JPH0369996B2 - - Google Patents
Info
- Publication number
- JPH0369996B2 JPH0369996B2 JP57207417A JP20741782A JPH0369996B2 JP H0369996 B2 JPH0369996 B2 JP H0369996B2 JP 57207417 A JP57207417 A JP 57207417A JP 20741782 A JP20741782 A JP 20741782A JP H0369996 B2 JPH0369996 B2 JP H0369996B2
- Authority
- JP
- Japan
- Prior art keywords
- plating
- plated surface
- plated
- chemical conversion
- conversion treatment
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000007747 plating Methods 0.000 claims description 54
- 239000000126 substance Substances 0.000 claims description 36
- 238000006243 chemical reaction Methods 0.000 claims description 35
- 229910000831 Steel Inorganic materials 0.000 claims description 28
- 239000010959 steel Substances 0.000 claims description 28
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 238000000576 coating method Methods 0.000 claims description 7
- 239000008151 electrolyte solution Substances 0.000 claims description 7
- 239000011248 coating agent Substances 0.000 claims description 6
- 238000009713 electroplating Methods 0.000 claims description 5
- 238000011282 treatment Methods 0.000 description 38
- 238000005260 corrosion Methods 0.000 description 19
- 230000007797 corrosion Effects 0.000 description 19
- 239000010408 film Substances 0.000 description 19
- 238000000034 method Methods 0.000 description 17
- 238000005868 electrolysis reaction Methods 0.000 description 12
- 239000000243 solution Substances 0.000 description 11
- 239000003792 electrolyte Substances 0.000 description 9
- 238000005406 washing Methods 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 239000013078 crystal Substances 0.000 description 6
- 238000005498 polishing Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000002161 passivation Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000007739 conversion coating Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 239000011701 zinc Substances 0.000 description 3
- 229910001335 Galvanized steel Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 238000005238 degreasing Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000008397 galvanized steel Substances 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 239000003973 paint Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 125000000129 anionic group Chemical group 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- -1 carbon ions Chemical class 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 231100001010 corrosive Toxicity 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- KFZAUHNPPZCSCR-UHFFFAOYSA-N iron zinc Chemical compound [Fe].[Zn] KFZAUHNPPZCSCR-UHFFFAOYSA-N 0.000 description 1
- RYZCLUQMCYZBJQ-UHFFFAOYSA-H lead(2+);dicarbonate;dihydroxide Chemical compound [OH-].[OH-].[Pb+2].[Pb+2].[Pb+2].[O-]C([O-])=O.[O-]C([O-])=O RYZCLUQMCYZBJQ-UHFFFAOYSA-H 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 238000011179 visual inspection Methods 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- LRXTYHSAJDENHV-UHFFFAOYSA-H zinc phosphate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LRXTYHSAJDENHV-UHFFFAOYSA-H 0.000 description 1
- 229910000165 zinc phosphate Inorganic materials 0.000 description 1
Description
この発明は非メツキ面の化成処理性の向上を図
つた片面電気メツキ鋼板の製造方法に関する。
片面電気メツキ鋼板は、自動車用鋼板の分野に
おいて、高度の合理化要求に応える素材として最
近広く用いられるようになつた。
自動車用等に用いられるメツキ鋼板は、一般に
電着塗装を行いさらに中塗り、上塗り塗装を施し
て使用されるため、これらの塗装下地処理として
リン酸塩処理等の化成処理が行われるが通例であ
る。
この化成処理を行うに際しては、周知の如く被
