JP2004332009A

JP2004332009A - Heavy corrosion preventive coated steel having excellent peeling resisting corrosion preventability

Info

Publication number: JP2004332009A
Application number: JP2003125745A
Authority: JP
Inventors: Nobuki Yoshizaki; 信樹吉崎; Hiroyuki Mimura; 博幸三村; Yoshiyuki Harada; 佳幸原田; Masahiro Yamamoto; 正弘山本
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2003-04-30
Filing date: 2003-04-30
Publication date: 2004-11-25
Anticipated expiration: 2023-04-30
Also published as: JP4299575B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heavy corrosion preventive coated steel having excellent peeling resisting corrosion preventability in response to that it is needed to extereamely extend the service life of the heavy corrosion preventive steel and it is necessary to obtain a method low in cost and satisfactory in productivity other than the coating of titanium metal. <P>SOLUTION: An oxygen shielding film is incorporated into a heavy corrosion preventive covering. For example, the conventional heavy corrosion preventive covering or a heavy corrosion preventive covering obtained by subjecting a substrate to chemical conversion treatment is stacked with an organic resin film 6 shielding the penetration of oxygen. By the oxygen shielding film, oxygen penetrating from the upper part of the covering is suppressed, and the destruction of the stuck boundaries is suppressed, so that the propagation of deterioration in the sticking from the edge parts or damaged parts of the covering can be suppressed. In this way, the corrosion preventive covering having higher reliability than heretofore can be obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、重防食被覆を施した鋼材の被覆端部及び傷部からの剥離進展が少なく長期の防食性に優れる重防食被覆鋼材に関する。
【０００２】
【従来の技術】
海洋等の厳しい腐食環境での鋼材使用には重防食被覆が必須である。重防食被覆は数十年の耐久性が期待されるために、その信頼性向上が要求される。重防食被覆は、被覆に使用されるプラスチックの耐久性が非常に高いために、その機能維持には被覆端部や疵部の耐剥離性が重要である。また、重防食被覆は陰極防食が併用されることから耐陰極剥離性も重要となる。
【０００３】
激しい腐食環境に使用される海洋鋼構造物等の鋼材は防食塗装が行われ、なかでも厚みが数ｍｍに及ぶ重防食塗装が有効である。数十年に及ぶ長期耐久性が必要とされる場合、電気絶縁性、耐薬品性等の種々の防食性に優れ、安価な樹脂であるポリオレフィン、あるいはポリウレタンといった樹脂を被覆材として使用した重防食被覆鋼材が製造されている。重防食被覆では、特許文献１に示される様な特殊な鋼材の下地処理、プライマー処理に防食被覆を組み合わせることで長期の接着耐久性が確保されている。
【０００４】
同様にラインパイプ等で長期防食性が要求される場合、ポリオレフィン樹脂を被覆した重防食被覆鋼管が使用される。配管は埋設で使用される場合が多いために、樹脂被覆鋼管では搬送や施行工事において貫通疵発生を想定し、疵部の鋼材腐食を抑制するため陰極防食が併用される。ところが、陰極防食は疵周辺部の被覆接着力を低下させる陰極剥離を生じさせるため、ラインパイプに使用する重防食被覆鋼管では耐陰極剥離性が重要である。これに対して従来は、重防食被覆はそのままに下地処理にクロメート処理、樹脂プライマー処理を施すことで耐陰極剥離性を向上させていた。例えば、下地処理に用いるクロメート処理剤に特許文献２に示されるように高温の陰極剥離性を改善した燐酸クロメートがある。
