JPH0214435B2

JPH0214435B2 -

Info

Publication number: JPH0214435B2
Application number: JP10789786A
Authority: JP
Inventors: Yukinobu Higuchi; Akinori Maruta; Kenichi Asakawa; Akimitsu Fukuda; Harumi Terada; Yoji Ono
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 1986-05-12
Filing date: 1986-05-12
Publication date: 1990-04-09
Also published as: JPS62263997A

Description

[Detailed description of the invention]

（産業上の利用分野）本発明は、金属表面処理鋼板の表面に、外観、
耐食性、及び塗装性能の優れた、陰極電解皮膜、
及び陽極電解皮膜からなる、複合クロメート皮膜
を形成させる、金属表面処理鋼板の表面処理法に
関するものである。ここでいう金属表面処理鋼板とは、亜鉛、及び
亜鉛合金メツキ鋼板、鉛及び鉛合金メツキ鋼板、
アルミ、及びアルミ合金メツキ鋼板のことであ
る。具体的に、亜鉛メツキ、及び亜鉛合金メツキ鋼
板としては、 (a) 電気メツキ、真空蒸着メツキによるメツキ
で、不可避的に不純物として混入してくる元素
を含む亜鉛メツキ鋼板 (b) Alを0.1〜0.3％、他物質としてPb、Cd、Fe、
Sb等の元素を１種又は２種以上含み、更に不
可避的不純物元素を含む、溶融亜鉛メツキ鋼板 (c) Feを５〜90％及び不可避的不純物元素を含
むFe−Zn合金メツキ鋼板 (d) Niを５〜20％及び不可避的不純物元素を含
むZn−Ni合金メツキ鋼板 (e) Alを３〜60％含み、又はこれにSi，Mg，ミ
ツシユメタル或いは不可避的不純物を含むZn
−Al合金メツキ鋼板等を挙げることができ、又、鉛メツキ、及び鉛合
金メツキ鋼板としては、 (a) 製造工程上、不可避的不純物を含む、鉛メツ
キ鋼板 (b) Snが30％以下含有され、場合によつてはSb，
Zn或いは不可避的不純物元素を含むPb−Sn合
金メツキ鋼板等を挙げることができ、更に、アルミ、及びアル
ミ合金メツキ鋼板としては、 (a) メツキ時に不可避的に、Fe及びその他の元
素を少量含む、アルミメツキ鋼板 (b) Si，Mgの１種又は２種以上を含み、Siが12
％以下、或いはMgが５％以下であるアルミ合
金メツキ鋼板等を挙げることができる。（従来の技術）金属表面処理鋼板の、電解クロメート処理技術
は、既に、亜鉛メツキ鋼板用としては、特公昭47
−44417（CrO₃−H₂SO₄処理液で陰極電解処理す
る方法）、特開昭60−110896号公報（CrO₃−SiO₂
処理液で陰極電解処理する方法）、又、亜鉛、ア
ルミ、スズ及びそれらの合金メツキ鋼板用として
は、特公昭49−14457号公報（CrO₃−各種金属イ
オン−弗素又は塩素処理液で陰極電解処理する方
法）等で開示されいるが、これらは総て、陰極電
解処理により、金属表面処理鋼板の表面にクロメ
ート皮膜を形成させる方法である。一般に、これら陰極電解皮膜は、塗装性能は良
好であるが、耐食性が不十分であるといわれてい
る。従つて、これらの陰極電解皮膜は、皮膜形成量
（主にクロム付着量）を多くすることにより耐食
性を補つている。しかし、クロメート皮膜は皮膜
形成量が多くなると着色し、被処理材の外観が損
なわれ、又、更に塗装性能が低下するという欠点
があるため、外観、耐食性、塗装性能共に優れた
皮膜の形成が困難であつた。又、亜鉛メツキ鋼板の陰極電解法の場合では、
亜鉛メツキ鋼板等を連続して処理すると、Zn²⁺
イオンが処理液中に蓄積し、耐食性が著しく低下
する等の問題を有していた。次に、陽極電解処理であるが、金属表面処理鋼
板を陽極電解処理しても、クロメート皮膜の形成
は可能であるが、得られる皮膜は耐食性や塗装性
能に乏しく、又、亜鉛メツキ鋼板では、フアラデ
ーの法則に従い、被処理材の金属が溶解し、処理
液が不安定となり、工業的に安定な処理が困難で
ある等の問題を有していた。（発明が解決しようとする問題点）本発明は、従来の陰極電解クロメート処理技術
の欠点である、外観良好時の耐食性の劣下、及び
連続処理時の耐食性の低下等を改善し、外観、耐
食性、塗装性能の優れた皮膜を、工業的に安定し
て、金属表面処理鋼板の表面に形成させることが
目的である。（問題点を解決のための手段）上記の諸問題を解決する、金属表面処理鋼板の
表面処理方法として、種々検討を行つた結果クロ
メート処理液で陰極電解処理後、直ちに陽極電解
処理するという、複合電解処理により、金属表面
処理鋼板を表面処理する方法を開発したものであ
り、即ち本発明の要旨とするところは、クロメー
ト処理液で、金属表面処理鋼板を陰極電解処理
し、クロメート皮膜を形成させた後、直ちに陽極
電解処理し、陽極電解皮膜を形成させることによ
り、前記の陰極電解皮膜を改質処理することを特
徴とする金属表面処理鋼板の表面処理方法であ
る。（発明の構成）本発明における陰極電解処理とは、表面処理鋼
板を陰極とし、その表面に陰極皮膜を形成するた
めに行われ、皮膜形成量（クロム付着量）の調整
は、電流密度及び電解時間により行われる。陰極
電解処理の電流密度、及び電解時間は特定するも
のではないが、電流密度を３〜50A／ｄm²の範囲
にし、電解時間で皮膜形成量を調整することによ
り、一層好ましい結果が得られる。次に陽極電解であるが、これは、前記の陰極電
解皮膜が形成された表面処理鋼板を、陽極とし、
陽極電解皮膜を形成させ、前記の陰極電解皮膜を
改質処理するために行われるものであり、その陽
極電解処理は、電流密度が１〜50A／ｄm²、特に
好ましくは５〜40A／ｄm²、クーロン量が0.1〜
