherable steel material of the present invention, the phosphate compound is preferably selected from zinc phosphate, calcium phosphate, magnesium phosphate, and condensed phosphate.
In the surface-treated weatherable steel material of the present invention, the pigment is iron oxide, carbon black, organic pigment, titanium dioxide, talc, precipitated barium sulfate, kaolin clay, calcium carbonate, alumina, silica powder, gypsum powder, vanadium compound, It is preferable to be selected from a molybdenum compound, a nitric acid compound, and a manganese compound.
In the surface-treated weather-resistant steel material of the present invention, when used outdoors, rust is formed above and below the resin-based coating, and the rust and the resin-based coating are combined and integrated to form a rust on the surface of the steel base. -It is preferable that the resin-based film composite integrated layer is formed and covered.
The surface treatment agent for weathering steel of the present invention is a surface treatment agent containing a resin, a phosphate compound, and a pigment, and the phosphoric acid compound and the pigment are based on the total dry mass of the surface treatment agent. Is 40 to 95% by mass, and the content ratio of the phosphate compound is 3 to 40% by mass.
The method for producing a surface-treated weather-resistant steel material according to the present invention comprises, on at least one surface of a substrate made of a weather-resistant steel material, a coating liquid containing the surface treatment agent according to claim 6, and a dry film thickness of 2 to 100 μm. And dried by heating at room temperature or at an ambient temperature of 200 ° C. or less to give 1000 to 5000 g / m 2.²-It is characterized by forming a resin-based film having a water vapor permeability of 24 hours.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
In the surface-treated weatherable steel material of the present invention, the purpose of the resin-based film formed on the substrate is (1) to promote the formation of protective rust on the steel material, and (2) to suppress the generation of flowing rust. And (3) obtaining a surface-treated weathering-resistant steel material exhibiting a uniform rust appearance without uneven appearance. Hereinafter, the film design of the present invention that has simultaneously solved these three requirements will be described for each item.
[0011]
In order to achieve the requirements (1) to (3), while forming a resin-based film containing a resin, a phosphate compound and a pigment on the surface of the weather-resistant steel, the water vapor permeability is determined so as not to hinder the formation of rust. Large film structure. The required properties of the film are as follows: in the air having a thickness of 2 to 100 μm and a relative humidity of 90 ± 2% at a temperature of 20 ± 0.5 ° C. in accordance with the method described in JIS K-5400. Water vapor permeability measured at 1000 to 5000 g / m²・ 24 h, more preferably 1500 to 4000 g / m²・ It is 24h. Water vapor transmission rate of 1000 g / m²If the time is less than 24 hours, the permeability of water and oxygen of the resin-based film becomes too small, and the elution of iron ions due to corrosion from the steel base material becomes slow, so that the protective rust formation rate is not sufficient. In addition, the water vapor transmission rate is 5000 g / m²-If it exceeds 24 hours, the resin-based coating has large and numerous voids, and the permeability of water and oxygen becomes excessive, so that the progress of the corrosion reaction becomes too fast, so that the outflow of flowing rust becomes conspicuous. . When the thickness of the resin-based coating is less than 2 μm, it is substantially difficult to obtain a resin-based coating having no defects. When the thickness of the resin-based coating exceeds 100 μm, the water vapor transmission rate is 1000 g / m 2.²・ It becomes difficult to obtain a film exceeding 24 hours. The thickness of the resin-based coating is 5 to 60 μm, and the water vapor permeability is 1000 to 5000 g / m²-More preferably, it is set to 24h. By controlling the film thickness and the water vapor transmission rate of the resin-based film within the above ranges, when the rust layer grows, the resin-based film is taken into the rust layer with the passage of time so that these are combined and integrated. become.
[0012]
Acrylic resin, alkyd resin, epoxy resin, urethane resin, polyester resin, epoxy polyester resin, vinyl acetate resin, styrene butadiene resin and the like can be used as the resin forming the resin film for the present invention. When the resin-based coating is made hydrophilic, a particularly high water vapor transmission rate can be obtained. Therefore, in order to form a hydrophilic resin-based coating, it is preferable to form the coating from a water-soluble resin and / or an aqueous emulsion resin. . In addition, when forming a film, it is preferable to use an aqueous liquid of the above hydrophilic resin in order to reduce generation of VOC (Volatile organic compound, volatile organic substance). In forming the resin-based coating for the present invention, the preferable properties of the resin are (a) excellent adhesiveness in order to obtain a coating having a high pigment ratio, and (b) appearance unevenness occurring over time. In order to reduce the weather resistance. Therefore, it is preferable to use an acrylic-modified epoxy resin or the like, each of which plays a role in order to obtain a high water vapor transmission rate and to ensure both adhesion and weather resistance in a well-balanced manner. As the acryl-modified epoxy resin, a resin having a resin skeleton in which a bisphenol-based epoxy resin structure is contained in a resin molecule at a content of 10 to 90% by mass is preferable.
[0013]
In the present invention, in order to form a resin film having high water vapor permeability, it is preferable to include a phosphate compound and a pigment in the dry resin film. The total content of the phosphate compound and the pigment in the resin-based coating is determined in relation to the thickness of the resin-based coating, and is 40 to 95% by mass. The total content of the phosphate compound and the pigment in the dried film is preferably from 60 to 85% by mass, and more preferably from 70 to 80% by mass. When the blending amount is less than 40% by mass, the water vapor transmission rate of the resin-based film is set to 1000 g / m at a practical film thickness.²-It is difficult to make it longer than 24 hours, so that the protective rust formation rate becomes insufficient. If the amount is more than 95% by mass, the voids formed in the obtained resin film layer are large and large, so that the water vapor permeability of the resin film is 5,000 g / m 2 at a practical film thickness.²-It exceeds 24 hours, the permeability of water and oxygen becomes excessive, the progress of the corrosion reaction is fast, and the flow rust easily flows out. Furthermore, in this case, the mechanical strength of the obtained resin-based film may be insufficient in practical use.