【０００５】
下地処理以外で防食被覆の耐久性を向上させる手法としては、表層にチタン等の耐食金属を更に積層して、表面強度向上と、光、酸素、水等の劣化要因を完全に遮断して、耐傷性と被覆の信頼性を向上させる手法が提案されている。しかしながら耐食金属を表層に被覆する方法は、生産性や材料コスト、適用鋼材形状の自由度の問題を解決することが難しいという問題があった。
【０００６】
【特許文献１】
特開平３−２３５２７号公報
【特許文献２】
特許第１６９６９９２号
【０００７】
【発明が解決しようとする課題】
重防食の下地処理工程の化成処理には主としてクロメート処理が行われており、クロム化合物を含まない化成処理では十分な性能を確保するのが難しいという問題があった。一方、重防食の長期耐久性を向上させる耐食金属を表面に貼る方法は鋼管以外の構造物では製造が困難であることに加え、耐食金属そのものが高価であることから一般的な防食方法としての適用は難しく、別の安価な耐久性向上手法が要望されていた。
【０００８】
現在重防食に使用されているポリオレフィン及びポリウレタン樹脂は、安価で耐久性に優れ、実環境での実績による信頼性も高い。また、数ｍｍの厚膜であることから、一般塗装に比較して耐傷性にも優れる。ポリオレフィンやポリウレタン樹脂が数ｍｍ被覆されていれば、鋼材腐食が問題となる量の水や酸素、イオン成分が防食被覆表面から鋼材に到達することを抑制することが可能である。しかしながら、腐食は問題とならない程の微量な水分や酸素でも、鋼材と樹脂の接着力を低下させる可能性があるため、接着耐久性や耐剥離性といった接着性能の保持には優れた下地処理とプライマー処理との組み合わせが必要であった。被覆の透過を抑制する対策に防食被覆の厚みを増やす方法が考えられるが、非常に効率が悪い。更に厚みが厚くなると、被覆の内部応力も増加して剥離の要因として作用し、厚みに比例した効果を得にくいという問題がある。
【０００９】
そこで、本発明では従来の厚膜重防食被覆で防食は十分と考えられていた樹脂材料の改良に着目し、従来防食層に酸素透過抑制機能を持つ薄膜フィルムを組み合わせることによって、コストや内部応力にも問題無く、耐剥離性に優れた新しい重防食被覆を提案するものである。
【００１０】
【課題を解決するための手段】
すなわち、本発明の耐剥離性に優れた重防食被覆鋼材とは、酸素透過度を１００ｃｍ^３（標準）／ｍ^２・ｄａｙ・ａｔｍ（２０℃）以下に調整された酸素遮断膜を防食被覆の内部またはその表面に有するものである。その被覆構成として例えば、図１の断面図に示す如く、鋼材１の表面に下地処理層２（もちろんショットブラスト処理などは層として存在しないが、本発明ではその場合も含むものである）、プライマー層３、防食樹脂被覆層４、接着層５、酸素遮断フイルム層６を順次積層したものである。表層フィルムの耐候性が問題になる場合には、図２に示す如く、耐候性に優れた保護層として更に着色フイルム層７を酸素遮断フイルム層６の表面に積層する。防食樹脂被覆層４及び接着層５の各フイルムは熱ラミネート、粘着材、接着剤を使用して積層する。防食樹脂層３としては、変性ポリオレフィン単独、又は変性ポリオレフィン接着剤層とポリオレフィンの２層被覆、あるいはポリウレタン系の樹脂被覆が望ましい。以上の積層被覆により耐剥離性に優れた重防食被覆鋼材を提供するものである。
【００１１】
【発明の実施の形態】
以下、本発明について詳細に説明する。
本発明に使用する鋼材とは普通鋼、あるいはＣ、Ｓｉ、Ｍｎ及び窒素、酸素を制御した鋼材、及び、Ｃｕ，Ｎｉ，Ｃｒ，Ｍｏ，Ｎｂ，Ｔｉ，Ａｌ，Ｍｇ，Ｖ，Ｃａ等の元素を添加した合金鋼である。その代表的な品種としては重防食被覆が適用される鋼管、また、海洋構造物等で使用される鋼管杭、鋼管矢板、鋼矢板、Ｈ形鋼、線材等である。これらの鋼材はその表面のスケール、汚染物等を除去するため、アルカリ脱脂〜酸洗、サンドブラスト処理、グリッドブラスト処理、ショットブラスト処理等のいずれかの下地処理を必ず行なう。更に、性能向上のために化成処理を行っても良く、性能要求の高い場合はクロメート処理を行う。化成処理にクロメート以外のクロム化合物を含まない処理リン酸亜鉛処理や、その他の水溶性化成処理を施しても、本発明の重防食被覆を行うことで、従来のクロメートを用いた従来被覆構成の重防食と同等以上の性能が期待出来る。
【００１２】
本発明の下地処理後に施す重防食被覆について説明する。まず、防食被覆と鋼材の接着性、耐陰極剥離性、防食性を向上させるためにプライマー処理を実施する。プライマーには熱硬化性の樹脂を用い、エポキシ樹脂、ポリウレタン樹脂、ポリエステル樹脂、あるいはこれらの変性物に硬化剤と無機顔料を添加したものを主成分として用いると良い。ポリウレタン樹脂としてはプレポリマーを使用した湿気硬化型の１液タイプのもの、あるいはイソシアネートとポリオールとの反応を利用した２液硬化タイプのものが代表的である。プライマーにはエポキシ樹脂を用いる場合、一般にその主成分としてはビスフェノールＡ型、ビスフェノールＦ型の樹脂を単独、もしくは混合して使用する。高温特性が要求される場合、多官能性のフェノールノボラックやハロゲン化樹脂を上記のビスフェノールＡ型あるいは、ビスフェノールＦ型の樹脂と組み合わせて用いる。
