JPS6119719B2

JPS6119719B2 -

Info

Publication number: JPS6119719B2
Application number: JP8003282A
Authority: JP
Inventors: Kango Sakai; Katsushi Saito; Hirobumi Nakano; Ryoichi Yoshihara
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 1982-05-14
Filing date: 1982-05-14
Publication date: 1986-05-19
Also published as: JPS58197292A

Description

【発明の詳細な説明】本発明は高効率で品質の良いガンマー組織の
Ni−Zn合金メツキ鋼板を製造する方法に関する
ものである。電気亜鉛メツキ鋼板は、その優れた特性から家
庭電気製品、建材、シヨーケース、自動販売機、
等の防錆素材として多岐に使用されている。特に
近年、自動車々体に対する社会的要求から車体の
耐久性の向上が急速にクローズアツプされてい
る。この要求に答える素材として亜鉛メツキ鋼板
の需要が伸びている。自動車々体の腐食は、内部
および外部塗装面両面に生じており、特に下廻り
の内部袋構造部、突き合せ部は腐食が激しく車体
に穴明きが生ずる。構造的にこの部分は、リン酸
塩処理皮膜及び電着塗膜が不充分もしくは全く未
塗装状態が生ずるためである。従つて、従来の亜
鉛メツキでは、かなりメツキ厚の高い鋼板が必要
であつた。一方、外面部の腐食は小石等の衝撃やその他物
理的な作用で塗膜に傷が入りその傷を発端として
スキヤプコロージヨン、フイリフオームコロージ
ヨン等の外面錆が生ずる。外面錆に対しては、亜
鉛メツキが有効であるが、鉄面との接触腐食や、
塗装後の性能が不充分である点等から、純亜鉛メ
ツキに代る合金亜鉛メツキ鋼板が要求されてい
る。内面部に対しても純亜鉛メツキでは前述した
如く厚メツキ品になることのため、溶接性、再資
源化に悪影響があり、又、近年のカチオン電着化
の変化で薄メツキ厚の合金メツキが要求されてい
る。自動車々体に限らず、従来使用された分野に
おいても品質の優れた合金亜鉛メツキ思考が急速
になされている。これ等の社会的要求に対処出来る合金亜鉛メツ
キ鋼板の具備条件としては、広範囲の腐食環境に
対して薄メツキで耐食性および塗装後の耐久性に
優れ、溶接性、溶着性が良く、且つ、コストの安
い素材でなければならない。これ等の要求に対処
出来る合金メツキ鋼材としてNi−Zn系の合金亜
鉛メツキ鋼板を挙げることが出来る。Ni−Zn合
金メツキ鋼板は特にｒ組織のNi7〜20％好ましく
はNi10〜15％の組成は品質的に優れている。亜鉛メツキ系の鋼板の製造方法としては、溶融
メツキ法と電気メツキ法に大別され連続的に大量
に製造され、その生産量は年間500万ｔにも及ん
でいる。溶融亜鉛メツキプロセスは厚メツキ品の
製造に通しており、目付量40ｇ/m²以上の純亜鉛
メツキ鋼板、Fe−Zn熱拡散合金メツキ鋼板等の
製品が建材、自動車等に使用されている。一方電
気亜鉛メツキプロセスでは、厚メツキ製品の製造
は、電力費の増大、Ｔ／Ｈの低下等の理由でコス
トの高い製品となるため通常は目付量10〜20ｇ/
m²の薄メツキ製品が製造される。電気メツキプロ
セスは溶融メツキプロセスに比べ鋼材の機械的性
質への影響が少ないこと、片面メツキを製造し易
い、広範囲な合金メツキ製品を製造出来る利点を
持つており、前述した現代の自動車々体を中心と
する要求に答える素材の製造プロセスとして有利
である。しかしながら、基本的に電気的な還元力
でメツキするためコスト高になる宿命を内含して
いる。従つて電力費の安いＴ／Ｈの高い高効率な
生産方法を開発する必要がある。そのためには、
極間を近接し高い電流密度で電気メツキを行う製
造方法即ち、高効率電解が不可欠である。更に加
えて、前述した如く、自動車々体等を中心した合
金メツキ鋼板を高効率で製造する方法を確立する
ことが急務である。電気メツキにおいて電流密度を上げると電解槽
においては、可溶性アノードの場合の陽極不動態
化、不陽性陽極の場合のガス留り電圧上昇、電流
効率確保難などの問題、品質方面ではメツキや
け、むら、結晶粗大化による表面粗れ、ピンホー
ル、ヌケ、密着不良更に合金メツキでは均一組成
が得られないなどの問題を慮起し、電流密度DK
＝20〜50A/dm²が限界電流密度であつた。本発明はかかる点に艦みなされたもので、本発明はメツキセルとして、 (1) 電極とストリツプとを近接化出来ること、 (2) ガス除去が出来るセルとすること、 (3) 大電流通電法テムの機能を持たせたこと。などの条件を満すものを用いて、高電流密度メツ
キを行うに際して、メツキ浴として、 (1) 高伝導度であること、(2) 流速に依存しな
い浴であること（むらが生じたり）(3) 電流効率
が良いこと、(4) メツキやけ、むらのないこと、
(5) 合金組成の変動がないこと。など前記高電流密度メツキに対応した亜鉛−ニツ
ケル合金メツキ浴の同発を目的としてなされたも
のである。即ち本発明は電極面と被メツキ面との間に電解
液を噴出せしめて、極面と被メツキ面との間に液
を保持しながら電気亜鉛−ニツケル合金めつきを
行う方法において、めつき浴としてZnSO₄・
7H₂OとNiSO₄・6H₂Oとの和が400〜700ｇ/、
Ni／Zn比1.0〜2.0H₂SO₄5〜20ｇ/からなる浴を
使用し、浴温60℃以上、ストリツプと電解液の相
対速度を1.0m/sec、以上でメツキすることを特
徴とする高効率Ni−Zn合金メツキ鋼板の製造方
法である。本発明により外観が良く、合金組成分
安定した亜鉛−ニツケル合金メツキを高効率で製
造することができる。次に本発明について更に詳細に説明する。本発
明は高電流密度による亜鉛−Ni合金メツキが可
能になつた点に最も時数を有する。その結果メツ
キの析出速度が高く厚メツキが可能となつた。従
来技術は極間距離が25〜50mm：DK30〜50A/dm²
が限度であつた。その理由として限度以上に電流
密度を上げると“めつきやけ”、“めつきむら”、
“めつき結晶粗大化”が生じ、さらに、合金組成
が電流密度によつて変化するため高電流密度によ
るNi−Zn合金メツキ鋼板の製造は不可能であつ
た。本発明を実施する場合にはプロセス的には、例えば本出願人がすでに開発している高電流密
度操業可能なセル（特開昭56−127789に開示）を
使用し、メツキ浴としてZnSO₄・7H₂Oと
NiSO₄・6H₂Oの和が400〜700ｇ/で、且つ
H₂SO₄5〜20ｇ/、Ni／Zn比1.0〜2.0からなる浴
を使用することで実施できる。即ち本発明を実施
する場合の電解装置の例を第１図で説明する。電
解装置はストリツプ１を電解液３に浸漬すること
なく空間に保持した状態で通板させる電解槽２
と、該電解槽２内の所定位置に、前記ストリツプ
１面に対向して近接して配置しかつストリツプ面
に電解液を噴射すると共に該流体によりストリツ
プ面に静圧を作用せしめるノズル孔を形成した電
極パツド４とからなる。このように電解槽内でのストリツプを電解液に
浸漬せずに空間に保持せしめ、しかも槽内の所定
位置にストリツプ面に対向して配置した静圧パツ
ドとしても機能を併せもつ電極パツドにより、ス
トリツプ面に電解メツキ液を噴射して電解処理を
実施することを特色としている。したがつて、こ
の電解槽は従来の浸漬タイプと全く異質であつ
て、電解液が充満しておらず、しかも電解を行な
うための電極が中空のボツクス構造であつてその
ノズル孔からストリツプに向つて電解液を噴出す
るものであるから、浸漬タイプに見られた種々の
不利益が解消されると共に、下ロールをもコンダ
クターロールとして利用でき、加えてストリツプ
の振動を防止してかつ形状不良を矯正して安定し
た通敬が行なえるメリツトが得られる。以上、本発明で使用できるメツキ装置の１例を
