JP2004197113A

JP2004197113A - Organic composite galvanized steel

Info

Publication number: JP2004197113A
Application number: JP2002363348A
Authority: JP
Inventors: Koichi Nose; 幸一能勢; Kiyokazu Ishizuka; 清和石塚
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2002-12-16
Filing date: 2002-12-16
Publication date: 2004-07-15

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic composite galvanized steel which is excellent in various properties such as corrosion resistance and workability. <P>SOLUTION: The organic composite galvanized steel is composed in such a manner that a galvanizing film, a zinc phosphate based film of ≥0.3 g/m<SP>2</SP>, and an organic film of 0.3 to 2 g/m<SP>2</SP>are successively formed on at least a part of the steel surface. The zinc phosphate based film comprises ≥20 mg/m<SP>2</SP>Mg, and the mass ratio of Mg/P is ≥0.15. The organic film comprises clay mineral essentially consisting of phyllosilicate as a rust prevention additive. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、自動車、家電、建材等の用途に用いられる耐食性、加工性等の諸特性に優れた有機複合亜鉛系めっき鋼材に関するものである。
【０００２】
【従来の技術】
自動車、家電、建材等の用途に用いられる亜鉛系めっき鋼材は、従来から、リン酸塩処理、クロメート処理、更には有機被覆処理を施し、耐食性、加工性等の付加価値を向上させて使用されることが多かった。近年環境上の問題から、特にクロメート処理された鋼板は、６価のクロムを含む可能性があることから嫌われる傾向にあり、リン酸塩処理に対する要望が高まっている。また、耐食性、加工性の観点からは、Ｚｎ−Ｎｉ系の合金めっき鋼板が良好な特性を示すことから、広く用いられているが、Ｎｉを含む合金めっきであることから製造コストが高価になるといった問題がある。このため、製造コストの安価な電気亜鉛めっき鋼板、溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板等にリン酸塩処理を施し、付加価値を向上させる試みがなされている。
【０００３】
しかし、電気亜鉛めっき鋼板、溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板等に対する従来のリン酸塩処理では、Ｚｎ−Ｎｉ系合金めっき鋼板に比較して、必ずしも十分な加工性が得られていない。更には、Ｚｎ−Ｎｉ系合金めっき上にクロメート皮膜、有機皮膜を形成した有機複合鋼板に比較すると、耐食性の点からも劣る。リン酸塩処理皮膜上に更に有機皮膜を形成した鋼板も公知ではあるが、十分な耐食性を確保しようとすると、有機皮膜の膜厚が厚くなり、溶接性や加工性、更にはコストの問題もあり、広く実用化されるには至っていない。
【０００４】
上記課題に対し、本発明者等は、特開２００１−１３１７６３号公報（特許文献１）において、Ｍｇを含有する特定のリン酸亜鉛皮膜の上に有機皮膜を形成した、耐食性、加工性に優れた有機複合亜鉛系めっき鋼板を提案した。この鋼板は、良好な耐食性を有するも、近年、例えば自動車用途においては、防錆保証期間の延長の動きがあるように、いっそうの耐食性向上が望まれている。
【０００５】
【引用文献】
（１）特許文献１（特開２００１−１３１７６３号公報）
【０００６】
【発明が解決しようとする課題】