【００１３】
硬化剤には、２液硬化型のアミン系硬化剤、あるい潜在性硬化剤であるイミダゾール化合物にジシアンジアミド、またはフェノール系硬化剤を単独又は混合して用いると密着性、耐食性に優れる。また、無機顔料を全体積に対して３〜３０ｖｏｌ％の範囲で添加することで収縮歪みが低減され、密着特性が大きく改善出来る。無機顔料には、シリカ、酸化チタン、ウォラストナイト、マイカ、タルク、カオリン、酸化クロム、ホウ酸亜鉛、燐酸亜鉛等の顔料、もしくは亜鉛、Ａｌ等の金属粉、あるいはセラミック粉等、その他にリン酸バナジウム等の防錆顔料を適宜用いることが出来る。これらの顔料は樹脂との濡れ性を良くするために、その表面にシランカップリング処理を施してもよい。樹脂プライマーは液体で供給される場合、ロール又は刷毛塗装、しごき塗り、エアースプレー塗装等の方法を用いる。粉体で供給される場合、静電粉体塗装等の方法を用い、２０〜１０００μｍの範囲で塗装する。膜厚が２０μｍより薄い場合にはピンホールが多数発生する。一方、膜厚の上限は樹脂の種類によって異なるが、５００μｍを越える厚膜塗装では低温での耐衝撃性は低下しやすい。
【００１４】
重防食被覆に使用するポリオレフィン樹脂は、その主成分としては低密度ポリエチレン、中密度ポリエチレン、高密度ポリエチレン、直鎖状低密度ポリエチレン、ポリプロピレンなどの従来公知のポリオレフィン、及びエチレン−プロピレンブロックまたはランダム共重合体、ポリアミド−プロピレンブロック叉はランダム共重合体等公知のポリオレフィン共重合体を含む樹脂である。他成分としては、耐熱性、耐候性対策としてカーボンブラック又はその他の着色顔料、充填強化剤、酸化防止剤、紫外線吸収剤、ヒンダードアミン系の耐候剤等を任意の組み合わせて添加する。ポリオレフィン樹脂を被覆に用いる場合、下地のプライマーと接触する下層部分にはポリオレフィンを変性した接着剤を用いる。
【００１５】
この接着剤は、ポリエチレン、ポリプロピレン、ナイロンなどの公知のポリオレフィン、及び公知のポリオレフィン共重合体樹脂を、マレイン酸、アクリル酸、メタアクリル酸などの不飽和カルボン酸または、その酸無水物で変性したもの、あるいは、その変性物をポリオレフィン樹脂で適宜希釈したもの等、従来公知の変性ポリオレフィンである。５０〜７００μｍの薄い変性ポリオレフィン接着剤層に０．３〜５ｍｍのポリオレフィン樹脂層を組み合わせて用いる方法が価格、性能のバランスからは好ましいが、ポリオレフィン被覆層を省略し、変性ポリオレフィン樹脂層を０．３ｍｍ以上被覆して防食層として用いても良い。
【００１６】
ポリオレフィン被覆の方法としては、例えばダイスを用いて加熱溶融した樹脂を直接鋼材に被覆する押出被覆方法を用いる。あるいは、加熱した鋼材に予め成形したポリオレフィンシートを貼り付ける方法、粉砕したポリオレフィンを粉体塗装して溶融して皮膜を形成する方法がある。これらの方法により０．３ｍｍ以上の膜厚を有するポリオレフィン防食被覆層を形成する。
【００１７】
重防食被覆にはポリウレタン樹脂を塗装する方法もある。ポリウレタン樹脂は、ポリオールと充填無機顔料、着色顔料の混合物からなる主剤と、イソシアネート化合物からなる硬化剤を２液混合塗装する。ポリオールとしてはポリエステルポリオール、ポリブタジエンポリオール、ポリプロピレングリコールなどのポリエーテルポリオール、アクリルポリオール、ひまし油誘導体、その他含水酸基化合物を用いる。イソシアネートとしてはメチレンジフェニルジイソシアネートなどの一般市販のイソシアネートを使用する。充填無機顔料としては、シリカ、酸化チタン、カオリンクレーなどの一般市販の無機顔料を用いる、また着色顔料には、樹脂に耐候性を付与するため、一般的にはカーボンブラックを用いる。意匠性から他の着色顔料を用いる場合には、紫外線吸収剤を併せて添加する。被覆厚みとしては重防食層としての機能と経済性を考慮し、０．５〜６ｍｍまでの間が望ましい。
【００１８】
本発明では重防食被覆層の内部あるいは表層に含有する酸素遮断膜には、厚み１０〜５００μｍで酸素透過度が１００ｃｍ^３（標準）／ｍ^２・ｄａｙ・ａｔｍ（２０℃）＜測定方法はＪＩＳＫ７１２６による＞以下に調整した樹脂フイルムを用いることが重要である。酸素透過度は膜の厚みが厚い方が良いが、厚いと形状に対する追従性や接着性が悪くなるため、厚くても５００μｍまでのものを使用する。樹脂の種類は酸素透過係数が小さいものほど、本発明の目的を達せられるが、樹脂の柔軟性や強度、接着性を鑑みて選択される。酸素透過係数の小さい樹脂には、例えばポリ塩化ビニル、ポリ塩化ビニリデン、ポリエステル（例：ポリエチレンテレフタレート、−［ＯＣＨ_２ＣＨ_２ＯＯＣ−（Ｃ_６Ｈ_４）−ＣＯ］_ｎ−）、ナイロン、ポリビニルアルコール等があげられる。但し、同種の樹脂フィルムでも分子構造や添加剤、延伸によって酸素透過係数を小さくする方法を用いることが出来る。また、いくつかの異なる樹脂フィルムをラミネート積層した多層ラミネート品であっても良い。
【００１９】