示したが、本発明はこの例に限定されるものでは
なく、電極面と被メツキ面との間に電解液を噴射
して電極面と被メツキの間にメツキ液を保持しな
がら、ストリツプと電解液の相対速度を1.0m/se
ｃ以上にしてメツキできる装置であれば良い。そのような条件に適合するその他の例として特
公昭50−8020に開示したようにストリツプの進向
方向と向流的にストリツプと電極間に電解液を噴
射する電解メツキ装置、又特願昭55−176518に開
示したように電極の中央部からストリツプ面に電
解液を噴射する装置などがあげられる。さらに本
出願人が特許出願中の特願昭57−18836に開示し
た静圧流体パツドを備えた水平電解装置があげら
れる。又本発明においては極間距離は近接化する
ほど好ましい。その理由としては例えば電流密度
を100A/dm²又は200A/dm²に設定した場合に極間
距離が大きいと極間電圧は20〜30Vをこえてしま
い電力費、整流器の容量が大きくなり実用的では
ない。本発明は極間電圧を少くとも20V未満望ま
しくは10V以下を目標としている。従つて極間距
離を近接化するほど（好ましくは15mm以下）極間
電圧が減少し、結果としてコストを大巾に節減す
ることができる。従つて極間距離を小さくするほどコスト的には
有利であるが極間きよりを極端に小さくするとス
トリツプと電極が接触するおそれがあるので極間
きよりは５mmが実用上の限界といえる。なお本発明では前記のように極間距離をなるべ
く近接化してメツキを行うが、メツキ中のストリ
ツプの振動や位置変動或はカテナリーを少なくし
て極間距離をより縮少するために、前記説明した
特開昭56−127789と特願昭57−18836に示したよ
うな静圧流体パツドを有するメツキ装置を用いて
静圧流体でストリツプを支持しながらメツキを行
うことが最も好ましい。その結果ストリツプは電
極間の中心に静圧で自動的にセンターリングされ
るので極間距離を大巾に短縮できしかも安定して
メツキを行うことができる。（この場合には最高
250A/dm²での電解が可能である）以上説明したような電解装置を用いて電極面と
被メツキ面との間に電解液を噴出せしめて極間と
被メツキ面との間に液を保持しながらメツキを行
なう場合には“ガス溜り”がなく極間距離が近接
可能であるので通電抵抗が小さくなるため電圧の
上昇を抑制することが可能となる。さらに相対ス
ピード（ラインスピード−流速）によるイオン供
給、液置換効率がよいことなどのため高電流密度
によるメツキが可能となる。以下本発明のメツキ
浴について説明する。本発明者らは前記の高効率が可能な電解槽を開
発したが、実際にNi−Zn合金メツキを行うと、
まだ解決すべき課題があることが分つた。以下Ni−Zn合金メツキの課題と本発明の方法
について詳述する。亜鉛は水素過電圧が高い性質から高い電流効率
でメツキ出来る特性がある。しかし、Niは水素
過電圧が低く、合金メツキにおいては電流効率が
低くなる。一方メツキヤケ、液抵抗を下げるため
には硫酸の添加が効果的であるが、水素の発生が
多くなり電流効率は著しく低下する欠点がある。
そこで本発明者等は近接高電流密度電解に対応し
た亜鉛−ニツケル合金メツキ浴を新規に見い出す
ことによつて前記の果題を解決することができ
た。本発明においては浴にH₂SO₄を５〜20ｇ/
添加することによりPHを下げ液抵抗の低下を計る
と同時に、金属イオン濃度の上昇を向上せしめて
いる。一般には低PHにすると水素が出やすくなり
電流効率が低下する。特にNcが析出するめつき
では水素が発生し易く、従来ではPHの低下は電流
効率に対して負効果をもたらすと考えられてい
た。しかしながらPHを低くした本発明浴では低電
流密度では従来通りであるが、高電流密度の場合
には逆に良くなることが解つた。第２図は本発明浴（曲線１）と従来実施されて
いる高PH、低濃度浴（曲線２）とを使用し、電流
効率と電流密度との関係を比較したものである。本発明１はZnSO₄・7H₂O＋NiSO₄・6H₂O＝480
ｇ/（Ni／Zn＝1.5）Na₂SO₄＝100ｇ/、
H₂SO₄10ｇ/、PH＝１の浴を用い温度60℃、流
速１m/secでメツキを行つた。比較２はZnSO₄・
7H₂O＋NiSO₄・6H₂O＝300ｇ/（Ni／Zn＝
1.5）、Na₂SO₄100ｇ/、H₂SO₄ ２ｇ/PH＝2.5
の浴を用い浴温60℃通常の浸漬法でメツキを行つ
た。本発明１は100A/dm²以上の高電流密度でも
電流効率は82％以上を確保できる。しかしながら
電流密度が300A/dm²では本発明浴においても電
流効率の低下やメツキむらが生じはじめるため、
本発明の好ましい電流密度は100〜250A/dm²、最
も好ましくは150〜200A/dm²である。更に合金めつきを均一組成にする条件として従
来の考え方は、電流密度を一定にする。浴組成を一定にする。（濃度、PH）錆塩を加える。緩衝剤を加える。流速を一定にする。温度も一定にする。などの設定条件が多く非常に生産し難いものであ
つた。本発明においては錆塩、緩衝剤を添加せず単純
組成浴で低PH（H₂SO₄5〜20ｇ/）温度（60℃以
上）、流速：ストリツプとの相対速度を一定値以
上（１m/s）、高濃度浴（ZnSO₄・7H₂O＋
NiSO₄・6H₂O＝400〜700ｇ/）で広い浴組成
（Ni／Zn＝１〜２）という広い管理条件下で電流
密度に依存したりめつき条件を見出した。また高電流密度用電解槽は高流速で、メツキ液
噴射を行なうため、噴出ノズル部における流速と
その他の部分の流速が異なつてくる。合金メツキ
においてはこの流速とメツキ皮膜合金組成とはか
なりの相関を示しメツキむら等が発生する。特に
従来用いていた浴条件ではこの傾向が強く現れて
しまい、噴出ノズルの位置設定ノズル形状が非常
にシビアである。しかし本発明の浴条件ではこの
流速と合金組成との関連はあまり見られなくなり
噴出ノズルの位置設定ノズル形状は自在である。
後述する相対スピードと合わせて本発明の浴条件
を用いることによつて外観の良い合金組成の安定
した亜鉛−ニツケル合金メツキを従来浴条件に比
べてはるかに広い範囲の操業条件で容易に製造す
ることが可能である。 Zn−Ni合金メツキで最も耐食性の良いNi量は
10〜15％の範囲である。第３図はメツキ皮膜中の
Ni％と電解液のNi／Zn比との関係を示すもので
ある。これよりメツキ中の斜線で示したNi量10
〜15％を満足するためにはNi／Zn比を1.0〜2.0に
調整する必要がある。また、第４，５図は合金メツキ層中のNi％と
電解液−ストリツプ間の相対速度Ｖとの関係を示
す。第４図は本発明の条件であり、第５図は比較
の浴条件の例である。（メツキ浴は第２図におけ
る場合と同一浴を使用）第５図より比較浴を用い
た場合、電流密度DK（曲線１は200A/dm²曲線２
は100A/dm²）によつてNi％が大きく変化し、こ
の傾向は相対速度Ｖを増加してもほとんど安定し
ない。従つて操業条件によつて得られるNi％が
変化してしまい製品品質が安定せず、品質管理が
困難である。しかしながら第４図に示すように本
発明の浴条件を用いればNi％はDKに対して非常
に良い安定性を示し、特にＶ＝１m/s以上になる
と電流密度を変えてもNi最適量である10〜15％
組成のメツキを安定して行なうことが可能であ
る。従つて本発明の浴条件はNi−Zn合金メツキ
を行なう上で操業条件範囲が広く実用的である。
しかしながら本発明条件でもＶ＝１m/s以下では
要求されるNi％が必ずしも得られない。また浴温については浴の電導度は温度と供に高
くなるため浴温は高いほど電解電圧は下り、電力
費を消減することが可能である。またメツキ外観
に対しても浴温は高い方が良くなる傾向にあるた
め、本発明条件では浴温を60℃以上にするのが最
も好ましい。第６図はH₂SO₄量と電導度Ｋ及び電流効率７と
の関係を示す。これよりH₂SO₄量の増加とともに
Ｋは直線的に増加し、電解電圧も下がるが、
