JP2004183024A

JP2004183024A - Inexpensive sludgeless electrode

Info

Publication number: JP2004183024A
Application number: JP2002349635A
Authority: JP
Inventors: Keiichiro Torisu; 慶一郎鳥巣; Akihiro Ota; 明宏太田; Shiro Taguchi; 史朗田口; Kazuhiro Yamada; 和広山田
Original assignee: KYUTOKU KK; Nippon Steel Corp
Current assignee: KYUTOKU KK; Nippon Steel Corp
Priority date: 2002-12-02
Filing date: 2002-12-02
Publication date: 2004-07-02

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead dioxide electrode for electroplating in which even an inexpensive metallic substrate can stably be used. <P>SOLUTION: The sludgeless electrode is composed in such a manner that the energizing face is made of lead dioxide, and the other part is coated with a resin, so that corrosion can be prevented. Desirably, it has a structure where the outer frame part of the energizing face is formed of the resin so as to be higher than the energizing face, so that the energizing face is protected. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、金属板を電気メッキする際に使用される安価型スラッジレス電極に関するものである。
【０００２】
【従来の技術】
従来、金属板に異種金属を電気メッキする工程、例えば鋼板にクロムメッキを施すような工程では、一般的に金属帯を連続的にメッキセル中に浸漬し、通電する方法が採られている。メッキセル中には金属帯に被覆される金属イオンを含むメッキ液が充填され、金属帯は両側に設置された電極間を通過することによりメッキ処理される。この時、使用される電極表面においては酸化還元反応が起こり、スラッジと呼ばれる電極物質の酸化物が発生する。
【０００３】
通常このスラッジはメッキセルの下部に沈降、堆積しているが、生産性向上のために通板速度を上げるとメッキ液の攪拌によりスラッジが浮上、板とロールの間に噛み込んで押疵と呼ばれる製品欠陥となる。また、長期の使用によりスラッジが大量に堆積しても同様の現象となるばかりか、金属帯にも付着して健全なメッキ層の形成を妨げる。このようなことを回避すべく、これまではメッキ液の交換やフィルター濾過等の方法が採られてきたが、この方法は生産性の阻害や膨大な投資につながるという不具合があった。
【０００４】
このような不便を解決するために、メッキ浴中でスラッジが発生し難い電極が開発されてきている。中でも二酸化鉛を使用した電極はその効果が高いことが知られており、例えば特開平９−４１１９６号公報（特許文献１）等に開示されている。二酸化鉛は金属の基体上に電着形成する方法で製造するが、特に弗化物イオンを含むクロムメッキ液中で電極として使用した場合には、二酸化鉛は溶出しないものの基体の金属が溶出し、電極構造が破壊される問題があった。
【０００５】
この課題に対しては基体をＴｉやＮｂ等の耐食性金属とする方法が採られてきた。特に腐食性の強いメッキ液に対しては高価なＮｂを使用するしかなく、その場合には電極コストの悪化を招いていた。また、二酸化鉛は非常に脆く、板破断等の通板トラブルによる衝撃で簡単に崩れるために、プロテクター等の補強が必要で、構造の複雑化、それに伴うトラブル、例えば、プロテクター組立ボルトの腐食等が避けられなかった。
【０００６】
【引用文献】
（１）特許文献１（特開平９−４１１９６号公報）
【０００７】
【発明が解決しようとする課題】
本発明は、安価な金属基体でも安定的に使用可能な、電気メッキ用二酸化鉛電極を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明者らは、金属には強腐食性を示すメッキ液が、樹脂（例えば、塩化ビニル樹脂）にはほとんど影響を及ぼさないことに着目し、通電面となる二酸化鉛以外の金属基体を樹脂にて被覆することで、電極の寿命を飛躍的に向上しうることを知見した。その発明の要旨とするところは、
（１）通電面を二酸化鉛とし、それ以外の部分を樹脂で被覆することにより腐食を防止する構造としたことを特徴とする安価型スラッジレス電極。
（２）通電面の外枠部分を樹脂で通電面より高く成形し、通電面を保護する構造を持つことを特徴とする前記（１）に記載の安価型スラッジレス電極。
（３）通電面の面積が０．５ｍ^２以下の電極を複数組み合わせられた構成であることを特徴とする前記（１）または前記（２）に記載の安価型スラッジレス電極である。
【０００９】
【発明の実施の形態】
以下、本発明について詳細に説明する。
二酸化鉛は内部の残留応力による反りが発生するため、通常は３００ｍｍ四方程度の板状に製造されることが多いが、この大きさに合うように予め樹脂のケースを作成しておき、このケース内に樹脂製充填剤を用いて二酸化鉛の板を収めるようにすれば簡便である。さらにこの時、樹脂ケースの枠を二酸化鉛の板が収まる面よりも高くなるように成形すれば、板破断等の通板トラブル時に板やその他の飛来物から電極表面を保護することができ、これまで必要であったプロテクターが不要となる。
【００１０】
また、電極を目的の大きさにするには、前述の３００ｍｍ四方程度の小電極を組み合わせることにより達成することができる。なお、本発明者らは、この小電極の面積が０．５ｍ^２以下であれば、反りの問題なく使用できることを繰り返し実験の中から知見するに至った。従って、通電面の面積が０．５ｍ^２以下の電極を複数組み合せて、所望の大きさとすることが望ましい。
【００１１】
このように、二酸化鉛以外の部分を樹脂で被覆せしめ、二酸化鉛を囲む部分を高く成形した小電極を組み合わせることで、安価に長寿命電極を供給することができる。その効果確認のため、ＦＲＰ（ガラス繊維強化プラスティック）にて全面を被覆し、通電面のみを研磨によって露出させた二酸化鉛と鉛の電極、及び被覆をしないままの二酸化鉛の電極を陽極とし、陰極に鉄板を用いて弗化物を含むクロム酸溶液中で通電を行った。この時、電極の面積は全て０．３ｄｍ^２とし、電流密度は５０〜６０Ａ／ｄｍ^２となるようにした。この結果を表１に示す。
【００１２】
【表１】

