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JP3791182B2 - Electrogalvanization of secondary molded products - Google Patents

Electrogalvanization of secondary molded products Download PDF

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Publication number
JP3791182B2
JP3791182B2 JP12066098A JP12066098A JP3791182B2 JP 3791182 B2 JP3791182 B2 JP 3791182B2 JP 12066098 A JP12066098 A JP 12066098A JP 12066098 A JP12066098 A JP 12066098A JP 3791182 B2 JP3791182 B2 JP 3791182B2
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Japan
Prior art keywords
water
solution
secondary molded
degreasing
tank
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JP12066098A
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JPH11310900A (en
Inventor
猛雄 沖
記生 野村
裕士 阿部
輝明 中西
昌 川本
元洋 片桐
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Yuken Industry Co Ltd
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Yuken Industry Co Ltd
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Description

【0001】
【発明の属する技術分野】
本発明は、二次成形品の電気亜鉛系めっき法、特に、排水処理への負荷を低減あるいは無くした二次成形品の電気亜鉛系めっき法に関する。以下、本発明を電気亜鉛めっきを例にとり説明する。
【0002】
【従来の技術】
従来の二次加工品の電気亜鉛めっき処理にあっては、以下の3種のめっき浴が主流をなしてきたが、各々次のような問題点を包含していた。
【0003】
シアン浴:青化ソーダ (猛毒) を主成分として含有するめっき浴であって、作業環境が悪い。
ジンケート浴:高濃度の苛性ソーダを含有するめっき浴であって、やはり作業環境が悪い。
【0004】
塩化アンモン浴:めっき浴が高濃度の窒素 (アンモニウム) を含んでいるため排水処理が問題となる。また排水処理に際しても亜鉛イオンの沈降性が悪く、しかもその後の処理水はCOD、BOD値が高い。
【0005】
【発明が解決しようとする課題】
ところで、一般的には、電気亜鉛めっき法として硫酸めっき浴を用いる方法も公知であるが、そのような硫酸めっき浴は、つきまわり性と光沢性に劣り、そのためその適用が一次成形品 (例: 帯鋼) のように単調な形状の処理物だけに限定されてきた。つまり、そのような一次成形品にさらにプレス成形等の二次加工を行って製作した二次成形品 (例: 筒状体) の場合、高い光沢性、つきまわり性が要求され、かつ多種多様な形状をしており、したがって、かかる二次成形品のめっき処理には硫酸めっき浴の適用が不可能であり、実際、これまで工業的に適用された例はなかった。
【0006】
一方、今日では環境保全問題への対応から資源のリサイクルおよび処理系のクローズド化 (以下、「リサイクル・クローズド化」または「リサイクル・クローズド・システム」という) が求められている。従来から電気亜鉛めっきについてもこの「リサイクル・クローズド化」という概念は存在したものの、次に示すような克服困難な課題があり、現在のところ実現には至っていない。従って、様々な化学物質を含んだ排水が各めっきライン当たり10〜100m3/日放出されているのが現状である。
【0007】
すなわち、リサイクル・クローズド・システムを採用する場合、従来は排水処理設備にて一括して処理していた汚染水洗水の浄化もしくは処分が最大の課題であった。前者については、汚染水洗水の浄化システムを用いたライン内リサイクル化を想定したとしても、その精度、能力、コストに大きな課題があり実用化に至らない。さらに、このライン内リサイクル化それ自体についても、「めっき液と水洗水の濃縮を図り、それにより生ずる給水の必要量を新しい水洗水として供給する」ことは想定されるものの、コスト的に実用的な濃縮技術がなく、実用化に至っていない。
【0008】
また、アルカリ浴を使っためっきでは、めっき液の汲み出しがない場合、陽極における電解酸化反応により液中の有機物より生じる炭酸根に加えて、気液界面より中和反応を経て吸収する炭酸根が液中に蓄積する。このように炭酸根が蓄積し続けると、通電性の低下、槽底析出、さらには処理物上への付着等の問題を生ずる。
【0009】
ところで、めっき浴温度を上げることで「めっき液の蒸発→濃縮」を行い、その補充水分としてめっき槽に供給される水洗水、つまり、めっき製品の水洗水を利用することも考えられるが、めっき性能の多くを有機添加剤に頼っている現状ではそのような有機添加剤がめっき液を蒸発する際の高温によって分解してしまうばかりでなく、分解生成物が蓄積することからも、光沢性、つきまわり性等のめっき性能が大きく低下する。
【0010】
ここに、本発明の目的は、二次成形品に電気亜鉛めっきを行う際に、排水の流出を防止し完全なリサイクル・クローズド化を可能とする電気亜鉛めっき法を提供することである。
さらに本発明の目的は有機添加剤の使用量を可及的少とし、かつめっき処理設備の簡略化を可能とする電気亜鉛めっき法を提供することである。
【0011】
【課題を解決するための手段】
本発明者らは、リサイクル・クローズド化の実現に一番問題となるのが、水洗水確保のためのめっき液濃縮技術、つまり高温浴めっき技術であって、従来のめっき液濃縮技術が有機添加剤の分解・蓄積を不可避的に伴うことから、可及的低温でめっき液を蒸発させること、さらに要すれば硫酸亜鉛めっき浴を用いてパルス電流によるめっきを行うことが有利であることに着目した。
【0012】
そこでさらに本発明者らは検討を重ね、次のような知見を得た。
(i) 各工程において個別化した処理水の蒸発・冷却による回収系を設けることで、めっき工程全体の無排水クローズド化が実現容易になる。
【0013】
(ii)各工程において大気蒸発装置を設けるとともに、高温(60〜70℃)にてバブリングやスプレーを行い、薬液の収容槽の水を大量(10 〜20 l/hr)に蒸発させ、また蒸発量と同量の水洗水 (薬液を含んだ水) を薬液収容槽へ回収することにより、めっき工程全体の無排水クローズド化が可能となる。
【0014】