処理金属面を清浄化し、化成皮膜結晶の核発生や
成長を阻害しないような性状としておく必要があ
る。しかし片面電気メツキ鋼板の非メツキ面は、
片面電気メツキする過程でメツキ液により腐食
し、その結果表面に生じる腐食生成物が前記化成
皮膜結晶の核発生等を阻害するので、非メツキ面
の良好な化成処理性を得るためには上記腐食生成
物の生成を防止するか又は生成した腐食物を化成
処理前に除去しておかなければならない。
上記非メツキ面の腐食生成物に対する対策とし
ては従来一般に、生成した腐食生成物をメツキ後
に除去する方法が行われている。すなわち、上記
腐食生成物の付着状態が極めて強固で、通常の簡
単な水洗等では完全除去が困難であるので、メ
ツキの後処理として特別に非メツキ面を機械的に
研磨する工程を設けて表面黄色層や腐食残存物等
を除去する方法、メツキ後酸中で電解酸洗して
腐食生成物を除去し、次いでZn等の特定の金属
の極微量を表面に分散して析出させてメツキし、
化成処理性を向上する方法等である。
しかしの表面研磨の方法では腐食生成物の完
全除去のためには多段の研磨設備を必要としコス
トが嵩むばかりでなく、仮に除去できたとしても
研磨の程度によつて化成処理の際の化成結晶の大
きさにムラを生じ化成処理性が損なわれるという
問題、また必然的に研磨痕が残り、程度によつて
は塗装性（塗装仕上がりの外観および耐食性）に
影響を及ぼす問題がある。また研磨後の水洗の際
に非メツキ面に残存する水膜により水酸化物の黄
色錆を生じ、このため化成処理性が劣化するとい
う問題もある。
の特定金属をメツキする方法は、非メツキ面
にのみ特定金属を析出させるためには、例えばラ
ジアルセルの如き特定の設備を必要とし経費が嵩
むばかりでなく、通常酸性のメツキ液が用いられ
るので、メツキ槽中で本来の片面メツキ皮膜の溶
解あるいは変色等が起こり、片面電気メツキ鋼板
の商品価値を大きく損じる恐れが多分にある。
そこで上記の従来方法に代えて非メツキ面
に、よりすぐれた化成処理性を付与し得るような
片面電気メツキ鋼板の製造方法の開発が望まれて
いた。
本発明は上記要望に応えるためになされたもの
であつて、従来の非メツキ面に生成した腐食生成
物を除去する方法に代えて、メツキ過程で非メツ
キ面にもメツキを施して腐食の発生を防止し、メ
ツキ後に非メツキ面を陽極とする電解処理を行つ
て前記メツキ皮膜を除去して非メツキ面の化成処
理性の向上を図るようにした片面電気メツキ鋼板
の製造方法を提供するものである。
本発明者らは、メツキ液中での非メツキ面の腐
食を防止して清浄化を保持し、化成処理性の向上
を図るべく種々実験、研究を重ねた。その結果、
メツキに際して非メツキ面にも陰極電流を流して
薄目付量のメツキを施すことにより、メツキ液中
での非メツキ面の腐食を完全に防止することがで
き、さらにメツキ処理後に非メツキ面を陽極とし
て電解することによつて前記非メツキ面のメツキ
皮膜を除去し得るとともに除去後の非メツキ面に
不働態皮膜が形成され、メツキ後の非メツキ面の
化成処理性を冷延鋼板並のすぐれた水準に保ち得
るという新たな事実を知見した。
非メツキ面にも陰極電流を流してメツキを施
し、さらにメツキ後に非メツキ面を陽極として電
解処理しようとするに際して、上記非メツキ面の
薄目付量のメツキを得るために必要とされる最適
の陰極電流密度は、ラインスピード、液流速、温
度、PH等のメツキ条件の変化により変動がある
が、基本的には次のような考え方のもとに決定さ
れる。すなわち、メツキ槽でメツキが行われるの
は、通過する鋼板に相対する陽電極が存在する区
間であり、存在しない区間ではメツキ液による腐
食が起こる。そこでこの腐食を防止するために必
要とするメツキの目付量は、最終メツキ槽出側の
陽極の存在しない区間において、メツキ皮膜がメ
ツキ液によりなくならない程度の薄目付量で十分
であり、前記薄目付量を得るに要する陰極電流密
度を最適とする。この理由は、前記メツキ皮膜
は、メツキ後非メツキ面を陽極とする電解処理に
より除去するものであるが、このメツキ皮膜が薄
目付である程電解による除去は容易であり、かつ
電解に要する陽極電流密度も小さくて済み、電力
費用の低減にもつながり有利となるからである。
次にメツキ後、非メツキ面を陽極とし、電解液
組成および液流速、PH、電流密度等の電解条件を
ラインスピードに対応して適正として電解する
と、非メツキ面に金属の溶解反応および激しい酸
素発生反応を生じ、これらの反応により非メツキ
面のメツキ皮膜は除去され、また上記電解によつ
てメツキ皮膜除去後の非メツキ面に不働態皮膜が
生成される。この不働態化によつて、電解後の水
洗時に発生する錆層の生成が効果的に阻止され
る。またこの不働態化された非メツキ面は化成処
理に際して、酸化物の緻密な薄膜である不働態皮
膜に不均一、局所的な溶解を生じ、アノード部、
カソード部の固定がなく、化成皮膜結晶の核発生
や成長がスムーズに進行し、良好な化成処理性を
示すことが明らかとなつた。
本発明は上記知見に基いてなされたもので、そ
の要旨とするところは、片面電気メツキ鋼板の製
造において、非メツキ面にも陰極電流を流して薄
目付量の電気メツキを行い、しかる後前記非メツ
キ面をPH８〜12の電解液中において陽極として電
解し、前記電解により非メツキ面に薄メツキ皮膜
を溶解・除去するとともに、非メツキ鋼板表面を
不働態化することにより、非メツキ面の化成処理
性を向上させることを特徴とする片面電気メツキ
鋼板の製造方法にある。
次に本発明の片面電気メツキ鋼板の製造方法を
図面に基いて説明する。
第１図は本発明方法の一例を示す片面電気メツ
キラインの模式図である。図において、アンコイ
ラー２から連続的に送り出される鋼板１は脱脂槽
３、水洗槽４を経て、メツキ槽５に入りメツキ面
に所要の片面電気メツキを施すとともに非メツキ
面にも薄目付量をメツキを施した後、水洗槽６を
経て処理槽７に入る。処理槽７において非メツキ
面を陽極とする電解を行つた後、水洗槽８、乾燥
装置９を経て再びコイラー１０でコイルに巻取ら
れて次工程に送られる。
第２図は上記メツキ槽５の縦断正面図であり、
図において、鋼板１は上側をメツキ面、下側を非
メツキ面として陰極に印加されて、槽５内のメツ
キ液１１中において上下に配設された陽電極１
２，１３の間の通板する。その際、上側の陽電極
１２からは常法に従つて所要の陰極電流（矢印１
４で示す）を流して所要の片面メツキを行うとと
もに、下側の陽電極１３からは非メツキ面の腐食
防止に必要な陰極電流（矢印１５で示す）を流し
て薄目付量のメツキを行うのである。
第１図に示した処理槽７中の電解液としては常
用のNa2SO4、Na2SO4＋NaOH、Na2CO3、
Na2B2O7等の溶液が用いられ、Na2SO4、
Na2CO3、Na2B2O7の濃度としては５〜15％程度
が好ましい。電解液の温度は35〜50℃程度が適当
である。電解液のPHは、非メツキ面を不働態化す
ることにより化成処理性を改善するために８〜12
の範囲内とする必要がある。PHが８未満になるか
又は12を超えると、非メツキ面の薄目付のメツキ
膜が溶解除去された後鋼板表面が不働態化するま
でに若干の溶解反応が生じ、鋼板自身の表面が溶
解され化成処理性を劣化させる。鋼板表面が溶解
されると化成処理性が劣化する原因については定
かでないが、化成処理も鋼板の溶解反応を利用し
たものであるから、電解により鋼板表面を溶解す
ると、“溶け易い”活性点を失なつてしまうこと
になり、化成皮膜生成がスムーズに進行しなくな
るためと考えらえる。
電解液のアニオン種（SO4 2-、CO3 2-、
NO3 -etc.）によつて不働態化のし易さにある程
度の差異はあるものの、一義的にはPHを上記範囲
に限定することにより、鋼板表面を速やかに不働
態化して化成処理性を良好に保つことが可能であ
る。また、電流密度は非メツキ面から薄メツキ皮