30クーロン／ｄm²、特に好ましくは２〜20クーロ
ン／ｄm²の範囲で行われる。電流密度が1A／ｄ
m²より低い時は、良好な皮膜が形成され難く、耐
食性が不良であり、50A／ｄm²より高くしても、
それ以上の効果はない。クーロン量が0.1クーロン／ｄm²より少ない時
は、皮膜形成量が少ないため改質効果が低下し、
耐食性が不良であり、30クーロン／ｄm²より多く
しても、それ以上の効果はない。又、クーロン量を多くすると、被処理材のメツ
キ皮膜を構成する金属の溶解量、例えば亜鉛メツ
キ鋼板の場合は、亜鉛の溶解量が大きくなり、処
理液が不安定となるため、工業的には30クーロ
ン／ｄm²が限度と考えられる。次に本発明におけるクロメート処理液である
が、このクロメート処理液は、陰極電解時、及び
陰極電解後の陽極電解時に、皮膜を形成させるた
めのものであり、処理液の組成としては公知の陰
極電解処理液も適用できるが、特に好ましい処理
液の組成は、 (a) Cr⁶⁺イオン、PO₄ ^3-イオン及び／又は弗素化
合物を含むクロメート処理液 (b) Cr⁶⁺イオン、シリカ及び／又はケイ酸塩を含
むクロメート処理液 (c) Cr⁶⁺イオン、PO₄ ^3-イオン及び／又は弗素化
合物、シリカ及び／又はケイ酸塩を含むクロメ
ート処理液であり、これらの処理液は、陰極電解、及び陽極
電解の、両方に適用することができるので、同一
の処理液で陰極電解、及び陽極電解を行うことが
でき、又、陰極電解、及び陽極電解を、それぞれ
異なる組成の処理液で電解処理することもでき
る。クロメート処理液中のCr⁶⁺イオンとしては、無
水クロム酸、重クロム酸、及びクロム酸、重クロ
ム酸のアルカリ金属塩類、アンモニウム塩の、１
種又は混合物が任意に適用でき、濃度をCr⁶⁺とし
て５〜70ｇ／の範囲にすることにより、一層好
ましい結果が得られる。 PO₄ ^3-イオンとしては、リン酸、リン酸のアル
カリ金属塩類、及びリン酸アンモニウム等、又、
弗素化合物としては、弗化水素酸、ケイ弗化水素
酸、ホウ弗化水素酸、チタン弗化水素酸、ジルコ
ン弗化水素酸、又はこれらの塩類、弗化アルミ等
の、１種又は混合物が任意に適用でき濃度を、
PO₄ ^3-イオンと弗素化合物の合計として１〜100
ｇ／の範囲にすることにより、一層好ましい結
果が得られる。シリカ及び／又はケイ酸塩は、コロイダルシリ
カを形成するために処理液に加えられるものであ
り、コロイダルシリカ、及びアルカリ金属のケイ
酸塩の１種又は混合物が任意に適用でき濃度を
SiO₂として、0.1〜100ｇ／の範囲にすることに
より、一層好ましい結果が得られる。処理液のpHは0.3〜６、特に好ましくはpH0.6
〜４である。pHが0.3より低い処理液は、効果を
確認するための製造が困難である。又、pHを高
くしても、皮膜の耐食性、及び塗装性能な変わら
ないが、陽極電解処理時に形成される皮膜が、黄
色に着色するので、外観の優れた皮膜を形成させ
るためには、pH6が限界である。処理液のpHをコントロールするためには、硫
酸、硝酸、水酸化アンモニウム、アルカリ金属水
酸化物、及びアルカリ金属炭酸化合物等から任意
に選んで、処理液に加えることができる。又、本
発明の陰極電解処理時の還元反応により生成する
Cr³⁺イオンを、予め、Cr³⁺の水酸化物、及び炭酸
化合物として、或いは、Cr⁶⁺とアルコール類、澱
粉類、及びタンニン酸等の有機化合物との酸化還
元反応生成物として、処理液に加えることもでき
る。しかしながら、本発明の電解処理後（陰極電
解後、陽極電解処理）、水洗しないで乾燥する場
合には水酸化アンモニウム、及びCr³⁺イオンに限
定される。処理液の温度としては、常温〜80℃である。80
℃より高くしても、形成される皮膜の特性に変化
はいが、不経済になるので、工業的には80℃が限
度である。本発明により、電解処理（陰極電解後、陽極電
解処理）された亜鉛メツキ鋼板は、水洗したのち
乾燥して、防食用又は塗装下地として適用される
が、水洗せずにスキイジーロールを通した後、乾
燥して適用することもできる。又、必要に応じて
は、一般に行われている。クロメート水溶液、及
び防食性有機化合物による、後処理もできる。（発明の効果）本発明は、表面処理鋼板、即ち亜鉛、及び亜鉛
合金メツキ鋼板、鉛及び鉛合金メツキ鋼板、アル
ミ、及びアルミ合金メツキ鋼板の表面を、前述の
クロメート水溶液で、陰極電解処理し、クロメー
ト皮膜を形成させた後、直ちに陽極電解処理し、
陽極電解皮膜を形成させることにより、前記の陰
極電解皮膜を改質処理することにより、外観、耐
食性、及び塗装性能の優れた、陰極電解皮膜、及
び陽極電解皮膜からなる、複合クロメート皮膜を
形成させるものである。一般に、陰極電解法によるクロメート皮膜は、
耐食性向上のために、クロム付着量を多くする
と、皮膜は着色し、被処理材の外観を損なわれ、
又、更に塗装性能が低下する。又、亜鉛メツキ鋼
板の場合、亜鉛メツキ鋼板等を連続して処理する
と、Zn²⁺イオンが処理液中に蓄積し、耐食性が
著しく低下する。しかし、本発明は第１表に示すごとく、陰極電
解後、陽極電解処理することにより、外観を損な
うことなく耐食性を著しく改善することができ
る。又、本発明は、例えば第１図に示すごとく亜
鉛メツキ鋼板の表面処理において、処理液中に
Zn²⁺イオンが蓄積しても、耐食性は良好である
ため、前述の陰極電解法の問題点、つまり、耐食
性向上のために、クロム付着量を多くすると、皮
膜は着色し、被処理材の外観を損なわれ、又、更
に塗装性能が低下するという欠点、及び亜鉛メツ
キ鋼板の表面処理において、Zn²⁺イオンが処理
液中に蓄積し、耐食性が著しく低下するという欠
点が改善され、外観、耐食性、及び塗装性能の優
れた皮膜を、工業的に安定して得ることができ
る。他の表面処理鋼板の場合における被処理材か
らの処理液中に対する金属イオンの蓄積について
も同様の効果が得られる。本発明における、好ましいクロム付着量は、５