(iii) 前処理〜めっき処理〜後処理にて、各処理槽から処理済物品を引き上げた時にシャワー水洗を行い、水洗槽への薬液負荷を低減し、ライン全体の水洗槽スペースの縮小化を図ることができる。
【0015】
(iv)水洗槽下部にいくつかの小さな水洗水タンクを設け、その水を使用して単槽の水洗槽内にてスプレー水洗を行う。その際に、タンク水は処理すべき物品に対し向流とすることにより、水洗性能の向上が図れ、しかも単槽にて水洗が可能となる。
【0016】
(v) 各工程において用いる薬液を、後工程に持ち込まれても殆ど悪影響のない薬液を選択することで、中間の洗浄工程の負荷が軽減し、装置全体を簡略化することができ、設備投資負担を少なくすることができる。
【0017】
(vi)めっき浴として硫酸めっき浴を用いるとともにパルス電流によるめっき処理を行うことで使用薬液の量を最少とすることができ、処理系全体のリサイクル・クローズド化が促進される。
【0018】
ここに、本発明は、次のとおりである。
(1)めっき処理すべき二次成形品を、脱脂工程と、酸洗浄工程と、電解洗浄工程と、電気亜鉛めっき工程とを順次経て処理することから構成される二次成形品の電気亜鉛めっき法であって、
前記工程の少なくとも1つにおいて、脱脂液、酸洗浄液、電解液または亜鉛めっき液を蒸発させること、前記工程の少なくとも1つの工程の後に、単槽内でスプレー洗浄を多段に行う多段水洗工程を設けること、および、該多段水洗工程における各段の水洗の際に水洗済み排水を回収し、次回の水洗工程において、それぞれ上流段の水洗水として用いて水洗すべき二次成形品に対して向流関係で水洗することを特徴とする二次成形品の電気亜鉛めっき法。
【0021】
(2)前記脱脂工程でアルカリ溶液を二次成形品にスプレーすることにより脱脂を行うことを特徴とする上記(1)記載の二次成形品の電気亜鉛めっき法。
【0022】
(3)前記脱脂工程、酸洗浄工程、電解洗浄工程、および電気亜鉛めっき工程の少なくとも1において、それぞれの処理を行う槽内での処理終了後に、処理済の二次成形品に対して槽上でスプレー水洗を行うことを特徴とする上記(1)または(2)記載の二次成形品の電気亜鉛めっき法。
【0023】
(4)前記脱脂工程における脱脂液として水酸化物の水溶液を用い、前記酸洗浄工程における酸洗浄液として硫酸液を用い、前記電解洗浄工程における電解液として水酸化物の水溶液を用い、そして前記電気亜鉛めっき工程においてめっき液として硫酸液を用いることを特徴とする上記(1)ないし(3)のいずれかに記載の二次成形品の電気亜鉛めっき法。
【0024】
(5)前記電気亜鉛めっき工程において硫酸亜鉛めっき浴を用い、パルス波形の電流を供給することを特徴とする記(1)ないし(4)のいずれかに記載の二次成形品の電気亜鉛めっき法。
【0025】
上記「二次成形品」は圧延などの一次加工により得た帯鋼などの一次成形品に対する用語であって、プレス、押出、絞り等の二次加工により得た成形品であり、特にそれに制限はされないが、車両用部品等の管 (筒) 状体、輪状体、凹凸多面体を例示できる。以下にあっては、「処理すべき物品」、あるいは単に「物品」とも称する。
【0026】
【発明の実施の形態】
図1は、本発明にかかるめっき法の模式的説明図である。
本発明によれば、めっきすべき物品は次の各工程を経て電気亜鉛めっきが行われる。なお、図示例では、電気亜鉛めっきに引き続いて、クロメート処理を行っているが、これは必ずしも必要ではない。
【0027】
脱脂工程:
本発明における脱脂工程(I) は、スプレー脱脂槽10において一般的にはKOH 3%、界面活性剤などの添加剤0.5 %を含む水酸化物の水溶液などのアルカリ水溶液を脱脂液として用い、スプレーノズル12を見掛け上移動させて物品全面にこの脱脂液14を当てることにより行う。回収された脱脂液の浮上油はオイルセパレータ16にて分離を行うことで回収して、燃料として使用してもよい。
【0028】
この工程に設けられる大気蒸発装置、つまり常圧の濃縮装置20は、以下の各工程においても同様であるが、例えば、処理すべき水溶液の温度を高めてから大気中に散布することで、あるいは加熱された媒体 (例:空気) を使って散布あるいは噴霧もしくはバブリングすることによって蒸発させてもよい。
【0029】
具体的には、上記大気加熱装置は、スプレー脱脂槽10内から回収された脱脂液を収容する収容槽22aからの脱脂液を、電気ヒータなどの加熱手段で加熱されファンなどにて送り込まれた熱風に、噴霧して熱風との接触面積を増やして蒸発しやすくさせる大気下での蒸気発生手段と、蒸発した水蒸気を大気冷却する冷却手段と、そして得られた冷却水を回収する手段とから構成される。別法としては、液温度を70℃程度に高めておいて、これを単に噴霧するだけでかなりの量の水を蒸発できる。
【0030】
特に、本発明によれば、かかる大気蒸発装置20は、例えば脱脂工程というように各工程に個別化されているため、負荷も少なくて済むことから、通常の手段でもって構成でき、脱脂工程自体の実質的なクローズド化を実現できる。
【0031】
また、本発明の好適態様においては、脱脂工程としてアルカリ溶液をスプレーすることから、例えば70℃でスプレーすることにより、短時間にて脱脂できるばかりでなく、70℃でスプレーすることにより脱脂槽それ自体を大気蒸発装置として機能させてもよい。
【0032】
このように大気蒸発装置から発生する水蒸気を回収し、冷却して得た冷却水は、水洗水として再利用できる。つまり、大気蒸発装置を設けることにより、脱脂液を濃縮し、水洗水を脱脂液の収容槽に回収することができる。70℃程度では脱脂液が分解・劣化することはない。
【0033】
なお、使用するアルカリ液は、苛性カリ(KOH) +添加剤の場合、脱脂液は乳化せず、次工程の酸洗浄工程の酸洗浄液に持ち込まれても悪影響は殆どない。また、苛性カリは空気中の炭酸ガスと反応し炭酸カリウムにもなるが、カリウム塩は潮解性が良いため、吸湿しやすく、ナトリウム塩の場合のように脱脂槽のまわりを白粉状にすることはない。
【0034】
次に、本発明の好適態様によれば、槽上スプレー水洗42が設けられ、また、脱脂工程の出側には単槽の多段水洗装置24が設けられている。脱脂された物品に対して、一旦槽上で水洗し、さらに単槽内で対向する単段または多段に設けたスプレーノズル26を用いて、何回にも分けて、つまり多段に、しかも向流で水洗を行うのである。
【0035】
図示例にあっては、水洗槽下部に4つの小さな水洗水タンクを設け、その水を使用して単槽の水洗槽内にてスプレー水洗を行う。その際に、まず第1タンク水にてスプレー水洗し、流れ落ちた水をタンクに回収し、その後、第2、第3、第4の各タンク水にて同様に水洗・回収を行う。タンク水は処理すべき物品に対し向流で水洗されるため、水洗性能の向上が図れ、しかも単槽にて水洗が可能となる。なお、使用済みの第1タンク水は収容槽22aを経て前述の大気蒸発装置に送られ、一方、使用後に回収された第2、第3、第4の各タンク水は、次回の水洗に際してそれぞれ第1、第2、第3のタンク水として水洗に用いられる。以下順次これを繰り返す。
【0036】