[0014]
The phosphate compound contained in the resin-based film is added to the resin-based film as a solid. Specifically, the phosphate compound can be appropriately selected and used from metal compounds having a phosphate group, such as zinc phosphate, calcium phosphate, and magnesium phosphate. Phosphorous metal compounds such as condensed phosphates can also be used. Phosphoric acid compounds have the effect of controlling the water vapor permeability like other pigments simultaneously contained in the resin-based coating, but also have the effect of promoting the formation of protective rust and the effect of suppressing flow rust. . The phosphate radicals supplied into the resin-based coating due to the gradual dissolution of the phosphate compound in the resin-based coating promote the formation of protective rust on the weather-resistant steel. Further, the phosphate compound added to the resin-based coating is Cl, which is an inhibitory factor for protective rusting, in order to make the coating cation-permeable.⁻And effectively removes Fe from the steel surface.²⁺With Fe³⁺Has the effect of immobilizing it as a phosphate compound in the film.
[0015]
In the present invention, the amount of the phosphate compound in the resin-based film is preferably 3 to 40% by mass, more preferably 5 to 30% by mass of the dry film mass, in consideration of actions other than the adjustment of the water vapor permeability. %, And more preferably 10 to 20% by mass. When the compounding amount is less than 3% by mass, the supply of phosphate ions into the resin-based film is small, and the above effect of the phosphate compound may not be sufficiently exerted. When the amount is more than 40% by mass, the effect is saturated. In particular, when an aqueous resin is used for forming the resin-based film, the phosphate compound is eluted into the aqueous resin, and therefore, The storage stability of the contained treating agent may be poor.
[0016]
In the present invention, it is preferable to use various coloring pigments and various extenders as pigments contained in the resin-based coating. As a coloring pigment, in order to color the resin-based coating to a rust-like color, Fe₂O₃, Fe₃O₄And various iron oxides such as FeOOH, carbon black, and organic dyes. Further, as the extender pigment, titanium dioxide, talc, precipitated barium sulfate, kaolin clay, calcium carbonate, alumina, silica powder, gypsum powder and the like can be used. These pigments preferably have an average particle size of 0.1 to 1 μm. The other pigments include pigments having an oxidizing effect, such as vanadium compounds, molybdenum compounds, nitric acid compounds, manganese compounds and the like. By including such an oxidizing pigment in the resin-based coating, the resin-based coating is incorporated into the rust layer, as described below, and the effect of being combined with and integrated with the rust layer more remarkably. It is possible to demonstrate.
[0017]
In the present invention, the resin-based film is taken into the rust layer formed on the steel material from the early stage of exposure to the atmosphere, and thereafter exists in the rust layer in a state of being combined with the rust layer for a long period of time. In the conventional rust stabilization treatment, a rust layer grows under the treated film with the passage of time, and the treated film itself gradually disappears from the surface layer portion, and the appearance unevenness tends to occur. That is, the appearance unevenness due to aging is mainly caused by a difference in color tone between a portion where the treated film is weathered and the rust layer is exposed and a remaining treated film portion. On the other hand, the resin-based coating of the present invention exhibits a uniform rust appearance over a long period of time from its initial stage when used outdoors, since it is taken in a continuous state into the continuous rust layer formed on the steel material. It has the feature of. That is, the surface-treated weather-resistant steel material of the present invention is such that iron ions flowing out of the weather-resistant steel base form a dense rust under the resin-based film with the passage of time in outdoor use. Appears on the film surface through the system film and adheres to the film to give a uniform rust appearance. In such a process, the resin-based film is taken into the rust layer. This means that the water vapor permeability at 20 ° C. of the resin-based film coated with a thickness of 2 to 100 μm is 1000 to 5000 g / m 2.²• A phenomenon that is manifested by controlling to 24 h, which is 1000 g / m²If it is 24 hours or less, it takes a long time until the surface of the resin-based coating is covered with rust, and as time passes, spots due to weathering of the resin-based coating become noticeable. In addition, the water vapor permeability is 5000 g / m²When the time exceeds 24 hours, the resin-based film is complexed with the rust layer, but the generation of flowing rust becomes excessive and the appearance unevenness becomes remarkable.
[0018]
The reason why the surface-treated weather-resistant steel material of the present invention can effectively suppress the generation of flow rust even though a film having a high water vapor permeability is formed on the surface thereof is considered as follows. As described above, the ion permeability of the resin-based film in the present invention is exhibited by the base resin and the phosphate compound added as required, and has a remarkable cation permeability. Although this resin-based film shows cation permeability, it contains Fe contained as a component in flowing rust.²⁺And other polyvalent cations exhibit an extremely high blocking ability, that is, a high ability to suppress flow rust. It is considered that the cause of the development of this property is that the size of the path through which various ions in the resin-based coating penetrate is controlled to such an extent that a polyvalent cation having a large ion radius does not pass. The ability to suppress flow rust is also exhibited by the formation of iron phosphate by phosphoric acid gradually eluted from the phosphate compound, and by the carboxyl group in the resin that easily forms salts with metal cations. Further, by configuring the structure of the resin-based coating as described above, the generation rate at which iron ions are generated from the steel material surface, the amount and speed at which iron ions permeate the resin-based coating, and the iron ions are applied to the resin-based coating surface. It is possible to control the fixing speed and the like in a well-balanced manner. As a result, it is possible to provide a surface-treated weather-resistant steel material that exhibits a uniform rust appearance over the entire surface at an early stage and does not cause uneven appearance.
