JP2004076066A - Rustproofing liquid and rustproof metal product - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、防錆性及び加熱後の防錆性に優れる低環境負荷性の防錆皮膜を金属面上に形成できる防錆処理液と、その処理液を塗布、乾燥して得られる高耐食性金属製品に関する。
【０００２】
【従来技術】
各種金属材料の耐食性や上塗り塗装皮膜との密着性等を改良するため、多くの場合、金属表面に無機系、有機系、又は両者を組み合せた防錆皮膜の形成処理がなされているが、２００℃を超える高温環境下でも長時間使用できるものは、耐熱性の観点から無機系皮膜、耐熱有機成分からなる皮膜、又は両者を組み合せた無機−耐熱有機複合皮膜である。耐熱有機成分（芳香族系の耐熱樹脂や有機化合物等）は、高価であったり、高温でないと皮膜形成反応が速やかに進まない（成膜しない）ものが殆どであり、実用上は、金属材料の耐熱性防錆処理は無機系皮膜に限定される。
【０００３】
工業的に広く活用されている無機系皮膜の代表例は、クロメート又はりん酸塩による化成処理皮膜であり、中でもクロメート処理は、金属材料表面に形成された６価クロムを含む不働態皮膜が、腐食因子に対する優れた遮蔽性と皮膜損傷に対する自己修復機能を発揮するため、非常に有効な防錆皮膜である。さらに、上塗り塗装皮膜との密着性に優れた塗装下地処理としても機能し、家電、建材、自動車部品等の分野で広く用いられている。鋼板メ−カ−のめっきラインでクロメート処理する場合、十分な防錆性を発揮する皮膜付着量（膜厚）を得るまでの処理時間が数秒から数十秒と短いため、通常のラインスピ−ドでの連続短時間処理が可能なことも大きな利点である。
【０００４】
ところが、近年の地球環境問題に対する関心の高まりを背景に、６価及び３価クロム（特に環境負荷性の高い６価クロム）を全く含まない防錆処理金属材料が求められており、クロメート処理を用いない、金属材料の６価及び３価クロムフリ−防錆処理技術の開発が盛んに進められている。６価及び３価クロムを含まない金属系化合物の中には、ある程度の腐食抑制機能を持つ皮膜を金属材料表面に形成するものが既に見出されており、クロメート処理液の主成分であるクロム酸塩と同様に、古くから金属材料の防錆処理に利用されてきた。
【０００５】
例えば、酸化力の強い過マンガン酸塩をベースとした処理液は金属材料の腐食をかなり軽減するが、安定性や効力においてクロム酸塩には及ばない〔前田重義、表面、２１、３７（６）、１９９９；腐食防食協会編、”金属防蝕技術便覧（新版４版）”、ｐ．５５１、日刊工業新聞社（１９７７）〕。また、バナジン酸塩、モリブデン酸塩、タングステン酸塩等は、クロム酸塩と同様のオキソ酸化合物であり、多くの金属面を不働態化するが、単独使用ではクロム酸塩による皮膜の防錆力には及ばない。タングステン酸塩を除くこれらの金属系化合物の多くは、６価クロムほどではないものの環境負荷性、安全性の面からも問題があり、例えば、バナジン酸塩には毒性がある。過マンガン酸塩、モリブデン酸塩は、６価及び３価クロム化合物と同様、「特定化学物質の環境への排出量の把握等及び管理の改善の促進に関する法律」（以下、ＰＲＴＲ法と略）の対象となる第一種指定化学物質に該当し、取り扱いにあたり、環境への排出量の届け出や製品安全データシート（ＭＳＤＳ）の交付等が義務付けられているため、環境負荷物質として、工業的な製造、管理面から大きな制約を受ける。
【０００６】
一方、有害性が殆どない非金属系の無機系処理の例として、金属表面に安定な保護皮膜を形成するポリりん酸塩、ポリけい酸塩等の無機系高分子皮膜が用いられているが〔腐食防食協会編、”金属防蝕技術便覧（新版４版）”、ｐ．５５１、日刊工業新聞社（１９７７）；腐食防食協会編、”防食技術便覧（初版）”、ｐ．６５２、日刊工業新聞社（１９８６）〕、クロメート処理皮膜の防錆力に及ばないのが現状である。
【０００７】
クロメート処理と並ぶ代表的な無機系処理として、りん酸亜鉛、りん酸マンガン等のりん酸塩による化成処理があり、６価及び３価クロムを含まない皮膜を形成する。これらは、金属材料の上塗り塗装後の耐食性、上塗り塗膜の密着性、加工時の潤滑性等を高めるため、自動車外板、家電ハウジング等の下地処理や摺動部品等に広く用いられている。しかしながら、りん酸亜鉛等の化成処理皮膜は、結晶性でポ−ラスなため腐食因子に対するバリア性に劣り、防錆力はクロメート処理のそれに全く及ばない。
【０００８】
また、りん酸塩結晶を金属表面上に均一にかつ速やかに析出させるため、結晶核形成剤（例えばチタンコロイド）で予め金属表面調整を行ったり、りん酸塩処理液の成分濃度や温度を結晶析出の最適状態に制御しなければならず、１工程処理で非晶質皮膜を形成できるクロメート処理に比べ、りん酸塩化成処理は、基本的に金属表面調整とりん酸塩皮膜形成の２工程処理が必要で、かつ操業管理が煩雑という欠点を有する。
【０００９】
皮膜の防錆能力を高めるため、クロム酸系水溶液を用いてりん酸塩皮膜の細孔をシーリング処理したり（シーリングクロメート処理）、結晶性のりん酸塩皮膜の上層に非晶質で緻密なりん酸塩皮膜を形成させて金属材料の耐食性を改善する試みがなされているが（特開２０００−３０９８８０号公報）、これでは皮膜形成処理が実質的に３工程になり、さらに煩雑になるだけでなく、新たな設備コストもかかり不利である。皮膜の防錆性を高める他の例として、りん酸塩皮膜中に高濃度のマグネシウムを含有させる技術が提案されているが（特開２００１−１５２３５６号公報）、基本的には表面調整とりん酸塩皮膜形成の２工程処理であり、また、皮膜付着量（膜厚）の割に防錆性はなお不十分であった。鋼板メーカーの亜鉛めっきラインで亜鉛めっき後に連続してりん酸塩処理を行う場合は、数秒から数十秒程度の短時間の皮膜形成処理が必要であり、このようなニ−ズに応えるため、りん酸塩皮膜を１〜４秒程度で形成する技術が提案されているが（特開２００１−２０７２７０号公報）、この技術も表面調整とりん酸塩皮膜形成の煩雑な２工程処理であることに変わりはない。
【００１０】
さらに、皮膜の形成性、摺動性、上塗り塗膜の耐水二次密着性等を高めるため、りん酸塩化成処理液には、前記ＰＲＴＲ法の対象となる第一種指定化学物質を含む場合が多く（例えば、耐摩耗性の皮膜形成剤としてりん酸マンガン、皮膜の結晶核形成剤としてニッケルイオンやマンガンイオン、金属表面エッチング剤としてフッ化水素酸等）、低環境負荷性の処理とは言えない。ＰＲＴＲ法の指定化学物質を使わないようにする動きの例として、ニッケルイオンを含まないりん酸塩処理液による化成処理方法が開示されているが（特開２００１−４９４５１号公報）、従来技術と同様、金属表面調整後にりん酸塩化成処理が続く煩雑な２工程処理であり、改良技術としては不十分であった。
以上、これまでに実施あるいは提案されている種々の無機系処理技術について特徴を説明したが、ＰＲＴＲ法の指定化学物質を含まない無機系の金属表面処理技術で、かつクロメート処理の優れた防錆力や操業性（１工程処理で防錆皮膜を形成できる簡便性）に匹敵するものは見当たらなかった。
【００１１】
【発明が解決しようとする課題】
本発明は、前記のような従来技術の問題点（煩雑な皮膜形成工程、ＰＲＴＲ法に抵触する化学物質の含有、防錆力の不足）を解決するためになされたものであり、ＰＲＴＲ法の指定化学物質を含まない防錆処理液と、該処理液で金属材料表面を１工程処理することにより、２００℃を超える高温環境下でも使用でき、クロメート処理された金属材料並みの優れた耐食性を発現する防錆処理金属製品を提供することを目的としている。
【００１２】
【課題を解決するための手段】
本発明者らは、前記課題を解決するために種々の検討を行った結果、ＰＲＴＲ法の指定化学物質を含まない特定の防錆処理液を用いれば、金属材料表面に塗布し直ちに加熱乾燥するだけで、十分な耐食性や、加熱後耐食性を発現する表面処理金属製品が得られることを見出した。
本発明は、このような知見を基にして完成されたものであり、その要旨とするところは、
（１）Ｂｅ、Ｂ、Ｃｒ、Ｍｎ、Ｃｏ、Ｎｉ、Ａｓ、Ｓｅ、Ｍｏ、Ｃｄ、Ｓｂ、Ｈｇ、Ｐｂ、Ｉｎ及びＴｅを除く元素のりん酸塩及び／又は亜りん酸塩（Ａ）、酸解離定数ｐＫａ ≦３の強酸性の無機酸（Ｂ）、及び、水を主成分とする防錆処理剤であって、前記りん酸塩及び／又は亜りん酸塩（Ａ）が、水に対し難溶性又は不溶性で、酸解離定数ｐＫａ ≦３の強酸に溶解性を有し、かつ、前記りん酸塩及び／又は亜りん酸塩（Ａ）と前記無機酸（Ｂ）の不揮発分質量比がＡ：Ｂ＝９０：１０〜２０：８０の範囲であることを特徴とする防錆処理液。
【００１３】
（２）前記りん酸塩及び／又は亜りん酸塩（Ａ）が、２価又は３価の金属の正りん酸塩、りん酸一水素塩又は正亜りん酸塩の１種又は２種以上である前記（１）に記載の防錆処理液。