このように、本発明によれば、水洗水をその都度回収してこれも多段に設けた水収容槽、つまりタンクに収容する。回収された水洗水は、次回の物品の処理に際して、一つ上流側の段における水洗に用いられる。つまり、向流関係で水洗が行われて、このようにして徐々にきれいな水を使うようになり、最初の段の水洗スプレーに供給され、回収された水洗水は前述の収容槽22aで混合され脱脂液として使用してから大気蒸発装置に送られ、蒸発処理を受けるようにしてもよい。なお、図示していないが、最終段で使用される新しい水洗水は、大気蒸発装置からの冷却水を用いることが好ましい。
【0037】
酸洗浄工程 :
酸洗浄液 (本発明の好適態様では硫酸液)を収容している酸洗槽40内に物品を浸漬することで酸洗浄工程(II)を行うが、このとき温度による硫酸鉄の溶解度差を利用した冷却パネル (図示せず) によって回収される硫酸鉄 (例えば、2kg/day)は建築材料として再利用が可能である。
【0038】
特に、本発明の酸洗浄工程にあっても、好ましくは酸洗浄終了後に、多段水洗装置24による水洗工程に移行するまえに、酸洗槽40内において、槽上スプレー水洗42が行われる。これにより酸洗槽40からの酸洗浄液の持ち出しを可及的少とする。
【0039】
このように、本発明の場合、硫酸浴のため、高温(70 ℃) 、低濃度 (5%) 、短時間にて酸洗ができる。
酸洗工程(II)にあっても、前述の脱脂工程(I) と同様に、酸洗工程にだけ個別化した大気蒸発装置20が設けられ、また、出側にも同様に単槽内多段水洗槽24が設けられる。
【0040】
このような大気蒸発装置20および単槽内多段水洗槽24はすでに説明したと同様であって、これ以上の説明は行わないが、特に酸洗浄工程(II)では、酸洗浄液は大気蒸発装置20および70℃でバプリングされる酸洗槽40にて水は蒸発し、酸洗浄液の収容槽22bにおいては酸洗浄液が濃縮するとともに水洗水を多段水洗装置24から回収することができる。この一旦濃縮した状態で冷却パネル (図示せず) によって、温度による硫酸鉄の溶解度差を利用して硫酸鉄などの固形物を効果的に分離回収することができる。その後の酸洗浄液は上述の水洗水あるいはさらに冷却水でもって希釈、調整して再び酸洗浄液として用いる。もちろん、例えば硫酸液の場合70℃程度の高温では酸洗浄液は何ら劣化することがない。
【0041】
電解洗浄工程 :
電解洗浄工程(III) は電解脱脂槽50においてアルカリ電解を行うことで、亜鉛電気めっきの予備処理、活性化処理を行うもので、通常、NaOHの5%水溶液を用い、収容槽22cに回収されたアルカリ液は温度による炭酸ソーダの溶解度差を利用した炭酸ソーダ除去装置 (図示せず) により回収された炭酸ソーダは脱硫剤として使用できる。
【0042】
特に、本発明の電解洗浄工程(III) にあっては、電解洗浄終了後に、多段水洗装置24による水洗工程に移行するまえに、電解洗浄槽内において、槽上スプレー水洗42が行われる。これにより電解洗浄槽50からのアルカリ液の持ち出しを可及的少とする。
【0043】
電解洗浄工程(III) においても、前述の脱脂工程(I) および酸洗工程(II)と同様に、大気蒸発装置20が設けられ、また、出側にも同様に単槽内多段水洗槽24が設けられる。
【0044】
したがって、本発明によれば、電解洗浄工程(III) においても、大気蒸発装置20により70℃でバブリングにて発生する水蒸気を回収し、冷却して水洗水として再利用する。もちろん、かかる大気蒸発によって、例えばNaOH水溶液のような電解洗浄液が劣化することはない。
【0045】
なお、この電解洗浄液が苛性ソーダのときは、めっき液に持ち込まれても悪影響は殆どないことから、出側に設けられる水洗槽24は必ずしも必要としない。槽上スプレー水洗42が行われることで十分である。
【0046】
電気亜鉛めっき工程 :
電気亜鉛めっき工程(IV)では亜鉛めっき槽60において、例えば ZnSO4・7H2Oを60%含有する硫酸めっき液62を調製し、好ましくは例えばこれにパルスめっきを行う。めっき液の補給は例えば不溶性陽極 (図示せず) を使用する場合は炭酸亜鉛を化学的に溶解して行えばよい。
【0047】
特に、本発明の電気亜鉛めっき工程(IV)にあっても、好ましくは、亜鉛めっき終了後に、多段水洗装置24による水洗工程に移行するまえに、亜鉛めっき槽60内において、槽上スプレー水洗42が行われる。これにより亜鉛めっき槽10からの硫酸めっき液の持ち出しを可及的少とする。
【0048】
電気亜鉛めっき工程(IV)にあっても、前述の脱脂工程(I) 、酸洗浄工程(II)、および電解洗浄工程(III) と同様に、大気蒸発装置20が設けられ、そして出側では単槽内多段水洗が行われる。
このような大気蒸発装置20および単槽内多段水洗槽24はすでに説明したと同様であって、これ以上の説明は行わない。
【0049】
本発明の場合、めっき液の収容槽22dにめっき液を回収しているが、めっき浴ばかりでなくこの収容槽にも酸性めっき浴を用いれば炭酸根の蓄積はみられず、また硫酸浴を用することから光沢剤などの有機添加剤は不用ということで、電気亜鉛めっき工程それ自体においても上述のようなリサイクル・クローズド化が一層容易に促進可能であるが、その電気分解生成物がめっきにさほどの強い影響を及ぼさないものであれば、少量の有機添加剤はめっき浴に加えることができる。特に、少なくとも電気亜鉛めっき工程だけに個別化されたリサイクル・クローズド化を採用するときは、そのような有機添加剤の添加の問題もローカルな問題として、処理系全体の問題と切り離して対処でき、比較的容易に対処できる。
【0050】
本発明の好適態様にあっては、めっき槽60での電気亜鉛めっきはパルス波形のめっき電流を供給することで行われる。
本発明のさらなる好適態様にあっては、硫酸亜鉛めっき浴を用いた電気亜鉛めっきに際してパルス電源を用いてパルス波形のめっき電流を供給する。
【0051】
ここに、パルス波形の電流とは、矩形波、三角波、あるいは一部それらへ直流を重畳する方法等を用いた周期的電流中断法(Unipolar)による波の電流、もしくは単相半波、単相不完全整流波等の非対称交流波の電流も含まれる。
【0052】
次に、本発明において用いるめっき浴組成 (硫酸浴組成) は、実用上からは、一般には ZnSO4・7H2O:50〜600 g/L であれば充分である。好適態様によれば、100 〜450g/Lである。 ZnSO4・7H2O:100g/L未満では、コゲが発生し易く、めっき速度も低下する。450g/L超では、つきまわり性が低下し、かつ他方では水洗水の汚染が激しくリサイクル・クローズド化を困難にする。
【0053】
その他、特に硫酸亜鉛濃度が低い時に通電性の確保のために、H2SO4 、Na2SO4、(NH4)2SO4 、硼酸ナトリウム、スルファミン酸ナトリウム、酢酸ナトリウム、酢酸アンモニウム等の導電性塩を併用してもよい。
【0054】
有機添加剤は必ずしも添加は必要なく、むしろその添加によって本発明のリサイクル・クローズド化が悪影響を受けることも考えられるが、例えばその電気分解生成物がめっきにさほどの強い影響を及ぼさないものであれば、必要に応じて少量添加してもよい。また湿潤剤として、濡れ性改善等の必要時に、界面張力低下効果を有するもの等を少量添加してもよい。
【0055】
このように電気亜鉛めっきを終了してからは、そのまま最終製品としてもよく、また必要によりさらにクロメート処理工程を設けて、電気亜鉛めっきされた物品にさらにクロメート処理を行ってもよい。