膜の除去および非メツキ面の不働態化に必要な電
解電流が得られる密度とする必要がある。この所
要の電流密度は、電解液の組成、PH、ラインスピ
ード等の電解条件により種々異なるが、例えば電
解液が15％、Na2SO4＋NaOH、PH８、ラインス
ピード100ｍ／ｓの電解条件では、80A／ｄm2の
電流密度を必要とするが、上記と同じラインスピ
ードで電解液に電解効率（通電流に対する不働態
化に要する電流の割合）の高い炭素イオンを含む
10％Na2CO3溶液を用いてPH12とすれば、所要の
電流密度は60A／ｄm2で十分となる。また同様の
ラインスピードで電解液に10％Na2SO4＋10％
Na2CO3を用いPH12とすれば、さらに電解効率は
高くなり40A／ｄm2の電流密度で十分となる。
次に本発明の実施例について説明する。
片面電気鉄−亜鉛メツキ鋼板の製造ラインにお
いて、メツキ浴組成を〔Fe2+〕／〔Fe2+〕＋〔Zn2+〕＝
0.65、
PH２、浴温50℃として900mm巾×0.8mm厚の冷延鋼
板に目付量35ｇ／m2の片面電気鉄−亜鉛メツキを
施すとともに、非メツキ面に目付量８ｇ／m2の同
様の薄メツキを施した後、第１図の処理槽７にて
非メツキ面を陽極とし、電解液組成、PHを種々に
変えてラインスピード100ｍ／ｓで、非メツキ面
の不働態化に十分な電流密度の電解電流を通して
電解処理を行い本発明例の供試材１〜４を得た。
また比較のため、上記と同様に片面電気鉄−亜鉛
メツキ鋼板を製造し、非メツキ面にメツキを施さ
ず、かつ電解処理を行わないで比較例の供試材５
を得た。ひきつづいて上記各供試材を市販のリン
酸亜鉛処理剤（BT3030商品名、日本パーカー社
製）に浸漬して化成処理を行い化成処理性の良否
を調査した。上記各供試材のメツキ後または電解
後の外観検査および化成処理性の調査結果を第１
表にまとめて示す。
The present invention relates to a method for producing a single-sided electroplated steel sheet that improves the chemical conversion treatment properties of the non-plated surface. Single-sided electroplated steel sheets have recently become widely used in the field of automotive steel sheets as a material that meets the demands for high-level rationalization. Plated steel sheets used for automobiles etc. are generally electroplated and then coated with intermediate and top coats, so chemical conversion treatments such as phosphate treatment are usually performed as a base treatment for these coatings. be. When carrying out this chemical conversion treatment, as is well known, it is necessary to clean the metal surface to be treated and to make it in a state that does not inhibit the generation or growth of nuclei of chemical conversion coating crystals. However, the non-plated side of a single-sided electroplated steel sheet is
In the process of single-sided electroplating, the plating solution causes corrosion, and the resulting corrosion products generated on the surface inhibit nucleation of the chemical conversion coating crystals, so in order to obtain good chemical conversion treatment properties on the non-plated surface, The formation of products must be prevented or the corrosives formed must be removed before chemical conversion treatment. Conventionally, as a countermeasure against the corrosion products on the unplated surface, a method has been generally used in which the generated corrosion products are removed after plating. In other words, the adhesion of the above-mentioned corrosion products is extremely strong and it is difficult to completely remove them by normal simple washing with water. Therefore, as a post-plating treatment, a special process of mechanically polishing the non-plated surface is carried out to remove the corrosion products. A method for removing yellow layers and corrosion residues, etc. After plating, electrolytic pickling in acid is performed to remove corrosion products, and then extremely small amounts of specific metals such as Zn are dispersed and precipitated on the surface for plating. ,