酸素遮断フイルムは防食層の内部、あるいはその表層に接着剤を介して積層する。積層に試用する接着剤は樹脂種類の組み合わせの影響が大きいので粘着性を持たせたものが好ましく、変性ポリオレフィン、アクリル系、シリコン系、ゴム系、ポリウレタン系等の樹脂を用いることが出来る。酸素遮断フィルムを被覆する行程は、一つは鋼材に重防食を形成した後に粘着、あるいは熱硬化タイプの接着剤を用いて貼り付ける方法がある。一方、ポリオレフィン被覆ではポリエチレンシートを貼り付ける行程が用いられており、酸素遮断フィルムを予めポリエチレンシートとラミネートしておいてから貼り付けても良い。また、大径鋼管のポリオレフィン被覆ではＴダイスを用いて押し出したシートを巻き付ける行程が一般的であるため、押し出したポリオレフィン防食シートを巻き付けると同時に、その中間、あるいは表層に接着剤をラミネートした酸素遮断フィルムをスパイラル状に被覆に巻き付けて製造する方法がある。いずれの方法を用いても、本発明の酸素遮断フィルムが接着積層されていれば問題無い。
【００２０】
酸素遮断フィルムが防食層の表層になる場合には、更にその表層に着色フィルムを積層しても良い。酸素遮断フィルムの耐水性や、耐候性が十分で無い場合、その機能を補うために表層フィルムには耐候性や耐水性に優れる樹脂を用いると良い。例えば、アクリル系、フッ素系、ポリオレフィン系変性ポリオレフィン系等の樹脂がある。
【００２１】
【実施例及び比較例】
９×１００×１５０ｍｍの熱延鋼板に、グリッドブラスト処理を施した。この後、何も化成処理をしない場合と、微粒子シリカを含む部分還元クロメート処理、あるいは水溶性エマルジョン樹脂とシリカ成分を含有する化成処理の２種の処理を施した。この後、エポキシ樹脂プライマーを５０μｍ塗装し、加熱硬化させた後に、変性ポリオレフィン樹脂を粉砕して生成した粉体接着剤を３００μｍ塗布して加熱溶融させた。この後、２ｍｍ厚のポリエチレンと各種酸素遮断フィルムを熱ラミネートしたシートを貼り付けて、本発明の酸素遮断フィルムを有する重防食被覆鋼材を製造した。また、０．２ｍｍ厚みのチタン箔を熱可塑性の接着剤でラミネートしたシートを貼り付けた比較例の重防食被覆鋼材を作製した。
【００２２】
作製した重防食鋼材は長期使用における剥離を模擬する目的で、裏面にはエポキシ樹脂でシール塗装を施して５０℃の人工海水中に１８０日間浸漬した。人工海水にはエアーを吹き込むことにより攪拌と酸素の供給を行った。試験後、ポリエチレン被覆を除去して、被覆端部から鋼材面が露出する部分の距離を測定した。ただし、露出する鋼材面は、接着力は低下していても腐食は生じておらず防食面では接着が低下していても問題は見られなかった。
【００２３】
表１に各種フィルムの種類、厚みと端部からの鋼材露出面の距離、酸素透過度を示す。比較例１のクロメート処理を用いた重防食被覆鋼材は被覆端部からの接着劣化が生じにくい。一方、比較例２のように従来防食被覆仕様においては、クロメート処理が無い場合には接着劣化距離が増大する。しかしながら、比較例３のチタン金属被覆を有する重防食被覆鋼材では、クロメート処理が無くても被覆の遮蔽効果により、端部からの接着劣化距離が短い。
【００２４】
フィルムを表面に貼り付ける場合、比較例４〜１０の結果から明らかなように、フィルムの酸素透過度が本発明の範囲で無い場合は、厚みに関係無く接着劣化距離は大きい。しかしながら、本発明の実施例１１〜２３では接着劣化距離が大きく減少する。また、実施例２４〜２６のようにクロメート処理以外の化成処理を用いても、従来のクロメート処理を用いた防食被覆と同等以上の性能が得られる。更に、下地にクロメート処理を用いた実施例２７〜２９の場合、比較例１の従来の重防食被覆に対しても接着劣化距離を小さく保つことが出来る。すなわち、フィルムの酸素透過度はフィルムの種類や厚みによって大きく変化するが、酸素透過度を１００ｃｍ^３（標準）／ｍ^２・ｄａｙ・ａｔｍ（２０℃）以下にした酸素遮断フィルムを積層することで端部からの接着低下が抑制され、防食性能を従来の防食被覆よりも向上させることが可能である。
【００２５】
【表１】

【００２６】
【発明の効果】
本発明の如く重防食被覆に酸素遮断膜を含有させることで、従来重防食被覆の防食性を飛躍的に向上することが出来る。酸素遮断膜の被覆表面からの酸素透過を大幅に減少する機構により、本発明の重防食被覆鋼材は傷部や端部からの接着劣化進展を従来の重防食被覆に比べて大幅に抑制することが出来る。この結果、下地処理として従来の塗布型クロメート処理の省略、あるいはクロム化合物を含まない他の化成処理への代替えも可能である。
【図面の簡単な説明】
【図１】本発明の重防食被覆鋼材の被覆構成断面図の一例を示す。
【図２】本発明の重防食被覆鋼材の被覆構成断面図の他の例を示す。
【符号の説明】
１鋼材
２下地処理被膜
３プライマー樹脂
４防食被覆層
５接着層
６酸素遮断フィルム
７着色フィルム[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a heavy-corrosion-coated steel material which has little corrosion progress from a coating end portion and a scratched portion of a steel material provided with a heavy-duty corrosion protection and has excellent long-term corrosion resistance.