【0056】
図示例では、クロメート処理槽70によりクロメート処理を行っており、そして、かかるクロメート処理工程にあっても、処理系のクローズド化を図るために、これまでの処理工程と同様に収容槽22eおよび大気蒸発装置20を備えるとともに、槽上スプレー水洗42、および出側における単槽内多段水洗24を行ってもよい。
【0057】
以上、本発明について各処理工程を順次説明してきたが、本発明によれば、ほぼ完全なクローズド化が可能になるとともに、処理設備自体の簡略化が可能となり、例えば、図1の各工程のめっき設備の場合、従来は、脱脂工程からクロメート処理工程までほぼ20メートルの長さを有していたのが、13メートル程度とほぼ2/3 となり、大幅な設備コストの低下を図ることができる。なお、本発明の場合も、亜鉛めっき槽それ自体の長さは従来と同様にほぼ9メートルであった。
次に、実施例によって本発明の作用効果をさらに具体的に説明する。
【0058】
【実施例】
本例では、図1に示すめっき装置を用い、カップ形状の二次加工品である鉄鋼部品を図1の工程に従って電気亜鉛めっきを行った。各工程において個別的に大気蒸発装置を用いて処理水のリサイクルを行うことで、処理系全体としてリサイクル・クローズド化を行った。
このときの各工程の処理条件は次の通りであった。
【0059】
脱脂工程:
脱脂液はKOH 3%水溶液を用い、これに0.5 %の界面活性剤を添加した。液温度は70℃とし、大気蒸発装置ではこのような脱脂液を使用後に回収し、脱脂液を噴霧しながら熱風を吹き込むことにより、15 l/hr の割合で蒸発させ、冷却後、冷却水として回収した。油の回収量は5kg/dayであった。なお、単槽内多段水洗は3段に分けて行った。
【0060】
酸洗浄工程:
H2SO4 の4.5%水溶液(70 ℃) を用い、硫酸鉄は2kg/day 回収した。出側での水洗は3段に分けて行った。
【0061】
電解洗浄工程:
70℃のNaOH5%水溶液を用い、通常の電解条件で電解洗浄を行った。この場合にも出側での水洗は3段に分けて行った。
【0062】
電気亜鉛めっき工程:
本例で使用しためっき浴組成はZnSO4 ・7H2Oを60%含む液温度70℃の水溶液であった。めっき槽は20槽設け、電気亜鉛めっきは連続的に行った。この場合にも、出側のスプレー水洗は3段に分けて行った。本例の電気亜鉛めっきは、1msに流れる電流密度25A/dm2 のパルス電解にて行った。平均電流密度は2.5A/dm2であった。
【0063】
クロメート処理工程:
本発明にしたがって電気亜鉛めっきを行った物品は、水洗浄後、慣用の処理条件で黄色クロメート処理を施し、70℃で乾燥した。しかし、本例では、これまでの各処理工程と同様に、個別化された大気蒸発装置を設け、この処理工程自体で一つのクローズド系を構成するようにしている。クロメート剤としては通常の塗布型のそれを用い、本例ではそれをスプレー塗布した。槽上ではスプレー水洗を行い、そして出側に設けた水洗槽でも3段に分けて水洗を行った。
【0064】
かくして、本発明によれば、排水量をほぼゼロとすることができた。めっきに要する時間も、前処理時間および後処理時間も含めて従来が40〜60分を要していたのに対して、本発明ではほぼ29分に短縮することができた。
【0065】
水補給量は、従来は、2000〜5000l/day も要していたのに対して、本発明では200 〜500l/dayとほぼ1/10にまで低減できた。本発明の場合、排水量がほぼゼロであるので、理論的には補給水も実質ゼロとなる筈であるが、蒸発による損失を補給する必要があるからである。
さらに、本発明の場合、油の回収量が4〜5kg/day、また硫酸第1鉄・7水和物の回収量も1 〜2kg/day であった。
【0066】
【発明の効果】
以上説明したように、本発明によれば、次のような優れた効果が得られる。
(1) 各処理工程におけるリサイクル化、クローズド化が実現され、めっき処理工程全体としてもほぼ100 %リサイクル化が実現できる。
したがって、めっきラインより排出される排水の処理費用 (イニシャルコスト:設備費、ランニングコスト:薬品費用、電力、メンテナンス費用) の削減もしくは大幅な削除が可能となる。
【0067】
(2) 有価製品 (油および硫酸鉄) も回収でき、コスト低減に大きく寄与する。
(3) めっき設備全体をほぼ2/3 の長さに短縮可能となり、設備費および建屋費の大幅な低減を可能とする。
(4) これらを総合した評価として、経済性ばかりでなく、環境問題の改善に対して大きな寄与をする優れた技術である。
【0068】
すなわち、水洗水、排水の100 %リサイクル・クローズド化を実現することにより次のような環境向上への寄与が考えられる。
(1) 生態、自然界への有害性が現在認められている物質に限らず、今後確認され得る物質についても、その放出が未然に防止でき、環境保全へ役立つ。
【0069】
(2) 排水に含まれ、アルキルフェノール系界面活性剤に代表される物質群に関わるエンドクリン問題への対応が可能となる。
(3) 排水に含まれるCOD、BOD値低下の原因物質の自然界への放出の削減もしくは回避が図れる。
(4) 排水に含まれる亜鉛金属イオンの自然界への放出の削減もしくは回避が図れる。
【図面の簡単な説明】
【図1】本発明にかかるめっき方法の各工程の模式的説明図である。
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrozinc plating method for a secondary molded product, and more particularly to an electrozinc plating method for a secondary molded product that reduces or eliminates the load on wastewater treatment. Hereinafter, the present invention will be described by taking electrogalvanization as an example.
[0002]
[Prior art]
In the conventional electrogalvanizing treatment of a secondary processed product, the following three types of plating baths have been mainstream, but each of them contained the following problems.
[0003]
Cyan bath: A plating bath that contains sodium blue soda (very toxic) as its main component and has a poor working environment.
Zincate bath: A plating bath containing a high concentration of caustic soda, which also has a poor working environment.