This is a method of improving chemical conversion treatment properties. However, the surface polishing method requires multi-stage polishing equipment to completely remove corrosion products, which not only increases costs, but even if it can be removed, chemical crystals may be generated during chemical conversion treatment depending on the degree of polishing. There is a problem that the size of the paint becomes uneven, impairing chemical conversion treatment properties, and that polishing marks inevitably remain, which, depending on the degree, affects the paintability (the appearance and corrosion resistance of the finished paint). There is also the problem that during water washing after polishing, a water film remaining on the non-plated surface causes yellow rust of hydroxide, which deteriorates chemical conversion treatment properties. This method of plating specific metals requires specific equipment such as a radial cell, which increases costs, in order to deposit specific metals only on non-plated surfaces, and typically requires an acidic plating solution. There is a great possibility that the original single-sided plating film may dissolve or change color in the plating tank, and the commercial value of the single-sided electroplated steel sheet will be greatly impaired. Therefore, it has been desired to develop a method for manufacturing single-sided electroplated steel sheets that can impart better chemical conversion treatment properties to the non-plated surface in place of the above-mentioned conventional methods. The present invention was made in response to the above-mentioned needs, and instead of the conventional method of removing corrosion products generated on non-plated surfaces, the present invention also applies plating to non-plated surfaces during the plating process to prevent corrosion from occurring. To provide a method for producing a single-sided electroplated steel sheet, which prevents the above-mentioned plating and removes the plating film by performing electrolytic treatment using the non-plated surface as an anode after plating, thereby improving the chemical conversion treatment property of the non-plated surface. It is. The present inventors have repeatedly conducted various experiments and studies in order to prevent corrosion of the non-plated surface in the plating solution, maintain cleanliness, and improve chemical conversion treatment properties. the result,
By applying a cathode current to the non-plated surface during plating and applying a thin layer of plating to the non-plated surface, corrosion of the non-plated surface in the plating solution can be completely prevented. By electrolyzing the plated surface as described above, the plating film on the non-plated surface can be removed, and a passive film is formed on the non-plated surface after removal. We have discovered a new fact that it is possible to maintain a certain level at a certain level. When plating is applied to the non-plated surface by passing a cathode current, and the non-plated surface is then electrolytically treated using the non-plated surface as an anode, it is necessary to apply the optimum The cathode current density varies depending on changes in plating conditions such as line speed, liquid flow rate, temperature, and pH, but it is basically determined based on the following concept. That is, plating is performed in the plating tank in the section where the positive electrode facing the passing steel plate exists, and in the section where the positive electrode does not exist, corrosion occurs due to the plating solution. Therefore, in order to prevent this corrosion, the amount of plating required is such that the plating film is not lost by the plating solution in the section where the anode does not exist on the exit side of the final plating tank. Optimize