〜300mg／m²であり、より好ましい範囲は10〜100
mg／m²である。（作用及び実施例）本発明の作用効果を明確するために、幾つかの
実施例、及び比較例を挙げ具体的に説明する。実施例１公知の方法で清浄にした電気亜鉛メツキ鋼板
を、次の条件で、陰極電解処理液、直ちに陽極電
解処理し、処理後水洗し、乾燥した試料を実施例
１とし、比較例１と比較した結果、第１表に示す
ように、本発明の電解処理皮膜は、従来の陰極電
解クロメート法皮膜と比較し、良好な皮膜外観
で、優た耐食性、及び塗装性能を示した。〔処理液組成：組成１〕無水クロム酸 15ｇ／（Cr⁶⁺＝7.8ｇ／）リン酸（98％） 10ｇ／（PO₄ ^-イオンと弗
素化合物の合計が12.3ｇ／）ホウ弗化水素酸（20％） 15ｇ／（水酸化ナトリウムよりpHを２に調整）〔電解条件〕陰極電解；電流密度＝20A／ｄm²、電解時間
＝２秒、温度＝40℃ 陽極電解；クーロン量＝0.1、５、20クーロ
ン／ｄm² （電流密度、及び電解時間により調整）、温度
＝40℃ 比較例１実施例１の、陽極電解処理を行わないものを、
比較例１とし、第１表に示す。実施例２公知の方法で清浄にした電気亜鉛メツキ鋼板
を、次の条件で、陰極電解処理後、直ちに陽極電
解処理し、処理後水洗し、乾燥した試料を実施例
２とし、比較例２と比較した結果、第１表に示す
ように、本発明の電解処理皮膜は、従来の陰極電
解クロメート法皮膜、及び陽極電解クロメート皮
膜と比較し、良好な皮膜外観で、優れた耐食性、
及び塗装性能を示した。〔処理液組成：組成２〕無水クロム酸 50ｇ／（Cr⁶⁺＝26.0ｇ／）リン酸（98％）
20ｇ／（PO₄ ^-イオンとして19.3ｇ／）（この時のpHは0.6であつた）〔電解条件〕陰極電解；電流密度＝15A／ｄm²、電解時間
＝４秒、温度50℃ 陽極電解；電流密度量＝15A／ｄm²、電解時
間＝0.2秒、温度＝40℃ （クーロン量＝３クーロン／ｄm²）比較例２公知の方法で清浄にした電気亜鉛メツキ鋼板
を、実施例２の処理液を用い、陰極電解処理、又
は陽極電解処理したものを比較例２とし、第１表
に示す。実施例３、４、５公知の方法で清浄にした電気亜鉛メツキ鋼板を
次の条件で、陰極電解処理後、直ちに陽極電解処
理し、処理後水洗し、乾燥した試料をそれぞれ実
施例３、４、５とし、比較例３、４、５と比較し
た結果、第１表に示すように、本発明の電解処理
皮膜は、従来の陰極電解クロメート法皮膜と比較
し、良好な皮膜外観で、優れた耐食性、及び塗装
性能を示した。実施例３の条件〔処理液組成：組成３〕無水クロム酸 50ｇ／（Cr⁶⁺＝26.0ｇ／）スノーテツクス−０100ｇ／（日産化学製
SiO₂20％含有のコロイド溶液）（塩基性炭酸クロムによりpHを３に調整）〔電解条件〕陰極電解；電流密度＝40A／ｄm²、電解時間＝１秒、温度＝30℃ 陽極電解；電流密度＝40A／ｄm²、電解時間＝0.2秒、温度＝30℃ （クーロン量＝８クーロン／ｄ
m²）実施例４の条件〔処理液組成：組成４〕重クロム酸アンモン
100ｇ／（Cr⁶⁺＝41.6ｇ／）ケイ弗化水素酸（40％）
50ｇ／（弗素化合物の合計が24.8ｇ／）弗化水素酸（30％） 16 （炭酸ナトリウムでpHを５に調整）〔電解条件〕陰極電解；電流密度＝5A／ｄm²、電解時間＝４秒、温度＝50℃ 陽極電解；電流密度＝5A／ｄm²、電解時間＝２秒、温度＝50℃ （クーロン量＝10クーロン／ｄ
m²）実施例５の条件〔処理液組成：組成５〕無水クロム酸 30ｇ／（Cr⁶⁺＝15.6ｇ／）弗化アルミ
１ｇ／（弗素化合物の合計が1.5ｇ／）弗化水素酸（30％） 1.6ｇ／（炭酸ナトリウムでpHを５に調整）〔電解条件〕陰極電解；電流密度＝50A／ｄm²、電解時間＝２秒、温度＝30℃ 陽極電解；電流密度＝15A／ｄm²、電解時間＝0.4秒、温度＝30℃ （クーロン量＝６クーロン／ｄ
m²）比較例３、４、５実施例３、４、５の、陽極電解処理を行わない
ものを、それぞれ比較例３、４、５とし、第１表
に示す。実施例６公知の方法で清浄にした電気亜鉛メツキ鋼板
を、次の条件で、陰極電解処理後、直ちに陽極電
解処理し、処理後水洗し、乾燥した試料を実施例
６とし、比較例６と比較した結果、第２表、第１
図に示すように、本発明の電解処理皮膜は、処理
液中にZn²⁺イオンが混入しても耐食性の低下が
なく、従来の陰極電解クロメート法皮膜と比較
し、優れた耐食性を示した。〔処理液組成：組成６〕無水クロム酸 20ｇ／（Cr⁶⁺＝10.4ｇ／）ケイ弗化水素酸（40％）16ｇ／（PO₄ ^3-イオ
ンと弗素化合物の合計が29.1ｇ／）リン酸（98％） 30ｇ／（上記処理液に、Zn²⁺イオン０、１、３、６
ｇ／を酸化亜鉛で添加後、各々の処理液のpH
が２になるよう硫酸で調整）〔電解条件〕陰極電解；電流密度＝30A／ｄm²、電解時間＝1.5秒、温度＝30℃ 陽極電解；電流密度＝30A／ｄm²、電解時間＝0.2秒、温度＝30℃ （クーロン量＝６クーロン／ｄ
m²）比較例６実施例６の、陽極電解処理を行わないものを、
比較例６とし、第２表に示す。実施例７、８、９、10 公知の方法で清浄にした、真空蒸着亜鉛メツキ
鋼板、溶融亜鉛メツキ鋼板、Zn−５％Al合金メ
ツキ鋼板、Al−10％Si合金メツキ鋼板、及びPb
−10％合金メツキ鋼板を、次の条件で、陰極電解
処理後、直ちに陽極電解処理し、処理後水洗し、
乾燥した試料をそれぞれ実施例７、８、９、10と
し、比較例７、８、９、10と比較した結果、第３
表、第４表に示すように、本発明の電解処理皮膜
は、いずれの表面処理鋼板においても、従来の陰
極電解クロメート法皮膜と比較し、良好な皮膜外
観で、優れた耐食性、及び塗装性能を示した。実施例７、８、９、10の電解処理条件は、総て
以下の条件とした。〔電解条件〕陰極電解；電流密度＝20A／ｄm²、電解時間＝２秒、温度＝40℃ 陽極電解；電流密度＝20A／ｄm²、電解時間＝0.2秒、温度＝40℃ （クーロン量＝４クーロン／ｄ