[0004]
Ammonium chloride bath: Wastewater treatment becomes a problem because the plating bath contains a high concentration of nitrogen (ammonium). Moreover, the sedimentation property of zinc ions is poor during wastewater treatment, and the treated water thereafter has high COD and BOD values.
[0005]
[Problems to be solved by the invention]
By the way, in general, a method using a sulfuric acid plating bath as an electrogalvanizing method is also known, but such a sulfuric acid plating bath is inferior in throwing power and glossiness. : Steel strip), which has been limited to monotonous processed products. In other words, in the case of a secondary molded product (e.g., a cylindrical body) manufactured by performing secondary processing such as press molding on the primary molded product, high glossiness and throwing power are required, and a wide variety Therefore, it is impossible to apply a sulfuric acid plating bath to the plating treatment of such a secondary molded product, and there has actually been no example of industrial application so far.
[0006]
On the other hand, today, there is a demand for resource recycling and processing system closure (hereinafter referred to as “recycling / closed system” or “recycling / closed system”) in response to environmental conservation problems. Conventionally, although the concept of “recycling / closing” has existed for electrogalvanizing, there are the following problems that are difficult to overcome and have not yet been realized. Therefore, at present, wastewater containing various chemical substances is released 10 to 100 m 3 / day for each plating line.
[0007]
That is, when adopting a recycle closed system, purification or disposal of contaminated washing water, which has been treated collectively in the waste water treatment facility, has been the biggest problem. As for the former, even if in-line recycling using a purification system for contaminated washing water is assumed, there are significant problems in accuracy, capacity, and cost, and it will not be put into practical use. Furthermore, although it is assumed that the in-line recycling itself “concentrates plating solution and washing water and supplies the necessary amount of water supply as new washing water”, it is practical in terms of cost. Has not been put into practical use.
[0008]
In addition, in plating using an alkaline bath, when the plating solution is not pumped, in addition to carbonate radicals generated from organic substances in the solution by electrolytic oxidation reaction at the anode, carbonate radicals that are absorbed through a neutralization reaction from the gas-liquid interface. Accumulate in liquid. If the carbonate radicals continue to accumulate in this way, problems such as a decrease in electrical conductivity, precipitation at the bottom of the tank, and adhesion to the treated material occur.
[0009]
By the way, it is conceivable to raise the plating bath temperature to “evaporate the plating solution → concentrate” and use washing water supplied to the plating tank as supplementary moisture, that is, use washing water for plating products. In the present situation where most of the performance relies on organic additives, such organic additives are not only decomposed due to the high temperature when the plating solution evaporates, but also because decomposition products accumulate, gloss, Plating performance such as throwing power is greatly reduced.
[0010]
Here, an object of the present invention is to provide an electrogalvanizing method that prevents drainage outflow and enables complete recycling and closing when electrogalvanizing a secondary molded product.
Furthermore, an object of the present invention is to provide an electrogalvanizing method that makes it possible to reduce the amount of the organic additive used as much as possible and to simplify the plating processing equipment.
[0011]
[Means for Solving the Problems]
The present inventors have the biggest problem in realizing recycling / closed plating solution concentration technology for securing washing water, that is, high-temperature bath plating technology, and conventional plating solution concentration technology is organically added. Since it is unavoidable to decompose and accumulate the agent, it is advantageous to evaporate the plating solution at the lowest possible temperature and, if necessary, to perform plating with pulsed current using a zinc sulfate plating bath. did.
[0012]
Therefore, the present inventors further studied and obtained the following knowledge.
(i) By providing a collection system by evaporating and cooling the treated water that is individualized in each process, it becomes easy to realize non-drainage closed in the entire plating process.
[0013]
(ii) An air evaporation device is installed in each process, and bubbling and spraying are performed at high temperature (60 to 70 ° C) to evaporate the water in the chemical solution storage tank to a large amount (10 to 20 l / hr) and evaporate. By collecting the same amount of washing water (water containing chemical solution) into the chemical solution storage tank, it becomes possible to make the entire plating process drainless closed.
[0014]
(iii) In pre-treatment-plating treatment-post-treatment, shower water is washed when the treated article is pulled up from each treatment tank, reducing the chemical load on the washing tank, and reducing the washing tank space of the entire line. Can be planned.
[0015]
(iv) Several small flush tanks are provided at the bottom of the flush tank, and spray water washing is performed in the single flush tank using the water. At that time, the tank water is counterflowed with respect to the article to be treated, so that the water washing performance can be improved, and the water can be washed in a single tank.
[0016]
(v) By selecting the chemicals used in each process so that there is almost no adverse effect even if they are brought into the subsequent process, the load on the intermediate cleaning process can be reduced, and the entire system can be simplified, and capital investment can be made. The burden can be reduced.
[0017]
(vi) By using a sulfuric acid plating bath as a plating bath and performing a plating treatment with a pulse current, the amount of chemicals used can be minimized, and recycling and closing of the entire treatment system is promoted.
[0018]
Here, the present invention is as follows.
(1) Secondary galvanizing of a secondary molded article comprising processing a secondary molded article to be plated through a degreasing process, an acid cleaning process, an electrolytic cleaning process, and an electrogalvanizing process in order. Law,
At least one on Oite of the steps, degreasing liquid, acid cleaning liquid, Rukoto evaporated electrolyte or zinc plating solution, after at least one step of the process, a multi-stage washing to perform spray cleaning in multiple stages in a single tank For the secondary molded product that is to be washed with water at each stage in the multi-stage water washing process and to collect the drained water that has been washed and to be used as the upstream water in the next water washing process. Electrogalvanizing method for secondary molded products, characterized by washing with countercurrent flow .
[0021]
(2) the electrolytic zinc plating of the secondary molded article (1) Symbol placement and performing degreasing by spraying the secondary molded article alkaline solution in the degreasing step.
[0022]
(3) In at least one of the degreasing step, the acid cleaning step, the electrolytic cleaning step, and the electrogalvanizing step, the tank is formed on the processed secondary molded product after completion of the processing in the tank for performing each processing. The electrogalvanizing method for the secondary molded article according to the above (1) or (2) , wherein spray washing is performed above.
[0023]
(4) A hydroxide aqueous solution is used as a degreasing solution in the degreasing step, a sulfuric acid solution is used as an acid cleaning solution in the acid cleaning step, a hydroxide aqueous solution is used as an electrolytic solution in the electrolytic cleaning step, and the electric The electrogalvanizing method for a secondary molded article according to any one of the above (1) to (3), wherein a sulfuric acid solution is used as a plating solution in the galvanizing step.
[0024]
(5) using a zinc sulfate plating bath in the electrolytic zinc plating process, electrolytic zinc secondary molded article according to any one of (1) above no and supplying a current pulse waveform (4) Plating method.
