JP2011111633A - Method for producing zinc based composite electroplated steel sheet - Google Patents
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本発明は、主に、家電・自動車・建材などに用いられる亜鉛系複合電気めっき鋼板の製造方法であり、特に、少ない亜鉛の使用量でも優れた耐食性及び外観均一性を有する亜鉛系複合電気めっき鋼板の製造方法に関するものである。 The present invention is a method for producing a zinc-based composite electroplated steel sheet mainly used for home appliances, automobiles, building materials, etc., and in particular, a zinc-based composite electroplating having excellent corrosion resistance and appearance uniformity even with a small amount of zinc used. The present invention relates to a method for manufacturing a steel sheet.
亜鉛系めっき鋼板は、良好な耐食性を有する点や、コストの点などから、現在、多くの用途に用いられているが、かかるめっき鋼板に用いられる亜鉛は、枯渇性資源の１つであり、今後の価格高騰も考えられることから、亜鉛めっき付着量の減量化や、亜鉛めっきに替わる表面処理皮膜の開発が要求されている。 Zinc-based plated steel sheets are currently used in many applications because of their good corrosion resistance and cost. However, zinc used in such plated steel sheets is one of the depleting resources. Since price increases in the future are also considered, it is required to reduce the amount of galvanized coating and to develop surface treatment coatings that can replace galvanizing.
素材鋼板上に亜鉛系めっき層を形成する技術としては、溶融めっき又は電気めっきが一般的である。ただし、溶融めっきによって亜鉛系めっき層の形成を行った場合、亜鉛系めっき付着量の減量化を図るためには、溶融亜鉛を鋼板上に付着させた後にワイピングによってめっき付着量を減らす必要があることから、低ラインスピードでの操業を余儀なくされ、十分な生産性が得られないという問題がある。加えて、溶融めっきでは、めっき付着量を減らした場合、均一な亜鉛系めっき層を得ることが非常に困難であるという問題がある。そのため、亜鉛系めっき付着量の減量化を目的とした場合には、電気量によってめっき付着量を制御でき、さらに、低付着量であっても比較的均一なめっき層を得ることができる電気めっきが有効であると考えられる。 As a technique for forming a zinc-based plating layer on a material steel plate, hot dipping or electroplating is generally used. However, when the zinc-based plating layer is formed by hot dipping, in order to reduce the amount of zinc-based plating, it is necessary to reduce the amount of plating by wiping after adhering hot-dip zinc on the steel sheet. For this reason, there is a problem that operation at a low line speed is forced and sufficient productivity cannot be obtained. In addition, in hot dipping, there is a problem that it is very difficult to obtain a uniform zinc-based plating layer when the amount of plating adhesion is reduced. Therefore, when the purpose is to reduce the amount of zinc-based plating, the amount of plating can be controlled by the amount of electricity, and furthermore, a relatively uniform plating layer can be obtained even with a low amount of adhesion. Is considered effective.
また、電気めっきにより亜鉛系めっき付着量の減量化を図る方法の１つとして、めっき層の耐食性を向上させる技術が挙げられる。めっき層の耐食性が向上すれば、めっき層を薄くすることができ、亜鉛の使用量の低減が可能となるからである。ここで、亜鉛系めっき層の耐食性を向上させる技術としては、例えば特許文献１に開示されているように、Ni、Co、Fe、Mn、Cr等を用いた亜鉛めっき層の合金化や、特許文献２に開示されているように、SiO2、TiO2等の分散粒子を含有させた亜鉛系めっき層を形成することが挙げられる。 Further, as one method for reducing the amount of zinc-based plating adhesion by electroplating, there is a technique for improving the corrosion resistance of the plating layer. This is because if the corrosion resistance of the plating layer is improved, the plating layer can be thinned and the amount of zinc used can be reduced. Here, as a technique for improving the corrosion resistance of the zinc-based plating layer, for example, as disclosed in Patent Document 1, alloying of a zinc plating layer using Ni, Co, Fe, Mn, Cr, etc. As disclosed in Document 2, a zinc-based plating layer containing dispersed particles such as SiO 2 and TiO 2 can be mentioned.