H₂SO₄が20ｇ/を越えると７が急激に低下して
しまい実用的ではなくなる。また第７図はZnSO₄・7H₂O＋NiSO₄・6H₂O量
とＫ、７の関係を示すが、これよりZnSO₄・
7H₂O＋NiSO₄・6H₂O の増加は電導度を若干減
少させ、特に700ｇ/以上になると急激な低下を
示す。また、７についてはZnSO₄・7H₂O＋
NiSO₄・6H₂O400ｇ/以上で80％以上の高効率
となる。従つてZnSO₄・7H₂O＋NiSO₄・6H₂Oの
量は400〜700ｇ/の範囲が最適である。第８図はH₂SO₄及びZnSO₄・7H₂O＋NiSO₄・
6H₂Oとメツキ外観の関係を示す。図中にＯで示
すものがメツキ外観が良好である。これより
H₂SO₄5ｇ/以上、且つZnSO₄・7H₂O＋NiSO₄・
6H₂O400ｇ/以上で良好なメツキ外観が得られ
る。以上第６，７，８図より本発明浴はH₂SO₄＝５
〜20ｇ/、ZnSO₄・7H₂O＋NiSO₄・6H₂O＝400
〜700ｇ/に限定される。尚、本発明の合金メツキはZn−Niを主成分と
する高効率製造方法であるが、要求特許等により
第３、第４成分として合金成分を添加した場合も
しくは不純物として入る場合も同様の条件でZn
−Niを主成分とする合金メツキを製造可能であ
る。これらの添加成分としてはFe、Co、Cr等で
ある。許容される含有量としては浴中でNi／Zn
比が１〜２におけるZn量の1/2以下である。以上本発明について詳細に述べた、以下実施例
を上げ本発明を説明する。実施例１第１図に示した電解装置を用いて第１表に示す
浴条件、メツキ条件で合金メツキを行つた。その
結果第１表に示す如き結果を得た。本発明例
No.1、２、３、４、はｒ組織のNi−Zn合金メツ
キ皮膜が高効率で得られ、被膜中のNi含量は安
定していた。又皮膜の外観も良好であつた。これ
に対して従来の浴を用いた比較例であるNo.5、
No.6、No.7はいずれも電流効率が悪く、メツキ
皮膜外観もメツキやけが発生して劣つていた。【表】[Detailed Description of the Invention] The present invention provides a highly efficient and high quality gamma structure.
The present invention relates to a method of manufacturing a Ni-Zn alloy plated steel sheet. Due to its excellent properties, electrogalvanized steel sheets are used in home appliances, building materials, show cases, vending machines,
It is widely used as a rust-preventing material. Particularly in recent years, improvements in the durability of vehicle bodies have rapidly become a focus due to social demands for vehicle bodies. Demand for galvanized steel sheets is increasing as a material that meets this demand. Corrosion of automobile bodies occurs on both the internal and external painted surfaces, and the corrosion is particularly severe in the internal bag structure and butt parts of the undercarriage, causing holes in the car body. Structurally, this is because the phosphate treatment film and electrodeposition coating are insufficient or completely unpainted in this area. Therefore, conventional galvanizing requires a steel plate with a considerably high plating thickness. On the other hand, corrosion on the outer surface is caused by scratches on the coating film due to impacts from pebbles or other physical effects, and these scratches lead to outer surface rust such as skip corrosion and filliform corrosion. Galvanizing is effective against external rust, but it can cause contact corrosion with steel surfaces,
Since the performance after painting is insufficient, alloy galvanized steel sheets are required to replace pure galvanized steel sheets. As mentioned above, pure zinc plating on the inner surface results in a thick plated product, which has a negative impact on weldability and recycling.Also, due to recent changes in cationic electrodeposition, alloy plating with a thinner plating thickness is required. is required. The idea of high-quality alloy galvanizing is rapidly being developed not only in automobile bodies but also in fields where it has been used conventionally. The requirements for alloy galvanized steel sheets that can meet these social demands are that they are thinly plated and have excellent corrosion resistance and durability after painting in a wide range of corrosive environments, have good weldability and adhesion, and are cost effective. It must be made of cheap material. An example of an alloy-plated steel material that can meet these demands is a Ni-Zn alloy galvanized steel sheet. Ni--Zn alloy plated steel sheets are especially excellent in quality when they have an r-structure with a