（３）前記りん酸塩及び／又は亜りん酸塩（Ａ）が、りん酸三カルシウム〔Ｃａ３ （ＰＯ４ ）２ 〕、りん酸第二鉄（ＦｅＰＯ４ ）、りん酸亜鉛〔Ｚｎ３ （ＰＯ４ ）２ 〕、りん酸一水素カルシウム（ＣａＨＰＯ４ ）、りん酸一水素マグネシウム（ＭｇＨＰＯ４ ）又は亜りん酸カルシウム（ＣａＰＨＯ３ ）の１種又は２種以上である前記（２）に記載の防錆処理液。
【００１４】
（４）前記無機酸（Ｂ）が、りん酸（Ｈ３ ＰＯ４ ）、亜りん酸（Ｈ３ ＰＯ３ ）、次亜りん酸（Ｈ３ ＰＯ２ ）、ポリりん酸〔Ｈｎ＋２ Ｐｎ Ｏ３ｎ＋１（ｎ＝２〜６の整数）の単品又はこれらの２種以上の混合物〕又は硝酸（ＨＮＯ３ ）の１種又は２種以上である前記（１）に記載の防錆処理液。
（５）前記防錆処理液に無機系防錆添加剤（Ｃ）を更に含有し、前記りん酸塩及び／又は亜りん酸塩（Ａ）と前記無機酸（Ｂ）の合計と前記無機系防錆添加剤（Ｃ）の不揮発分質量比が（Ａ＋Ｂ）：Ｃ＝９９．５：０．５〜６０：４０の範囲である前記（１）〜（４）のいずれかに記載の防錆処理液。
【００１５】
（６）前記無機系防錆添加剤（Ｃ）が、コロイダルシリカ、二次凝集シリカ、又は金属の次亜りん酸塩の少なくとも１種である前記（５）に記載の防錆処理液。
（７）金属製品の表面に前記（１）〜（６）のいずれかに記載の防錆処理液を塗布、乾燥して防錆皮膜を形成してなる防錆処理金属製品であって、該防錆皮膜中のりん酸塩及び／又は亜りん酸塩が、非晶体、０．２μｍ未満の結晶サイズの微結晶体又は両者の混合構造体であることを特徴とする防錆処理金属製品。
（８）金属製品の表面に、前記（１）〜（６）のいずれかに記載の防錆処理液を塗布後、金属製品の表面温度を３０秒以内に１００℃以上に加熱し、乾燥することを特徴とする防錆処理金属製品の製造方法である。
【００１６】
【発明の実施の形態】
以下、本発明の実施の形態を詳述する。
本発明の防錆処理液においては、水に対し難溶性又は不溶性のりん酸塩及び／又は亜りん酸塩を強い酸性を示す無機酸で溶かして、環境負荷物質を含まない水性防錆処理液を調製する。また、本発明の防錆処理金属製品においては、前記防錆処理液を金属表面に塗布、加熱乾燥させることにより、耐熱性の防錆皮膜を形成する。本発明に用いるりん酸塩及び／又は亜りん酸塩は水に難溶性又は不溶性であり、金属面上に緻密なバリア層を形成し、水性腐食因子の金属面への進入を抑制する。また、無機酸は、りん酸塩及び／又は亜りん酸塩を溶解させるためだけではなく、金属面をエッチングして防錆皮膜と金属面との密着性を高めたり、金属面と反応して皮膜の一部となりその耐食性を高めることも目的として添加される。りん酸塩及び／又は亜りん酸塩を溶解し、かつ金属面との反応性の高い酸解離定数ｐＫａ ≦３の無機酸を選択することが、十分な耐食性を発現する防錆皮膜を得るための大きな技術上のポイントである。
【００１７】
本発明の防錆処理液で用いるりん酸塩及び／又は亜りん酸塩（Ａ）は、ＰＲＴＲ法の指定化学物質を含んでいてはならない。従って、ＰＲＴＲ法の第一種指定化学物質の中で、Ｂｅ、Ｂ、Ｃｒ、Ｍｎ、Ｃｏ、Ｎｉ、Ａｓ、Ｓｅ、Ｍｏ、Ｃｄ、Ｓｂ、Ｈｇ、またはＰｂを含み、水に対し難溶性又は不溶性のりん酸塩及び／又は亜りん酸塩、及び、第二種指定化学物質の中で、Ｉｎ又はＴｅを含み、水に対し難溶性又は不溶性のりん酸塩及び／又は亜りん酸塩は、本発明の（Ａ）から除外される。例えば、りん酸コバルト、りん酸マンガン、りん酸ニッケル、亜りん酸コバルト等は除外される。
【００１８】
また、本発明の防錆処理液で用いるりん酸塩及び／又は亜りん酸塩（Ａ）は、水に対し難溶性又は不溶性、具体的には、２５℃における水への溶解度が０．５ｇ／水１００ｇ以下でなければならない。２５℃における水への溶解度が０．５ｇ／水１００ｇを超える場合、皮膜の保湿性が高まるため、湿気、及び湿気と共に皮膜に侵入する親水性の腐食因子により皮膜のバリア性が低下し、防錆性が不十分になる。
【００１９】
本発明の防錆処理液で用いるりん酸塩及び／又は亜りん酸塩（Ａ）は、前記の２条件、即ち、▲１▼ＰＲＴＲ法の指定化学物質でない、▲２▼２５℃における水への溶解度が０．５ｇ／水１００ｇ以下、という条件を満たした上で、２価又は３価の金属の正りん酸塩（Ｍが２価金属の場合Ｍ３ （ＰＯ４ ）２ 、Ｍが３価金属の場合ＭＰＯ４ ）、りん酸一水素塩（Ｍが２価金属の場合ＭＨＰＯ４ 、Ｍが３価金属の場合Ｍ２ （ＨＰＯ４ ）３ 又は正亜りん酸塩（Ｍが２価金属の場合ＭＰＨＯ３ 、Ｍが３価金属の場合Ｍ２ （ＰＨＯ３ ）３ の１種又は２種以上の混合物であることが好ましい。
【００２０】
本発明の防錆処理液を金属製品表面に塗布、乾燥して防錆皮膜を形成する際、後述する非晶体を皮膜中に形成しやすいものとしては、前記の好ましいりん酸塩の内、りん酸第二鉄（ＦｅＰＯ４ ）、りん酸三カルシウム〔Ｃａ３ （ＰＯ４ ）２ 〕やりん酸第一錫〔Ｓｎ３ （ＰＯ４ ）２ 〕等の正りん酸塩が挙げられる。また、皮膜乾燥条件により、後述する非晶体や０．２μｍ未満の結晶サイズの微結晶体を皮膜中に形成可能なものとしては、前記の好ましいりん酸塩及び／又は亜りん酸塩の内、りん酸亜鉛〔Ｚｎ３ （ＰＯ４ ）２ 〕、りん酸マグネシウム〔Ｍｇ３ （ＰＯ４ ）２ 〕、りん酸第一鉄〔Ｆｅ３ （ＰＯ４ ）２ 〕、りん酸マグネシウムアンモニウム〔Ｍｇ（ＮＨ４ ）ＰＯ４ 〕、りん酸第一セリウム（ＣｅＰＯ４ ）、りん酸第二鉄（ＦｅＰＯ４ ）、りん酸ビスマス（ＢｉＰＯ４ ）等の正りん酸塩、りん酸一水素カルシウム（ＣａＨＰＯ４ ）、りん酸一水素第一錫（ＳｎＨＰＯ４ ）、りん酸一水素マグネシウム（ＭｇＨＰＯ４ ）等のりん酸一水素塩、亜りん酸カルシウム（ＣａＰＨＯ３ ）、亜りん酸マグネシウム（ＭｇＰＨＯ３ ）、亜りん酸第一鉄（ＦｅＰＨＯ３ ）等の正亜りん酸塩が挙げられる。
【００２１】
これらは、非晶性、結晶性に関わらず、１種又は２種以上の混合物として用いてもよいが、後述するように、０．２μｍ以上のサイズの粗い結晶が生じないように、皮膜乾燥条件に留意する必要がある。また、これらの好ましい例の内、りん酸三カルシウム〔Ｃａ３ （ＰＯ４ ）２ 〕、りん酸第二鉄（ＦｅＰＯ４ ）、りん酸亜鉛〔Ｚｎ３ （ＰＯ４ ）２ 〕、りん酸一水素カルシウム（ＣａＨＰＯ４ ）、りん酸一水素マグネシウム（ＭｇＨＰＯ４ ）、亜りん酸カルシウム（ＣａＰＨＯ３ ）の１種又は２種以上の混合物が、コストや性能の点から特に好ましい。
【００２２】
本発明の防錆処理液では、２価又は３価金属以外のりん酸塩で、水に対し難溶性のものとして、例えば、１価金属の難溶性りん酸塩であるりん酸リチウム（Ｌｉ３ ＰＯ４ ）も用いることができる。りん酸リチウム（Ｌｉ３ ＰＯ４ ）は結晶性のため、後述するように、０．２μｍ以上のサイズの粗い結晶が生じないように、皮膜乾燥条件に留意する必要がある。
本発明の防錆処理液において、水に難溶性又は不溶性のりん酸塩及び／又は亜りん酸塩を溶解し、かつ防錆皮膜成分の一部となる酸（Ｂ）は、水溶液中で酸解離定数ｐＫａ ≦３の強酸性を示す無機酸で、かつＰＲＴＲ指定化学物質以外のものでなければならない。炭素原子を含む有機酸には、２００℃を超える高温環境下での長期使用に耐えることができないものが多く、有機酸を用いると皮膜の加熱後の防錆性が著しく低下するため、炭素原子を含まない無機酸を用いる必要がある。
【００２３】
また、酸解離定数ｐＫａ ＞３の弱酸は、水に対し難溶性又は不溶性のりん酸塩及び／又は亜りん酸塩を殆ど溶解できないか、又は溶解できても多量の酸が必要な場合が多く、本発明の処理液の作液には不適である。ここで、酸解離定数ｐＫａ とは、水溶液中での酸の解離平衡
ＨＡ＋Ｈ２ Ｏ ←→ Ｈ３ Ｏ＋ ＋Ａ− （ＨＡ：ブレンステッド酸、Ａ− ：ＨＡの共役塩基）において、Ｋａ＝［Ｈ３ Ｏ＋ ］［Ａ− ］／［ＨＡ］（［ ］は各成分の濃度を表わす）であり、ｐＫａ ＝−ｌｏｇＫａ のことである。
【００２４】
本発明の防錆処理液では、水溶液中で酸解離定数ｐＫａ ≦３を示す強酸性の無機酸で、かつＰＲＴＲ指定化学物質以外のものとして、例えば、りん酸（Ｈ３ ＰＯ４ ）、亜りん酸（Ｈ３ ＰＯ３ ）、次亜りん酸（Ｈ３ ＰＯ２ ）、ポリりん酸〔Ｈｎ＋２ Ｐｎ Ｏ３ｎ＋１（ｎ＝２〜６の整数）の単品又はこれらの２種以上の混合物〕、硝酸（ＨＮＯ３ ）、硫酸（Ｈ２ ＳＯ４ ）、亜硫酸（Ｈ２ ＳＯ３ ）、過塩素酸（ＨＣｌＯ４ ）、塩素酸（ＨＣｌＯ３ ）、亜塩素酸（ＨＣｌＯ２ ）、臭素酸（ＨＢｒＯ３ ）、ヨウ素酸（ＨＩＯ３ ）、過酸化水素（Ｈ２ Ｏ２ ）等のオキソ酸、塩酸（ＨＣｌ）、臭化水素酸（ＨＢｒ）、ヨウ化水素酸（ＨＩ）等の水素酸、チオ硫酸（Ｈ２ Ｓ２ Ｏ３ ）、等のチオ酸等を用いることができる。これらの中で、りん酸（Ｈ３ ＰＯ４ ）、亜りん酸（Ｈ３ ＰＯ３ ）、次亜りん酸（Ｈ３ ＰＯ２ ）、ポリりん酸〔Ｈｎ＋２ Ｐｎ Ｏ３ｎ＋１（ｎ＝２〜６の整数）の単品又はこれらの２種以上の混合物〕、硝酸（ＨＮＯ３ ）、又はこれらの２種以上の混合物が、コストや性能の点から好ましい。