また、亜鉛系めっき付着量の減量化を図る別の方法としては、例えば特許文献３に開示されているように、Al及びCrから選択された少なくとも1種の金属の化合物、及びMo、W、Be、Ca、Mg、Sr、Ba、Ti、Zr、La、Yから選択された少なくとも1種の化合物を含む亜鉛系複合めっき層を形成することで、鋼板の耐食性を向上させる方法がある。 Further, as another method for reducing the amount of zinc-based plating adhesion, for example, as disclosed in Patent Document 3, at least one metal compound selected from Al and Cr, and Mo, W, There is a method of improving the corrosion resistance of a steel sheet by forming a zinc-based composite plating layer containing at least one compound selected from Be, Ca, Mg, Sr, Ba, Ti, Zr, La, and Y.
特許文献１に記載された技術では、初期段階では比較的高い耐食性が得られる場合が多い。しかしながら、合金化できる元素は、通常、亜鉛よりもイオン化傾向が低い元素（いわゆる貴な元素）であり、亜鉛部分が優先的に腐食されるため、一旦腐食が始まると、亜鉛及び素材鋼板の腐食が促進し、早期に鋼板の穴あき腐食が発生するという問題があった。 In the technique described in Patent Document 1, relatively high corrosion resistance is often obtained in the initial stage. However, elements that can be alloyed are usually elements that have a lower ionization tendency than zinc (so-called noble elements), and the zinc part is preferentially corroded, so once corrosion begins, the corrosion of zinc and the steel sheet However, there was a problem that perforated corrosion of the steel sheet occurred early.
また、特許文献２に記載された技術では、前記酸化物等の粒子を長期間安定的に分散させておくことが困難であるため、経時的にめっき浴組成が変化する結果、長期間安定して同一組成の亜鉛系めっき層を得ることができないという問題があった。 Further, in the technique described in Patent Document 2, it is difficult to stably disperse the particles such as the oxide for a long period of time. Thus, there is a problem that a zinc-based plating layer having the same composition cannot be obtained.
特許文献３では、所定の亜鉛系複合めっき層を形成するための方法として、（１）複合金属イオンとNO3 −、NO2 −、BrO3 −などの酸化剤を共存させためっき浴で電解を行い、Znと複合金属化合物とを共存させる方法、及び、（２）金属化合物をめっき浴中に分散懸濁させた浴中でめっきする方法が開示されている。 In Patent Document 3, as a method for forming a predetermined zinc-based composite plating layer, (1) electrolysis is performed in a plating bath in which a composite metal ion and an oxidizing agent such as NO 3 − , NO 2 − and BrO 3 − coexist. And a method in which Zn and a composite metal compound coexist, and (2) a method of plating in a bath in which a metal compound is dispersed and suspended in a plating bath.
しかしながら、上記（１）のめっき方法では、前記めっき浴の攪拌によって生じた噴流に起因して、前記めっき層にムラが発生するという問題があった。さらに、上記（２）のめっき方法では、特許文献２の場合と同様に、経時的に浴組成が変化し、それに伴い陰極電解で得られるめっき組成が変化する結果、長期間安定して同一組成のめっき層を得ることができないという問題があった。 However, the plating method (1) has a problem that unevenness occurs in the plating layer due to the jet generated by the stirring of the plating bath. Further, in the plating method of (2), as in the case of Patent Document 2, the bath composition changes over time, and as a result, the plating composition obtained by cathodic electrolysis changes accordingly. There was a problem that it was not possible to obtain a plating layer.
本発明の目的は、めっき条件の適正化を図ることで、めっき層の付着量を少なくした場合であっても、優れた耐食性及び外観均一性を有する亜鉛系複合電気めっき鋼板の製造方法を提供することにある。 An object of the present invention is to provide a method for producing a zinc-based composite electroplated steel sheet having excellent corrosion resistance and appearance uniformity even when the amount of adhesion of a plating layer is reduced by optimizing plating conditions There is to do.