m²）〔実施例７の処理液組成：組成７〕無水クロム酸 20ｇ／（Cr⁶⁺＝10.4ｇ／）リン酸（98％）20ｇ／（PO₄ ^-イオンと弗素
化合物の合計が23.6ｇ／）チタン弗化水素酸（20％） 20ｇ／（水酸化ナトリウムによりpHを２に調整）〔実施例８の処理液組成：組成８〕無水クロム酸 50ｇ／（Cr⁶⁺＝10.4ｇ／）スノーテツクAK50ｇ／（日産化学製SiO₂20
％含有のコロイド溶液）（水酸化ナトリウムによりpHを２に調整）〔実施例９の処理液組成：組成９〕無水クロム酸 80ｇ／（Cr⁶⁺＝41.6ｇ／）ジルコン弗化水素酸（20％）
50ｇ／（弗素化合物の合計が14.8ｇ／）弗化水素酸（30％） 16ｇ／（炭酸ナトリウムでpHを２に調整）〔実施例−10の処理液組成：組成10〕無水クロム酸 30ｇ／（Cr⁶⁺＝15.6ｇ／）弗化アルミ５ｇ／（PO₄ ^3-イオンと弗素化合
物の合計が15.4ｇ／）弗化水素酸（30％）２ｇ／リン酸（98％） 10ｇ／（炭酸ナトリウムでpHを２に調整）比較例７、８、９、10 実施例７、８、９、10の、陽極電解処理を行わ
ないものを、それぞれ比較例７、８、９、10と
し、第３表、第４表に示す。 (Industrial Application Field) The present invention provides an appearance,
Cathode electrolytic coating with excellent corrosion resistance and coating performance,
The present invention relates to a surface treatment method for a metal surface-treated steel sheet, which forms a composite chromate film comprising anodic electrolytic film and anodic electrolytic film. The metal surface-treated steel sheets mentioned here include zinc and zinc alloy plated steel sheets, lead and lead alloy plated steel sheets,
It refers to aluminum and aluminum alloy plated steel sheets. Specifically, galvanized steel sheets and zinc alloy-plated steel sheets include: (a) Galvanized steel sheets that contain elements that are unavoidably mixed in as impurities when plated by electroplating or vacuum evaporation plating; (b) Al content of 0.1~ 0.3%, other substances include Pb, Cd, Fe,
Hot-dip galvanized steel sheet containing one or more elements such as Sb and unavoidable impurity elements (c) Fe-Zn alloy-plated steel sheet containing 5 to 90% Fe and unavoidable impurity elements (d) Zn-Ni alloy plated steel sheet containing 5 to 20% Ni and unavoidable impurity elements (e) Zn containing 3 to 60% Al, or Si, Mg, Mitsushi metal, or unavoidable impurities
-Al alloy plated steel sheets, etc.; lead plated and lead alloy plated steel sheets include (a) lead plated steel sheets containing unavoidable impurities during the manufacturing process; (b) containing 30% or less of Sn; and in some cases Sb,
Examples include Pb-Sn alloy plated steel sheets that contain Zn or other unavoidable impurity elements; furthermore, aluminum and aluminum alloy plated steel sheets include (a) unavoidable amounts of Fe and other elements during plating; , aluminized steel sheet (b) Contains one or more of Si and Mg, and Si is 12
% or less, or an aluminum alloy plated steel plate with Mg content of 5% or less. (Prior technology) Electrolytic chromate treatment technology for metal surface-treated steel sheets has already been applied to galvanized steel sheets since 1973.