[0019]
In the present invention, the resin-based film formed on the weather-resistant steel substrate is present in a composite and integrated state in the rust layer formed on the steel substrate for a long period of time due to the exposure. The effect of suppressing chlorine ion intrusion continues for a long time until a protective rust layer is formed on the steel base. In addition, the ability of the resin-based coating to suppress flow rust similarly maintains its action over a long period of time.
[0020]
The surface treatment agent of the present invention contains a resin, a phosphate compound and a pigment, and the total content of the phosphate compound and the pigment in the resin-based film obtained by applying the surface treatment agent and then drying is And 40 to 95% by mass based on the total dry mass of the surface treatment agent. When a dry film having a thickness of 2 to 100 μm is formed by this surface treatment agent, the water vapor permeability at 20 ° C. is 1000 to 5000 g / m²・ It will be 24h. Examples of the resin used in the surface treatment agent of the present invention include acrylic resins, alkyd resins, epoxy resins, urethane resins, polyester resins, epoxy polyester resins, vinyl acetate resins, styrene-butadiene copolymer resins, and the like. Although it can be used, one composed of an aqueous acrylic-modified epoxy resin is particularly preferred. The treating agent of the present invention is composed of a resin, a phosphoric acid compound and a pigment which are the above-mentioned components of the film. The above may be contained.
[0021]
In the method for producing a surface-treated weather-resistant steel material of the present invention, the coating liquid containing the surface treatment agent of the present invention is coated on at least one surface of a substrate made of the weather-resistant steel material such that the dry film thickness is 2 to 100 μm. At room temperature and dried at room temperature, or dried by heating at an ambient temperature of 200 ° C. or less,²Form a resin-based film having a water vapor permeability of 24 h.
[0022]
The solid content concentration of the coating solution of the surface treatment agent of the present invention is determined in consideration of the coating workability, but is preferably 20 to 80% by mass, and more preferably 30 to 60% by mass. At the time of application of the coating liquid, each component is used as a one-part preparation. The surface treating agent of the present invention may be divided into a plurality of component agents in consideration of the stability during storage, mixed at the time of use to prepare a coating solution, and a method of applying the same. it can.
[0023]
In the present invention, the substrate made of a weather-resistant steel material is usually subjected to a blast treatment prior to the application of the surface treatment agent coating liquid. The surface treatment agent coating liquid is applied on the surface of the weather-resistant steel base material so that the dry film thickness becomes 2 to 100 μm, and preferably 5 to 60 μm. When the film thickness is less than 2 μm, it is not possible to uniformly coat the surface of the weather-resistant steel base material roughened by the blast treatment, and the bare base is partially exposed to reduce the flow rust. Will not be fully demonstrated. On the other hand, when the thickness exceeds 100 μm, the resulting resin-based coating has low water and oxygen permeability, and the effect of promoting the formation of protective rust is not exhibited.
[0024]
The coating liquid of the surface treatment agent is usually spray-coated, but roller coating, brush coating, dipping coating (dip coating) or the like is possible depending on the coating environment and the like. Usually, the surface treatment agent coating liquid is applied in one step, but may be applied several times over and over. The viscosity of the surface treatment agent coating liquid is determined in consideration of the coating workability, but it is usually preferably 10 to 60 seconds in a Ford cup # 4 test.
[0025]
The applied surface treatment agent coating liquid layer is dried at room temperature or by heating at a temperature up to 200 ° C. to form a film. In particular, when drying at room temperature, although it depends on the relative humidity of the atmosphere, it generally dries in about 1 to 3 hours to form a film, so that in-situ application is possible. In addition, the surface treatment method of the present invention may be performed at a steel plate stage, or may be performed at a stage where a steel plate is cut, processed, and assembled into a product shape and dimensions, and after the product is installed at a final installation location. The processing step may be selected in consideration of cost, workability, and the like.
[0026]
As the weather-resistant steel used as the base material in the present invention, a low-alloy steel containing Cu, Ni, Cr, P, Mo or the like is preferably used, but the type is not particularly limited. Also, when performing a surface treatment on the weather-resistant steel material based on the treatment method of the present invention, the surface treatment may be performed at the steel plate stage, and the surface treatment is performed at the stage of cutting, processing, and assembling the steel plate into the product shape and dimensions. Alternatively, the surface treatment may be performed after the product is installed at the final installation location, and the construction stage may be selected in consideration of cost, workability, and the like.
[0027]
【Example】
The present invention is further described by the following examples.
[0028]
Examples 1 to 5 and Comparative Examples 1 to 5
In each of Examples 1 to 5 and Comparative Examples 1 to 5, the following operation was performed.
(1) Preparation of coating solution for surface treatment agent
A phosphoric acid compound, a pigment and an additive were mixed with the aqueous resin liquid shown in Table 1 and dispersed using a desktop sand mill until the particle size became 20 μm or less to prepare an aqueous surface treating agent coating liquid. Table 1 shows the compositions of the aqueous surface treatment agent coating liquids (A1 to A7 in the table). However, the coating liquid A4 was prepared using a solvent (xylol).
[0029]
[Table 1]