本発明者らは、亜鉛含有めっき浴中で、素材鋼板を陰極として電解することで、前記素材鋼板の表面に亜鉛系複合電気めっき層を形成する亜鉛系複合電気めっき鋼板の製造方法について、上記の課題を解決するべく鋭意検討を重ねた結果、前記めっき浴に、0.2mol／L以上のZnイオンと、Al、Sc、Y、La、Ce、Nd、Zr及びVから選択される少なくとも一種の金属イオンと、0.0005〜0.1mol／Lの硝酸イオンとを含有させ、前記素材鋼板に対する前記めっき浴中のめっき液の相対流速を0.6m／s以上とすることで、めっき層の付着量を少なくした場合であっても、優れた耐食性及び外観均一性を有する亜鉛系複合電気めっき鋼板を製造できることを見出した。 In the zinc-containing plating bath, the present inventors electrolyze a raw steel plate as a cathode, thereby forming a zinc-based composite electroplated layer on the surface of the raw steel plate, the method for producing a zinc-based composite electroplated steel plate, As a result of intensive studies to solve the above problem, the plating bath contains at least one selected from 0.2 mol / L Zn ions and Al, Sc, Y, La, Ce, Nd, Zr and V. By containing metal ions and 0.0005 to 0.1 mol / L nitrate ions, and making the relative flow rate of the plating solution in the plating bath with respect to the material steel plate to be 0.6 m / s or more, the coating amount of the plating layer is reduced. It has been found that a zinc-based composite electroplated steel sheet having excellent corrosion resistance and appearance uniformity can be produced even in such a case.
本発明は、このような知見に基づきなされたもので、その要旨は以下の通りである。
（１）亜鉛含有めっき浴中で、素材鋼板を陰極として電解することで、前記素材鋼板の表面に亜鉛系複合電気めっき層を形成する亜鉛系複合電気めっき鋼板の製造方法であって、前記めっき浴は、0.2mol／L以上のZnイオンと、Al、Sc、Y、La、Ce、Nd、Zr及びVから選択される少なくとも一種の金属イオンと、0.0005〜0.1mol／Lの硝酸イオンとを含有し、前記素材鋼板に対する前記めっき浴中のめっき液の相対流速が0.6m／s以上であることを特徴とする亜鉛系複合電気めっき鋼板の製造方法。
The present invention has been made based on such findings, and the gist thereof is as follows.
(1) A method for producing a zinc-based composite electroplated steel sheet in which a zinc-based composite electroplated layer is formed on a surface of the material steel sheet by electrolysis using the material steel sheet as a cathode in a zinc-containing plating bath, wherein the plating The bath contains 0.2 mol / L or more of Zn ions, at least one metal ion selected from Al, Sc, Y, La, Ce, Nd, Zr and V, and 0.0005 to 0.1 mol / L of nitrate ions. A method for producing a zinc-based composite electroplated steel sheet, characterized in that a relative flow rate of a plating solution in the plating bath with respect to the material steel sheet is 0.6 m / s or more.
（２）前記めっき浴のpHが、1.5〜2.3の範囲である上記（１）記載の亜鉛系複合電気めっき鋼板の製造方法。 (2) The method for producing a zinc-based composite electroplated steel sheet according to (1) above, wherein the pH of the plating bath is in the range of 1.5 to 2.3.
（３）前記金属イオンの含有量は、合計で0.05mol／L以上である上記（１）又は（２）記載の亜鉛系複合電気めっき鋼板の製造方法。 (3) The method for producing a zinc-based composite electroplated steel sheet according to (1) or (2), wherein the total content of the metal ions is 0.05 mol / L or more.
（４）前記電解は、その電流密度が30A／dm2以上である上記（１）〜（３）のいずれか１項に記載の亜鉛系複合電気めっき鋼板の製造方法。 (4) The method for producing a zinc-based composite electroplated steel sheet according to any one of (1) to (3), wherein the electrolysis has a current density of 30 A / dm 2 or more.
本発明によれば、めっき層の付着量を少なくした場合であっても、優れた耐食性及び外観均一性を有する亜鉛系複合電気めっき鋼板の製造方法を提供することが可能となった。 ADVANTAGE OF THE INVENTION According to this invention, even if it was a case where the adhesion amount of a plating layer was decreased, it became possible to provide the manufacturing method of the zinc-type composite electroplating steel plate which has the outstanding corrosion resistance and external appearance uniformity.