[0025]
The above-mentioned “secondary molded product” is a term for a primary molded product such as a strip obtained by primary processing such as rolling, and is a molded product obtained by secondary processing such as pressing, extrusion, drawing, etc. Although not carried out, pipe (cylinder) -like bodies such as vehicle parts, ring-like bodies, and concavo-convex polyhedrons can be exemplified. In the following, it is also referred to as “article to be processed” or simply “article”.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic explanatory view of a plating method according to the present invention.
According to the present invention, the article to be plated is electrogalvanized through the following steps. In the illustrated example, the chromate treatment is performed subsequent to the electrogalvanization, but this is not always necessary.
[0027]
Degreasing process :
In the degreasing step (I) in the present invention, an alkaline aqueous solution such as a hydroxide aqueous solution containing 3% KOH and 0.5% additive such as a surfactant is generally used as a degreasing liquid in the spray degreasing tank 10. The degreasing liquid 14 is applied to the entire surface of the article by apparently moving the nozzle 12. The recovered defatted floating oil may be recovered by separation with the oil separator 16 and used as a fuel.
[0028]
The atmospheric evaporation apparatus provided in this step, that is, the normal pressure concentrating device 20, is the same in the following steps, for example, by increasing the temperature of the aqueous solution to be treated and then spraying it in the atmosphere, or It may be evaporated by spraying or spraying or bubbling with a heated medium (eg air).
[0029]
Specifically, the above-mentioned atmospheric heating device was heated by heating means such as an electric heater, and fed with a fan or the like, after the degreasing liquid from the storage tank 22a containing the degreasing liquid recovered from the spray degreasing tank 10 Steam generating means under the atmosphere that sprays hot air to increase the contact area with the hot air to facilitate evaporation, cooling means for cooling the evaporated water vapor to the atmosphere, and means for recovering the obtained cooling water Composed. Alternatively, a significant amount of water can be evaporated by simply spraying the liquid temperature to about 70 ° C.
[0030]
In particular, according to the present invention, the atmospheric evaporation apparatus 20 is individualized in each process, for example, a degreasing process, so that the load can be reduced. Can be substantially closed.
[0031]
In the preferred embodiment of the present invention, since the alkaline solution is sprayed as the degreasing step, for example, spraying at 70 ° C. not only enables degreasing in a short time, but also spraying at 70 ° C. The device itself may function as an atmospheric evaporation device.
[0032]
Thus, the cooling water obtained by recovering and cooling the water vapor generated from the atmospheric evaporation device can be reused as flush water. That is, by providing the atmospheric evaporation device, the degreasing liquid can be concentrated and the washing water can be collected in the degreasing liquid storage tank. At about 70 ° C, the degreasing solution does not decompose or deteriorate.
[0033]
When the alkaline solution used is caustic potash (KOH) + additive, the degreasing solution is not emulsified, and even if it is brought into the acid cleaning solution in the next acid cleaning step, there is almost no adverse effect. Caustic potash reacts with carbon dioxide in the air to form potassium carbonate, but potassium salt has good deliquescence, so it is easy to absorb moisture, and white powder around the degreasing tank as in the case of sodium salt. There is no.
[0034]
Next, according to a preferred embodiment of the present invention, the tank spray water washing 42 is provided, and a single tank multi-stage water washing device 24 is provided on the outlet side of the degreasing step. The degreased article is once washed with water on the tank, and further divided into multiple times, that is, in multiple stages and counter-current, using the spray nozzle 26 provided in a single stage or multiple stages facing each other in the single tank. Wash with water.
[0035]
In the illustrated example, four small flush water tanks are provided at the bottom of the flush tank, and the water is used for spray washing in a single flush tank. At that time, spray water is first washed with the first tank water, and the water that has flowed down is collected in the tank, and then the water is washed and collected in the same manner with the second, third, and fourth tank water. Since the tank water is washed countercurrently to the article to be treated, the water washing performance can be improved, and the water can be washed in a single tank. The used first tank water is sent to the atmospheric evaporation device through the storage tank 22a. On the other hand, the second, third, and fourth tank waters collected after use are respectively used in the next water washing. The first, second, and third tank water is used for water washing. This is repeated in turn.
[0036]
Thus, according to the present invention, the flush water is collected each time and is also accommodated in a multi-stage water storage tank, that is, a tank. The recovered flush water is used for flushing one upstream stage when the next article is processed. That is, flushing is performed in a countercurrent relationship, and clean water is gradually used in this way. The first flushing spray is supplied and the collected flushing water is mixed in the storage tank 22a. After being used as a degreasing liquid, it may be sent to an atmospheric evaporation device and subjected to an evaporation process. In addition, although not shown in figure, it is preferable to use the cooling water from an atmospheric | air evaporation apparatus for the new washing water used at the last stage.
[0037]
Acid cleaning process :
The acid washing step (II) is performed by immersing the article in the pickling tank 40 containing the acid washing solution (in the preferred embodiment of the present invention, the sulfuric acid solution). At this time, the difference in solubility of iron sulfate depending on the temperature is used. Iron sulfate (for example, 2 kg / day) recovered by a cooled panel (not shown) can be reused as building material.
[0038]
In particular, even in the acid cleaning step of the present invention, preferably, after the completion of the acid cleaning, the spray water washing 42 on the tank is performed in the pickling tank 40 before shifting to the water washing process by the multistage water washing device 24. As a result, the pickling solution from the pickling tank 40 is taken out as much as possible.
[0039]
Thus, in the case of the present invention, since it is a sulfuric acid bath, it can be pickled in a high temperature (70 ° C.), a low concentration (5%) and in a short time.
Even in the pickling step (II), as in the degreasing step (I) described above, an air evaporation device 20 that is individualized only for the pickling step is provided, and the multistage in the single tank is also provided on the outlet side. A rinsing tank 24 is provided.
[0040]
Such an atmospheric evaporation device 20 and the single-stage multi-stage water washing tank 24 are the same as those already described, and no further explanation will be given, but particularly in the acid cleaning step (II), the acid cleaning liquid is the atmospheric evaporation device 20 The water evaporates in the pickling tank 40 bubbled at 70 ° C., and the acid cleaning liquid is concentrated in the acid cleaning liquid storage tank 22 b, and the washing water can be recovered from the multi-stage water washing device 24. Once concentrated, a cooling panel (not shown) can effectively separate and recover solids such as iron sulfate using the difference in solubility of iron sulfate depending on the temperature. Thereafter, the acid cleaning solution is diluted and adjusted with the above-described washing water or further with cooling water and used again as the acid cleaning solution. Of course, for example, in the case of sulfuric acid solution, the acid cleaning solution is not deteriorated at a high temperature of about 70 ° C.
[0041]
Electrolytic cleaning process :
The electrolytic cleaning step (III) is a pretreatment and activation treatment of zinc electroplating by performing alkaline electrolysis in the electrolytic degreasing tank 50, and is usually recovered in the storage tank 22c using a 5% aqueous solution of NaOH. In addition, the sodium carbonate recovered by a sodium carbonate removing device (not shown) using the difference in solubility of sodium carbonate depending on the temperature can be used as a desulfurizing agent.