-44417 (method of cathodic electrolytic treatment using CrO ₃ -H ₂ SO ₄ treatment solution), JP-A-60-110896 (CrO ₃ -SiO ₂
For zinc, aluminum, tin, and their alloy plated steel sheets, see Japanese Patent Publication No. 14457-1987 (Cathode electrolysis method using CrO ₃ - various metal ions - fluorine or chlorine treatment solution). All of these methods involve forming a chromate film on the surface of a metal surface-treated steel sheet by cathodic electrolytic treatment. Generally, these cathode electrolytic coatings have good coating performance, but are said to have insufficient corrosion resistance. Therefore, these cathode electrolytic coatings compensate for corrosion resistance by increasing the amount of film formed (mainly the amount of chromium deposited). However, chromate coatings have the drawback of becoming colored when the amount of coating increases, impairing the appearance of the treated material, and further reducing coating performance. It was difficult. In addition, in the case of cathodic electrolysis of galvanized steel sheets,
When galvanized steel sheets etc. are processed continuously, Zn ²⁺
There were problems such as ions accumulating in the treatment solution and significantly reducing corrosion resistance. Next, regarding anodic electrolytic treatment, it is possible to form a chromate film by anodic electrolyzing a metal surface-treated steel sheet, but the resulting film has poor corrosion resistance and coating performance, and on galvanized steel sheets, According to Faraday's law, the metal of the material to be treated dissolves, making the treatment solution unstable, making it difficult to perform industrially stable treatment. (Problems to be Solved by the Invention) The present invention improves the shortcomings of conventional cathodic electrolytic chromate treatment technology, such as the deterioration of corrosion resistance when the appearance is good and the deterioration of the corrosion resistance during continuous treatment, and improves the appearance and The purpose is to form an industrially stable film with excellent corrosion resistance and coating performance on the surface of metal surface-treated steel sheets. (Means for solving the problems) As a surface treatment method for metal surface-treated steel sheets that solves the above-mentioned problems, we have conducted various studies and found that anodic electrolysis treatment is performed immediately after cathodic electrolysis treatment with a chromate treatment solution. A method has been developed for surface treating a metal surface-treated steel sheet using a composite electrolytic treatment.The gist of the present invention is to cathodically electrolytically treat a metal surface-treated steel sheet using a chromate treatment solution to form a chromate film. This is a surface treatment method for a metal surface-treated steel sheet, characterized in that the cathodic electrolytic coating is modified by immediately carrying out an anodic electrolytic treatment to form an anodic electrolytic coating. (Structure of the Invention) The cathodic electrolytic treatment in the present invention is performed to form a cathode film on the surface of a surface-treated steel sheet as a cathode. It is done by time. Although the current density and electrolysis time of cathodic electrolytic treatment are not specified, more preferable results can be obtained by setting the current density in the range of 3 to 50 A/dm ² and adjusting the amount of film formed by the electrolysis time. Next is anodic electrolysis, which uses the surface-treated steel sheet on which the cathode electrolytic film is formed as an anode,
This is carried out to form an anodic electrolytic film and to modify the cathodic electrolytic film, and the anodic electrolytic treatment is performed at a current density of 1 to 50 A/dm ² , particularly preferably 5 to 40 A/dm ² , the amount of coulombs is 0.1~
30 coulombs/dm ² , particularly preferably in the range from 2 to 20 coulombs/dm ² . Current density is 1A/d
When it is lower ^than 50A/ ^dm2 , it is difficult to form a good film and the corrosion resistance is poor.
There is no further effect. When the amount of coulombs is less than 0.1 coulombs/ ^dm2 , the amount of film formed is small, so the modification effect decreases,
Corrosion resistance is poor, and even if the amount exceeds 30 coulombs/dm ² , there is no further effect. In addition, when the amount of coulombs is increased, the amount of dissolved metal that makes up the plating film of the material to be treated (for example, in the case of galvanized steel sheets, the amount of dissolved zinc) increases, making the treatment solution unstable, so it is not suitable for industrial use. The limit is considered to be 30 coulombs/ ^dm2 . Next, regarding the chromate treatment liquid in the present invention, this chromate treatment liquid is for forming a film during cathodic electrolysis and during anodic electrolysis after cathodic electrolysis, and the composition of the treatment liquid is a known cathode treatment liquid. Although an electrolytic treatment solution can also be applied, particularly preferred compositions of the treatment solution include: (a) chromate treatment solution containing Cr ⁶⁺ ions, PO ₄ ^3- ions and/or fluorine compounds; (b) Cr ⁶⁺ ions, silica and/or fluorine compounds; (c) A chromate treatment solution containing Cr ⁶⁺ ions, PO ₄ ^3- ions and/or fluorine compounds, silica and/or silicate; Since it can be applied to both electrolysis and anodic electrolysis, cathodic electrolysis and anodic electrolysis can be performed with the same treatment solution, and cathodic electrolysis and anodic electrolysis can be performed with treatment solutions of different compositions. It can also be electrolytically treated. The Cr ⁶⁺ ions in the chromate treatment solution include chromic anhydride, dichromic acid, alkali metal salts of chromic acid, dichromic acid, and ammonium salts.