本発明では、上記問題を解決し、優れた耐食性等の諸特性を有する有機複合亜鉛系めっき鋼材を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明者等は、リン酸塩処理亜鉛系めっき鋼材の耐食性、加工性等の諸性能を改善するため、リン酸塩処理皮膜上に更に有機皮膜を形成することを検討した。しかし、公知の処理の組み合わせでは、リン酸塩皮膜と有機皮膜間の密着性が十分ではないこと、電着塗装時にフクレが発生しやすいこと、等の理由から、耐食性、加工性とも大きな改善効果が期待できないという問題があった。これら問題に対して鋭意検討を重ねた結果、亜鉛系めっき鋼材表面に、Ｍｇを必須成分として含有するリン酸亜鉛系処理を施し、更にその上層に特定の防錆添加剤を含有する有機皮膜を形成すれば、極めて良好な特性を得ることができることを見いだし、本発明に至った。
【０００８】
すなわち、本発明の要旨とするところは、以下の通りである。
（１）鋼材表面の少なくとも一部に、亜鉛系めっき皮膜、０．３ｇ／ｍ²以上のリン酸亜鉛系皮膜、０．３〜２ｇ／ｍ²の有機皮膜が順次形成されてなる有機複合亜鉛系めっき鋼材であって、前記リン酸亜鉛系皮膜が、２０ｍｇ／ｍ²以上のＭｇを含有し、及び、Ｍｇ／Ｐ（質量比）が０．１５以上であり、前記有機皮膜が、防錆添加剤として層状珪酸塩を主とする粘土鉱物を含有することを特徴とする有機複合亜鉛系めっき鋼材。
【０００９】
（２）前記粘土鉱物が、Ｃａ又はＭｇの内の１種以上を含有する層状珪酸塩粘土鉱物である前記（１）記載の有機複合亜鉛系めっき鋼材。
（３）前記防錆添加剤として、更にコロイダルシリカを含有する前記（１）記載の有機複合亜鉛系めっき鋼材。
（４）前記有機皮膜が、防錆添加剤と、エポキシ樹脂または変性エポキシ樹脂を少なくとも含有する前記（１）〜（３）のいずれかに記載の有機複合亜鉛系めっき鋼材。
【００１０】
（５）前記有機皮膜の成分が、有機樹脂の固形分１００質量部に対して、コロイダルシリカと他の防錆添加剤合計の固形分で１０質量部以上１００質量部以下であり、かつ、コロイダルシリカ以外の防錆添加剤の固形分が５質量部以上５０質量部以下である前記（１）〜（４）のいずれかに記載の有機複合亜鉛系めっき鋼材。
【００１１】
（６）前記亜鉛系めっき皮膜が、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉの内の１種又は２種以上を、質量％の合計で０．０５〜１５％含有する前記（１）記載の有機複合亜鉛系めっき鋼材。
（７）前記亜鉛系めっき皮膜が、Ｃａ、Ｍｇ、Ｃｅ、Ｙ、Ｚｒ、Ｌａの内の１種又は２種以上を、質量％の合計で０．０１〜１％含有する前記（１）又は（５）に記載の有機複合亜鉛系めっき鋼材にある。
【００１２】
【発明の実施の形態】
本発明に用いる亜鉛系めっき皮膜には、特に限定がなく、純亜鉛めっき、亜鉛系合金めっきのいずれの皮膜でも使用でき、その良好な耐食性、加工性改善効果を享受できるが、製造コストの観点からは、電気亜鉛めっき、溶融亜鉛めっき、合金化溶融亜鉛めっき等が好ましい。また、単層めっき、複層めっきのいずれも使用できるし、Ｎｉ、Ｃｕ等のプレめっき上に形成した亜鉛系めっきであっても構わない。さらに、めっき層中に特性上有効な有機あるいは無機の分散剤を分散させたいわゆる分散めっきであっても何ら問題となるところはなく、本特許の範疇とすることが出来る。
【００１３】
Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ：これらの合金めっき成分は、いずれか１種あるいは２種以上をめっき層に共存させることで、０．０５％程度含有されたこれらの微量合金成分でも従来の亜鉛系合金めっきより高い耐食性を示すので、より高い耐食性を得たい場合には、これらの合金の１種あるいは２種以上を共存させた合金めっきを亜鉛系めっき被膜として採用できる。０．０５％未満ではその効果が十分でなく、１５％超ではその効果が飽和し、かつ加工性が著しく劣ってくるので、その範囲を０．０１５〜１５％とした。
【００１４】
Ｃａ、Ｍｇ、Ｃｅ、Ｙ、Ｚｒ、Ｌａ：これらの微量添加元素は、亜鉛の耐食性腐食生成物である塩基性塩化亜鉛を安定化させたり、環境によっては単独で保護性の被膜を生成したり、他に保護性の水和被膜を生成する元素のある場合はそれらの水和被膜を補強したりして、耐食性を増すことができるので、さらに耐食性を必要とする場合には、これらの微量添加元素の内１種又は２種以上を含有させることができる。その場合、これらの質量％の合計で０．０１％未満では効果が無いため、０．０１％以上添加することが望ましく、１％近傍でその効果が飽和し、且つ１％超含有させることが難しいため、上限を１％とした。
【００１５】
亜鉛系めっき皮膜の上に形成されるリン酸亜鉛系皮膜には、Ｍｇを含有することが必須であって、この点は本発明のポイントの一つである。Ｍｇの量としては、Ｍｇ／Ｐ（質量比）で０．１５以上必要であり、この値未満では耐食性の向上効果はない。また、上限については特に限定されないが、一般的には０．７８程度であり、これ以上Ｍｇを含有させることは容易ではない。前記Ｍｇ／Ｐ比でＭｇを含有したリン酸亜鉛系皮膜を形成することで、その上層に形成する有機皮膜との密着性が極めて良好になるとともに、電着塗装の場合のフクレ発生を効果的に抑制できるようになる。このような効果の得られる理由は必ずしも明確ではないが、Ｍｇの存在により、リン酸亜鉛系皮膜の可撓性が向上し、リン酸亜鉛系皮膜層での凝集破壊が抑制されること、また、アルカリ環境での溶解性が抑制されるようになること、等が考えられる。また、ＭｇはＺｎの腐食生成物を安定化する効果が強いことからも、腐食の進行を抑え、耐食性の改善に寄与する。