【００２５】
無機酸（Ｂ）は、処理液を金属面に塗布、加熱乾燥する過程で、被塗金属面と反応してその金属の難溶性塩や錯塩を形成したり、自身が脱水縮合したり、そのまま固化したりして、防錆皮膜成分の一部となる。このように（Ｂ）から生じた皮膜成分は、後述するように、（Ａ）の場合と同様、０．２μｍ以上のサイズの粗い結晶が生じないように、皮膜乾燥条件に留意する必要がある。
【００２６】
本発明の防錆処理液において、水に対し難溶性又は不溶性のりん酸塩及び／又は亜りん酸塩（Ａ）と水溶液中で酸解離定数ｐＫａ ≦３を示す強酸性の無機酸（Ｂ）の不揮発分質量比は、９０：１０〜２０：８０、好ましくは８０：２０〜３０：７０の範囲になければならない。（Ａ）の不揮発分質量比が２０％未満の場合、金属面上の形成皮膜中のバリア層構成成分が少なく、防錆効果が不十分になる。（Ａ）の不揮発分質量比が９０％を超える場合、（Ａ）が相対的に多すぎて、（Ｂ）により完全溶解できないため、皮膜を形成できないか、又は、皮膜を形成できても未溶分が混在する欠陥の多いものとなり、防錆効果が不十分になる。
【００２７】
本発明の防錆処理液には、りん酸塩及び／又は亜りん酸塩（Ａ）、無機酸（Ｂ）以外に無機系防錆添加剤（Ｃ）をさらに添加してもよい。（Ｃ）は、防錆皮膜中で腐食抑制機能を発揮し、本発明の水性処理液に溶解、均一分散あるいは懸濁させることができ、かつＰＲＴＲ指定化学物質以外のものであれば、どのような添加剤を用いてもよい。また、（Ｃ）は、処理液に直接添加しても、予め水に溶解、分散あるいは懸濁させてから処理液に添加してもよい。しかしながら、（Ｃ）と水との濡れ性を高めるため湿潤剤を用いたり、処理液中での（Ｃ）の分散性を高めるため分散剤（界面活性剤）を用いたり、湿潤剤と分散剤を併用したり、粒子の沈降を防ぐため増粘剤を添加したりする場合は、これらの薬剤が、加熱により劣化する有機化合物である場合が多いため、必要最小限の使用量に抑え、防錆皮膜が長時間加熱後も劣化せずに、緻密性、防錆性を保持するように、留意する必要がある。
【００２８】
本発明に用いる無機系防錆添加剤（Ｃ）の例としては、タングステン酸塩、アルミナ、チタニア、ジルコニア、イットリア、セリア、シリカ等の無機系ゾル、防錆顔料、シロキサン結合を有する化合物、シランカップリング剤、チタンカップリング剤、次亜りん酸塩等が挙げられるが、コロイダルシリカ、二次凝集シリカ、及び次亜りん酸塩が好ましい。コロイダルシリカや二次凝集シリカは、金属の腐食抑制機能に加え、皮膜強度を高めたり、金属表面と皮膜との密着性を高める機能もある。これらの機能を効果的に発揮するためには、一次粒子径は２〜３０ｎｍ、二次凝集シリカの場合は、さらに二次凝集粒子径が２００ｎｍ以下が好ましい。次亜りん酸塩としては、次亜りん酸ナトリウム、次亜りん酸カルシウムが特に好ましい。
【００２９】
本発明で前記の防錆添加剤（Ｃ）を処理液に添加する場合、りん酸塩及び／又は亜りん酸塩（Ａ）と無機酸（Ｂ）の合計（Ａ＋Ｂ）と該防錆添加剤（Ｃ）の不揮発分質量比は、９９．５：０．５〜６０：４０、好ましくは９９：１〜７０：３０の範囲内が好ましい。（Ｃ）の不揮発分質量比が０．５％未満の場合、皮膜中での存在量が少ないため添加効果が得にくい。（Ｃ）の不揮発分質量比が４０％を超える場合、（Ｃ）が（Ａ＋Ｂ）に比べ相対的に多くなるため皮膜の緻密性が低下しやすく、皮膜の本来のバリア効果が十分に発揮できないおそれがある。
【００３０】
本発明の防錆処理液には、前記の防錆添加剤（Ｃ）以外にも、その目的を損なわない範囲で、各種の無機系あるいは有機系の化合物を含んでいても差し支えない。このような添加剤の例としては、無機系潤滑剤、前記以外の無機系ゾル、各種の無機系顔料、耐熱樹脂、耐熱性の有機腐食抑制剤等が挙げられる。
本発明の防錆処理液は、各種金属に適用でき、例えば、アルミニウム、チタン、亜鉛、銅、ニッケル、そして鋼等が適用可能である。このうち、鋼を使用する場合には、成分を特に限定せず、普通鋼であってもＣｒ含有鋼であっても良い。
【００３１】
また、鋼の表面に被覆めっき層があってもよいが、その種類を特に限定せず、適用可能なめっき層としては、例えば、亜鉛、アルミニウム、コバルト、錫、ニッケルのいずれか１種からなるめっき、及び、これらの金属元素やさらに他の金属元素、非金属元素を含む合金めっきが挙げられる。めっき層の形成方法も特に限定せず、例えば電気めっき、無電解めっき、溶融めっき、気相めっき等を用いることができる。めっき処理方法は、連続式、バッチ式のいずれでもよく、例えば溶融めっきでは、連続式は主に薄板材、線材類に用いられ、バッチ式のめっきは、管類、圧延材、加工品、ボルト・ナット類、鋳鍛造品類等の最終製品に成形した後に溶融めっき浴に浸漬することによる（いわゆる後めっき）。
また、鋼板へのめっき後の処理として、溶融めっき後の外観均一処理であるゼロスパングル処理、めっき層の改質処理である焼鈍処理、表面状態や材質調整のための調質圧延等があり得るが、本発明においては特にこれらを限定せず、いずれを適用することも可能である。
【００３２】
本発明において、防錆処理皮膜と金属との界面にＰＲＴＲ法の指定化学物質を含有しない下地処理皮膜を設けてもよい。該皮膜組成を特に限定しないが、金属面と上層防錆皮膜のそれぞれに対し密着性に優れ、かつ腐食抑制能を有する化合物により形成されることが好ましい。例えば、ジルコニウム、タングステン又は希土類元素の１種又は２種以上を含む金属系化合物、該金属系化合物以外のりん酸塩、亜りん酸塩、シロキサン結合を有する化合物、シランカップリング剤、チタンカップリング剤等から選ばれた１種又は２種以上の化合物が挙げられる。
【００３３】
本発明の金属製品では、金属面上に形成された防錆皮膜に、りん酸塩及び／又は亜りん酸塩が、非晶体、０．２μｍ未満の結晶サイズの微結晶体、又は両者の混合構造体の状態で存在しなければならない。０．２μｍ以上の結晶サイズのりん酸塩及び／又は亜りん酸塩の結晶粒を含む場合、皮膜はポ−ラスとなり、非晶構造、０．２μｍ未満の結晶サイズの微結晶構造又は両者の混合構造のりん酸塩及び／又は亜りん酸塩を含む皮膜に比べ、腐食因子のバリア性に劣るため、優れた防錆性が得られない。なお、ここでいう非晶体とは、如何なる分析法によっても結晶を確認できないアモルファス、無定形構造体のことである。また、ここでいう微結晶体とは、単一結晶あるいは２種以上の混合晶の存在を確認できるが結晶の最大長さがいずれも０．２μｍ未満である構造体のことである。非晶体と微結晶体の混合構造体とは、前記の非晶構造と微結晶構造が混在した構造体のことである。
【００３４】
また、本発明で用いる無機酸（Ｂ）は、処理液を金属面に塗布、加熱乾燥する過程で、被塗金属面と反応してその金属の難溶性塩や錯塩を形成したり、自身が脱水縮合したり、そのまま固化したりして防錆皮膜成分の一部となるが、このように（Ｂ）から生じた皮膜成分も、同様に、皮膜中で、非晶体、０．２μｍ未満の結晶サイズの微結晶体、又は両者の混合構造体でなければならない。０．２μｍ以上の結晶サイズの結晶粒を含む場合、皮膜はポ−ラスとなり、非晶構造、０．２μｍ未満の結晶サイズの微結晶構造又は両者の混合構造からなる皮膜に比べ、腐食因子のバリア性に劣るため、優れた防錆性が得られない。
【００３５】
前記のりん酸塩の中で、りん酸第二鉄は、水和水の数により結晶体（２水和物）と非晶体の２種が得られるが、非晶体が得られるように皮膜乾燥条件を工夫すればよく、例えば、りん酸第二鉄を含む防錆処理液を金属表面に塗布直後に、３０秒以内で金属表面到達温度が１００℃以上になるように加熱乾燥する。また、りん酸三カルシウム〔Ｃａ３ （ＰＯ４ ）２ 〕やりん酸第一錫〔Ｓｎ３ （ＰＯ４ ）２ 〕は、基本的に非晶性であるが、余分な水和水を皮膜形成と同時に除くため、防錆処理液を金属表面に塗布し、りん酸第二鉄の場合と同様に、３０秒以内で金属表面到達温度が１００℃以上になるように加熱乾燥すればよい。
【００３６】
また、結晶体を形成しやすいりん酸塩及び／又は亜りん酸塩の場合、０．２μｍ以上の結晶サイズのりん酸塩結晶及び／又は亜りん酸塩結晶が生じない皮膜乾燥条件を選ぶ必要がある。例えば、結晶性りん酸塩及び／又は結晶性亜りん酸塩を含む処理液を金属表面に塗布した直後に、０．２μｍ以上のサイズの粗い結晶が生じないように、急速に加熱乾燥すればよい。最適な乾燥条件は、結晶性りん酸塩及び／又は亜りん酸塩の種類により異なるが、処理液を金属表面に塗布した直後に３０秒以内で金属表面到達温度が１００℃以上になるように急速加熱乾燥すれば、大抵のりん酸塩、亜りん酸塩の場合、０．２μｍ以上のサイズの粗い結晶は生じない。このような乾燥条件で０．２μｍ以上のサイズの粗い結晶が生じる場合は、金属表面の昇温速度をさらに速めたり、金属表面到達温度を高めたりすればよい。