[0002]
[Prior art]
Heavy corrosion protection is indispensable for use of steel materials in severe corrosive environments such as the ocean. Since anti-corrosion coatings are expected to last for several decades, improved reliability is required. Since the heavy corrosion protection coating has extremely high durability of the plastic used for the coating, peeling resistance of the coating end and flaws is important for maintaining its function. In addition, the cathodic protection is also used in the heavy corrosion protection coating, so that the cathodic peeling resistance is also important.
[0003]
Steel materials such as marine steel structures used in severely corrosive environments are subjected to anticorrosion coating, and heavy anticorrosion coating with a thickness of several mm is particularly effective. When long-term durability is required for several decades, heavy corrosion protection using a resin such as polyolefin or polyurethane, which is an inexpensive resin excellent in various anticorrosion properties such as electrical insulation and chemical resistance, as a coating material. Coated steel is manufactured. In the heavy-duty anticorrosion coating, long-term adhesion durability is secured by combining the anticorrosion coating with a base treatment and a primer treatment of a special steel material as shown in Patent Document 1.
[0004]
Similarly, when long-term corrosion resistance is required for a line pipe or the like, a heavy corrosion-resistant coated steel pipe coated with a polyolefin resin is used. Since pipes are often used buried, in the case of resin-coated steel pipes, it is anticipated that through flaws will occur during transportation and construction work, and cathodic protection is also used to suppress corrosion of steel at flaws. However, since cathodic protection causes cathodic peeling to reduce the coating adhesive strength at the periphery of the flaw, cathodic peeling resistance is important for heavy corrosion-resistant coated steel pipes used for line pipes. On the other hand, conventionally, the cathodic peeling resistance has been improved by subjecting the undercoat treatment to chromate treatment and resin primer treatment with the heavy corrosion protection coating as it is. For example, as a chromate treating agent used for a base treatment, there is a phosphoric chromate having improved high-temperature cathodic peelability as shown in Patent Document 2.
[0005]
As a method of improving the durability of the anticorrosion coating other than the base treatment, a corrosion-resistant metal such as titanium is further laminated on the surface layer to improve the surface strength and completely shut off deterioration factors such as light, oxygen, and water. Techniques have been proposed to improve the scratch resistance and coating reliability. However, the method of coating the corrosion-resistant metal on the surface layer has a problem that it is difficult to solve the problems of productivity, material cost, and flexibility in the shape of the applied steel material.
[0006]
[Patent Document 1]
JP-A-3-23527 [Patent Document 2]
Patent No. 1696992 [0007]
[Problems to be solved by the invention]
Chromate treatment is mainly performed in the chemical conversion treatment of the heavy corrosion protection base treatment step, and there is a problem that it is difficult to secure sufficient performance by the chemical conversion treatment not containing a chromium compound. On the other hand, the method of applying a corrosion-resistant metal to the surface to improve the long-term durability of heavy corrosion protection is difficult as a general corrosion protection method because the corrosion-resistant metal itself is expensive in addition to being difficult to manufacture with structures other than steel pipes. The application is difficult, and another inexpensive durability improving method has been demanded.
[0008]
Polyolefin and polyurethane resins currently used for heavy-duty corrosion protection are inexpensive, have excellent durability, and have high reliability based on their actual environment. Further, since it is a thick film having a thickness of several mm, it is excellent in scratch resistance as compared with general coating. If the polyolefin or the polyurethane resin is coated by several mm, it is possible to suppress the amount of water, oxygen, and ionic components that cause corrosion of the steel material from reaching the steel material from the surface of the anticorrosion coating. However, even a very small amount of moisture or oxygen, which does not cause corrosion, can reduce the adhesive strength between the steel material and the resin. Combination with primer treatment was required. As a measure to suppress the transmission of the coating, a method of increasing the thickness of the anticorrosion coating can be considered, but it is very inefficient. When the thickness is further increased, the internal stress of the coating increases, which acts as a factor of peeling, and there is a problem that it is difficult to obtain an effect proportional to the thickness.
[0009]
In view of the above, the present invention focuses on the improvement of the resin material, which was considered to be sufficient for the corrosion prevention with the conventional heavy-film heavy-corrosion protection coating. The present invention proposes a new heavy-duty anticorrosive coating having excellent peel resistance without any problem.