composition of 7 to 20% Ni, preferably 10 to 15% Ni. The manufacturing methods for galvanized steel sheets are broadly divided into hot-dip plating and electroplating, and they are manufactured continuously in large quantities, with the annual production amount reaching 5 million tons. The hot-dip galvanizing process is used to manufacture thick plated products, and products such as pure galvanized steel sheets with a basis weight of 40 g/m ² or more and Fe-Zn heat diffusion alloy plated steel sheets are used for building materials, automobiles, etc. On the other hand, in the electrogalvanizing process, the production of thickly plated products results in high cost products due to increased electricity costs, decreased T/H, etc., so the basis weight is usually 10 to 20 g/
m ² thin plating products are produced. Compared to the hot-dip plating process, the electroplating process has the advantages of having less influence on the mechanical properties of steel materials, making it easy to produce single-sided plating, and being able to produce a wide range of alloy-plated products. It is advantageous as a manufacturing process for materials that meet core requirements. However, since plating is basically done using electrical reducing power, the cost is high. Therefore, it is necessary to develop a highly efficient production method with low power costs and high T/H. for that purpose,
A manufacturing method in which electroplating is performed with electrodes close together and at high current density, that is, high-efficiency electrolysis is essential. In addition, as mentioned above, there is an urgent need to establish a method for producing alloy-plated steel sheets with high efficiency mainly for use in automobile bodies and the like. Increasing the current density in electrolytic plating causes problems such as anode passivation in the case of soluble anodes, an increase in gas retention voltage in the case of non-positive anodes, and difficulty in ensuring current efficiency, and problems in terms of quality such as plating fading and unevenness. , considering problems such as surface roughness due to coarse crystals, pinholes, missing parts, poor adhesion, and the inability to obtain a uniform composition with alloy plating, the current density DK
The critical current density was 20 to 50 A/ ^dm2 . The present invention has been made with these points in mind, and the present invention provides a Metsuki cell that (1) allows electrodes and strips to be placed close to each other, (2) allows gas removal, and (3) allows large current to flow. Having the function of a legal system. When performing high current density plating using a plating bath that satisfies the following conditions, the plating bath must (1) have high conductivity, and (2) be a bath that does not depend on the flow rate (no unevenness may occur). (3) good current efficiency; (4) no plating or unevenness;
(5) No fluctuation in alloy composition. This was done with the aim of producing a zinc-nickel alloy plating bath compatible with the above-mentioned high current density plating. That is, the present invention provides a method for performing electrolytic zinc-nickel alloy plating by jetting an electrolytic solution between an electrode surface and a surface to be plated, and maintaining the liquid between the electrode surface and the surface to be plated. _ZnSO4 as bath
The sum of 7H ₂ O and NiSO ₄ 6H ₂ O is 400 to 700 g/,