Species or mixtures can be applied optionally, and more favorable results are obtained with concentrations ranging from 5 to 70 g/Cr ⁶⁺ . Examples of PO ₄ ^3- ion include phosphoric acid, alkali metal salts of phosphoric acid, ammonium phosphate, etc.
As the fluorine compound, one type or a mixture of hydrofluoric acid, hydrofluorosilicic acid, borofluoric acid, titanium hydrofluoric acid, zirconium hydrofluoric acid, salts thereof, aluminum fluoride, etc. Can be applied to any concentration,
1 to 100 as the sum of PO ₄ ^3- ions and fluorine compounds
More preferable results can be obtained by adjusting the amount to a range of g/. Silica and/or silicates are added to the processing solution to form colloidal silica, and one or a mixture of colloidal silica and alkali metal silicates can be optionally applied to adjust the concentration.
More preferable results can be obtained by setting the amount of SiO ₂ in the range of 0.1 to 100 g/. The pH of the treatment solution is 0.3 to 6, particularly preferably pH 0.6.
~4. Processing solutions with a pH lower than 0.3 are difficult to manufacture in order to confirm their effectiveness. In addition, even if the pH is raised, the corrosion resistance and coating performance of the film will not change, but the film formed during anodic electrolysis will be colored yellow, so in order to form a film with an excellent appearance, it is necessary to is the limit. In order to control the pH of the treatment solution, any compound selected from sulfuric acid, nitric acid, ammonium hydroxide, alkali metal hydroxides, alkali metal carbonates, etc. can be added to the treatment solution. In addition, it is generated by the reduction reaction during the cathodic electrolytic treatment of the present invention.
Cr ³⁺ ions are treated in advance as Cr ³⁺ hydroxide and carbonate compounds, or as redox reaction products of Cr ⁶⁺ and organic compounds such as alcohols, starches, and tannic acid. It can also be added to liquids. However, in the case of drying without washing with water after the electrolytic treatment (after cathodic electrolysis, anodic electrolytic treatment) of the present invention, ammonium hydroxide and Cr ³⁺ ions are limited. The temperature of the treatment liquid is room temperature to 80°C. 80
Even if the temperature is higher than 80°C, the characteristics of the film formed will change, but it will be uneconomical, so 80°C is the industrial limit. According to the present invention, galvanized steel sheets that have been subjected to electrolytic treatment (cathode electrolysis followed by anodic electrolysis treatment) are washed with water and then dried to be used for corrosion protection or as a base for painting. It can also be applied after drying. Moreover, it is generally carried out as necessary. Post-treatment with an aqueous chromate solution and an anticorrosive organic compound is also possible. (Effects of the Invention) The present invention provides cathodic electrolysis treatment of the surfaces of surface-treated steel sheets, that is, zinc and zinc alloy-plated steel sheets, lead and lead alloy-plated steel sheets, aluminum, and aluminum alloy-plated steel sheets with the aforementioned chromate aqueous solution. , After forming the chromate film, immediately perform anodic electrolysis treatment,
By forming an anodic electrolytic film, the cathodic electrolytic film is modified to form a composite chromate film consisting of a cathodic electrolytic film and an anodic electrolytic film, which has excellent appearance, corrosion resistance, and coating performance. It is something. Generally, the chromate film produced by cathodic electrolysis is
When increasing the amount of chromium deposited to improve corrosion resistance, the film becomes colored and the appearance of the treated material is impaired.
Moreover, the coating performance is further deteriorated. In addition, in the case of galvanized steel sheets, if the galvanized steel sheets are treated continuously, Zn ²⁺ ions will accumulate in the treatment solution, resulting in a significant decrease in corrosion resistance. However, in the present invention, as shown in Table 1, by performing anodic electrolysis treatment after cathodic electrolysis, corrosion resistance can be significantly improved without impairing the appearance. Furthermore, the present invention provides a method for surface treatment of galvanized steel sheets, for example, as shown in FIG.
Even if Zn ²⁺ ions accumulate, the corrosion resistance is good, so the problem with the cathode electrolysis method mentioned above, that is, if the amount of chromium deposited is increased to improve corrosion resistance, the film will be colored and the material to be treated will be damaged. The disadvantages that the appearance is damaged and the coating performance is further reduced, and the disadvantage that Zn ²⁺ ions accumulate in the treatment solution during surface treatment of galvanized steel sheets and the corrosion resistance is significantly reduced are improved. A film with excellent corrosion resistance and coating performance can be stably obtained industrially. A similar effect can be obtained with respect to the accumulation of metal ions in the treatment liquid from the material to be treated in the case of other surface-treated steel sheets. In the present invention, the preferred amount of chromium deposited is 5
-300mg/ ^m2 , more preferred range is 10-100
mg/ ^m2 . (Functions and Examples) In order to clarify the effects of the present invention, several Examples and Comparative Examples will be given and specifically explained. Example 1 An electrolytic galvanized steel sheet cleaned by a known method was subjected to cathodic electrolytic treatment under the following conditions, immediately subjected to anodic electrolytic treatment, washed with water after treatment, and dried. Examples 1 and Comparative Example 1 and As a result of the comparison, as shown in Table 1, the electrolytically treated film of the present invention had a good film appearance, excellent corrosion resistance, and coating performance compared to the conventional cathodic electrolytic chromate film. [Treatment liquid composition: Composition 1] Chromic anhydride 15g/(Cr ⁶⁺ =7.8g/) Phosphoric acid (98%) 10g/(Total of PO ₄ ^- ion and fluorine compound is 12.3g/) Borohydrofluoric acid (20%) 15g/ (pH adjusted to 2 with sodium hydroxide) [Electrolysis conditions] Cathode electrolysis; current density = 20A/dm ² , electrolysis time = 2 seconds, temperature = 40℃ Anodic electrolysis; Coulomb amount = 0.1, 5, 20 coulombs/dm ² (adjusted by current density and electrolysis time), temperature = 40°C Comparative example 1 Example 1 without anodic electrolysis treatment,
This is referred to as Comparative Example 1 and is shown in Table 1. Example 2 An electrolytic galvanized steel sheet cleaned by a known method was subjected to cathodic electrolytic treatment and immediately anodic electrolytic treatment under the following conditions, and after the treatment, the sample was washed with water and dried. Examples 2 and Comparative Example 2 As a result of the comparison, as shown in Table 1, the electrolytically treated film of the present invention has a better appearance, better corrosion resistance, and better corrosion resistance than the conventional cathodic electrolytic chromate film and anodic electrolytic chromate film.