the cathode current density required to obtain the coating amount. The reason for this is that the plating film is removed by electrolytic treatment using the non-plated surface as an anode after plating, but the thinner the plating film, the easier it is to remove by electrolysis, and the anode required for electrolysis is This is because the current density only needs to be small, which is advantageous as it leads to a reduction in power costs. Next, after plating, when electrolysis is performed using the unplated surface as an anode and electrolytic conditions such as electrolyte composition, liquid flow rate, PH, current density, etc. are appropriate according to the line speed, metal dissolution reaction occurs on the unplated surface. Generative reactions occur, and the plating film on the non-plated surface is removed by these reactions, and a passive film is generated on the non-plated surface after the plating film has been removed by the electrolysis. This passivation effectively prevents the formation of a rust layer that occurs during washing with water after electrolysis. In addition, during chemical conversion treatment, this passivated non-plated surface causes uneven and local dissolution of the passivation film, which is a dense thin film of oxide, resulting in
It has become clear that the cathode part is not fixed, nucleation and growth of chemical conversion coating crystals proceed smoothly, and good chemical conversion treatment properties are exhibited. The present invention has been made based on the above findings, and the gist thereof is that in the production of single-sided electroplated steel sheets, a cathode current is also applied to the non-plated surface to conduct electroplating with a light coating weight, and then the The non-plated surface is electrolyzed as an anode in an electrolytic solution with a pH of 8 to 12, and the electrolysis dissolves and removes the thin plating film on the non-plated surface, as well as passivates the surface of the non-plated steel sheet. The present invention provides a method for producing a single-sided electroplated steel sheet, which is characterized by improving chemical conversion treatment properties. Next, a method for producing a single-sided electroplated steel sheet according to the present invention will be explained based on the drawings. FIG. 1 is a schematic diagram of a single-sided electroplating line showing an example of the method of the present invention. In the figure, a steel plate 1 is continuously sent out from an uncoiler 2, passes through a degreasing tank 3, a washing tank 4, and then enters a plating tank 5, where the plating surface is electroplated to the required degree, and the non-plated surface is also plated with a light coating weight. After that, it passes through a washing tank 6 and enters a treatment tank 7. After electrolysis is performed using the non-plated surface as an anode in the processing tank 7, the material passes through a washing tank 8 and a drying device 9, and is again wound into a coil by a coiler 10 and sent to the next process. FIG. 2 is a longitudinal sectional front view of the plating tank 5,
In the figure, a steel plate 1 has a plating surface on the upper side and a non-plating surface on the lower side, and a voltage is applied to the cathode, and the positive electrodes 1 are placed above and below in the plating liquid 11 in the tank 5.