It is characterized by plating using a bath consisting of a Ni/Zn ratio of 1.0 to 2.0 H ₂ SO ₄ 5 to 20 g, at a bath temperature of 60°C or higher, and at a relative speed of 1.0 m/sec or higher between the strip and the electrolyte. This is a method for producing highly efficient Ni-Zn alloy plated steel sheets. According to the present invention, zinc-nickel alloy plating with good appearance and stable alloy composition can be manufactured with high efficiency. Next, the present invention will be explained in more detail. The present invention has the most success in making zinc-Ni alloy plating possible at high current densities. As a result, the plating deposition rate was high and thick plating was possible. Conventional technology has a distance between poles of 25 to 50mm: DK30 to 50A/dm ²
was the limit. The reason for this is that if you increase the current density beyond the limit, you will experience ``burnt eyes'' and ``uneven eyesight''.
"Coarsening of plating crystals" occurs, and furthermore, the alloy composition changes depending on the current density, making it impossible to manufacture Ni-Zn alloy plated steel sheets at high current densities. In carrying out the present invention, for example, a cell capable of high current density operation that the applicant has already developed (disclosed in Japanese Patent Application Laid-Open No. 127789/1989) is used, and ZnSO ₄ is used as the plating bath. 7H ₂ O and
The sum of NiSO ₄ and 6H ₂ O is 400 to 700 g/, and
This can be carried out by using a bath containing 5 to 20 g of H ₂ SO ₄ and a Ni/Zn ratio of 1.0 to 2.0. That is, an example of an electrolytic apparatus for carrying out the present invention will be explained with reference to FIG. The electrolyzer is an electrolytic cell 2 in which the strip 1 is passed through the electrolytic solution 3 while being held in a space without being immersed in it.
and a nozzle hole is formed at a predetermined position in the electrolytic cell 2, the nozzle hole being disposed in close proximity to the surface of the strip 1 and injecting an electrolytic solution onto the surface of the strip and causing static pressure to be applied to the surface of the strip by the fluid. It consists of an electrode pad 4. In this way, the strip in the electrolytic cell is held in space without being immersed in the electrolyte, and the electrode pad also functions as a static pressure pad placed at a predetermined position in the cell facing the strip surface. The feature is that electrolytic treatment is carried out by spraying electrolytic plating solution onto the strip surface. Therefore, this electrolytic cell is completely different from the conventional immersion type, in that it is not filled with electrolyte, and the electrode for electrolysis has a hollow box structure and is directed from the nozzle hole to the strip. Since the electrolyte is spouted through the strip, various disadvantages seen with the immersion type are eliminated, and the lower roll can also be used as a conductor roll. In addition, it prevents vibration of the strip and prevents poor shape. It has the advantage of being able to correct and stabilize the passage. Although one example of a plating device that can be used in the present invention has been shown above, the present invention is not limited to this example. While holding the plating liquid between the plating, the relative velocity between the strip and the electrolyte is set to 1.0 m/se.