[0010]
[Means for Solving the Problems]
That is, the heavy corrosion protection coated steel material excellent in the peeling resistance of the present invention means that the oxygen barrier film whose oxygen permeability is adjusted to 100 cm ³ (standard) / m ² · day · atm (20 ° C.) or less is formed of a corrosion protection coating. It has something inside or on its surface. For example, as shown in the cross-sectional view of FIG. 1, as a coating configuration, an undercoating treatment layer 2 (of course, shot blasting treatment does not exist as a layer, but this is included in the present invention), a primer layer 3 on the surface of a steel material 1. , An anticorrosion resin coating layer 4, an adhesive layer 5, and an oxygen barrier film layer 6 are sequentially laminated. When the weather resistance of the surface film becomes a problem, as shown in FIG. 2, a colored film layer 7 is further laminated on the surface of the oxygen barrier film layer 6 as a protective layer having excellent weather resistance. Each film of the anticorrosion resin coating layer 4 and the adhesive layer 5 is laminated using a heat lamination, an adhesive or an adhesive. The anticorrosion resin layer 3 is preferably a modified polyolefin alone, a two-layer coating of a modified polyolefin adhesive layer and a polyolefin, or a polyurethane resin coating. The present invention provides a heavy-duty anticorrosion-coated steel material excellent in peeling resistance by the above-mentioned laminated coating.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The steel material used in the present invention includes ordinary steel, steel material in which C, Si, Mn and nitrogen and oxygen are controlled, and elements such as Cu, Ni, Cr, Mo, Nb, Ti, Al, Mg, V, and Ca. Alloy steel to which is added. Typical varieties are steel pipes to which heavy corrosion protection is applied, and steel pipe piles, steel pipe sheet piles, steel sheet piles, H-section steels, wire rods and the like used in marine structures and the like. In order to remove scales, contaminants, and the like on the surface of these steel materials, any of base treatments such as alkali degreasing, pickling, sand blasting, grid blasting, and shot blasting is always performed. Further, a chemical conversion treatment may be performed to improve the performance, and a chromate treatment is performed when the performance requirement is high. Even if the chemical conversion treatment does not include a chromium compound other than chromate, which is treated with zinc phosphate, or other water-soluble chemical conversion treatment, by performing the heavy duty anticorrosion coating of the present invention, the conventional coating configuration using the conventional chromate It can be expected to have performance equal to or better than heavy corrosion protection.
[0012]
The heavy duty anticorrosion coating applied after the base treatment of the present invention will be described. First, a primer treatment is carried out in order to improve the adhesion between the anticorrosion coating and the steel, the cathodic peeling resistance, and the anticorrosion. A thermosetting resin is used for the primer, and an epoxy resin, a polyurethane resin, a polyester resin, or a modified product thereof to which a curing agent and an inorganic pigment are added is preferably used as a main component. Typical examples of the polyurethane resin include a moisture-curable one-pack type using a prepolymer, and a two-pack type using a reaction between an isocyanate and a polyol. When an epoxy resin is used for the primer, generally, bisphenol A type and bisphenol F type resins are used singly or in combination as a main component. When high-temperature properties are required, a polyfunctional phenol novolak or a halogenated resin is used in combination with the above-mentioned bisphenol A type or bisphenol F type resin.
[0013]
As a curing agent, when a two-part curing type amine curing agent or an imidazole compound as a latent curing agent is used alone or in combination with dicyandiamide or a phenolic curing agent, adhesion and corrosion resistance are excellent. Further, by adding the inorganic pigment in the range of 3 to 30 vol% with respect to the total volume, the shrinkage distortion is reduced, and the adhesion properties can be greatly improved. Examples of inorganic pigments include pigments such as silica, titanium oxide, wollastonite, mica, talc, kaolin, chromium oxide, zinc borate, and zinc phosphate; metal powders such as zinc and Al; ceramic powders; Rust preventing pigments such as vanadium acid can be used as appropriate. These pigments may be subjected to a silane coupling treatment on the surface in order to improve the wettability with the resin. When the resin primer is supplied as a liquid, a method such as roll or brush painting, ironing, air spray painting or the like is used. When supplied as a powder, the powder is applied in a range of 20 to 1000 μm by using a method such as electrostatic powder coating. When the film thickness is smaller than 20 μm, many pinholes are generated. On the other hand, the upper limit of the film thickness varies depending on the type of the resin, but the impact resistance at a low temperature tends to decrease in a thick film coating exceeding 500 μm.
[0014]
The polyolefin resin used for the heavy-duty anticorrosion coating is mainly composed of a conventionally known polyolefin such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, and ethylene-propylene block or random copolymer. It is a resin containing a known polyolefin copolymer such as a polymer, a polyamide-propylene block or a random copolymer. As other components, carbon black or other coloring pigments, a filler, an antioxidant, an ultraviolet absorber, a hindered amine-based weathering agent and the like are added in any combination as a measure against heat resistance and weather resistance. When a polyolefin resin is used for coating, an adhesive modified from polyolefin is used for a lower layer portion that comes into contact with the primer of the base.