【００１３】
表１に示すように、樹脂被覆を施した二酸化鉛電極は全く変化がないのに対し、被覆をしないままの二酸化鉛電極ではＴｉの基体が腐食して二酸化鉛が剥落した。また、樹脂被覆を施した鉛電極にはスラッジが大量に発生、電極面にも２〜３ｍｍ厚のスラッジが生成、付着した。
【００１４】
【実施例】
２８０ｍｍ×２８０ｍｍのＴｉ製のラス（金網）を同寸のＴｉ板にスポット溶接し、ラス面側に陽極電着法にて二酸化鉛を約１ｍｍ厚に電着した。この板を厚さ２０ｍｍの塩ビ製ケースに二酸化鉛の面を上にしてエポキシ充填剤を用いて収め、縦３枚、横４枚となるように並べて約１２００ｍｍ×１０００ｍｍの電極とした。図１は、本発明に係る電極の構造を示す図である。図１（ａ）は本発明に係る電極の斜視図であり、図１（ｂ）は平面図である。この図に示すように、塩ビ製ケース１の外枠２は二酸化鉛３の面から３０ｍｍ高くなるように施工した。この電極をティンフリースチール製造実機に設置し、弗化物を含む５０℃のクロム酸メッキ液中で５０〜１００Ａ／ｄｍ^２の電流密度にて乾燥して、他の電極との劣化度合いを比較した。その結果は表２に示すように、ＦＲＰで被覆したラボでのテストとほぼ同等の結果となった。
なお、本試験中に２度の板破断が当該メッキセル付近にて発生したが、衝撃による二酸化鉛の欠落等は発生しなかった。
【００１５】
【表２】