Any device that can plate at c or higher is sufficient. Other examples that meet such conditions include an electrolytic plating device that injects an electrolyte between the strip and the electrodes in a countercurrent direction to the advancing direction of the strip, as disclosed in Japanese Patent Publication No. 50-8020; Examples include a device that sprays electrolyte from the center of the electrode onto the strip surface, as disclosed in No. 176518. Further, there is a horizontal electrolyzer equipped with a hydrostatic fluid pad disclosed in Japanese Patent Application No. 57-18836, which is currently pending patent application by the present applicant. Further, in the present invention, it is preferable that the distance between the poles be closer. The reason for this is, for example, when the current density is set to 100A/dm ² or 200A/dm ² and the distance between the electrodes is large, the voltage between the electrodes will exceed 20 to 30V, which increases the power cost and rectifier capacity, making it impractical. isn't it. The present invention aims at a voltage between electrodes of at least 20V or less, preferably 10V or less. Therefore, as the distance between the electrodes becomes closer (preferably 15 mm or less), the voltage between the electrodes decreases, and as a result, the cost can be significantly reduced. Therefore, the smaller the distance between the electrodes, the more advantageous it is in terms of cost, but if the distance between the electrodes is made too small, there is a risk that the strip and the electrode will come into contact with each other, so 5 mm can be said to be the practical limit for the distance between the electrodes. In the present invention, as described above, plating is performed by making the distance between the electrodes as close as possible. However, in order to further reduce the distance between the electrodes by reducing vibrations, positional fluctuations, or catenaries of the strip during plating, the above-mentioned method is used. It is most preferable to perform plating while supporting the strip with static pressure fluid using a plating device having a static pressure fluid pad as shown in Japanese Patent Application Laid-Open No. 56-127789 and Japanese Patent Application No. 57-18836. As a result, the strip is automatically centered between the electrodes using static pressure, so the distance between the electrodes can be greatly shortened, and moreover, plating can be performed stably. (in this case the best
Electrolysis at 250 A/dm ² is possible) Using the electrolytic device as explained above, an electrolyte is jetted between the electrode surface and the surface to be plated, and the liquid is spread between the electrodes and the surface to be plated. When plating is performed while holding the electrodes, there is no "gas accumulation" and the distance between the electrodes can be made close to each other, so that the resistance to conduction becomes small and it is possible to suppress the rise in voltage. Furthermore, plating with high current density is possible due to the high ion supply and liquid replacement efficiency based on relative speed (line speed - flow rate). The plating bath of the present invention will be explained below. The present inventors have developed an electrolytic cell capable of the above-mentioned high efficiency, but when actually performing Ni-Zn alloy plating,
It turns out that there are still issues to be solved. Below, the problems of Ni-Zn alloy plating and the method of the present invention will be explained in detail. Zinc has the characteristic of being able to be plated with high current efficiency due to its high hydrogen overvoltage. However, Ni has a low hydrogen overvoltage and the current efficiency is low in alloy plating. On the other hand, the addition of sulfuric acid is effective in reducing staining and liquid resistance, but it has the disadvantage of increasing hydrogen generation and significantly reducing current efficiency.
Therefore, the present inventors were able to solve the above problem by discovering a new zinc-nickel alloy plating bath that is compatible with close proximity high current density electrolysis. In the present invention, 5 to 20 g/H ₂ SO ₄ is added to the bath.
By adding it, the pH is lowered and the liquid resistance is lowered, and at the same time, the increase in metal ion concentration is improved. In general, lowering the pH makes it easier for hydrogen to come out and reduces current efficiency. Particularly in plating where Nc precipitates, hydrogen is likely to be generated, and it was conventionally thought that a decrease in pH would have a negative effect on current efficiency. However, in the bath of the present invention in which the pH was lowered, it was found that although it was the same as before at low current densities, it was conversely better at high current densities. FIG. 2 compares the relationship between current efficiency and current density using the bath of the present invention (curve 1) and a conventional high pH, low concentration bath (curve 2). Invention 1 is ZnSO ₄ 7H ₂ O + NiSO ₄ 6H ₂ O = 480
g/(Ni/Zn=1.5) _Na2SO4 = _100g /,
Plating was carried out using a bath containing 10 g of H ₂ SO ₄ and pH=1 at a temperature of 60° C. and a flow rate of 1 m/sec. Comparison 2 is _ZnSO4・
7H ₂ O＋NiSO ₄・6H ₂ O＝300g/(Ni/Zn＝
1.5), Na ₂ SO ₄ 100g/, H ₂ SO ₄ 2g/PH=2.5
Plating was carried out using a bath with a bath temperature of 60°C and the usual immersion method. The present invention 1 can ensure current efficiency of 82% or more even at a high current density of 100 A/dm ² or more. However, at a current density of 300 A/dm ² , even in the bath of the present invention, a decrease in current efficiency and uneven plating begin to occur.