【００３７】
本発明において、金属又は金属面の下地処理皮膜上への防錆処理皮膜形成の方法としては、（Ａ）及び（Ｂ）が、金属面上の防錆皮膜中で、非晶体、皮膜中で０．２μｍ未満の結晶サイズの微結晶体、又は両者の混合構造体になるような方法であれば、特に限定しない。このような方法としては、例えば、防錆処理浴への金属のディップ、防錆処理液のロ−ルコ−ト、バ−コ−ト、刷毛塗り、あるいはスプレ−等の後、熱風等で加熱乾燥すればよいが、他の方法で塗布、皮膜形成させてもよく、ここで掲げた方法に限定しない。しかしながら、安定製造の観点から、塗布後３０秒以内で金属表面到達温度が１００℃以上になるようにすることが好ましい。本発明において、金属表面上への防錆皮膜の付着量は、０．０５〜３ｇ／ｍ２ が好ましく、０．１〜２ｇ／ｍ２ が特に好ましい。０．０５ｇ／ｍ２ 未満では、腐食因子の透過抑止効果が小さく十分な耐食性が得られない可能性がある。３ｇ／ｍ２ を超えると、腐食因子の透過抑止効果は優れるが、皮膜コストが大幅に上昇する懸念がある。
【００３８】
【実施例】
以下、本発明を実施例及び比較例によって具体的に説明するが、本発明は、これらの実施例により限定されるものではない。
［金属の種類］
（１）ＥＧ：電気亜鉛めっき鋼板（板厚０．８ｍｍ）
（２）ＧＩ：溶融亜鉛めっき鋼板（板厚０．８ｍｍ）
（３）ＧＡ：合金化溶融亜鉛めっき鋼板（板厚０．８ｍｍ）
（４）ＺＬ：Ｚｎ−Ｎｉ系合金めっき鋼板（板厚０．８ｍｍ）
（５）ＳＺ：Ｚｎ−５％Ａｌ系合金めっき鋼板（板厚０．８ｍｍ）
（６）ＳＤ：Ｚｎ−１１％Ａｌ−３％Ｍｇ−Ｓｉ合金めっき鋼板（板厚０．８ｍｍ）
【００３９】
［防錆処理皮膜の形成］
水に対し難溶又は不溶で、酸解離定数ｐＫａ ≦３の強酸に溶解するりん酸塩又は亜りん酸塩（Ａ）、酸解離定数ｐＫａ ≦３の強酸性の無機酸（Ｂ）を必須成分とし、さらにＡ、Ｂ以外の無機系防錆添加剤（Ｃ）を必要に応じて含有する水性防錆処理液を作成し、前記金属にバ−コ−タにより塗布し、直ちに、金属表面到達温度が１５０℃になるように２５０℃の熱風炉内に約２０秒間静置し、乾燥、成膜し、その後直ちに水冷して被験材とした。
【００４０】
比較材として、水溶性りん酸塩や酸解離定数ｐＫａ ＞３の無機酸を用いた処理液を作成し、前記と同様に加熱乾燥し、金属面に成膜した。また、他の比較材として、金属面を結晶核形成剤で表面調整後、処理液をバ−コ−タにより塗布、６０℃の熱風炉内で徐々に風乾してりん酸塩の粗結晶が析出した皮膜を有する金属を用いた。りん酸塩の結晶は、走査型電子顕微鏡で皮膜表面を観察することにより確認した。各処理液の作成に用いた薬品類を表１に示す。これらの薬品の内、水和数不明の含水塩の形で入手したりん酸第二鉄（ＦｅＰＯ４ ・ｍＨ２ Ｏ）、２〜６量体の混合物の形で入手したポリりん酸〔Ｈｎ＋２ Ｐｎ Ｏ３ｎ＋１（ｎ＝２〜６の整数）］については、それぞれｍ＝２．５、ｎ＝４として、処理液中の不揮発分質量計算に用いた。各皮膜の構成成分とそれらの質量比、皮膜付着量等を表２〜４に示す。
【００４１】
【表１】
［比較クロメート皮膜の形成］
前記の処理皮膜に対する比較材として、前記の各金属にＣｒ付着量３０ｍｇ／ｍ２ の塗布型クロメート処理を行ったものを用い、前記の防錆処理皮膜を形成した金属と耐食性を相対比較した。
【００４３】
［耐食性の評価（加熱処理なし）］
（１）平板耐食性
前記の防錆処理金属及び比較クロメート材についてＪＩＳ−Ｚ２３７１に準拠した塩水噴霧試験を行い、１２０時間後の白錆発生面積を測定し、防錆処理金属と対応する比較クロメート材の白錆発生面積を相対比較することにより、耐食性の合否を判定した。防錆処理金属、比較クロメート材の白錆発生面積率をそれぞれＸ％、Ｙ％とすると、判定基準は、
評点 ４ Ｘ＜Ｙ
３ Ｘ≒Ｙ
２ Ｙ＜Ｘ＜２Ｙ
１ ２Ｙ≦Ｘ
とし、評点３以上を合格とした。
【００４４】
（２）加工部耐食性
前記の防錆処理金属及び比較クロメート材に７ｍｍのエリクセン加工を施し、ＪＩＳ−Ｚ２３７１に準拠した塩水噴霧試験を行い、１２０時間後の加工部における白錆発生面積を測定し、防錆処理金属と対応する比較クロメート材の白錆発生面積を相対比較することにより加工部耐食性の合否を判定した。判定基準は前記の平板耐食性の場合と同じで、
評点 ４ Ｘ＜Ｙ
３ Ｘ≒Ｙ
２ Ｙ＜Ｘ＜２Ｙ
１ ２Ｙ≦Ｘ
とし、評点３以上を合格とした。
【００４５】
［耐食性の評価（加熱処理後）］
（１）加熱処理後の平板耐食性
前記の防錆処理金属及び比較クロメート材のうち、ＥＧをベースとしたもの以外について、大気雰囲気下、熱風炉で３００℃、５時間加熱処理し、放冷した。また、ＥＧベースの防錆処理金属及びクロメート材は、大気雰囲気下、熱風炉で２００℃、５時間加熱処理し、放冷した。これらを被験材としてＪＩＳ−Ｚ２３７１に準拠した塩水噴霧試験を行い、１２０時間後の白錆発生面積を測定し、防錆処理金属と対応する比較クロメート材の白錆発生面積を相対比較することにより耐食性の合否を判定した。判定基準は、加熱処理なしの耐食性評価の場合と同じである。
【００４６】
（２）加熱処理後の加工部耐食性
前記と同様に加熱処理した防錆処理金属及び比較クロメート材に７ｍｍのエリクセン加工を施し、ＪＩＳ−Ｚ２３７１に準拠した塩水噴霧試験を行い、１２０時間後の白錆発生面積を測定し、防錆処理金属と対応する比較クロメート材の白錆発生面積を相対比較することにより耐食性の合否を判定した。判定基準は、加熱処理なしの耐食性評価の場合と同じである。
【００４７】
【表２】
【表３】
【表４】
以上の評価結果をまとめて表２〜４に示す。
水に対し難溶又は不溶で酸解離定数ｐＫａ ≦３の強酸に溶解するりん酸塩及び／又は亜りん酸塩（Ａ）、酸解離定数ｐＫａ ≦３の強酸性の無機酸（Ｂ）、あるいはさらに（Ａ）、（Ｂ）以外の無機系防錆添加剤（Ｃ）を必須成分とする水性防錆処理液の内、本発明の要件を満たすものを金属面に塗布後、急速加熱乾燥処理すると、クロメート処理材のレベルに匹敵する十分な耐食性、及び加熱処理後の耐食性を発現する金属製品が得られることがわかる。これらの防錆処理液は、ＰＲＴＲ法の指定化学物質を含まず低環境負荷性であり、かつ金属表面の１工程処理で皮膜形成できる。
【００５１】
一方、水溶性りん酸塩を用いた処理液を用いた場合（Ｎｏ．６９、７０）、皮膜を形成した金属製品の耐食性は、クロメート処理材のレベルに全く及ばない。酸解離定数ｐＫａ ＞３の無機酸を用いた処理液を用いた場合（Ｎｏ．２５、２６、５４、５５）、水に対し難溶又は不溶のりん酸塩を殆ど溶解できないため、金属面に皮膜形成できなかった。さらに、本発明で規定したりん酸塩及び／又は亜りん酸塩（Ａ）と無機酸（Ｂ）を用いていても、（Ｂ）に対する（Ａ）の不揮発分質量比が本発明で許容する範囲より小さな場合（Ｎｏ．３、１３、４２）、皮膜を形成した金属製品の耐食性はクロメート処理材のレベルに及ばず、また、（Ｂ）に対する（Ａ）の不揮発分質量比が本発明で許容する範囲より大きな場合（Ｎｏ．４、１４、４３）には、りん酸塩を完全溶解できず、金属面に皮膜形成できなかった。処理液を金属面に塗布後、６０℃で徐々に風乾して、りん酸塩の粗結晶が析出した皮膜では（Ｎｏ．２７、２８）、金属製品の耐食性はクロメート処理材のレベルに及ばなかった。
【００５２】
【発明の効果】
本発明の防錆処理液は、ＰＲＴＲ法に抵触する環境負荷物質を含まず、かつ防錆皮膜を１工程処理で金属面上に形成できるため、家電／ＯＡ機器、建築／土木、自動車／車輌分野等で広く用いられている金属製品の防錆処理液として好適である。また、本発明に係る防錆処理液で金属を表面処理することにより、クロメート処理材レベルの優れた耐食性を有する金属製品を安価な防錆処理コストで提供することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a rust preventive treatment solution capable of forming a low environmental load rust preventive film having excellent rust preventive properties and rust preventive properties after heating on a metal surface, and a high corrosion resistance obtained by applying and drying the treatment liquid. Metal products.