【００１６】
Ｍｇの絶対量は、２０ｍｇ／ｍ²以上必要であり、この条件で良好な耐食性が得られる。また、リン酸亜鉛系皮膜に、Ｍｇ以外にＮｉ、Ｍｎ、Ｃｏ、Ｆｅ、Ｃｕ、Ａｌ、Ｃａの１種又は２種以上を含有させることも好適であり、いっそうの耐食性、加工性改善効果が得られる。前記リン酸亜鉛系皮膜量は、０．３ｇ／ｍ²以上、好ましくは０．３〜２ｇ／ｍ²であり、この下限未満では耐食性が不足する。上限を超えると、厳しい加工を実施した際の皮膜剥離が発生する恐れが高くなる。
【００１７】
前記リン酸亜鉛系皮膜を形成する処理液としては、Ｚｎイオン、リン酸イオンを主成分として、更にＺｎ以外の金属イオン、硝酸イオン、フッ化物等も必要に応じて添加された市販の処理液に、硝酸Ｍｇを多量に添加した浴が好適に用いられる。皮膜中のＭｇの量及びＭｇ／Ｐ比は、硝酸Ｍｇの添加量によってコントロ−ルできるし、また、リン酸亜鉛皮膜の付着量は、処理時間を変化させることによって調整できる。
【００１８】
有機皮膜については、防錆添加剤を含有することが優れた耐食性を得るために必須であり、防錆添加剤としては、層状珪酸塩を主とする粘土鉱物を必須成分として含有することが、本発明のもう一つのポイントである。層状珪酸塩を主とする粘土鉱物としては、蛇紋石−カオリン族、タルク−パイロフィライト族、スメクタイト族、バーミキュライト族、雲母族、層間欠損型雲母族、脆雲母族、緑泥石族、等を例示できる。粘土鉱物は、その微粒子性と珪酸塩であることから、コロイダルシリカと同様な耐食作用が期待できるが、さらにその構成成分としてＣａあるいはＭｇ、あるいはその両者を含有するものは防錆効果が高い。
【００１９】
構成成分としてＣａ、Ｍｇ又はその両者を含有する層状珪酸塩粘土鉱物としては、タルク、モンモリロナイト、バーミキュライト、アタパルジャイト等が例示できる。また、モンモリロナイト等のイオン交換性のあるものでは、イオン交換してＣａ、Ｍｇの含有量を増加させたものは、より防錆効果が高く、工業的には止水剤等で用いられるカルシウムベントナイト等が挙げられる。
【００２０】
特に、Ｃａ、Ｍｇを含有した層状珪酸塩粘土鉱物では、ＣａやＭｇがアルカリ環境で耐食性の皮膜を形成すること、あるいはＺｎの耐食性腐食生成物である塩基性塩化亜鉛を安定化させる効果がある。これら層状珪酸塩粘土鉱物の利用は、環境への悪影響のほとんど無いこと、その入手が容易で工業的にも安価に精製・製造され市販されていることもメリットの一つである。
防錆添加剤として、更にコロイダルシリカを防錆添加剤として共存させることによって極めて優れた耐食性が得られる。この理由は明確でないが、コロイダルシリカの成膜作用と層状珪酸塩を主とする粘土鉱物の腐食抑制作用の協奏効果ではないかと推定される。
【００２１】
有機皮膜の付着量は、０．３〜２ｇ／ｍ²であり、この下限未満では耐食性、加工性改善効果が不足し、上限を超えると、溶接性が悪化する。
有機皮膜中の樹脂成分としては、エポキシ樹脂又は変性エポキシ樹脂が、耐食性、密着性の観点から望ましい。なお、有機樹脂、前述の防錆添加剤に加えて、ポリエチレン等のワックス成分、色調を制御するための顔料成分も必要に応じて共存させることが可能である。
【００２２】
有機皮膜の組成として、有機樹脂の固形分１００質量部に対して、コロイダルシリカと他の防錆添加剤合計の固形分で１０質量部以上１００質量部以下、かつ、コロイダルシリカ以外の防錆添加剤の固形分が５質量部以上５０質量部以下とすることが望ましい。いずれの下限を下回っても耐食性が低下し、上限を超えても耐食性が低下するだけでなく溶接性も低下する傾向にあるからである。
【００２３】
本発明の構成である、亜鉛系めっき皮膜＋特定のリン酸塩皮膜＋特定の有機皮膜は、鋼材の表面の少なくとも一部に形成されていれば良く、例えば、鋼板の場合、鋼板の一方の面又は両面に形成すれば良い。鋼板の一方の面にのみ形成する場合には、例えば、自動車車体用途であれば、塗装がつき廻りにくくより高度な鋼板の耐食性が要求される車体内面に相当する面に、また、例えば、燃料タンク用途であれば、タンク内面に相当する面に、本発明の皮膜構成を適用すればよい。なお、この場合、反対面については、特段の制限はなく、非めっき鋼板、亜鉛系めっきのみ、亜鉛系めっき＋特定のリン酸塩皮膜、非めっき鋼板＋特定のリン酸塩皮膜、等いずれも適用でき、必要に応じて選択すれば良い。
【００２４】
【実施例】
以下に本発明の実施例を示す。
供試材としては、全て、板厚０．７ｍｍ、ｒ（ランクフォード）値＝１．９の冷延鋼板に、目付量３０ｇ／ｍ²（片面当たり）のめっきを両面に施した電気亜鉛めっき鋼板を使用した。
（実施例１〜８、比較例１〜４）
〈リン酸亜鉛系処理〉