[0030]
[Notes in Table 1]
<1> In Table 1, the value of the content of each component is% by mass, and the total amount thereof is 100% by mass. In addition, the content of each resin is represented by the nonvolatile content for convenience.
<2> Water-based acrylic-modified epoxy resin 1 contained 70% by mass of a bisphenol-based epoxy resin structure in the molecule, and was made water-based by neutralizing the carboxyl group in the molecule with triethylamine.
The resin skeletons of the water-based acrylic-modified epoxy resin 2 and the solvent-based acrylic-modified epoxy resin 1 are almost the same as those of the water-based acrylic-modified epoxy resin 1, and the water-based acrylic-modified epoxy resin 2 is formed into a water-based emulsion using a surfactant. Was something.
<3> The breakdown of each processing agent component comparison is as follows.
A1: Standard
A1: A2: Presence or absence of oxidizing agent
A1: A3: Influence of water-based means for resin
A1 vs. A4: Influence due to difference in treatment agent between water and solvent
A1: A5: content of phosphate compound
A1: A6: Effect when total content of phosphoric acid compound and pigment is too small
A1: A7: Effect when total content of phosphoric acid compound and pigment is excessive
<4> Phosphoric acid compound: ZnPO₄, (Trademark: ZP-DL, manufactured by Kikuchi Color Co., Ltd.)
<5> Pigment: barium sulfate (trademark: sedimentable barium sulfate 300, manufactured by Sakai Chemical Industry Co., Ltd.), red iron oxide (trademark: Todacolor Red 190ED, manufactured by Toda Kogyo Co., Ltd.), black iron oxide (trademark: todacolor) Black KN-320, manufactured by Toda Kogyo Co., Ltd.) in advance, in a mass ratio of barium sulfate: red iron oxide: black iron oxide = 58: 19: 23.
<6> Oxidizing agent Mo: (NH₄)₆Mo₇O₂₄・ 4H₂O, (trademark: none, manufactured by Wako Pure Chemical Industries, Ltd.)
<7> Solvent: Xylol
[0031]
(2) Preparation of steel plate test piece
First, a shot blasting process was performed on weather-resistant steel plates (B1, B2) having the composition shown in Table 2 and having dimensions of 70 mm × 150 mm and a thickness of 3.2 mm, and then the iron adhered to the surface by air blowing. The powder was removed.
[0032]
[Table 2]