and coating performance. [Treatment liquid composition: Composition 2] Chromic anhydride 50g/(Cr ⁶⁺ =26.0g/) Phosphoric acid (98%)
20g/(19.3g/ as PO ₄ ^- ions) (pH at this time was 0.6) [Electrolysis conditions] Cathode electrolysis; current density = 15A/dm ² , electrolysis time = 4 seconds, temperature 50°C Anodic electrolysis; Current density = 15 A/dm ² , electrolysis time = 0.2 seconds, temperature = 40°C (Coulomb amount = 3 coulombs/dm ² ) Comparative Example 2 An electrogalvanized steel sheet cleaned by a known method was treated in Example 2. Comparative Example 2 is a sample that was subjected to cathodic electrolytic treatment or anodic electrolytic treatment using a liquid, and is shown in Table 1. Examples 3, 4, and 5 Electrolytic galvanized steel sheets cleaned by a known method were subjected to cathodic electrolytic treatment and immediately anodic electrolytic treatment under the following conditions, and after the treatment, the samples were washed with water and dried. , 5, and compared with Comparative Examples 3, 4, and 5, as shown in Table 1, the electrolytically treated film of the present invention has a good film appearance and is superior to the conventional cathodic electrolytic chromate film. It showed excellent corrosion resistance and coating performance. Conditions for Example 3 [Treatment liquid composition: Composition 3] Chromic anhydride 50g/(Cr ⁶⁺ =26.0g/) Snowtex-0100g/(Nissan Chemical Co., Ltd.)
Colloidal solution containing 20% SiO ₂ ) (pH adjusted to 3 with basic chromium carbonate) [Electrolysis conditions] Cathode electrolysis; current density = 40A/dm ² , electrolysis time = 1 second, temperature = 30℃ Anodic electrolysis: current Density = 40A/dm ² , Electrolysis time = 0.2 seconds, Temperature = 30℃ (Coulomb amount = 8 coulombs/d
m ² ) Conditions of Example 4 [Treatment liquid composition: Composition 4] Ammonium dichromate
100g/(Cr ⁶⁺ =41.6g/) Hydrofluorosilicic acid (40%)
50g/(total of fluorine compounds: 24.8g/) Hydrofluoric acid (30%) 16 (pH adjusted to 5 with sodium carbonate) [Electrolysis conditions] Cathode electrolysis; current density = 5A/dm ² , electrolysis time = 4 seconds, temperature = 50℃ Anodic electrolysis; current density = 5A/dm ² , electrolysis time = 2 seconds, temperature = 50℃ (coulomb amount = 10 coulombs/d
m ² ) Conditions for Example 5 [Treatment liquid composition: Composition 5] Chromic anhydride 30g/(Cr ⁶⁺ = 15.6g/) Aluminum fluoride 1g/(total of fluorine compounds is 1.5g/) Hydrofluoric acid ( 30%) 1.6g/ (adjust pH to 5 with sodium carbonate) [Electrolysis conditions] Cathode electrolysis; current density = 50A/dm ² , electrolysis time = 2 seconds, temperature = 30℃ Anodic electrolysis; current density = 15A/dm ² , Electrolysis time = 0.4 seconds, temperature = 30℃ (coulomb amount = 6 coulombs/d
m ² ) Comparative Examples 3, 4, and 5 Examples 3, 4, and 5 that were not subjected to anodic electrolytic treatment were referred to as Comparative Examples 3, 4, and 5, respectively, and are shown in Table 1. Example 6 An electrolytic galvanized steel sheet cleaned by a known method was subjected to cathodic electrolytic treatment and immediately anodic electrolytic treatment under the following conditions, and after treatment, the sample was washed with water and dried. Examples 6 and Comparative Example 6 As a result of comparison, Table 2 and 1
As shown in the figure, the electrolytically treated film of the present invention did not deteriorate in corrosion resistance even when Zn ²⁺ ions were mixed into the treatment solution, and showed superior corrosion resistance compared to the conventional cathodic electrolytic chromate method film. . [Treatment liquid composition: Composition 6] Chromic anhydride 20g/(Cr ⁶⁺ = 10.4g/) Hydrofluorosilicic acid (40%) 16g/(Total of PO ₄ ^3- ion and fluorine compound is 29.1g/) Phosphorus Acid (98%) 30g/ (Zn ²⁺ ions 0, 1, 3, 6 in the above treatment solution)
g/ after adding zinc oxide, the pH of each treatment solution
(Adjust ^with sulfuric acid so ^that , temperature = 30℃ (amount of coulombs = 6 coulombs/d
m ² ) Comparative Example 6 Example 6, which was not subjected to anodic electrolysis treatment,
This is referred to as Comparative Example 6 and is shown in Table 2. Examples 7, 8, 9, 10 Vacuum deposited galvanized steel sheets, hot-dip galvanized steel sheets, Zn-5% Al alloy-plated steel sheets, Al-10% Si alloy-plated steel sheets, and Pb cleaned by known methods.