[0002]
[Prior art]
In order to improve the corrosion resistance of various metal materials and the adhesion to the top coat, etc., in many cases, a metal surface is treated with an inorganic or organic rust-preventive film or a combination of both. Those that can be used for a long time even in a high-temperature environment exceeding ℃ are inorganic coatings, coatings composed of heat-resistant organic components, or inorganic-heat-resistant organic composite coatings combining both from the viewpoint of heat resistance. Most of the heat-resistant organic components (such as aromatic heat-resistant resins and organic compounds) are expensive or the film-forming reaction does not proceed rapidly (does not form a film) unless the temperature is high. Is limited to inorganic coatings.
[0003]
A typical example of an inorganic coating widely used industrially is a chemical conversion coating with chromate or phosphate. Among them, a chromate treatment is a passive coating containing hexavalent chromium formed on the surface of a metal material. It is a very effective rust preventive film because it exhibits excellent shielding properties against corrosion factors and self-healing function against film damage. Furthermore, it functions as a coating base treatment having excellent adhesion to a top coat, and is widely used in the fields of home appliances, building materials, automobile parts, and the like. When performing a chromate treatment on a plating line of a steel plate manufacturer, the processing time required to obtain a coating amount (film thickness) exhibiting sufficient rust prevention is as short as several seconds to several tens of seconds. It is also a great advantage that continuous short-time processing is possible.
[0004]
However, with the growing interest in global environmental problems in recent years, anticorrosion-treated metal materials that do not contain hexavalent and trivalent chromium (especially hexavalent chromium, which has a high environmental load) have been demanded. The development of hexavalent and trivalent chromium-free anticorrosion treatment techniques for metallic materials that are not used has been actively pursued. Among the metal-based compounds that do not contain hexavalent and trivalent chromium, those that form a film having a certain degree of corrosion inhibitory function on the surface of the metal material have already been found. Like acid salts, they have long been used for rust prevention treatment of metallic materials.
[0005]
For example, treatment solutions based on permanganates, which have a strong oxidizing power, significantly reduce the corrosion of metallic materials, but are inferior to chromates in stability and efficacy [Shigeyoshi Maeda, Surface, 21, 37 (6) ), 1999; Corrosion and Corrosion Protection Association, "Metal Corrosion Protection Technical Handbook (New Edition 4th Edition)", p. 551, Nikkan Kogyo Shimbun (1977)]. In addition, vanadate, molybdate, tungstate, etc. are oxo acid compounds similar to chromate and passivate many metal surfaces. It is inferior to power. Many of these metal compounds other than tungstate, although not as high as hexavalent chromium, have problems in terms of environmental load and safety. For example, vanadate is toxic. Permanganates and molybdates, like hexavalent and trivalent chromium compounds, are enacted in the "Act on the Estimation of Emissions of Specified Chemical Substances into the Environment and the Promotion of Improved Management" (hereinafter abbreviated as PRTR Law) It is classified as a Class I Designated Chemical Substance, and it is compulsory to report emissions to the environment and issue a Material Safety Data Sheet (MSDS) when handling it. Subject to significant restrictions on manufacturing and management.
[0006]
On the other hand, as an example of a non-metallic inorganic treatment having almost no harm, an inorganic polymer film such as polyphosphate or polysilicate which forms a stable protective film on a metal surface is used. [Corrosion and Corrosion Protection Association, “Metal Corrosion Protection Technical Handbook (New Edition 4th Edition)”, p. 551, Nikkan Kogyo Shimbun (1977); edited by the Corrosion and Corrosion Prevention Association, “Handbook of Corrosion Protection Technology (First Edition)”, p. 652, Nikkan Kogyo Shimbun (1986)]. At present, it does not reach the rust-preventing power of chromate-treated films.
[0007]
As a typical inorganic treatment similar to the chromate treatment, there is a chemical conversion treatment with a phosphate such as zinc phosphate or manganese phosphate, which forms a film containing neither hexavalent nor trivalent chromium. These are widely used in the surface treatment of automobile outer panels, home appliance housings and the like, sliding parts, etc. in order to enhance the corrosion resistance after the top coat application of metal materials, the adhesion of the top coat, the lubricity during processing, and the like. . However, chemical conversion coatings such as zinc phosphate are crystalline and porous and thus have poor barrier properties against corrosive factors, and their rust-prevention ability is inferior to that of chromate treatment.
[0008]
In addition, in order to deposit phosphate crystals uniformly and quickly on the metal surface, the metal surface is adjusted in advance with a crystal nucleating agent (for example, titanium colloid), or the component concentration and temperature of the phosphating solution are adjusted. Phosphate conversion treatment basically consists of two steps: metal surface conditioning and phosphate film formation, compared to chromate treatment, in which an amorphous film can be formed in one process. There is a drawback that processing is necessary and operation management is complicated.
[0009]
In order to enhance the rust prevention ability of the coating, the pores of the phosphate coating can be sealed using a chromic acid-based aqueous solution (sealing chromate treatment). Attempts have been made to improve the corrosion resistance of metal materials by forming a phosphate film (Japanese Patent Laid-Open No. 2000-309880), but this involves substantially three steps of film formation treatment, which is only more complicated. However, it is disadvantageous because new equipment costs are required. As another example of improving the rust prevention of the coating, a technique of containing a high concentration of magnesium in a phosphate coating has been proposed (Japanese Patent Application Laid-Open No. 2001-152356). This was a two-step treatment for forming an acid salt film, and the rust prevention was still insufficient for the amount of film adhesion (film thickness). In the case of continuous phosphate treatment after galvanizing in a zinc plating line of a steel sheet manufacturer, a short-time film formation treatment of several seconds to several tens of seconds is necessary, and in order to respond to such needs, Although a technique for forming a phosphate film in about 1 to 4 seconds has been proposed (Japanese Patent Application Laid-Open No. 2001-207270), this technique is also a complicated two-step process of surface adjustment and phosphate film formation. Has not changed.
[0010]
Furthermore, in order to enhance the film formability, sliding property, water-resistant secondary adhesion of the overcoat film, etc., the phosphate chemical conversion treatment liquid contains a first-class designated chemical substance subject to the PRTR method. (Eg, manganese phosphate as a wear-resistant film-forming agent, nickel ion or manganese ion as a film nucleating agent, hydrofluoric acid as a metal surface etching agent), and low environmental load treatment I can not say. A chemical conversion treatment method using a phosphating solution containing no nickel ion is disclosed as an example of the movement to prevent the use of the specified chemical substance of the PRTR method (Japanese Patent Application Laid-Open No. 2001-49451). Similarly, it is a complicated two-step treatment in which a phosphate chemical conversion treatment is performed after the metal surface adjustment, and it is insufficient as an improved technique.
The features of the various inorganic treatment technologies that have been implemented or proposed so far have been described above. The inorganic metal surface treatment technology that does not contain the designated chemical substances of the PRTR method, and the excellent chromate treatment is excellent. Nothing comparable to the strength and operability (the simplicity of forming a rust-preventive film in one process) was not found.
[0011]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art (complex film formation process, inclusion of a chemical substance that conflicts with the PRTR method, and lack of rust prevention ability). By treating the surface of a metal material with a rust-preventive treatment solution that does not contain the specified chemical substance and the treatment solution in one step, it can be used even in a high-temperature environment exceeding 200 ° C and has excellent corrosion resistance equivalent to that of a chromate-treated metal material. The purpose is to provide a rust-proof treated metal product that expresses.
[0012]
[Means for Solving the Problems]
The present inventors have conducted various studies in order to solve the above-mentioned problems. As a result, when a specific rust preventive treatment solution containing no designated chemical substance of the PRTR method is used, it is applied to the surface of a metal material and immediately dried by heating. Alone, it has been found that a surface-treated metal product exhibiting sufficient corrosion resistance and corrosion resistance after heating can be obtained.
The present invention has been completed based on such findings, and the gist of the present invention is as follows.