供試材に表面調整（日本パーカライジング社製Ｐ１−Ｚｎ）の後、日本パーカライジング社製のリン酸亜鉛処理浴（Ｚｎイオン０．７ｇ／ｌ、Ｎｉイオン２．０ｇ／ｌ、リン酸イオン６．５ｇ／ｌ、硝酸イオン６ｇ／ｌ、フッ化物０．２ｇ／ｌ）をベースに、硝酸マグネシウム・６水和物をＭｇイオン濃度として０〜３０ｇ／ｌになるように、種々添加した浴を使用して、両面の処理を行った。処理はスプレー法により、処理時間１〜１０ｓｅｃの間で変化させて付着量（片面当たり）を調整した。
【００２５】
〈有機被覆〉
ビニル変性エポキシエステル樹脂にブロックイソシアネート硬化剤、変性ポリエチレンワックス、縮合アゾ系の赤色顔料を配合（それぞれの固形分質量比は、１００：１０：５：３）した水性樹脂をベースに、コロイダルシリカ（日産化学社製ＳＴ−ＮＳ）と層状珪酸塩粘土鉱物を各種配合比で添加した塗料を用い、ロールコータで回転数を制御しながら乾燥皮膜質量が０〜２．５ｇ／ｍ²（片面当たり）になるように両面に塗布し、その後到達板温度で１５０℃になるように焼き付け、水冷した（表１中にビニル変性エポキシエステル樹脂とコロイダルシリカと層状珪酸塩粘土鉱物の固形分質量比を示した。表１下に使用した層状珪酸塩粘土鉱物の種類を示した）。
【００２６】
〈性能評価方法〉
（１）リン酸亜鉛系皮膜中Ｍｇ、Ｐ量；皮膜を全て溶解し、ＩＣＰ分析により定量した。また、リン酸亜鉛系皮膜量は、前記Ｐ量から、Ｈｏｐｅｉｔｅの構造を仮定の上計算で算出した。
（２）有機皮膜量；蛍光Ｘ線分析によりＳｉを定量し、組成比から皮膜量に換算した。
【００２７】
（３）耐食性；サンプルを市販の洗浄油で洗浄後、Ｕビード曲げ加工（サンプル幅７０ｍｍ、ＢＨＦ＝１ｔｏｎ、加工高さ＝７０ｍｍ、ビード部ポンチＲ＝５ｍｍ、ビード部ダイスＲ＝３ｍｍ、ポンチＲ＝５ｍｍ、ダイスＲ＝５ｍｍ、加工速度＝２５ｓｐｍ）を行い、その側面（ダイス側）を切り出して、脱脂した後、端面と裏面を粘着テープシールし、下記に示すＣＣＴ試験を行った。２０サイクル後の赤錆発生状況を観察した。
評価基準は、「◎」；１％未満、「○」；１〜１０％未満、「△」；１０〜５０％、「×」；５０％超、とした。
【００２８】
（４）ＣＣＴ試験条件；塩水噴霧５％ＮａＣｌ、３５℃）６時間→乾燥（５０℃、４５％ＲＨ）３時間→湿潤（５０℃、９５％ＲＨ）１４時間→乾燥（５０℃、４５％ＲＨ）１時間を１サイクルとした繰り返し。
（５）加工性；球頭ポンチ張り出し成形（ビード付き）を行い、張り出し可能成形高さを求めた。加工条件は、ＢＨＦ＝３ｔｏｎ、ポンチ４０ｍｍφ、４０Ｒ、ブランク９８ｍｍφ、である。
評価基準は、「◎」；１７．０ｍｍ超、「○」；１６．５〜１７．０ｍｍ、「△」；１６．０〜１６．５ｍｍ未満、「×」；１６．０ｍｍ未満、とした。
【００２９】
（６）塗装密着性；サンプルを市販のアルカリ脱脂液（ｐＨ＝１０．５、４０℃、１分浸漬）、自動車用化成処理（日本ペイント製サーフダイン２５００ＭＺＬ）を施した後、自動車用カチオン電着塗装（日本ペイント製Ｖ２０、２０μｍ、１７０℃×２０分焼き付け）を行った。一昼夜放置後５０℃温水に浸漬し、１０日後取り出して１ｍｍ間隔の碁盤目カット疵を入れ、粘着テープでの剥離を行った。
評価基準は、「◎」；剥離面積率０％、「○」；剥離面積率５％未満、「△」；剥離面積率５〜５０％、「×」；剥離面積率５０％超、とした。
【００３０】
（７）溶接性；Ｃｕ−ＣｒのＣＦ型電極チップ（５ｍｍφ）を用い、加圧力１９６０Ｎ、通電時間１３サイクル、で適性電流範囲を測定した。
評価基準は、「◎」；１．５ｋＡ超、「○」；１．０〜１．５ｋＡ、「△」；０．３〜１．０ｋＡ未満、「×」；０．３ｋＡ未満、とした。
【００３１】
【表１】

【００３２】
表１に示す、(*) 防錆添加剤は、本発明例Ｎｏ．１〜２及び比較例Ｎｏ．９、１１、１２がカルシウムベントナイト、本発明例Ｎｏ．３〜４がタルク、本発明例Ｎｏ．５がモンモリロナイト、本発明例Ｎｏ．６がバーミキュウライト、本発明例Ｎｏ．７がアタパルジャイト、本発明例Ｎｏ．８がカルシウムベントナイトとタルクを質量比５０：５０とする混合物とした。なお、比較例Ｎｏ．１０には防錆添加剤を添加していない。
評価結果を表１に示すが、本発明の実施例では、良好な特性が得られるのに比較し、本発明の範囲から外れる比較例については、何らかの性能が悪化した。
【００３３】
【発明の効果】
本発明によって、耐食性、加工性等の諸特性が極めて優れた有機複合亜鉛系めっき鋼材を得ることが可能になる。本発明の鋼材は、製造方法も簡易でコスト的にも優れ、自動、家電、建材等各種の用途に好適なものである。[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to an organic composite zinc-based plated steel material excellent in various properties such as corrosion resistance and workability used for applications such as automobiles, home appliances, and building materials.