Thread the board between 2 and 13. At that time, the required cathode current (arrow 1
4) is applied to perform the required one-side plating, and at the same time, a cathode current (indicated by arrow 15) necessary to prevent corrosion of the non-plated surface is applied from the lower anode 13 to perform plating with a light coating weight. It is. The electrolytes in the treatment tank 7 shown in FIG. 1 include commonly used Na 2 SO 4 , Na 2 SO 4 +NaOH, Na 2 CO 3 ,
Solutions such as Na 2 B 2 O 7 are used, Na 2 SO 4 ,
The concentration of Na 2 CO 3 and Na 2 B 2 O 7 is preferably about 5 to 15%. The appropriate temperature of the electrolyte is about 35 to 50°C. The pH of the electrolyte is set between 8 and 12 to improve chemical conversion properties by passivating the non-plated surface.
Must be within the range. When the pH becomes less than 8 or exceeds 12, a slight dissolution reaction will occur after the thin plating film on the non-plated surface is dissolved and removed until the steel plate surface becomes passivated, and the surface of the steel plate itself will dissolve. and deteriorates chemical conversion treatment properties. It is not clear why chemical conversion treatment deteriorates when the surface of a steel sheet is melted, but since chemical conversion treatment also utilizes the melting reaction of the steel sheet, melting the surface of the steel sheet by electrolysis removes "easily soluble" active points. This is thought to be due to the fact that the chemical conversion film formation does not proceed smoothly. Anionic species in the electrolyte (SO 4 2- , CO 3 2- ,
Although there are some differences in the ease of passivation depending on the pH value (NO 3 - etc.), primarily by limiting the PH to the above range, the surface of the steel sheet can be quickly passivated and chemical conversion treatment is improved. It is possible to keep it in good condition. Further, the current density needs to be such that the electrolytic current necessary for removing the thin plating film from the non-plated surface and passivating the non-plated surface can be obtained. This required current density varies depending on the electrolytic conditions such as the composition of the electrolytic solution, PH, line speed, etc., but for example, under the electrolytic conditions where the electrolytic solution is 15%, Na 2 SO 4 + NaOH, PH 8, and the line speed is 100 m/s, A current density of 80 A/dm 2 is required, but at the same line speed as above, the electrolyte contains carbon ions with high electrolytic efficiency (ratio of current required for passivation to passed current).
If the pH is set to 12 using a 10% Na 2 CO 3 solution, a required current density of 60 A/dm 2 is sufficient. Also, at the same line speed, add 10% Na 2 SO 4 + 10% to the electrolyte.
If Na 2 CO 3 is used and the pH is set to 12, the electrolytic efficiency will further increase and a current density of 40 A/dm 2 will be sufficient. Next, examples of the present invention will be described. In the production line for single-sided electric iron-galvanized steel sheets, the plating bath composition is [Fe 2+ ]/[Fe 2+ ] + [Zn 2+ ]=
0.65, PH2, bath temperature 50℃, one side of a cold-rolled steel plate of 900 mm width x 0.8 mm thickness was plated with electric iron-zinc with a basis weight of 35 g/ m2 , and the non-plated side was plated with electric iron and zinc with a basis weight of 8 g/ m2. After applying thin plating, the non-plated surface was used as an anode in the treatment tank 7 shown in Fig. 1, and the electrolyte composition and pH were changed in various ways at a line speed of 100 m/s to achieve a sufficient level to passivate the non-plated surface. Electrolytic treatment was performed by passing an electrolytic current at a current density to obtain test materials 1 to 4 of examples of the present invention.