[0015]
This adhesive is a known polyolefin such as polyethylene, polypropylene, and nylon, and a known polyolefin copolymer resin, modified with an unsaturated carboxylic acid such as maleic acid, acrylic acid, or methacrylic acid, or an acid anhydride thereof. And conventionally known modified polyolefins such as those obtained by appropriately diluting a modified product thereof with a polyolefin resin. A method in which a thin modified polyolefin adhesive layer having a thickness of 50 to 700 μm is combined with a polyolefin resin layer having a thickness of 0.3 to 5 mm is preferable from the viewpoint of price and performance balance. It may be coated as 3 mm or more and used as an anticorrosion layer.
[0016]
As the polyolefin coating method, for example, an extrusion coating method in which a resin melted by heating using a die is directly coated on a steel material is used. Alternatively, there is a method in which a preformed polyolefin sheet is attached to a heated steel material, or a method in which a pulverized polyolefin is powder-coated and melted to form a film. A polyolefin anticorrosion coating layer having a thickness of 0.3 mm or more is formed by these methods.
[0017]
There is also a method of painting a polyurethane resin for the heavy-duty anticorrosion coating. As the polyurethane resin, a two-component mixture of a main agent composed of a mixture of a polyol, a filled inorganic pigment and a color pigment and a curing agent composed of an isocyanate compound is applied. Polyols such as polyester polyols, polybutadiene polyols, and polypropylene glycols, acrylic polyols, castor oil derivatives, and other hydrous compounds are used as polyols. As the isocyanate, a commercially available isocyanate such as methylene diphenyl diisocyanate is used. As the filled inorganic pigment, a commercially available inorganic pigment such as silica, titanium oxide or kaolin clay is used. As the coloring pigment, carbon black is generally used to impart weather resistance to the resin. When another color pigment is used from the viewpoint of design, an ultraviolet absorber is also added. The thickness of the coating is desirably 0.5 to 6 mm in consideration of the function and economy of the heavy anticorrosion layer.
[0018]
In the present invention, the oxygen barrier film contained in the heavy corrosion protection coating layer or in the surface layer has a thickness of 10 to 500 μm and an oxygen permeability of 100 cm ³ (standard) / m ² · day · atm (20 ° C.) <Measurement method is JIS K7126. It is important to use a resin film adjusted as follows. As for the oxygen permeability, it is better that the thickness of the film is thicker, but if it is thicker, the conformability to the shape and the adhesiveness are deteriorated. The type of the resin can achieve the object of the present invention as the oxygen permeability coefficient is smaller, but is selected in consideration of the flexibility, strength and adhesiveness of the resin. The resin having a low oxygen permeability coefficient, for example polyvinyl chloride, polyvinylidene chloride, polyester (e.g. polyethylene _{_{terephthalate, - [OCH 2 CH 2 OOC-}} (C 6 H 4) -CO] n -), nylon, polyvinyl alcohol And the like. However, a method of reducing the oxygen permeability coefficient by using the same type of resin film by molecular structure, additives, and stretching can be used. Further, it may be a multilayer laminate product in which several different resin films are laminated.
[0019]
The oxygen barrier film is laminated on the inside of the anticorrosion layer or on the surface thereof via an adhesive. Adhesives used for lamination are strongly affected by the combination of the types of resins, and are preferably provided with tackiness, and resins such as modified polyolefins, acrylics, silicones, rubbers, and polyurethanes can be used. As a process of coating the oxygen barrier film, there is a method of forming a heavy corrosion prevention on a steel material and then sticking it using an adhesive or a thermosetting adhesive. On the other hand, in the polyolefin coating, a process of attaching a polyethylene sheet is used, and the oxygen barrier film may be laminated on the polyethylene sheet in advance and then attached. Also, in the case of polyolefin coating of large-diameter steel pipes, the process of winding a sheet extruded using a T-die is generally performed. There is a method of manufacturing by winding a film around a coating in a spiral shape. No matter which method is used, there is no problem as long as the oxygen barrier film of the present invention is bonded and laminated.
[0020]
When the oxygen barrier film is to be a surface layer of the anticorrosion layer, a colored film may be further laminated on the surface layer. If the oxygen barrier film does not have sufficient water resistance and weather resistance, it is preferable to use a resin having excellent weather resistance and water resistance for the surface layer film in order to supplement its function. For example, there are acrylic, fluorine-based, and polyolefin-based modified polyolefin-based resins.