(1) Phosphate and / or phosphite (A) of an element other than Be, B, Cr, Mn, Co, Ni, As, Se, Mo, Cd, Sb, Hg, Pb, In and Te, Acid dissociation constant pK a A strongly acidic inorganic acid (B) of ≦ 3 and a rust preventive agent containing water as a main component, wherein the phosphate and / or phosphite (A) is hardly soluble in water or Insoluble, acid dissociation constant pK a Has a solubility in a strong acid of ≦ 3, and a non-volatile mass ratio of the phosphate and / or phosphite (A) to the inorganic acid (B) is A: B = 90: 10 to 20: A rust preventive solution having a range of 80.
[0013]
(2) The phosphate and / or phosphite (A) is one or more of divalent or trivalent metal orthophosphate, monohydrogen phosphate or orthophosphite. The rust preventive solution according to the above (1), which is:
(3) the phosphate and / or phosphite (A) is tricalcium phosphate [Ca 3 (PO 4 ) 2 ], Ferric phosphate (FePO 4 ), Zinc phosphate [Zn 3 (PO 4 ) 2 ], Calcium monohydrogen phosphate (CaHPO 4 ), Magnesium monohydrogen phosphate (MgHPO 4 ) Or calcium phosphite (CaPHO) 3 The rust preventive treatment liquid according to the above (2), which is one kind or two or more kinds of the above).
[0014]
(4) The inorganic acid (B) is phosphoric acid (H 3 PO 4 ), Phosphorous acid (H 3 PO 3 ), Hypophosphorous acid (H 3 PO 2 ), Polyphosphoric acid [H n + 2 P n O 3n + 1 (N = integer of 2 to 6) or a mixture of two or more thereof] or nitric acid (HNO 3 The rust preventive treatment liquid according to the above (1), which is one kind or two or more kinds of the above).
(5) The rust preventive treatment solution further contains an inorganic rust preventive additive (C), and the total of the phosphate and / or phosphite (A) and the inorganic acid (B) and the inorganic rust preventive additive are added. The rust preventive according to any one of the above (1) to (4), wherein the nonvolatile content mass ratio of the rust preventive additive (C) is in the range of (A + B): C = 99.5: 0.5 to 60:40. Processing liquid.
[0015]
(6) The rust preventive treatment liquid according to (5), wherein the inorganic rust preventive additive (C) is at least one of colloidal silica, secondary aggregated silica, and metal hypophosphite.
(7) A rustproofing metal product formed by applying the rustproofing solution according to any of (1) to (6) on the surface of the metal product and drying to form a rustproofing film. A rust-preventive metal product, wherein the phosphate and / or phosphite in the rust-preventive film is an amorphous material, a microcrystal having a crystal size of less than 0.2 μm, or a mixed structure of both.
(8) After applying the rust preventive solution according to any of (1) to (6) on the surface of the metal product, heat the surface temperature of the metal product to 100 ° C. or higher within 30 seconds and dry. A method for producing a rust-proof metal product, characterized in that:
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
In the rust preventive solution of the present invention, an aqueous rust preventive solution containing no environmentally hazardous substances by dissolving a phosphate and / or phosphite which is hardly soluble or insoluble in water with an inorganic acid showing strong acidity. Is prepared. Further, in the rust-proofing metal product of the present invention, a heat-resistant rust-proof coating is formed by applying the rust-proofing solution to the metal surface and drying by heating. The phosphate and / or phosphite used in the present invention is hardly soluble or insoluble in water, forms a dense barrier layer on a metal surface, and suppresses entry of an aqueous corrosion factor into the metal surface. In addition, the inorganic acid not only dissolves the phosphate and / or phosphite, but also etches the metal surface to increase the adhesion between the rust preventive film and the metal surface, or reacts with the metal surface. It is also added for the purpose of forming a part of the coating and increasing its corrosion resistance. An acid dissociation constant pK which dissolves phosphate and / or phosphite and has high reactivity with metal surfaces a Selecting an inorganic acid of ≦ 3 is a major technical point for obtaining a rust preventive film exhibiting sufficient corrosion resistance.
[0017]
The phosphate and / or phosphite (A) used in the rust preventive solution of the present invention must not contain a chemical substance specified by the PRTR method. Therefore, among the first-class designated chemical substances of the PRTR method, they include Be, B, Cr, Mn, Co, Ni, As, Se, Mo, Cd, Sb, Hg, or Pb, and are hardly soluble in water or Among the insoluble phosphates and / or phosphites and the second designated chemical substances, phosphates and / or phosphites that contain In or Te and are hardly soluble or insoluble in water are: , Are excluded from (A) of the present invention. For example, cobalt phosphate, manganese phosphate, nickel phosphate, cobalt phosphite and the like are excluded.
[0018]
Further, the phosphate and / or phosphite (A) used in the rust preventive solution of the present invention has a poor solubility or insolubility in water, specifically, a solubility in water at 25 ° C. of 0.5 g. / 100 g of water or less. When the solubility in water at 25 ° C. exceeds 0.5 g / 100 g of water, the moisture retention of the film is enhanced, and the barrier properties of the film are reduced by moisture and hydrophilic corrosion factors that enter the film together with the moisture, thus preventing Rust property becomes insufficient.
[0019]
Phosphate and / or phosphite (A) used in the rust preventive solution of the present invention may be used under the above two conditions, namely, (1) water which is not a designated chemical substance of the PRTR method, and (2) water at 25 ° C. Is 0.5 g / 100 g of water or less, and a bivalent or trivalent metal orthophosphate (when M is a divalent metal, M 3 (PO 4 ) 2 , MPO when M is a trivalent metal 4 ), Monohydrogen phosphate (MHPO when M is a divalent metal) 4 , When M is a trivalent metal, M 2 (HPO 4 ) 3 Or orthophosphite (MPHO when M is a divalent metal) 3 , When M is a trivalent metal, M 2 (PHO 3 ) 3 Or a mixture of two or more of the above.
[0020]
When the rust-preventive treatment liquid of the present invention is applied to the surface of a metal product and dried to form a rust-preventive film, an amorphous substance described later is easily formed in the film. Ferric acid (FePO 4 ), Tricalcium phosphate [Ca 3 (PO 4 ) 2 ] Or stannous phosphate [Sn 3 (PO 4 ) 2 ] And other normal phosphates. Further, among the above-mentioned preferred phosphates and / or phosphites, those which can form an amorphous material or a microcrystal having a crystal size of less than 0.2 μm in the film depending on the film drying conditions include the following: Zinc phosphate [Zn 3 (PO 4 ) 2 ], Magnesium phosphate [Mg 3 (PO 4 ) 2 ], Ferrous phosphate [Fe 3 (PO 4 ) 2 ], Magnesium ammonium phosphate [Mg (NH 4 ) PO 4 ], Cerous phosphate (CePO) 4 ), Ferric phosphate (FePO 4 ), Bismuth phosphate (BiPO 4 ), Calcium phosphate monohydrogen (CaHPO) 4 ), Stannous hydrogen phosphate (SnHPO) 4 ), Magnesium monohydrogen phosphate (MgHPO 4 ), Calcium phosphite (CaPHO) 3 ), Magnesium phosphite (MgPHO) 3 ), Ferrous phosphite (FePHO) 3 ) And the like.
[0021]
These may be used alone or as a mixture of two or more, regardless of amorphousness or crystallinity. However, as described later, the film is dried so that coarse crystals having a size of 0.2 μm or more are not generated. It is necessary to pay attention to the conditions. Among these preferred examples, tricalcium phosphate [Ca 3 (PO 4 ) 2 ], Ferric phosphate (FePO 4 ), Zinc phosphate [Zn 3 (PO 4 ) 2 ], Calcium monohydrogen phosphate (CaHPO 4 ), Magnesium monohydrogen phosphate (MgHPO 4 ), Calcium phosphite (CaPHO) 3 )) Or a mixture of two or more types) is particularly preferred from the viewpoint of cost and performance.
[0022]
In the rust preventive solution of the present invention, phosphates other than divalent or trivalent metals which are hardly soluble in water, for example, lithium phosphate (Li) which is a hardly soluble phosphate of monovalent metal 3 PO 4 ) Can also be used. Lithium phosphate (Li 3 PO 4 ) Is crystalline, so that it is necessary to pay attention to the film drying conditions so as not to generate coarse crystals having a size of 0.2 μm or more as described later.
In the rust preventive treatment solution of the present invention, the acid (B) which dissolves a phosphate or / and phosphite which is hardly soluble or insoluble in water and which becomes a part of the rust preventive film component is converted into an acid in an aqueous solution. Dissociation constant pK a It must be an inorganic acid showing strong acidity of ≦ 3 and not a PRTR-designated chemical substance. Many organic acids containing carbon atoms cannot withstand long-term use in a high-temperature environment exceeding 200 ° C, and the use of organic acids significantly reduces the rust resistance of the film after heating. It is necessary to use an inorganic acid containing no.
[0023]
Also, the acid dissociation constant pK a The weak acid of> 3 hardly dissolves phosphates and / or phosphites which are hardly soluble or insoluble in water, or often requires a large amount of acid even if it can be dissolved. It is not suitable for the preparation of Here, the acid dissociation constant pK a Is the dissociation equilibrium of acid in aqueous solution
HA + H 2 O ← → H 3 O + + A − (HA: Bronsted acid, A − : Conjugate base of HA) a = [H 3 O + ] [A − ] / [HA] ([] indicates the concentration of each component) and pK a = -LogK a That is.
[0024]
In the rust preventive solution of the present invention, the acid dissociation constant pK a As a strongly acidic inorganic acid showing ≦ 3 and other than the PRTR-designated chemical substance, for example, phosphoric acid (H 3 PO 4 ), Phosphorous acid (H 3 PO 3 ), Hypophosphorous acid (H 3 PO 2 ), Polyphosphoric acid [H n + 2 P n O 3n + 1 (N = integer of 2 to 6) or a mixture of two or more thereof], nitric acid (HNO 3 ), Sulfuric acid (H 2 SO 4 ), Sulfurous acid (H 2 SO 3 ), Perchloric acid (HClO 4 ), Chloric acid (HClO 3 ), Chlorous acid (HClO 2 ), Bromic acid (HBrO) 3 ), Iodic acid (HIO) 3 ), Hydrogen peroxide (H 2 O 2 ), Hydrochloric acid such as hydrochloric acid (HCl), hydrobromic acid (HBr), hydroiodic acid (HI), thiosulfuric acid (H 2 S 2 O 3 ), Etc. can be used. Among these, phosphoric acid (H 3 PO 4 ), Phosphorous acid (H 3 PO 3 ), Hypophosphorous acid (H 3 PO 2 ), Polyphosphoric acid [H n + 2 P n O 3n + 1 (N = integer of 2 to 6) or a mixture of two or more thereof], nitric acid (HNO 3 ) Or a mixture of two or more of these is preferred in terms of cost and performance.