以下、本発明の構成と限定理由を説明する。
本発明に従う亜鉛系複合電気めっき鋼板の製造方法は、亜鉛含有めっき浴中で、素材鋼板を陰極として電解することで、前記素材鋼板の表面に亜鉛系複合電気めっき層を形成する亜鉛系複合電気めっき鋼板の製造方法である。ここで、めっき方法を電気めっきにしたのは、めっき層の付着量を少なくするという目的に合致するためである。電気めっきに用いられる浴種については特に限定はせず、例えば、硫酸浴、塩化物浴、及びこれらの混合浴等を用いることができる。
Hereinafter, the configuration of the present invention and the reasons for limitation will be described.
The method for producing a zinc-based composite electroplated steel sheet according to the present invention includes a zinc-based composite electroplated layer in which a zinc-based composite electroplated layer is formed on the surface of the material steel sheet by electrolysis using the material steel sheet as a cathode in a zinc-containing plating bath It is a manufacturing method of a plated steel plate. Here, the reason why the plating method is electroplating is to meet the purpose of reducing the adhesion amount of the plating layer. The type of bath used for electroplating is not particularly limited, and for example, a sulfuric acid bath, a chloride bath, and a mixed bath thereof can be used.
そして、本発明は、前記めっき浴が、0.2mol／L以上のZnイオンと、Al、Sc、Y、La、Ce、Nd、Zr及びVから選択される少なくとも一種の金属イオンと、0.0005〜0.1mol／Lの硝酸イオンとを含有し、前記素材鋼板に対する前記めっき浴中のめっき液の相対流速が0.6m／s以上であることを特徴とする。 In the present invention, the plating bath comprises 0.2 mol / L or more of Zn ions, at least one metal ion selected from Al, Sc, Y, La, Ce, Nd, Zr and V, 0.0005 to 0.1 It contains mol / L nitrate ions, and the relative flow rate of the plating solution in the plating bath with respect to the material steel plate is 0.6 m / s or more.
めっき層の耐食性確保を目的として、Al、Sc、Y、La、Ce、Nd、Zr及びVの金属イオンをめっき浴中に含有せた場合、いずれも、Znに比べて電気化学的に卑な金属であり、水溶液中から金属としてZnと共析させるのは困難な元素である。ただし、Znを含まない酸性液中で陰極電解すれば、電解に伴う水素イオンの消費反応
2H＋＋2e−→H2
により陰極（素材鋼板）表面でpＨが上昇し、水酸化物として析出させることができると考えられる。
しかしながら、亜鉛含有めっき浴中では、Znの水素過電圧が大きく、上述の反応（2H＋＋2e−→H2）が大幅に抑制されるため、Znが金属として析出する亜鉛系複合めっきの場合、Al、Sc、Y、La、Ce、Nd、Zr及びVの金属イオンは水酸化物として析出されにくい。
For the purpose of ensuring the corrosion resistance of the plating layer, when metal ions of Al, Sc, Y, La, Ce, Nd, Zr and V are contained in the plating bath, all of them are electrochemically lower than Zn. It is a metal and is an element that is difficult to eutect with Zn as a metal from an aqueous solution. However, if cathodic electrolysis is performed in an acidic solution that does not contain Zn, the consumption reaction of hydrogen ions accompanying electrolysis
2H + + 2e - → H 2
It is considered that the pH rises on the surface of the cathode (material steel plate) and can be deposited as a hydroxide.
However, in the zinc-containing plating bath, the hydrogen overvoltage of Zn is large, and the above reaction (2H + + 2e − → H 2 ) is greatly suppressed, so in the case of zinc-based composite plating in which Zn is deposited as a metal, Al , Sc, Y, La, Ce, Nd, Zr, and V metal ions are hardly precipitated as hydroxides.