[0002]
[Prior art]
Zinc-based galvanized steel materials used for automobiles, home appliances, building materials, etc. have been conventionally subjected to phosphate treatment, chromate treatment, and even organic coating treatment to improve the added value such as corrosion resistance and workability. Many times. In recent years, due to environmental problems, particularly a chromate-treated steel sheet tends to be disliked because it may contain hexavalent chromium, and there is an increasing demand for phosphate treatment. In addition, from the viewpoint of corrosion resistance and workability, Zn-Ni-based alloy-plated steel sheets are widely used because they exhibit good characteristics, but the production cost is high because of alloy plating containing Ni. There is a problem. For this reason, attempts have been made to improve the added value by subjecting an electrogalvanized steel sheet, a hot-dip galvanized steel sheet, an alloyed hot-dip galvanized steel sheet, and the like, which are inexpensive to manufacture, to a phosphate treatment.
[0003]
However, conventional phosphate treatment of electrogalvanized steel sheets, hot-dip galvanized steel sheets, alloyed hot-dip galvanized steel sheets, etc., does not always provide sufficient workability compared to Zn-Ni-based alloy-coated steel sheets. . Furthermore, when compared with an organic composite steel sheet in which a chromate film and an organic film are formed on a Zn-Ni-based alloy plating, it is inferior in terms of corrosion resistance. A steel sheet further formed with an organic film on a phosphate-treated film is also known, but when trying to ensure sufficient corrosion resistance, the film thickness of the organic film becomes thicker, and the problems of weldability and workability, as well as cost, are raised. Yes, it has not been widely used.
[0004]
In order to solve the above-mentioned problems, the present inventors have disclosed in JP-A-2001-131763 (Patent Document 1) that an organic film is formed on a specific zinc phosphate film containing Mg, which is excellent in corrosion resistance and workability. We proposed an organic composite zinc-based coated steel sheet. Although this steel sheet has good corrosion resistance, in recent years, for example, in automotive applications, further improvement in corrosion resistance has been desired so as to extend the rust prevention guarantee period.
[0005]
[References]
(1) Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-131763)
[0006]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems and to provide an organic composite zinc-based plated steel material having various properties such as excellent corrosion resistance.
[0007]
[Means for Solving the Problems]
The present inventors have studied to further form an organic film on the phosphate-treated film in order to improve various properties such as corrosion resistance and workability of the phosphate-treated galvanized steel material. However, with the combination of the known treatments, the adhesion between the phosphate film and the organic film is not sufficient, blisters are easily generated during electrodeposition coating, and the like, so that the corrosion resistance and the processability are greatly improved. There was a problem that could not be expected. As a result of intensive studies on these problems, a zinc phosphate-based treatment containing Mg as an essential component was applied to the surface of the galvanized steel material, and an organic film containing a specific rust-preventive additive was further formed on the surface. It has been found that when formed, extremely good characteristics can be obtained, and the present invention has been achieved.
[0008]
That is, the gist of the present invention is as follows.
(1) at least a portion, galvanized coating, 0.3 g / m ² or more zinc phosphate coating, an organic composite zinc organic film of 0.3 to 2 g / m ^2, which are sequentially formed in the steel surface The zinc phosphate-based coating contains 20 mg / m ² or more of Mg, and has a Mg / P (mass ratio) of 0.15 or more, and the organic coating has rust prevention. An organic composite galvanized steel material comprising a clay mineral mainly composed of a layered silicate as an additive.
[0009]
(2) The organic composite zinc-based plated steel according to (1), wherein the clay mineral is a layered silicate clay mineral containing at least one of Ca and Mg.
(3) The organic composite zinc-plated steel material according to (1), further comprising colloidal silica as the rust preventive additive.
(4) The organic composite zinc-based plated steel according to any one of (1) to (3), wherein the organic film contains at least a rust preventive additive and an epoxy resin or a modified epoxy resin.
[0010]
(5) The component of the organic film is 10 parts by mass or more and 100 parts by mass or less in terms of the total solid content of colloidal silica and other rust-preventive additives based on 100 parts by mass of the solid content of the organic resin, and The organic composite zinc-plated steel material according to any one of (1) to (4), wherein the solid content of the rust preventive additive other than silica is 5 parts by mass or more and 50 parts by mass or less.