[0021]
[Examples and Comparative Examples]
Grid blasting was performed on a hot rolled steel sheet of 9 × 100 × 150 mm. Thereafter, two kinds of treatments were carried out: a case where no chemical conversion treatment was performed, a partial reduction chromate treatment containing fine-particle silica, and a chemical conversion treatment containing a water-soluble emulsion resin and a silica component. Thereafter, an epoxy resin primer was applied to a thickness of 50 μm and cured by heating. Then, a powder adhesive produced by pulverizing the modified polyolefin resin was applied to a thickness of 300 μm and melted by heating. Thereafter, a sheet obtained by thermally laminating a 2-mm-thick polyethylene and various oxygen-barrier films was adhered to produce a heavy-corrosion-coated steel material having the oxygen-barrier film of the present invention. Further, a heavy corrosion-resistant coated steel material of a comparative example was prepared by attaching a sheet in which a 0.2 mm thick titanium foil was laminated with a thermoplastic adhesive.
[0022]
For the purpose of simulating peeling during long-term use, the prepared heavy-corrosion-resistant steel material was subjected to seal coating with an epoxy resin on the back surface and immersed in artificial seawater at 50 ° C. for 180 days. Stirring and oxygen supply were performed by blowing air into the artificial seawater. After the test, the polyethylene coating was removed, and the distance between the end of the coating and the portion where the steel surface was exposed was measured. However, no corrosion was observed on the exposed steel surface even if the adhesive strength was reduced, and no problem was observed even if the adhesion was reduced on the anticorrosion surface.
[0023]
Table 1 shows the type, thickness, distance of the exposed surface of the steel material from the end, and oxygen permeability of each film. The heavy corrosion protection coated steel material using the chromate treatment of Comparative Example 1 is less likely to cause adhesive deterioration from the coated end. On the other hand, in the conventional anticorrosion coating specification as in Comparative Example 2, the adhesion deterioration distance increases when there is no chromate treatment. However, the heavy corrosion protection coated steel having the titanium metal coating of Comparative Example 3 has a short adhesion deterioration distance from the end due to the shielding effect of the coating even without the chromate treatment.
[0024]
When the film is attached to the surface, as is clear from the results of Comparative Examples 4 to 10, when the oxygen permeability of the film is not within the range of the present invention, the adhesion deterioration distance is large regardless of the thickness. However, in Examples 11 to 23 of the present invention, the adhesion deterioration distance is greatly reduced. In addition, even when a chemical conversion treatment other than the chromate treatment is used as in Examples 24 to 26, performance equal to or higher than that of the anticorrosion coating using the conventional chromate treatment can be obtained. Further, in the case of Examples 27 to 29 using the chromate treatment for the underlayer, the adhesion deterioration distance can be kept small even with the conventional heavy duty anticorrosion coating of Comparative Example 1. That is, the oxygen permeability of the film varies greatly depending on the type and thickness of the film, but by laminating an oxygen barrier film having an oxygen permeability of 100 cm ³ (standard) / m ² · day · atm (20 ° C.) or less. It is possible to suppress a decrease in adhesion from the end, and to improve the anticorrosion performance as compared with a conventional anticorrosion coating.
[0025]
[Table 1]

[0026]
【The invention's effect】
By including an oxygen barrier film in a heavy duty anticorrosion coating as in the present invention, the anticorrosion properties of conventional heavy duty anticorrosion coatings can be dramatically improved. Due to the mechanism that greatly reduces oxygen permeation from the coating surface of the oxygen barrier film, the heavy-corrosion-coated steel material of the present invention significantly suppresses the progress of adhesive deterioration from scratches and edges compared to conventional heavy-corrosion coating. Can be done. As a result, it is possible to omit the conventional coating type chromate treatment as a base treatment or to substitute another chemical conversion treatment containing no chromium compound.
[Brief description of the drawings]
FIG. 1 shows an example of a sectional view of a coating structure of a heavy-corrosion-coated steel material of the present invention.
FIG. 2 shows another example of a sectional view of the coating structure of the heavy-corrosion-coated steel material of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steel material 2 Base treatment coating 3 Primer resin 4 Corrosion protection coating layer 5 Adhesive layer 6 Oxygen barrier film 7 Colored film

Claims

In the heavy corrosion protection coated steel having a corrosion protection coating on the surface of the steel, the oxygen permeability was adjusted to 100 cm ³ (standard) / m ² · day · atm (20 ° C.) or less inside or on the surface of the corrosion protection coating. A heavy-duty corrosion-resistant coated steel material having an oxygen barrier film and excellent in peeling and corrosion resistance.

On the surface of the steel material, an undercoat treatment layer, a resin primer treatment layer, an anticorrosion resin layer having a thickness of 500 μm or more, an adhesive layer, and an oxygen permeability of 100 cm ³ (standard) / m ² · day · atm (20 ° C.) at a thickness of 10 to 500 μm. A heavy corrosion resistant coated steel material excellent in peeling and corrosion resistance, characterized by sequentially laminating oxygen barrier films adjusted as follows.

The heavy corrosion-resistant coated steel material having excellent peeling and corrosion resistance according to claim 2, wherein a colored film is further laminated on the surface layer of the oxygen barrier film layer.

The heavy corrosion protection coated steel material having excellent exfoliation and corrosion resistance according to claim 2 or 3, wherein the base treatment layer is a chemical conversion treatment layer containing no chromium compound.