[0025]
The inorganic acid (B) reacts with the metal surface to be coated to form a hardly soluble salt or complex salt of the metal during the process of applying the treatment liquid to the metal surface and drying by heating, or the dehydration and condensation of the metal itself, or It solidifies and becomes a part of the rust preventive film component. As described later, as in the case of (A), it is necessary to pay attention to the film drying conditions so that coarse crystals having a size of 0.2 μm or more are not generated in the film component generated from (B) as described later. .
[0026]
In the rust preventive solution of the present invention, a phosphate and / or phosphite (A) which is hardly soluble or insoluble in water and an acid dissociation constant pK in an aqueous solution. a The non-volatile mass ratio of the strongly acidic inorganic acid (B) showing ≦ 3 must be in the range of 90:10 to 20:80, preferably 80:20 to 30:70. When the nonvolatile content mass ratio of (A) is less than 20%, the constituent components of the barrier layer in the formed film on the metal surface are small, and the rust prevention effect becomes insufficient. When the nonvolatile content mass ratio of (A) exceeds 90%, (A) is relatively too large and cannot be completely dissolved by (B), so that a film cannot be formed, or even if a film can be formed, There will be many defects mixed with the dissolved components, and the rust prevention effect will be insufficient.
[0027]
In addition to the phosphate and / or phosphite (A) and the inorganic acid (B), an inorganic rust preventive additive (C) may be further added to the rust preventive treatment solution of the present invention. (C) exhibits a corrosion inhibiting function in the rust-preventive film, and can be dissolved, uniformly dispersed or suspended in the aqueous treatment liquid of the present invention, and any substance other than a PRTR-designated chemical substance can be used. Various additives may be used. Further, (C) may be directly added to the treatment liquid, or may be dissolved, dispersed or suspended in water before being added to the treatment liquid. However, a wetting agent is used to enhance the wettability between (C) and water, a dispersing agent (surfactant) is used to enhance the dispersibility of (C) in the treatment liquid, or a wetting agent and a dispersing agent are used. When using together or adding a thickening agent to prevent sedimentation of particles, these agents are often organic compounds that deteriorate by heating. Care must be taken so that the rust film does not deteriorate even after being heated for a long time, and maintains its denseness and rust prevention.
[0028]
Examples of the inorganic rust preventive additive (C) used in the present invention include inorganic sols such as tungstate, alumina, titania, zirconia, yttria, ceria, silica, rust preventive pigments, compounds having a siloxane bond, and silanes. Coupling agents, titanium coupling agents, hypophosphites and the like can be mentioned, but colloidal silica, secondary aggregated silica and hypophosphite are preferred. Colloidal silica and secondary agglomerated silica have the function of increasing the strength of the film and the adhesion between the metal surface and the film, in addition to the function of suppressing corrosion of the metal. In order to exhibit these functions effectively, the primary particle diameter is preferably 2 to 30 nm, and in the case of secondary aggregated silica, the secondary aggregated particle diameter is more preferably 200 nm or less. As the hypophosphite, sodium hypophosphite and calcium hypophosphite are particularly preferred.
[0029]
In the present invention, when the rust preventive additive (C) is added to the treatment liquid, the total (A + B) of the phosphate and / or phosphite (A) and the inorganic acid (B) and the rust preventive additive are added. The nonvolatile content mass ratio of (C) is preferably from 99.5: 0.5 to 60:40, and more preferably from 99: 1 to 70:30. When the nonvolatile content mass ratio of (C) is less than 0.5%, the effect of addition is difficult to obtain because the amount present in the film is small. When the nonvolatile content mass ratio of (C) exceeds 40%, (C) becomes relatively large as compared with (A + B), so that the denseness of the film tends to decrease, and the original barrier effect of the film cannot be sufficiently exhibited. There is a risk.
[0030]
The rust preventive solution of the present invention may contain various inorganic or organic compounds in addition to the rust preventive additive (C) as long as its purpose is not impaired. Examples of such additives include inorganic lubricants, inorganic sols other than those described above, various inorganic pigments, heat-resistant resins, heat-resistant organic corrosion inhibitors, and the like.
The rust preventive solution of the present invention can be applied to various metals, for example, aluminum, titanium, zinc, copper, nickel, and steel. Among them, when steel is used, the components are not particularly limited, and may be ordinary steel or Cr-containing steel.
[0031]
Further, there may be a coating plating layer on the surface of the steel, but the type thereof is not particularly limited, and applicable plating layers include, for example, any one of zinc, aluminum, cobalt, tin, and nickel. Plating, and alloy plating containing these metal elements, further other metal elements, and non-metal elements are included. The method for forming the plating layer is not particularly limited, and for example, electroplating, electroless plating, hot-dip plating, vapor phase plating, and the like can be used. The plating method may be either a continuous method or a batch method.For example, in hot-dip plating, the continuous method is mainly used for thin sheets and wires, and the batch-type plating is for pipes, rolled materials, processed products, bolts, and the like. -By forming into final products such as nuts and cast and forged products, and then immersing in a hot-dip plating bath (so-called post-plating).
Further, as the treatment after plating on the steel sheet, there may be a zero spangle treatment which is an appearance uniform treatment after the hot-dip plating, an annealing treatment which is a modification treatment of the plating layer, a temper rolling for adjusting the surface state and the material, and the like. However, in the present invention, these are not particularly limited, and any of them can be applied.
[0032]
In the present invention, an undercoating film that does not contain a chemical substance specified by the PRTR method may be provided at the interface between the rustproofing film and the metal. The coating composition is not particularly limited, but is preferably formed of a compound having excellent adhesion to the metal surface and the upper rust-preventive coating and having a corrosion inhibiting ability. For example, a metal compound containing one or more of zirconium, tungsten or a rare earth element, a phosphate, a phosphite, a compound having a siloxane bond other than the metal compound, a silane coupling agent, a titanium coupling One or more compounds selected from agents and the like.
[0033]
In the metal product of the present invention, the rust-preventive film formed on the metal surface contains an amorphous substance, a microcrystalline substance having a crystal size of less than 0.2 μm, or a mixture of both. Must exist in the form of a structure. When phosphate and / or phosphite grains having a crystal size of 0.2 μm or more are included, the coating becomes porous and has an amorphous structure, a microcrystalline structure having a crystal size of less than 0.2 μm, or both. Compared to a phosphate- and / or phosphite-containing coating having a mixed structure, it is inferior in barrier properties against corrosion factors, so that excellent rust prevention cannot be obtained. The term “amorphous” as used herein refers to an amorphous or amorphous structure whose crystals cannot be confirmed by any analysis method. The term “microcrystal” as used herein refers to a structure in which the presence of a single crystal or a mixed crystal of two or more types can be confirmed, but the maximum length of each crystal is less than 0.2 μm. The mixed structure of an amorphous body and a microcrystalline body is a structure in which the above-mentioned amorphous structure and microcrystalline structure are mixed.
[0034]
In addition, the inorganic acid (B) used in the present invention reacts with the metal surface to be coated to form a hardly soluble salt or a complex salt of the metal during the process of applying the treatment liquid to the metal surface and drying by heating. Dehydration-condensation or solidification as it is becomes a part of the rust-preventive film component. In this manner, the film component generated from (B) is also amorphous, less than 0.2 μm in the film. It must be a microcrystal of crystal size or a mixed structure of both. When the film contains crystal grains having a crystal size of 0.2 μm or more, the film becomes porous, and the corrosion factor is lower than that of a film having an amorphous structure, a microcrystalline structure having a crystal size of less than 0.2 μm, or a mixed structure of both. Because of poor barrier properties, excellent rust prevention cannot be obtained.
[0035]
Among the above phosphates, ferric phosphate can be obtained in two forms, crystalline (dihydrate) and amorphous, depending on the number of water of hydration. Conditions may be devised. For example, immediately after the anticorrosive treatment solution containing ferric phosphate is applied to the metal surface, the metal surface is heated and dried so that the metal surface temperature reaches 100 ° C. or higher within 30 seconds. Also, tricalcium phosphate [Ca 3 (PO 4 ) 2 ] Or stannous phosphate [Sn 3 (PO 4 ) 2 ] Is basically amorphous, but in order to remove excess water of hydration at the same time as film formation, a rust preventive treatment solution is applied to the metal surface, and the same as in the case of ferric phosphate, for 30 seconds. The heating and drying may be performed so that the temperature at which the metal surface reaches 100 ° C. or higher within the range.
[0036]
In the case of a phosphate and / or phosphite which easily forms a crystal, it is necessary to select a film drying condition which does not generate phosphate crystals and / or phosphite crystals having a crystal size of 0.2 μm or more. There is. For example, immediately after applying a treatment solution containing crystalline phosphate and / or crystalline phosphite to a metal surface, it is rapidly heated and dried so that coarse crystals having a size of 0.2 μm or more are not generated. Good. Optimum drying conditions vary depending on the type of crystalline phosphate and / or phosphite, but should be such that the temperature attained on the metal surface is 100 ° C. or higher within 30 seconds immediately after the treatment liquid is applied to the metal surface. With rapid heating and drying, most phosphates and phosphites do not produce coarse crystals having a size of 0.2 μm or more. When coarse crystals having a size of 0.2 μm or more are generated under such drying conditions, the rate of temperature rise on the metal surface may be further increased, or the temperature reached to the metal surface may be increased.