[0011]
(6) The organic according to (1), wherein the zinc-based plating film contains one or more of Cr, Mn, Fe, Co, and Ni in an amount of 0.05 to 15% by mass in total. Composite galvanized steel.
(7) The above (1) or wherein the zinc-based plating film contains one or more of Ca, Mg, Ce, Y, Zr, and La in an amount of 0.01 to 1% by mass%. An organic composite zinc-based plated steel according to (5).
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The zinc-based plating film used in the present invention is not particularly limited, and any of pure zinc plating and zinc-based alloy plating can be used, and its good corrosion resistance and workability improvement effect can be enjoyed. For this reason, electrogalvanizing, hot-dip galvanizing, alloyed hot-dip galvanizing and the like are preferable. Either single-layer plating or multiple-layer plating can be used, or zinc-based plating formed on pre-plating of Ni, Cu, or the like may be used. Further, so-called dispersion plating in which an organic or inorganic dispersant effective in characteristics is dispersed in a plating layer does not cause any problem, and can be included in the scope of the present patent.
[0013]
Cr, Mn, Fe, Co, Ni: One or more of these alloy plating components coexist in the plating layer, so that even a small amount of these 0.05% alloy components can be used. Since it exhibits higher corrosion resistance than zinc-based alloy plating, if higher corrosion resistance is desired, alloy plating in which one or more of these alloys coexist can be used as the zinc-based plating film. If it is less than 0.05%, the effect is not sufficient, and if it exceeds 15%, the effect is saturated and the workability is remarkably deteriorated. Therefore, the range is set to 0.015 to 15%.
[0014]
Ca, Mg, Ce, Y, Zr, La: These trace addition elements stabilize basic zinc chloride, which is a corrosion-resistant corrosion product of zinc, or form a protective film alone depending on the environment. However, if there are other elements that form a protective hydrated film, these hydrated films can be reinforced to increase corrosion resistance. One or more of the additional elements can be contained. In this case, if the total of these mass% is less than 0.01%, there is no effect. Therefore, it is preferable to add 0.01% or more, and the effect is saturated at around 1%, and more than 1% is contained. Because it is difficult, the upper limit was set to 1%.
[0015]
It is essential that the zinc phosphate-based film formed on the zinc-based plating film contains Mg, which is one of the points of the present invention. The amount of Mg needs to be 0.15 or more in terms of Mg / P (mass ratio), and if less than this value, there is no effect of improving corrosion resistance. Although the upper limit is not particularly limited, it is generally about 0.78, and it is not easy to further contain Mg. By forming a zinc phosphate-based film containing Mg at the Mg / P ratio, the adhesion to an organic film formed thereon is extremely improved, and blister generation in the case of electrodeposition coating is effectively prevented. Can be suppressed. Although the reason why such an effect is obtained is not necessarily clear, the presence of Mg improves the flexibility of the zinc phosphate-based coating, and suppresses cohesive failure in the zinc phosphate-based coating layer. And the solubility in an alkaline environment is suppressed. Further, since Mg has a strong effect of stabilizing the corrosion product of Zn, Mg suppresses the progress of corrosion and contributes to improvement of corrosion resistance.
[0016]
The absolute amount of Mg needs to be 20 mg / m ² or more, and good corrosion resistance can be obtained under these conditions. It is also preferable that the zinc phosphate-based coating contains one or more of Ni, Mn, Co, Fe, Cu, Al, and Ca in addition to Mg, thereby further improving the corrosion resistance and workability. can get. The amount of the zinc phosphate coating is 0.3 g / m ² or more, and preferably 0.3 to ² g / m ² , and if it is less than the lower limit, the corrosion resistance is insufficient. If the upper limit is exceeded, there is a high possibility that film peeling will occur when severe processing is performed.
[0017]
As the treatment liquid for forming the zinc phosphate-based coating, a commercially available treatment liquid containing Zn ions and phosphate ions as main components, and further adding metal ions other than Zn, nitrate ions and fluorides as necessary. In addition, a bath containing a large amount of Mg nitrate is preferably used. The amount of Mg and the Mg / P ratio in the film can be controlled by the amount of Mg nitrate added, and the amount of the zinc phosphate film deposited can be adjusted by changing the treatment time.
[0018]
As for the organic film, it is essential to contain an anticorrosive additive in order to obtain excellent corrosion resistance, and as the anticorrosive additive, it is necessary to contain a clay mineral mainly composed of a layered silicate as an essential component. This is another point of the present invention. Examples of clay minerals mainly composed of layered silicates include serpentine-kaolin, talc-pyrophyllite, smectite, vermiculite, mica, delaminated mica, brittle mica, chlorite, and the like. Can be illustrated. Clay minerals can be expected to have the same corrosion resistance as colloidal silica because of their fine particle properties and silicates, but those containing Ca or Mg or both as constituents have a high rust prevention effect.