For comparison, a single-sided electric iron-galvanized steel sheet was manufactured in the same manner as above, and the non-plated surface was not plated and the electrolytic treatment was not performed.
I got it. Subsequently, each of the above test materials was immersed in a commercially available zinc phosphate treatment agent (BT3030 trade name, manufactured by Nippon Parker Co., Ltd.) for chemical conversion treatment, and the quality of the chemical conversion treatment was investigated. The results of the visual inspection after plating or electrolysis and chemical conversion treatment of each of the above sample materials were evaluated in the first stage.
They are summarized in the table.
【表】
表中、外観評価欄の○印は銀白色の美麗な不働
態皮膜が生成され良好なもの、×印は腐食生成物
による黒変個所が多く不良なものを示す。また化
成処理性評価欄の○印は化成結晶が微細でかつ緻
密に生成し良好なもの、×印は化成結晶が粗大で
かつまばらで不良なものを示す。
表に見る通り、比較例５はメツキ工程において
非メツキ面にメツキを施さなかつたため非メツキ
面に腐食生成物が多く付着して汚染されており、
化成処理性が不良であつた。また、比較例の１〜
５では電解液のPHが本発明の範囲外であるため全
部化成処理性が不良となつた。これに対し本発明
例はいずれも電解により非メツキ面のメツキ皮膜
が完全に除去されしかも除去後の非メツキ面には
美麗な不働態皮膜が生成され、良好な化成処理性
が得られた。本発明例１は電解液に15％の
Na2SO4溶液を用いた代表的な電解例であり、本
発明例２、３は電解液に電解効率の高い炭酸イオ
ンを含む溶液を用いて電流密度を低減させて電力
費用の節減を図つた電解例、本発明例４は電解液
に５％Na2B2O7溶液を用いて電流密度の低減を
図つた例である。
以上の説明から明らかなように、本発明の片面
電気メツキ鋼板の製造方法は、メツキ工程におい
て非メツキ面にも薄目付量のメツキを施し、しか
る後非メツキ面を陽極とする電解処理を行うとい
う新規な方法で、清浄な非メツキ面が得られると
ともに、非メツキ面を不働態化することによつて
化成処理性にすぐれた非メツキ面を有する片面電
気メツキ鋼板が得られるので、片面電気メツキ鋼
板の品質の向上、製造コストの低減に顕著な効果
を発揮する。[Table] In the table, the mark ○ in the appearance evaluation column indicates a good product with a beautiful silver-white passive film, and the mark x indicates a poor product with many black spots due to corrosion products. Further, in the chemical conversion treatment evaluation column, the mark ○ indicates that the chemical crystals are fine and densely formed and is good, and the mark x indicates that the chemical crystals are coarse and sparse and poor. As shown in the table, in Comparative Example 5, the non-plated surface was not plated in the plating process, so the non-plated surface was contaminated with a lot of corrosion products adhering to it.
Chemical conversion treatment properties were poor. Also, Comparative Examples 1-
In No. 5, the pH of the electrolytic solution was outside the range of the present invention, so the chemical conversion treatment properties were poor in all cases. On the other hand, in all the examples of the present invention, the plating film on the non-plated surface was completely removed by electrolysis, and a beautiful passive film was formed on the non-plated surface after removal, and good chemical conversion treatment properties were obtained. Inventive Example 1 has a concentration of 15% in the electrolyte.