[0037]
In the present invention, as a method of forming a rust-preventive coating on a metal or a metal-substrate undercoat, (A) and (B) are used in a rust-preventive coating on a metal surface, in an amorphous body, in a coating. The method is not particularly limited as long as the method is a microcrystal having a crystal size of less than 0.2 μm or a mixed structure of both. Examples of such a method include, for example, dipping a metal into a rust prevention treatment bath, roll coating, bar coating, brush coating, or spraying a rust prevention treatment solution, and then heating with hot air or the like. Drying may be performed, but application and film formation may be performed by other methods, and the present invention is not limited to the methods listed here. However, from the viewpoint of stable production, it is preferable that the metal surface temperature reaches 100 ° C. or higher within 30 seconds after the application. In the present invention, the amount of the rust preventive film deposited on the metal surface is 0.05 to 3 g / m. 2 Is preferred, and 0.1 to 2 g / m 2 Is particularly preferred. 0.05g / m 2 If it is less than the above, there is a possibility that the effect of suppressing the permeation of the corrosion factor is small and sufficient corrosion resistance cannot be obtained. 3g / m 2 When the ratio exceeds 2, the effect of suppressing the permeation of corrosion factors is excellent, but there is a concern that the cost of the coating film will increase significantly.
[0038]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.
[Type of metal]
(1) EG: Electrogalvanized steel sheet (sheet thickness 0.8 mm)
(2) GI: hot-dip galvanized steel sheet (sheet thickness 0.8 mm)
(3) GA: galvannealed steel sheet (sheet thickness 0.8 mm)
(4) ZL: Zn-Ni alloy plated steel sheet (sheet thickness 0.8 mm)
(5) SZ: Zn-5% Al-based alloy plated steel sheet (sheet thickness 0.8 mm)
(6) SD: Zn-11% Al-3% Mg-Si alloy plated steel sheet (sheet thickness 0.8mm)
[0039]
[Formation of anti-rust coating]
Poor or insoluble in water, acid dissociation constant pK a Phosphate or phosphite (A) soluble in a strong acid ≦ 3, acid dissociation constant pK a An aqueous rust preventive treatment liquid containing a strongly acidic inorganic acid (B) of ≦ 3 as an essential component and further containing an inorganic rust preventive additive (C) other than A and B as necessary is prepared. Immediately after applying with a bar coater, it was left standing in a hot air oven at 250 ° C. for about 20 seconds so that the temperature reached the metal surface became 150 ° C., dried and formed into a film. did.
[0040]
As comparison materials, water-soluble phosphate and acid dissociation constant pK a A treatment liquid using an inorganic acid of> 3 was prepared, dried by heating in the same manner as described above, and a film was formed on a metal surface. As another comparative material, after treating the metal surface with a crystal nucleating agent, the treatment liquid was applied with a bar coater, and gradually air-dried in a 60 ° C. hot air oven to form coarse phosphate crystals. A metal having a deposited film was used. Phosphate crystals were confirmed by observing the film surface with a scanning electron microscope. Table 1 shows the chemicals used for preparing each treatment liquid. Among these chemicals, ferric phosphate (FePO4) obtained in the form of a hydrate having an unknown hydration number 4 ・ MH 2 O), polyphosphoric acid [H n + 2 P n O 3n + 1 (N = integer of 2 to 6)] were used for calculation of the mass of non-volatile components in the processing liquid, assuming that m = 2.5 and n = 4, respectively. Tables 2 to 4 show the constituent components of each film, their mass ratio, and the amount of the film adhered.
[0041]
[Table 1]
[Formation of comparative chromate film]
As a comparative material for the above-mentioned treated film, the amount of Cr attached to each of the above metals was 30 mg / m. 2 The corrosion resistance of the metal on which the rust-preventive film was formed was relatively compared with that of the rust-proof coating film obtained by performing the coating type chromate treatment.
[0043]
[Evaluation of corrosion resistance (no heat treatment)]
(1) Flat plate corrosion resistance
A salt spray test according to JIS-Z2371 is performed on the rust-proof treated metal and the comparative chromate material, and the white rust occurrence area after 120 hours is measured. Were compared to determine whether the corrosion resistance was acceptable or not. Assuming that the area ratio of white rust of the rust-prevention treated metal and the comparative chromate material is X% and Y%, respectively,
Rating 4 X <Y
3 X ≒ Y
2 Y <X <2Y
1 2Y ≦ X
And a score of 3 or more was regarded as a pass.
[0044]
(2) Corrosion resistance of processed part
The above-mentioned rust-proof metal and the comparative chromate material are subjected to a 7 mm Erichsen process, subjected to a salt spray test in accordance with JIS-Z2371, and the white rust occurrence area in the processed portion after 120 hours is measured. Pass / fail of the processed part corrosion resistance was determined by relative comparison of the white rust generation areas of the corresponding comparative chromate materials. The criterion is the same as in the case of the above plate corrosion resistance,
Rating 4 X <Y
3 X ≒ Y
2 Y <X <2Y
1 2Y ≦ X
And a score of 3 or more was regarded as a pass.
[0045]
[Evaluation of corrosion resistance (after heat treatment)]
(1) Flat plate corrosion resistance after heat treatment
Among the above rust-proofed metals and comparative chromate materials, those other than those based on EG were subjected to a heat treatment in a hot blast stove at 300 ° C. for 5 hours in an air atmosphere, and allowed to cool. The EG-based rust-proofing metal and the chromate material were heated in a hot air oven at 200 ° C. for 5 hours in an air atmosphere and allowed to cool. A salt water spray test in accordance with JIS-Z2371 was performed using these as test materials, the white rust occurrence area after 120 hours was measured, and the white rust occurrence areas of the rust-proof treated metal and the corresponding comparative chromate material were relatively compared. Pass / fail of corrosion resistance was determined. The criteria are the same as in the case of the corrosion resistance evaluation without heat treatment.
[0046]
(2) Corrosion resistance of processed part after heat treatment
A 7 mm Erichsen process was applied to the rust-prevention-treated metal and the comparative chromate material that were heat-treated in the same manner as described above, and a salt spray test in accordance with JIS-Z2371 was performed. Correspondence of corrosion resistance was determined by relatively comparing the white rust generation area of the metal and the comparative chromate material. The criteria are the same as in the case of the corrosion resistance evaluation without heat treatment.
[0047]
[Table 2]
[Table 3]
[Table 4]
Tables 2 to 4 summarize the above evaluation results.
Poor or insoluble in water, acid dissociation constant pK a Phosphate and / or phosphite (A) soluble in a strong acid ≦ 3, acid dissociation constant pK a Among the aqueous rust preventive treatment liquids containing ≦ 3 a strongly acidic inorganic acid (B) or an inorganic rust preventive additive (C) other than (A) and (B) as an essential component, the requirements of the present invention are as follows. It can be seen that a rapid heating and drying treatment after applying the filling material to the metal surface can provide a metal product exhibiting sufficient corrosion resistance equivalent to the level of a chromate-treated material and corrosion resistance after the heating treatment. These rust preventive solutions do not contain the chemical substances specified by the PRTR method, have low environmental load, and can form a film by one-step treatment of the metal surface.
[0051]
On the other hand, when a treatment solution using a water-soluble phosphate is used (Nos. 69 and 70), the corrosion resistance of the metal product on which the film is formed does not reach the level of the chromate treatment material at all. Acid dissociation constant pK a When a treatment liquid using an inorganic acid of> 3 was used (Nos. 25, 26, 54, and 55), since a phosphate that was hardly soluble or insoluble in water could hardly be dissolved, a film could not be formed on a metal surface. Was. Further, even when the phosphate and / or phosphite (A) and the inorganic acid (B) specified in the present invention are used, the non-volatile mass ratio of (A) to (B) is permitted in the present invention. When it is smaller than the range (Nos. 3, 13, 42), the corrosion resistance of the metal product on which the film is formed does not reach the level of the chromate-treated material, and the non-volatile mass ratio of (A) to (B) is in the present invention. When it was larger than the allowable range (Nos. 4, 14, 43), the phosphate could not be completely dissolved, and a film could not be formed on the metal surface. After the treatment liquid was applied to the metal surface, it was gradually air-dried at 60 ° C., and in the film in which coarse crystals of phosphate were deposited (Nos. 27 and 28), the corrosion resistance of the metal product was lower than that of the chromate-treated material. Was.
[0052]
【The invention's effect】
Since the rust preventive solution of the present invention does not contain an environmentally harmful substance that conflicts with the PRTR method and can form a rust preventive film on a metal surface in one process, it can be used for home appliances / OA equipment, construction / civil engineering, automobile / vehicle It is suitable as a rust preventive solution for metal products widely used in the field and the like. In addition, by treating the surface of a metal with the rust preventive solution according to the present invention, a metal product having excellent corrosion resistance at the level of a chromate treated material can be provided at a low rust preventive treatment cost.
Claims (8)
Priority Applications (1)
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| JP2002235904A JP3935022B2 (en) | 2002-08-13 | 2002-08-13 | Antirust treatment liquid and antirust treatment metal products |
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| JP2002235904A JP3935022B2 (en) | 2002-08-13 | 2002-08-13 | Antirust treatment liquid and antirust treatment metal products |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006161152A (en) * | 2004-11-11 | 2006-06-22 | Nippon Steel Corp | Metallic member, surface coating treatment agent and surface coating treatment method |
| JP2007126699A (en) * | 2005-11-02 | 2007-05-24 | Kobe Steel Ltd | Surface treated galvanized steel plate having excellent corrosion resistance and abrasion resistance, and its manufacturing method |
| JP2008101266A (en) * | 2005-11-16 | 2008-05-01 | Kobe Steel Ltd | Aluminum alloy material having excellent surface stability |
-
2002
- 2002-08-13 JP JP2002235904A patent/JP3935022B2/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006161152A (en) * | 2004-11-11 | 2006-06-22 | Nippon Steel Corp | Metallic member, surface coating treatment agent and surface coating treatment method |
| JP2007126699A (en) * | 2005-11-02 | 2007-05-24 | Kobe Steel Ltd | Surface treated galvanized steel plate having excellent corrosion resistance and abrasion resistance, and its manufacturing method |
| JP2008101266A (en) * | 2005-11-16 | 2008-05-01 | Kobe Steel Ltd | Aluminum alloy material having excellent surface stability |
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| JP3935022B2 (en) | 2007-06-20 |
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