[0019]
Examples of the layered silicate clay mineral containing Ca, Mg, or both as constituents include talc, montmorillonite, vermiculite, and attapulgite. In the case of montmorillonite and the like having ion exchange properties, those in which the contents of Ca and Mg are increased by ion exchange have a higher rust prevention effect, and calcium bentonite which is industrially used as a water stopping agent and the like is used. And the like.
[0020]
In particular, in a layered silicate clay mineral containing Ca and Mg, Ca and Mg have an effect of forming a corrosion-resistant film in an alkaline environment or stabilizing basic zinc chloride which is a corrosion-resistant corrosion product of Zn. . One of the advantages of using these layered silicate clay minerals is that they have almost no adverse effect on the environment, and that they are easily available, are industrially inexpensive, are purified, manufactured and marketed.
Extremely excellent corrosion resistance can be obtained by coexisting colloidal silica as a rust preventive additive. Although the reason for this is not clear, it is presumed that it is a synergistic effect between the film-forming action of colloidal silica and the corrosion-inhibiting action of a clay mineral mainly composed of layered silicate.
[0021]
The amount of the organic film adhered is 0.3 to ² g / m ^{2. If the} amount is less than the lower limit, the effect of improving corrosion resistance and workability is insufficient. If the amount exceeds the upper limit, the weldability deteriorates.
As the resin component in the organic film, an epoxy resin or a modified epoxy resin is desirable from the viewpoint of corrosion resistance and adhesion. In addition, in addition to the organic resin and the above-mentioned rust-preventive additive, a wax component such as polyethylene and a pigment component for controlling a color tone can be coexisted as necessary.
[0022]
As the composition of the organic film, the total solid content of colloidal silica and other rust-preventive additives is 10 parts by mass or more and 100 parts by mass or less, and rust-preventive additives other than colloidal silica are added to 100 parts by mass of the solid content of the organic resin. It is desirable that the solid content of the agent be 5 parts by mass or more and 50 parts by mass or less. It is because the corrosion resistance tends to decrease when the amount is below any of the lower limits, and when the amount exceeds the upper limit, not only the corrosion resistance but also the weldability tends to decrease.
[0023]
The zinc-based plating film + the specific phosphate film + the specific organic film, which is the constitution of the present invention, may be formed on at least a part of the surface of the steel material. What is necessary is just to form on a surface or both surfaces. When formed on only one surface of a steel sheet, for example, in the case of an automobile body application, the coating is difficult to cover and the surface corresponding to the inner surface of the vehicle body, which is required to have higher corrosion resistance of the steel sheet, and, for example, a fuel For a tank application, the film configuration of the present invention may be applied to a surface corresponding to the inner surface of the tank. In this case, there is no particular limitation on the opposite surface, and any of non-plated steel sheets, zinc-based plating only, zinc-based plating + specific phosphate film, non-plated steel sheet + specific phosphate film, etc. It can be applied and can be selected as needed.
[0024]
【Example】
Examples of the present invention will be described below.
As the test materials, electrogalvanizing was performed on both sides of a cold-rolled steel sheet having a thickness of 0.7 mm and an r (Rankford) value of 1.9, and a plating weight of 30 g / m ² (per side). A steel plate was used.
(Examples 1 to 8, Comparative Examples 1 to 4)
<Zinc phosphate treatment>
After surface conditioning (P1-Zn, manufactured by Nippon Parkerizing Co., Ltd.) on the test material, zinc phosphate treatment bath (0.7 g / l of Zn ion, 2.0 g / l of Ni ion, phosphate ion of 6, manufactured by Nippon Parkerizing Co., Ltd.). (5 g / l, nitrate ion 6 g / l, fluoride 0.2 g / l), and a bath containing various additions of magnesium nitrate hexahydrate so that the Mg ion concentration becomes 0 to 30 g / l. Then, both sides were processed. The treatment was carried out by a spray method and the amount of adhesion (per side) was adjusted by changing the treatment time from 1 to 10 sec.
[0025]
<Organic coating>
A colloidal silica (based on an aqueous resin in which a blocked isocyanate curing agent, a modified polyethylene wax, and a red pigment of a condensed azo compound are blended with a vinyl-modified epoxy ester resin (each solid content mass ratio is 100: 10: 5: 3)) Using a paint in which Nissan Chemical Industries' ST-NS) and a layered silicate clay mineral were added at various compounding ratios, the dry film mass was 0 to 2.5 g / m ² (per side) while controlling the rotation speed with a roll coater. And then baked to reach 150 ° C at the plate temperature and water-cooled (Table 1 shows the solids mass ratio of vinyl-modified epoxy ester resin, colloidal silica and layered silicate clay mineral. The type of layered silicate clay mineral used is shown below Table 1).
[0026]
<Performance evaluation method>
(1) Amount of Mg and P in zinc phosphate-based coating: All coatings were dissolved and quantified by ICP analysis. The amount of the zinc phosphate-based film was calculated from the P amount by assuming a Hopeite structure.
(2) Organic film amount: Si was quantified by X-ray fluorescence analysis and converted into a film amount from a composition ratio.