[0033]
(3) Surface treatment
On one surface of the steel sheet test piece, the surface treatment agent coating solution is applied in various thicknesses by an air spray method, and then left standing and dried in a room at 23 ° C. to obtain a surface-treated steel sheet test piece. Produced. Further, for visual observation of flowing rust, a white paint (two-component acrylic urethane paint) was applied over the lower 4 cm width of the dry coating surface of the resin-based coating layer of the surface-treated test piece. Table 3 shows the types of the weather-resistant steel materials, the types of the surface treatment agents, the thicknesses of the resin-based films, and the water vapor transmission rates used in Examples 1 to 5 and Comparative Examples 1 to 5, respectively.
[0034]
[Table 3]

[0035]
(4) Test
Each of the test pieces was exposed outdoors in Hiratsuka City, Kanagawa Prefecture (a residential area about 10 km from the coast to the inland area). The appearance change was observed. In addition, the test piece was installed at 90 degrees on the south side (perpendicular to the ground) so that the surface coated with the white paint faced down, and the south side was used as the evaluation plane.
[0036]
(5) Flow rust evaluation method
The occurrence of flow rust on the white paint was evaluated according to the following criteria.
X: Flowing rust was adhered to 30% or more of the white paint surface.
Δ: Flow rust was adhered to 5 to 30% of the white paint surface.
：: Flow rust was adhered to less than 5% of the white paint surface.
[0037]
(6) Appearance evaluation method
The change in the surface appearance of the test specimen was evaluated according to the following criteria.
-: The appearance of only the resin-based film was not changed at all from the initial stage.
×: Yellow rust was generated on 10% or more of the treatment agent-applied surface, and uneven appearance of yellow rust, black rust, and the resin-based film was observed.
Δ: Occurrence of yellow rust was less than 10%, but uneven appearance of black rust and the resin-based film was observed at various places on the surface.
：: The occurrence of yellow rust was less than 10%, there was no noticeable appearance unevenness on the surface, and a uniform black rust color was exhibited.
[0038]
(7) Evaluation of cross-sectional state
A part of the test piece was cut and sampled and then embedded in a resin, and the rust morphology of the cross section and the state of the resin film were observed with a polarizing metallographic microscope and EPMA.
-: The resin-based film hardly changed and rust was hardly generated.
Δ: A rust layer was formed under the resin-based film, but the surface layer was covered with only the resin.
：: The resin-based film and the rust layer were compositely integrated.
[0039]
Table 4 shows the test results.
[Table 4]