[0042]
In particular, in the electrolytic cleaning step (III) of the present invention, after the electrolytic cleaning is completed, before the transition to the water cleaning step by the multi-stage water cleaning device 24, the on-tank spray water cleaning 42 is performed. As a result, the alkaline liquid is taken out from the electrolytic cleaning tank 50 as much as possible.
[0043]
Also in the electrolytic cleaning step (III), an atmospheric evaporation device 20 is provided in the same manner as the degreasing step (I) and the pickling step (II) described above, and the single-stage multi-stage water washing tank 24 is also provided on the outlet side. Is provided.
[0044]
Therefore, according to the present invention, also in the electrolytic cleaning step (III), water vapor generated by bubbling at 70 ° C. is recovered by the atmospheric evaporation device 20, cooled, and reused as flush water. Of course, such atmospheric evaporation does not deteriorate the electrolytic cleaning solution such as NaOH aqueous solution.
[0045]
When this electrolytic cleaning solution is caustic soda, there is almost no adverse effect even if it is brought into the plating solution, so the water washing tank 24 provided on the outlet side is not necessarily required. It is sufficient that the tank spray water washing 42 is performed.
[0046]
Electrogalvanizing process :
In the electrogalvanizing step (IV), a sulfuric acid plating solution 62 containing, for example, 60% of ZnSO 4 .7H 2 O is prepared in the zinc plating tank 60, and preferably, for example, pulse plating is performed thereon. For example, when an insoluble anode (not shown) is used, the plating solution may be supplied by chemically dissolving zinc carbonate.
[0047]
In particular, even in the electrogalvanization step (IV) of the present invention, preferably, after completion of galvanization, before the transition to the water washing step by the multi-stage water washing device 24, in the galvanizing tank 60, on-bath spray water washing 42 Is done. As a result, the removal of the sulfuric acid plating solution from the galvanizing tank 10 is minimized.
[0048]
Even in the electrogalvanizing step (IV), the atmospheric evaporation apparatus 20 is provided, and the outlet side is provided in the same manner as the degreasing step (I), the acid cleaning step (II), and the electrolytic cleaning step (III). Multi-stage water washing is performed in a single tank.
Such an atmospheric evaporator 20 and the single-stage multi-stage water washing tank 24 are the same as those already described, and will not be further described.
[0049]
In the case of the present invention, the plating solution is recovered in the plating solution storage tank 22d. However, if an acidic plating bath is used not only in the plating bath but also in this storage tank, accumulation of carbonate radicals is not observed, and a sulfuric acid bath is used. Since the use of organic additives such as brighteners is unnecessary, recycling and closing as described above can be more easily promoted in the electrogalvanization process itself, but the electrolysis product is plated. A small amount of an organic additive can be added to the plating bath if it does not have a very strong effect. In particular, when adopting recycling / closed processing that is individualized only at least for the electrogalvanization process, the problem of addition of such organic additives can also be dealt with as a local problem separately from the problem of the entire processing system, It can be handled relatively easily.
[0050]
In the preferred embodiment of the present invention, electrogalvanization in the plating tank 60 is performed by supplying a plating current having a pulse waveform.
In a further preferred embodiment of the present invention, a pulse waveform plating current is supplied using a pulse power source in electrogalvanization using a zinc sulfate plating bath.
[0051]
Here, the current of the pulse waveform is a square wave, a triangular wave, or a wave current by a periodic current interruption method (Unipolar) using a method of superimposing a direct current on them, or a single-phase half-wave, single-phase Asymmetrical AC wave currents such as incomplete rectified waves are also included.
[0052]
Next, the plating bath composition (sulfuric acid bath composition) used in the present invention is generally sufficient if it is practically ZnSO 4 .7H 2 O: 50 to 600 g / L. According to a preferred embodiment, it is 100 to 450 g / L. ZnSO 4 · 7H 2 O: If it is less than 100 g / L, kogation is likely to occur, and the plating rate also decreases. If it exceeds 450 g / L, the throwing power will decrease, and on the other hand, the washing water will be heavily contaminated, making it difficult to recycle and close it.
[0053]
In addition, in order to ensure conductivity when the zinc sulfate concentration is low, conductivity such as H 2 SO 4 , Na 2 SO 4 , (NH 4 ) 2 SO 4 , sodium borate, sodium sulfamate, sodium acetate, ammonium acetate, etc. A salt may be used in combination.
[0054]
The organic additive does not necessarily need to be added. Rather, the addition of the organic additive may adversely affect the recycling / closing of the present invention. For example, the electrolysis product may not have a strong influence on the plating. If necessary, a small amount may be added as necessary. Further, as a wetting agent, a small amount of an agent having an effect of lowering the interfacial tension may be added when necessary to improve wettability.
[0055]
In this way, after the electrogalvanization is completed, the final product may be used as it is, or a chromate treatment process may be further provided if necessary, and the electrogalvanized article may be further chromated.
[0056]
In the illustrated example, the chromate treatment is performed by the chromate treatment tank 70, and even in such a chromate treatment process, in order to close the treatment system, the storage tank 22e and the atmosphere are treated in the same manner as the previous treatment process. In addition to the evaporation device 20, the tank spray water washing 42 and the single-stage multi-stage water washing 24 on the outlet side may be performed.
[0057]
As mentioned above, although each process process was demonstrated sequentially about this invention, according to this invention, while being able to make a substantially complete closed, process facilities itself can be simplified, for example, each process of FIG. In the case of plating equipment, the conventional length of 20 meters from the degreasing process to the chromate treatment process is approximately 2/3, approximately 13 meters, which can greatly reduce the equipment cost. . In the case of the present invention, the length of the galvanizing tank itself was about 9 meters as in the prior art.
Next, the effects of the present invention will be described more specifically with reference to examples.
[0058]
【Example】
In this example, using the plating apparatus shown in FIG. 1, steel parts, which are cup-shaped secondary processed products, were electrogalvanized according to the process of FIG. 1. By recycling the treated water individually using an atmospheric evaporator in each process, the entire treatment system was recycled and closed.
The processing conditions of each process at this time were as follows.
[0059]
Degreasing process:
As a degreasing solution, a 3% KOH aqueous solution was used, and 0.5% of a surfactant was added thereto. The liquid temperature is 70 ° C. In the atmospheric evaporation device, such a degreasing liquid is recovered after use, and hot air is blown in while spraying the degreasing liquid to evaporate at a rate of 15 l / hr. It was collected. The amount of oil recovered was 5 kg / day. In addition, the multistage washing in the single tank was performed in three stages.
[0060]
Acid cleaning process:
Using a 4.5% aqueous solution of H 2 SO 4 (70 ° C.), iron sulfate was recovered at 2 kg / day. Washing with water on the outlet side was performed in three stages.
[0061]
Electrolytic cleaning process:
Electrolytic cleaning was performed under normal electrolysis conditions using a 5% NaOH aqueous solution at 70 ° C. Also in this case, washing on the outlet side was performed in three stages.