そのため、本発明では、前記めっき浴中に、硝酸イオンを含有させることで、Al、Sc、Y、La、Ce、Nd、Zr及びVから選択された少なくとも一種の金属を、主に水酸化物として亜鉛と共析させ、複合化させることが可能となる。これは、前記めっき浴中の陰極表面において、
NO3 −＋9H＋＋8e−→NH3+3H2O
等の反応が起こり、陰極表面近傍のpＨ（素材鋼板）を効果的に上昇させることができるためである。
Therefore, in the present invention, by containing nitrate ions in the plating bath, at least one metal selected from Al, Sc, Y, La, Ce, Nd, Zr and V is mainly a hydroxide. As a result, it can be co-deposited with zinc and combined. This is the cathode surface in the plating bath,
NO 3 − + 9H + + 8e − → NH 3 + 3H 2 O
This is because the reaction such as the above occurs and the pH (material steel plate) in the vicinity of the cathode surface can be effectively increased.
しかし、ただ硝酸イオンをめっき浴中に含有させるだけでは、形成された亜鉛系複合電気めっき層が不均一になりやすいという問題や、耐食性が悪化するという問題があった。
そのため、本願発明では、前記めっき浴中のZnイオン濃度及び硝酸イオン濃度の適正化を図り、さらに、前記素材鋼板（陰極）に対するめっき液の相対流速を制御することによって、陰極表面近傍のpH上昇を均一にできるため、耐食性及び外観均一性に優れた亜鉛系複合電気めっき層を形成することが可能となった。
However, there is a problem that the formed zinc-based composite electroplating layer is likely to be non-uniform and corrosion resistance is deteriorated simply by containing nitrate ions in the plating bath.
Therefore, in the present invention, by optimizing the Zn ion concentration and the nitrate ion concentration in the plating bath, and further by controlling the relative flow rate of the plating solution with respect to the material steel plate (cathode), the pH increase near the cathode surface Therefore, it is possible to form a zinc-based composite electroplating layer excellent in corrosion resistance and appearance uniformity.
また、本願発明に係る製造方法に用いられるめっき浴は、Znイオンを0.2mol／L以上含有する必要がある。0.2mol／L未満では、電解時にZnイオンの供給が不十分となり、いわゆる「めっき焼け」の状態となるため、めっき外観が不均一となるからである。 Moreover, the plating bath used for the manufacturing method according to the present invention needs to contain 0.2 mol / L or more of Zn ions. If it is less than 0.2 mol / L, the supply of Zn ions becomes insufficient during electrolysis, so-called “plating burn” occurs, and the plating appearance becomes uneven.
めっき浴としては、硫酸浴が望ましい。硫酸イオンは安定しており、陰極及び陽極のいずれにおいても電気化学反応が起こらず、有害なガス等の副生成物を生じないためである。 As the plating bath, a sulfuric acid bath is desirable. This is because sulfate ions are stable and no electrochemical reaction occurs at either the cathode or the anode, and no by-products such as harmful gases are produced.
さらに、前記めっき浴は、Al、Sc、Y、La、Ce、Nd、Zr及びVから選択される少なくとも一種の金属イオンを含有する必要がある。これらのイオンを含有することで、Zn主体のめっき層中に、前記金属イオンの化合物（主に水酸化物）が複合化されるため、純粋な亜鉛めっきよりも高い耐食性を得ることができるからである。 Furthermore, the plating bath needs to contain at least one metal ion selected from Al, Sc, Y, La, Ce, Nd, Zr and V. By containing these ions, the metal ion compound (mainly hydroxide) is compounded in the Zn-based plating layer, so that higher corrosion resistance than pure galvanization can be obtained. It is.
さらにまた、前記金属イオンの含有量は、合計で0.05mol／L以上であることが好ましい。0.05mol／L以上とすると、前記金属イオンの含有量が十分となり、金属化合物の複合化量が減少することがなく耐食性が向上するためである。 Furthermore, the total content of the metal ions is preferably 0.05 mol / L or more. This is because when the amount is 0.05 mol / L or more, the content of the metal ion becomes sufficient, and the amount of complexing of the metal compound does not decrease and the corrosion resistance is improved.