[0040]
As is evident from the test results in Table 4, Examples 1 to 5 of the weather-resistant steel material subjected to the surface treatment of the present invention all exhibited good appearance in a short period of almost 6 months, and furthermore, generation of flow rust was observed. Was also suppressed. After 6 months, the resin-based film and the rust layer had already been combined and integrated, and protective rust had been formed under the resin-based film with good adhesion. On the other hand, in Comparative Examples 1 to 5, which are out of the scope of the present invention, generation of flowing rust in the initial stage is conspicuous, and both good appearance and suppression of flowing rust are satisfied in a good balance even after 24 months. Nothing was confirmed.
[0041]
【The invention's effect】
The present invention suppresses the occurrence of flowing rust until the protective rust is formed on the surface of the weather-resistant steel material, and promotes the formation of the protective rust. It is possible to provide a treated weather-resistant steel material, a surface-treating agent for the weather-resistant steel material for producing the same, and a method for producing the surface-treated weather-resistant steel material, which are of extremely high industrial value.

Claims

A base material made of a weather-resistant steel material, formed on at least one surface thereof, including a resin, a phosphate compound, and a resin-based coating containing a pigment;
The total content of the phosphate compound and the pigment is 40 to 95% by mass, and the content of the phosphate compound is 3 to 40% by mass, based on the total mass of the resin-based coating; and
A surface-treated weather-resistant steel material, wherein the resin-based coating has a thickness of 2 to 100 μm and a water vapor transmission rate at 20 ° C. of 1,000 to 5,000 g / m ² · 24 h.

The resin is selected from acrylic resin, alkyd resin, epoxy resin, urethane resin, polyester resin, epoxy polyester resin, vinyl acetate resin, styrene-butadiene copolymer resin, and acrylic-modified epoxy resin. The surface-treated weatherable steel material according to claim 1, wherein

The surface-treated weathering steel according to claim 1, wherein the phosphate compound is selected from zinc phosphate, calcium phosphate, magnesium phosphate, and condensed phosphate.

The pigment is iron oxide, carbon black, organic pigment, titanium dioxide, talc, precipitated barium sulfate, kaolin clay, calcium carbonate, alumina, silica powder, gypsum powder, vanadium compound, molybdenum compound, nitrate compound, and manganese compound The surface-treated weatherable steel material according to claim 1, which is selected.

When used outdoors, rust is formed above and below the resin-based coating, and this rust and the resin-based coating are combined and integrated to form a rust-resin-based coating composite integrated layer on the surface of the steel base. The surface-treated weather-resistant steel material according to any one of claims 1 to 4, which has been prepared.

A surface treating agent containing a resin, a phosphoric acid compound and a pigment, wherein the total content ratio of the phosphoric acid compound and the pigment is 40 to 95% by mass relative to the total dry mass of the surface treating agent. And a content ratio of the phosphate compound is 3 to 40% by mass.

A coating solution containing the surface treatment agent according to claim 6 is applied on at least one surface of a base material made of a weather-resistant steel material at normal temperature so that a dry film thickness is 2 to 100 μm, and this is applied at normal temperature. , or 200 ° C. and dried by heating at an ambient temperature below a method for producing a surface-treated weathering steel, which comprises forming a resin film having a water vapor permeability of 1000~5000g ^/ m 2 · 24h.