- A 10% alloy plated steel plate is subjected to cathodic electrolytic treatment and immediately anodic electrolytic treatment under the following conditions, followed by washing with water after treatment,
The dried samples were designated as Examples 7, 8, 9, and 10, respectively, and as a result of comparison with Comparative Examples 7, 8, 9, and 10, the third
As shown in Table 4, the electrolytically treated coating of the present invention has a better coating appearance, superior corrosion resistance, and coating performance on any surface-treated steel sheet compared to the conventional cathodic electrolytic chromate coating. showed that. The electrolytic treatment conditions in Examples 7, 8, 9, and 10 were all as follows. [Electrolysis conditions] Cathode electrolysis: Current density = 20A/dm ² , Electrolysis time = 2 seconds, Temperature = 40℃ Anodic electrolysis: Current density = 20A/dm ² , Electrolysis time = 0.2 seconds, Temperature = 40℃ (Coulomb amount = 4 coulombs/d
m ² ) [Treatment liquid composition of Example 7: Composition 7] Chromic anhydride 20 g/(Cr ⁶⁺ = 10.4 g/) Phosphoric acid (98%) 20 g/(Total of PO ₄ ^- ions and fluorine compounds is 23.6 g /) Titanium hydrofluoric acid (20%) 20g/ (pH adjusted to 2 with sodium hydroxide) [Treatment liquid composition of Example 8: Composition 8] Chromic anhydride 50g/(Cr ⁶⁺ = 10.4g/) Snowtech AK50g/(Nissan Chemical SiO ₂ 20
% colloidal solution) (pH adjusted to 2 with sodium hydroxide) [Treatment solution composition of Example 9: Composition 9] Chromic anhydride 80g/(Cr ⁶⁺ = 41.6g/) Zircon hydrofluoric acid (20 %)
50g/(Total of fluorine compounds is 14.8g/) Hydrofluoric acid (30%) 16g/ (pH adjusted to 2 with sodium carbonate) [Treatment liquid composition of Example-10: Composition 10] Chromic anhydride 30g/ (Cr ⁶⁺ = 15.6g/) Aluminum fluoride 5g/ (Total of PO ₄ ^3- ion and fluorine compound is 15.4g/) Hydrofluoric acid (30%) 2g/ Phosphoric acid (98%) 10g/ (Carbonic acid Adjustment of pH to 2 with sodium) Comparative Examples 7, 8, 9, 10 Examples 7, 8, 9, and 10, which were not subjected to anodic electrolysis treatment, were designated as Comparative Examples 7, 8, 9, and 10, respectively. It is shown in Tables 3 and 4.

【表】【table】

【表】＊２：ゴバン目エリクセン／衝撃
[Table] *2: Gobanme Eriksen/Shock

【表】＊２：ゴバン目エリクセン／衝撃
〔評価方法〕外観皮膜の着色度を肉眼観察し、◎、〇、△、×の
４段階で評価。着色の少ないものを最良；◎であ
る。耐食性 JIS−Ｚ−2371に準拠した塩水噴霧試験により、
特定時間後の発錆状態を肉眼で判定し、◎、〇、
△、×の４段階で評価。◎が最良である。塗装性能（塗装；市販のアルキツドメラミン系白
色塗料を、27〜30μ塗装。）碁盤目エリクセン試験塗膜に１mm間隔の碁盤目を100マス切つたのち、
エリクセン試験機で７mm押し出し、セロフアンテ
ープで剥離試験を行い、塗膜の剥離の程度を肉眼
で判定し、◎、〇、△、×の４段階で評価。◎が
最良である。デユポン式衝撃試験デユポン式衝撃試験器を使用し、塗膜面に衝撃
を加え、塗膜の剥離の程度を肉眼で判定し、◎、
〇、△、×の４段階で評価。◎が最良である。[Table] *2: Erichsenia spp./Impact [Evaluation method] Appearance The degree of coloration of the film was observed with the naked eye and evaluated in four stages: ◎, 〇, △, and ×. The one with the least coloring is the best; ◎. Corrosion resistance: Through salt spray test in accordance with JIS-Z-2371,
Judging the rusting state after a certain time with the naked eye, ◎, 〇,
Evaluation on a 4-level scale of △ and ×. ◎ is the best. Painting performance (Painting: Paint a commercially available alkyd melamine white paint with 27 to 30 μm.) Cross-cut Erichsen test After cutting 100 grid squares at 1 mm intervals on the paint film,
Extrude 7mm using an Erichsen tester, perform a peel test using cellophane tape, and visually judge the degree of peeling of the coating film using a 4-grade scale of ◎, 〇, △, and ×. ◎ is the best. Dupont impact test Using a Dupont impact tester, impact is applied to the coating surface, and the degree of peeling of the coating is determined with the naked eye.
Rated in 4 stages: 〇, △, ×. ◎ is the best.

[Brief explanation of drawings]

第１図は実施例における処理液中のZn²⁺イオ
ン濃度と皮膜の耐食性の関係を示す図である。 FIG. 1 is a diagram showing the relationship between the Zn ²⁺ ion concentration in the treatment solution and the corrosion resistance of the film in Examples.

Claims

[Claims]

1 After cathodic electrolyzing a metal surface-treated steel plate with a chromate treatment solution to form a chromate film,
A method for surface treatment of a metal surface-treated steel sheet, which comprises immediately performing an anodic electrolytic treatment to form an anodic electrolytic film, and at the same time, modifying the cathodic electrolytic film.