[0062]
Electrogalvanizing process:
The plating bath composition used in this example was an aqueous solution with a solution temperature of 70 ° C. containing 60% ZnSO 4 .7H 2 O. 20 plating tanks were provided, and electrogalvanization was continuously performed. Also in this case, the outlet spray washing was performed in three stages. The electrogalvanization in this example was performed by pulse electrolysis with a current density of 25 A / dm 2 flowing in 1 ms. The average current density was 2.5A / dm 2.
[0063]
Chromate treatment process:
Articles subjected to electrogalvanization according to the present invention were subjected to yellow chromate treatment under conventional treatment conditions after washing with water and dried at 70 ° C. However, in this example, as in each processing step so far, an individual atmospheric evaporation apparatus is provided, and this processing step itself constitutes one closed system. As a chromate agent, a normal coating type was used, and in this example, it was spray coated. Spray water washing was performed on the tank, and the water washing tank provided on the outlet side was also washed in three stages.
[0064]
Thus, according to the present invention, the amount of drainage could be made substantially zero. The time required for the plating, including the pretreatment time and the posttreatment time, conventionally required 40 to 60 minutes, but in the present invention, it could be shortened to approximately 29 minutes.
[0065]
The amount of water replenishment conventionally required 2000 to 5000 l / day, but in the present invention, it was reduced to approximately 1/10, 200 to 500 l / day. In the case of the present invention, since the amount of drainage is almost zero, the makeup water should theoretically become substantially zero, but it is necessary to supplement the loss due to evaporation.
Furthermore, in the case of the present invention, the amount of oil recovered was 4-5 kg / day, and the amount of ferrous sulfate heptahydrate recovered was 1-2 kg / day.
[0066]
【The invention's effect】
As described above, according to the present invention, the following excellent effects can be obtained.
(1) Recycling and closed processes are realized in each processing process, and the entire plating process can be almost 100% recycled.
Therefore, it is possible to reduce or drastically eliminate the treatment cost of waste water discharged from the plating line (initial cost: equipment cost, running cost: chemical cost, electric power, maintenance cost).
[0067]
(2) Valuable products (oil and iron sulfate) can be recovered, greatly contributing to cost reduction.
(3) The entire plating facility can be shortened to approximately 2/3 length, and the equipment and building costs can be greatly reduced.
(4) As a comprehensive evaluation of these, it is an excellent technology that greatly contributes not only to economic efficiency but also to the improvement of environmental problems.
[0068]
In other words, by realizing 100% recycling / closing of flush water and wastewater, the following environmental improvements can be considered.
(1) Not only substances that are currently recognized to be harmful to ecology and nature, but also substances that can be confirmed in the future can be prevented from being released in advance and contribute to environmental conservation.
[0069]
(2) It is possible to cope with the endocrine problem related to the substance group contained in the wastewater and represented by alkylphenol surfactants.
(3) It is possible to reduce or avoid the release of substances that cause COD and BOD values in wastewater to the natural world.
(4) Reduce or avoid the release of zinc metal ions contained in the wastewater to the natural world.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view of each step of a plating method according to the present invention.

Claims (5)

めっき処理すべき二次成形品を、脱脂工程と、酸洗浄工程と、電解洗浄工程と、電気亜鉛めっき工程とを順次経て処理することから構成される二次成形品の電気亜鉛めっき法であって、
前記工程の少なくとも1つにおいて、脱脂液、酸洗浄液、電解液または亜鉛めっき液を蒸発させること、前記工程の少なくとも1つの工程の後に、単槽内でスプレー洗浄を多段に行う多段水洗工程を設けること、および、該多段水洗工程における各段の水洗の際に水洗済み排水を回収し、次回の水洗工程において、それぞれ上流段の水洗水として用いて水洗すべき二次成形品に対して向流関係で水洗することを特徴とする二次成形品の電気亜鉛めっき法。
This is an electrogalvanizing method for a secondary molded article that is formed by sequentially processing a secondary molded article to be plated through a degreasing process, an acid cleaning process, an electrolytic cleaning process, and an electrogalvanizing process. And
At least one on Oite of the steps, degreasing liquid, acid cleaning liquid, Rukoto evaporated electrolyte or zinc plating solution, after at least one step of the process, a multi-stage washing to perform spray cleaning in multiple stages in a single tank For the secondary molded product that is to be washed with water at each stage in the multi-stage water washing process and to collect the drained water that has been washed and to be used as the upstream water in the next water washing process. Electrogalvanizing method for secondary molded products, characterized by washing with countercurrent flow .
前記脱脂工程でアルカリ溶液を二次成形品にスプレーすることにより脱脂を行うことを特徴とする請求項1記載の二次成形品の電気亜鉛めっき法。Electrolytic zinc plating of the secondary molded article according to claim 1 Symbol placement and performing degreasing by spraying the secondary molded article an alkaline solution in the degreasing process. 前記脱脂工程、酸洗浄工程、電解洗浄工程、および電気亜鉛めっき工程の少なくとも1つにおいて、それぞれの処理を行う槽内での処理終了後に、処理済の二次成形品に対して槽上でスプレー水洗を行うことを特徴とする請求項1または2記載の二次成形品の電気亜鉛めっき法。In at least one of the degreasing step, the acid cleaning step, the electrolytic cleaning step, and the electrogalvanizing step, the processed secondary molded product is sprayed on the tank after completion of the treatment in the tank in which each treatment is performed. 3. The method of electrogalvanizing a secondary molded article according to claim 1 or 2, wherein washing with water is performed. 前記脱脂工程における脱脂液として水酸化物の水溶液を用い、前記酸洗浄工程における酸洗浄液として硫酸液を用い、前記電解洗浄工程における電解液として水酸化物の水溶液を用い、そして前記電気亜鉛めっき工程においてめっき液として硫酸液を用いることを特徴とする請求項1ないしのいずれかに記載の二次成形品の電気亜鉛めっき法。An aqueous solution of hydroxide is used as a degreasing solution in the degreasing step, a sulfuric acid solution is used as an acid cleaning solution in the acid cleaning step, an aqueous solution of hydroxide is used as an electrolytic solution in the electrolytic cleaning step, and the electrogalvanizing step The method of electrogalvanizing a secondary molded product according to any one of claims 1 to 3, wherein a sulfuric acid solution is used as the plating solution. 前記電気亜鉛めっき工程において硫酸亜鉛めっき浴を用い、パルス波形の電流を供給することを特徴とする請求項1ないしのいずれかに記載の二次成形品の電気亜鉛めっき法。Electrolytic zinc plating of the secondary molded article according to any one of claims 1 to 4, characterized in that using a zinc sulfate plating bath, supplying the current pulse waveform at the electrolytic zinc plating process.
JP12066098A 1998-04-30 1998-04-30 Electrogalvanization of secondary molded products Expired - Fee Related JP3791182B2 (en)

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