This is a typical electrolysis example using a Na 2 SO 4 solution, and Examples 2 and 3 of the present invention use a solution containing carbonate ions with high electrolysis efficiency in the electrolyte solution to reduce the current density and reduce power costs. Inventive Example 4 is an example in which a 5% Na 2 B 2 O 7 solution was used as the electrolytic solution to reduce the current density. As is clear from the above description, in the method for manufacturing single-sided electroplated steel sheets of the present invention, the non-plated surface is also plated with a light coating weight in the plating process, and then electrolytic treatment is performed using the non-plated surface as the anode. With this new method, a clean non-plated surface can be obtained, and by passivating the non-plated surface, a single-sided electroplated steel sheet with a non-plated surface with excellent chemical conversion properties can be obtained. It has a remarkable effect on improving the quality of plated steel sheets and reducing manufacturing costs.
第１図は本発明方法を実施する連続片面電気メ
ツキラインの一例を示す模式図、第２図は本発明
方法におけるメツキ槽の一例を示す説明図で縦断
正面図である。
１：鋼板、２：アンコイラー、３：脱脂槽、
４，６，８：水洗槽、７：処理槽、９：乾燥装
置、１０：リコイラー、１１：メツキ液、１２，
１３：陽電極、１４，１５：陰極電流。
FIG. 1 is a schematic diagram showing an example of a continuous single-sided electroplating line for carrying out the method of the present invention, and FIG. 2 is an explanatory diagram showing an example of a plating tank in the method of the present invention, and is a longitudinal sectional front view. 1: Steel plate, 2: Uncoiler, 3: Degreasing tank,
4, 6, 8: Washing tank, 7: Processing tank, 9: Drying device, 10: Recoiler, 11: Plating liquid, 12,
13: positive electrode, 14, 15: cathode current.
Claims (1)
キ面にも陰極電流を流して薄目付量の電気メツキ
を行い、しかる後前記非メツキ面をPH８〜12の電
解液中において陽極として電解し、前記電解によ
り非メツキ面の薄メツキ皮膜を溶解・除去すると
ともに、非メツキ鋼板表面を不働態化することに
より、非メツキ面の化成処理性を向上させること
を特徴とする片面電気メツキ鋼板の製造方法。1. In the production of single-sided electroplated steel sheets, a cathode current is also applied to the non-plated surface to perform electroplating with a light coating weight, and then the non-plated surface is electrolyzed as an anode in an electrolytic solution with a pH of 8 to 12, and the electrolytic A method for producing a single-sided electroplated steel sheet, characterized in that the thin plating film on the non-plated surface is dissolved and removed, and the surface of the non-plated steel sheet is made passivated, thereby improving the chemical conversion treatability of the non-plated surface.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20741782A JPS5996292A (en) | 1982-11-25 | 1982-11-25 | Production of steel sheet electroplated on one side |
| US06/554,725 US4464232A (en) | 1982-11-25 | 1983-11-23 | Production of one-side electroplated steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20741782A JPS5996292A (en) | 1982-11-25 | 1982-11-25 | Production of steel sheet electroplated on one side |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5996292A JPS5996292A (en) | 1984-06-02 |
| JPH0369996B2 true JPH0369996B2 (en) | 1991-11-06 |
Family
ID=16539402
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP20741782A Granted JPS5996292A (en) | 1982-11-25 | 1982-11-25 | Production of steel sheet electroplated on one side |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5996292A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59126788A (en) * | 1983-01-07 | 1984-07-21 | Sumitomo Metal Ind Ltd | One side electroplating method |
| JPH02271000A (en) * | 1989-04-12 | 1990-11-06 | Nippon Steel Corp | Production of one-side zinc or zinc alloy electroplated steel sheet |
| AT393513B (en) * | 1989-07-24 | 1991-11-11 | Andritz Ag Maschf | METHOD FOR ONE-SIDED ELECTROLYTIC COATING OF FLAT WORKPIECE FROM STEEL |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58221290A (en) * | 1982-06-17 | 1983-12-22 | Nippon Steel Corp | Method for protecting iron surface of steel sheet electroplated on one side |
-
1982
- 1982-11-25 JP JP20741782A patent/JPS5996292A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58221290A (en) * | 1982-06-17 | 1983-12-22 | Nippon Steel Corp | Method for protecting iron surface of steel sheet electroplated on one side |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5996292A (en) | 1984-06-02 |
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