【００１６】
【発明の効果】
以上述べたように、本発明は従来Ｎｂ等の高価な金属しか二酸化鉛電極の基体として適用できなかった強腐食性環境に対して、単純な構造で安定的に安価金属を電極の基体として使用できるものであり、その工業的意義は極めて大きい。
【図面の簡単な説明】
【図１】本発明に係る電極の構造を示す図である。
【符号の説明】
１塩ビ製ケース
２外枠
３二酸化鉛[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an inexpensive sludgeless electrode used for electroplating a metal plate.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a process of electroplating a metal plate with a dissimilar metal, for example, a process of applying chromium plating to a steel plate, generally, a method of continuously immersing a metal strip in a plating cell and applying a current is employed. The plating cell is filled with a plating solution containing metal ions to be coated on the metal strip, and the metal strip is plated by passing between electrodes provided on both sides. At this time, an oxidation-reduction reaction occurs on the surface of the used electrode, and an oxide of the electrode material called sludge is generated.
[0003]
Normally, this sludge settles and accumulates in the lower part of the plating cell, but when the passing speed is increased to improve productivity, the sludge floats due to the stirring of the plating solution, and the sludge gets caught between the plate and the roll and is called a flaw. Product defects. In addition, even if a large amount of sludge is deposited due to long-term use, not only the same phenomenon occurs, but also sludge adheres to a metal band and prevents formation of a sound plating layer. In order to avoid such a situation, a method of exchanging a plating solution, filtering by a filter, or the like has been employed. However, this method has a problem that productivity is hindered and an enormous investment is caused.
[0004]
In order to solve such inconvenience, an electrode which is less likely to generate sludge in a plating bath has been developed. Among them, an electrode using lead dioxide is known to be highly effective, and is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-41196 (Patent Document 1). Lead dioxide is produced by electrodeposition on a metal substrate.Especially when used as an electrode in a chromium plating solution containing fluoride ions, lead dioxide does not elute but the metal of the substrate elutes, There was a problem that the electrode structure was destroyed.
[0005]
To solve this problem, a method has been adopted in which the substrate is made of a corrosion-resistant metal such as Ti or Nb. In particular, expensive Nb has to be used for a highly corrosive plating solution, in which case the cost of the electrode has been reduced. In addition, lead dioxide is very brittle and easily collapses due to the impact of passing through the board, such as breakage of the board. Therefore, it is necessary to reinforce the protector, etc., which complicates the structure and causes troubles such as corrosion of the protector assembly bolt. Was inevitable.
[0006]
[References]
(1) Patent Document 1 (Japanese Patent Application Laid-Open No. 9-41196)
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a lead dioxide electrode for electroplating, which can be used stably even with an inexpensive metal substrate.
[0008]
[Means for Solving the Problems]
The present inventors have paid attention to the fact that a plating solution having a strong corrosive property on a metal hardly affects a resin (for example, a vinyl chloride resin). It has been found that by coating with, the life of the electrode can be dramatically improved. The gist of the invention is that
(1) An inexpensive sludgeless electrode characterized in that the current-carrying surface is made of lead dioxide and the other parts are covered with a resin to prevent corrosion.
(2) The inexpensive sludgeless electrode according to the above (1), wherein the outer frame portion of the current-carrying surface is formed to be higher than the current-carrying surface with resin to protect the current-carrying surface.
(3) The inexpensive sludgeless electrode according to the above (1) or (2), wherein a plurality of electrodes having a current-carrying surface area of 0.5 m ² or less are combined.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
Since lead dioxide is warped due to residual internal stress, it is usually manufactured in a plate shape of about 300 mm square, but a resin case is prepared in advance to fit this size, and this case is formed. It is convenient if the lead dioxide plate is housed in a resin filler. Furthermore, at this time, if the frame of the resin case is formed so as to be higher than the surface on which the lead dioxide plate is accommodated, it is possible to protect the electrode surface from the plate and other flying objects at the time of passing trouble such as plate breakage, The need for a protector that has been required so far is eliminated.
[0010]
Further, the desired size of the electrode can be achieved by combining the aforementioned small electrodes of about 300 mm square. The present inventors have repeatedly found from experiments that the small electrode has an area of 0.5 m ² or less and can be used without a warp problem. Therefore, it is desirable to combine a plurality of electrodes having a current-carrying surface area of 0.5 m ² or less to obtain a desired size.
[0011]
As described above, by covering a portion other than lead dioxide with a resin and combining a small electrode in which the portion surrounding lead dioxide is formed high, a long-life electrode can be supplied at low cost. In order to confirm the effect, the entire surface is covered with FRP (glass fiber reinforced plastic), and the lead dioxide electrode and lead electrode with only the energized surface exposed by polishing, and the lead dioxide electrode without coating are used as the anode, Electric current was applied in a chromic acid solution containing fluoride using an iron plate as a cathode. In this case, all the area of the electrode was set to 0.3 dm ^2, the current density was set to be 50~60A / dm ^2. Table 1 shows the results.
[0012]
[Table 1]

[0013]
As shown in Table 1, the lead dioxide electrode coated with the resin did not change at all, whereas the lead dioxide electrode without coating was corroded by the Ti base and the lead dioxide was peeled off. In addition, a large amount of sludge was generated on the resin-coated lead electrode, and a sludge having a thickness of 2 to 3 mm was formed and adhered to the electrode surface.
[0014]
【Example】
A 280 mm × 280 mm Ti lath (wire mesh) was spot-welded to a Ti plate of the same size, and lead dioxide was electrodeposited to a thickness of about 1 mm on the lath surface by an anodic electrodeposition method. This plate was placed in a PVC case having a thickness of 20 mm, with the lead dioxide side facing up using an epoxy filler, and arranged side by side so as to be three in length and four in width to form an electrode of about 1200 mm × 1000 mm. FIG. 1 is a diagram showing a structure of an electrode according to the present invention. FIG. 1A is a perspective view of an electrode according to the present invention, and FIG. 1B is a plan view. As shown in this figure, the outer frame 2 of the PVC case 1 was constructed so as to be 30 mm higher than the surface of the lead dioxide 3. This electrode was placed on a tin-free steel production machine and dried in a chromic acid plating solution containing fluoride at 50 ° C. at a current density of 50 to 100 A / dm ² to compare the degree of deterioration with other electrodes. . As shown in Table 2, the results were almost the same as those in the laboratory test coated with FRP.
In addition, two plate breaks occurred in the vicinity of the plating cell during this test, but no loss of lead dioxide or the like due to impact occurred.
[0015]
[Table 2]

[0016]
【The invention's effect】
As described above, the present invention uses a cheap metal stably with a simple structure in a highly corrosive environment in which only expensive metals such as Nb can be conventionally used as a substrate for a lead dioxide electrode. It is possible, and its industrial significance is extremely large.
[Brief description of the drawings]
FIG. 1 is a diagram showing a structure of an electrode according to the present invention.
[Explanation of symbols]
1 PVC case 2 Outer frame 3 Lead dioxide

Claims

An inexpensive sludgeless electrode characterized in that the current-carrying surface is made of lead dioxide and the other parts are covered with resin to prevent corrosion.

2. The inexpensive sludgeless electrode according to claim 1, wherein an outer frame portion of the current-carrying surface is formed of resin to be higher than the current-carrying surface to protect the current-carrying surface.

Inexpensive type sludge-less electrode according to claim 1 or 2 area of the energizing surface, characterized in that a plurality combined constitute the 0.5 m ² or less of the electrode.