[0027]
(3) Corrosion resistance: After washing the sample with a commercially available cleaning oil, U bead bending (sample width 70 mm, BHF = 1 ton, processing height = 70 mm, bead part punch R = 5 mm, bead part die R = 3 mm, punch R) = 5 mm, die R = 5 mm, processing speed = 25 spm), the side face (die side) was cut out, degreased, and the end face and back face were sealed with an adhesive tape, and a CCT test shown below was performed. The state of occurrence of red rust after 20 cycles was observed.
The evaluation criteria were as follows: “◎”; less than 1%, “１〜”: less than 1 to 10%, “△”: 10 to 50%, “x”: more than 50%.
[0028]
(4) CCT test conditions: salt spray 5% NaCl, 35 ° C) 6 hours → dry (50 ° C, 45% RH) 3 hours → wet (50 ° C, 95% RH) 14 hours → dry (50 ° C, 45%) RH) Repeated with 1 hour as 1 cycle.
(5) Workability: Ball-head punch overhanging (with beads) was performed, and the overhanging molding height was determined. The processing conditions are BHF = 3 ton, punch 40 mmφ, 40R, blank 98 mmφ.
The evaluation criteria were as follows: “◎”: more than 17.0 mm, “○”: 16.5 to 17.0 mm, “△”: 16.0 to less than 16.5 mm, “×”: less than 16.0 mm.
[0029]
(6) Coating adhesion: The sample was subjected to a commercial alkaline degreasing solution (pH = 10.5, immersed in 40 ° C. for 1 minute) and a chemical conversion treatment for automobiles (Surf Dine 2500MZL manufactured by Nippon Paint Co., Ltd.). Color coating (Nippon Paint V20, 20 μm, baking at 170 ° C. for 20 minutes) was performed. After standing all day and night, it was immersed in warm water at 50 ° C., taken out after 10 days, cut into squares at 1 mm intervals, and peeled off with an adhesive tape.
The evaluation criteria were as follows: "A": 0% peeled area ratio, "O": Less than 5% peeled area ratio, "Δ": 5% to 50% peeled area ratio, "x": More than 50% peeled area ratio .
[0030]
(7) Weldability: Using a Cu-Cr CF electrode tip (5 mmφ), an appropriate current range was measured at a pressure of 1960 N and an energization time of 13 cycles.
The evaluation criteria were “◎”; more than 1.5 kA, “○”: 1.0 to 1.5 kA, “△”; 0.3 to less than 1.0 kA, “×”: less than 0.3 kA.
[0031]
[Table 1]

[0032]
The rust preventive additives (*) shown in Table 1 are the same as those of Example No. Nos. 1 and 2 and Comparative Example Nos. 9, 11 and 12 are calcium bentonite, Inventive Example No. 3 to 4 are talc; 5 is montmorillonite, Inventive Example No. 5 No. 6 is vermiculite, and Inventive Example No. 7 is attapulgite, Inventive Example No. 7 No. 8 was a mixture of calcium bentonite and talc in a mass ratio of 50:50. In addition, the comparative example No. No rust preventive additive was added to 10.
The evaluation results are shown in Table 1. In the examples of the present invention, good characteristics were obtained, but in the comparative examples out of the range of the present invention, some performance was deteriorated.
[0033]
【The invention's effect】
According to the present invention, it is possible to obtain an organic composite zinc-based plated steel material having extremely excellent properties such as corrosion resistance and workability. The steel material of the present invention has a simple manufacturing method and is excellent in cost, and is suitable for various uses such as automation, home appliances, and building materials.

Claims

At least a portion of the steel material surface, zinc-based plated coating, 0.3 g / m ² or more zinc phosphate coating, 0.3 to 2 g / m ² of the organic film is formed by sequentially forming an organic composite galvanized steel Wherein the zinc phosphate-based coating contains Mg of 20 mg / m ² or more, and Mg / P (mass ratio) is 0.15 or more, and the organic coating is used as a rust preventive additive. An organic composite galvanized steel material containing a clay mineral mainly composed of a layered silicate.

The organic composite zinc-plated steel material according to claim 1, wherein the clay mineral is a layered silicate clay mineral containing at least one of Ca and Mg.

The organic composite zinc-based plated steel material according to claim 1, further comprising colloidal silica as the rust preventive additive.

The organic composite zinc-based plated steel material according to any one of claims 1 to 3, wherein the organic film contains at least a rust preventive additive and an epoxy resin or a modified epoxy resin.

The component of the organic film is, based on 100 parts by mass of the solid content of the organic resin, from 10 parts by mass to 100 parts by mass in total solid content of colloidal silica and other rust-preventive additives, and other than colloidal silica. The organic composite zinc-based plated steel material according to any one of claims 1 to 4, wherein a solid content of the rust preventive additive is 5 parts by mass or more and 50 parts by mass or less.

The organic composite zinc-based composition according to claim 1, wherein the zinc-based plating film contains one or more of Cr, Mn, Fe, Co, and Ni in a total of 0.05 to 15% by mass%. Plated steel.

The zinc-based plating film according to claim 1 or 5, wherein one or more of Ca, Mg, Ce, Y, Zr, and La are contained in an amount of 0.01 to 1% by mass in total. Organic composite zinc-based plated steel.