The preferred current density of the present invention is 100-250 A/ ^dm2 , most preferably 150-200 A/ ^dm2 . Furthermore, the conventional way of thinking is to keep the current density constant as a condition for achieving a uniform composition for alloy plating. Keep the bath composition constant. (Concentration, PH) Add rust salt. Add buffer. Keep the flow rate constant. Also keep the temperature constant. It was extremely difficult to produce because of the many setting conditions. In the present invention, a bath with a simple composition is used without adding rust salts or buffers, at a low pH (H ₂ SO ₄ 5 to 20 g/), at a temperature (above 60°C), and at a flow rate relative to the strip above a certain value (1 m/ s), high concentration bath (ZnSO ₄ 7H ₂ O+
We found plating conditions that depended on current density under a wide range of control conditions, including NiSO ₄ .6H ₂ O = 400 to 700 g/) and a wide range of bath compositions (Ni/Zn = 1 to 2). Furthermore, since the electrolytic cell for high current density sprays the plating liquid at a high flow rate, the flow rate at the jet nozzle portion differs from the flow rate at other parts. In alloy plating, there is a considerable correlation between the flow rate and the plating film alloy composition, resulting in uneven plating and the like. This tendency is particularly strong under conventional bath conditions, and the nozzle shape for setting the position of the ejection nozzle is very severe. However, under the bath conditions of the present invention, there is little relationship between the flow rate and the alloy composition, and the nozzle shape for setting the position of the ejection nozzle can be freely determined.
By using the bath conditions of the present invention in conjunction with the relative speed described below, zinc-nickel alloy plating with a stable alloy composition and good appearance can be easily produced over a much wider range of operating conditions than conventional bath conditions. Is possible. The amount of Ni that provides the best corrosion resistance for Zn-Ni alloy plating is
It is in the range of 10-15%. Figure 3 shows the inside of the plating film.
It shows the relationship between Ni% and the Ni/Zn ratio of the electrolyte. From this, the amount of Ni shown by the diagonal line in the plating is 10
In order to satisfy ~15%, it is necessary to adjust the Ni/Zn ratio to 1.0 to 2.0. Furthermore, Figures 4 and 5 show the relationship between the Ni% in the alloy plating layer and the relative velocity V between the electrolyte and the strip. FIG. 4 shows the conditions of the present invention, and FIG. 5 shows an example of comparative bath conditions. (For the plating bath, use the same bath as in Figure 2.) From Figure 5, when using the comparison bath, the current density DK (Curve 1 is 200A/dm ^2Curve 2
(100 A/dm ² ), the Ni% changes greatly, and this tendency is hardly stabilized even if the relative speed V is increased. Therefore, the Ni% obtained changes depending on the operating conditions, resulting in unstable product quality and difficulty in quality control. However, as shown in Figure 4, if the bath conditions of the present invention are used, Ni% exhibits very good stability with respect to DK, and especially when V = 1 m/s or more, even if the current density is changed, the Ni content remains at the optimum level. Some 10-15%
It is possible to perform plating of the composition stably. Therefore, the bath conditions of the present invention have a wide range of operating conditions and are practical for Ni--Zn alloy plating.
However, even under the conditions of the present invention, the required Ni% cannot necessarily be obtained when V=1 m/s or less. Regarding the bath temperature, since the conductivity of the bath increases with temperature, the higher the bath temperature, the lower the electrolytic voltage becomes, making it possible to reduce power costs. Furthermore, since the plating appearance tends to improve as the bath temperature is higher, it is most preferable to set the bath temperature to 60° C. or higher under the conditions of the present invention. FIG. 6 shows the relationship between the amount of H ₂ SO ₄ and the conductivity K and current efficiency 7. From this, K increases linearly as the amount of H ₂ SO ₄ increases, and the electrolytic voltage also decreases.
When H ₂ SO ₄ exceeds 20g/, the value of 7 decreases rapidly, making it impractical. In addition, Fig. 7 shows the relationship between the amount of ZnSO ₄ .7H ₂ O + NiSO ₄ .6H ₂ O and K, 7, which shows that ZnSO ₄ .
An increase in 7H ₂ O+NiSO ₄ .6H ₂ O causes a slight decrease in electrical conductivity, and particularly when the amount exceeds 700 g/2, the conductivity decreases rapidly. Also, regarding 7, ZnSO ₄ 7H ₂ O+
NiSO ₄ 6H ₂ O 400g/or more has a high efficiency of 80% or more. Therefore, the optimal amount of ZnSO ₄ .7H ₂ O + NiSO ₄ .6H ₂ O is in the range of 400 to 700 g/. Figure 8 shows H ₂ SO ₄ and ZnSO ₄・7H ₂ O+NiSO ₄・
The relationship between 6H ₂ O and the appearance of plating is shown. Those indicated by O in the figure have a good plating appearance. Than this
H ₂ SO ₄ 5g/or more, and ZnSO ₄・7H ₂ O＋NiSO ₄・
A good plating appearance can be obtained with 400g/or more of 6H ₂ O. From the above figures 6, 7, and 8, the bath of the present invention has H ₂ SO ₄ =5.
~20g/, ZnSO ₄・7H ₂ O＋NiSO ₄・6H ₂ O=400
Limited to ~700g/. The alloy plating of the present invention is a highly efficient manufacturing method using Zn-Ni as the main component, but the same conditions apply when alloying components are added as the third or fourth component or as impurities according to the requested patent etc. In Zn
- It is possible to manufacture alloy plating whose main component is Ni. These additive components include Fe, Co, Cr, etc. The permissible content is Ni/Zn in the bath.
The amount of Zn is 1/2 or less when the ratio is 1 to 2. The present invention has been described in detail above, and the present invention will be explained below with reference to Examples. Example 1 Alloy plating was carried out using the electrolytic apparatus shown in FIG. 1 under the bath conditions and plating conditions shown in Table 1. As a result, the results shown in Table 1 were obtained. Examples of the present invention
In Nos. 1, 2, 3, and 4, Ni-Zn alloy plating films with r structure were obtained with high efficiency, and the Ni content in the films was stable. The appearance of the film was also good. On the other hand, No. 5, which is a comparative example using a conventional bath,
Both No. 6 and No. 7 had poor current efficiency, and the appearance of the plating film was poor with plating burns occurring. 【table】

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明に用いる流体パツドによる電解
セルの一例である。ストリツプに対向配置したパ
ツド３に設けたスリツトよりメツキ液を噴出さ
せ、ストツプとパツド間にメツキ液を保持し近接
で高電流密度で電解する。第２図は本発明条件に
よる１と比較条件２との電流密度と陰極電流効率
の関係を示す。第３図は電流密度200A/dm²相対
流速1.5m/secの時の浴中のNi／Zn比とメツキ被
膜中のNi含有率％を示す図である。第４図は浴
中のNi／Zn比が1.5電流密度200A/dm²の時の相対
流速Ｖとメツキ被膜中のNi含有率を示す本発明
条件による図である。第５図は、第４図に対応し
た本発明条件に入らない浴条件で行つた場合の図
である。第６〜８図は本発明の浴条件の決定を明
らかに示した図である。第６図は、浴中のH₂SO₄
濃度と電導度Ｋおよび電流効率Ｎの関係を示す。
第７図は浴中の（ZnSO₄・7H₂O＋NiSO₄・
6H₂O）の濃度と電導度Ｋおよび電流効率Ｎの関
係を示す図である。又、第８図はH₂SO₄および
（ZnSO₄・7H₂O＋NiSO₄・6H₂O）の濃度と電流密
度200A/dm²で行つた時のメツキ外観の関係を示
す図である。１……ストリツプ、２……電解槽、３……電解
液、４……電極パツド。 FIG. 1 is an example of an electrolysis cell using a fluid pad used in the present invention. A plating solution is jetted out from a slit provided in a pad 3 placed opposite to the strip, and the plating solution is held between the stop and the pad and electrolyzed in close proximity with a high current density. FIG. 2 shows the relationship between current density and cathode current efficiency under conditions 1 according to the present invention and under comparative conditions 2. FIG. 3 is a diagram showing the Ni/Zn ratio in the bath and the Ni content percentage in the plating film at a current density of 200 A/dm ² and a relative flow rate of 1.5 m/sec. FIG. 4 is a diagram showing the relative flow velocity V and the Ni content in the plating film under the conditions of the present invention when the Ni/Zn ratio in the bath is 1.5 and the current density is 200 A/dm ² . FIG. 5 is a diagram corresponding to FIG. 4 when the bath conditions are not included in the conditions of the present invention. Figures 6-8 clearly illustrate the determination of bath conditions according to the present invention. Figure 6 shows H ₂ SO ₄ in the bath.
The relationship between concentration, conductivity K, and current efficiency N is shown.
Figure 7 shows (ZnSO ₄ 7H ₂ O + NiSO ₄
6H ₂ O) concentration, conductivity K, and current efficiency N. FIG. Moreover, FIG. 8 is a diagram showing the relationship between the concentration of H ₂ SO ₄ and (ZnSO ₄ .7H ₂ O+NiSO ₄ .6H ₂ O) and the appearance of plating when carried out at a current density of 200 A/dm ² . 1... Strip, 2... Electrolytic cell, 3... Electrolyte, 4... Electrode pad.

Claims

【特許請求の範囲】[Claims]

１電極面と被めつき面との間に電解液を噴出せ
しめて極面と被めつき面との間に液を保持しなが
ら電気亜鉛ニツケル合金めつきを行う方法におい
てめつき浴としてZnSO₄・7H₂OとNiSO₄・6H₂O
との和が400〜700ｇ/、Ni／Zn比1.0〜2.0、
H₂SO₄5〜20ｇ/からなる浴を用い、浴温60℃以
上、ストリツプとめつき浴の相対速度が１m/sec
以上、電流密度100〜250A/dm²でめつきを行うこ
とを特徴とする高効率ガンマー亜鉛ニツケル合金
めつき鋼板の製造方法。1 ZnSO ₄ is used as a plating bath in a method of electrolytic zinc-nickel alloy plating by jetting an electrolytic solution between the electrode surface and the surface to be plated and maintaining the liquid between the electrode surface and the surface to be plated.・7H ₂ O and NiSO ₄・6H ₂ O
sum of 400 to 700 g/, Ni/Zn ratio 1.0 to 2.0,
Using a bath consisting of 5 to 20 g of H ₂ SO ₄ , the bath temperature is 60°C or higher, and the relative speed of the strip and plating bath is 1 m/sec.
The above is a method for producing a highly efficient gamma-zinc-nickel alloy plated steel sheet, which is characterized in that plating is performed at a current density of 100 to 250 A/ ^dm2 .