なお、前記金属イオン（Al、Sc、Y、La、Ce、Nd、Zr及びVから選択される少なくとも一種の金属イオン）のイオン源としては、酸性域で溶解するものであれば特に限定はしない。例えば、Al、Sc、Y、La、Ce及びNdのイオン源としては、これら金属の硫酸塩や、硝酸塩等があげられる。また、Zrのイオン源としては、Zrの硫酸塩や硝酸塩等の塩、又は、酸化硫酸ジルコニウム等があげられる。また、Vのイオン源としては，硫酸酸化バナジウム等があげられる。 The ion source of the metal ions (at least one metal ion selected from Al, Sc, Y, La, Ce, Nd, Zr and V) is not particularly limited as long as it dissolves in the acidic region. . For example, examples of the ion source of Al, Sc, Y, La, Ce, and Nd include sulfates and nitrates of these metals. Examples of the ion source of Zr include salts such as sulfate and nitrate of Zr, zirconium oxide sulfate, and the like. Examples of the V ion source include vanadium sulfate oxide.
また、前記めっき浴は、0.0005〜0.1mol／Lの硝酸イオンを含有する必要がある。前記硝酸イオンを含有することで、前記金属を主に水酸化物として亜鉛に共析・複合化させることが可能となる。ここで、前記硝酸イオンの濃度を0.0005〜0.1mol／Lの範囲としたのは、濃度が0.0005mol／L未満の場合、陰極（素材鋼板）表面近傍のpHを十分に上昇させることができず、めっき層中への前記金属イオンの複合化が進まないため、十分な耐食性を得ることができなくなるからであり、一方、濃度が0.1mol／Lを超えると、前記陰極表面近傍のpHが高くなりすぎるため、前記金属イオンの複合化が過度に進行し、前記めっき層の外観均一性が低下するからである。 The plating bath needs to contain 0.0005 to 0.1 mol / L of nitrate ions. By containing the nitrate ions, the metal can be co-deposited / complexed with zinc mainly as a hydroxide. Here, the concentration of the nitrate ion is in the range of 0.0005 to 0.1 mol / L because, when the concentration is less than 0.0005 mol / L, the pH in the vicinity of the surface of the cathode (material steel plate) cannot be sufficiently increased. This is because the composite of the metal ions in the plating layer does not proceed, so that sufficient corrosion resistance cannot be obtained. On the other hand, when the concentration exceeds 0.1 mol / L, the pH in the vicinity of the cathode surface is high. This is because the metal ions are excessively compounded and the appearance uniformity of the plating layer is lowered.
なお、前記硝酸イオンのイオン源としては、硝酸又は各種硝酸塩を用いることができる。好ましい硝酸塩の種類としては、例えば、ナトリウム塩、カリウム塩又は亜鉛塩等が挙げられる。 In addition, nitric acid or various nitrates can be used as the ion source of the nitrate ions. Examples of preferable nitrates include sodium salts, potassium salts, and zinc salts.
また、前記めっき浴中のめっき液の相対流速は0.6m／s以上である。前記めっき層を均一に形成することができるからであり、相対流速が0.6m／s未満の場合には、前記陰極表面近傍のｐH上昇が不均一になりやすく、陰極（素材鋼板）表面における前記めっき液の流速分布に対応したムラが発生するため、前記めっき層を均一に形成することができない。 The relative flow rate of the plating solution in the plating bath is 0.6 m / s or more. This is because the plating layer can be formed uniformly, and when the relative flow velocity is less than 0.6 m / s, the pH increase in the vicinity of the cathode surface tends to be non-uniform, and the surface of the cathode (material steel plate) Since unevenness corresponding to the flow velocity distribution of the plating solution occurs, the plating layer cannot be formed uniformly.
さらに、前記めっき浴のpHが、1.5〜2.3の範囲であることが好ましい。pHを1.5以上とすると、陰極（素材鋼板）表面近傍のpHを十分に上昇させることができ、めっき層中への前記金属イオンの複合化が進み、耐食性を十分に確保できるからであり、一方、pHを2.3以下とすると、陰極表面近傍で局部的なpＨの上昇が起こらないため、前記めっき層の外観均一性を確保できるからである。 Furthermore, the pH of the plating bath is preferably in the range of 1.5 to 2.3. If the pH is 1.5 or more, the pH in the vicinity of the surface of the cathode (material steel plate) can be sufficiently increased, and the complexing of the metal ions in the plating layer proceeds to ensure sufficient corrosion resistance. This is because, when the pH is 2.3 or less, local increase in pH does not occur in the vicinity of the cathode surface, so that the appearance uniformity of the plating layer can be ensured.
また、前記めっき浴の温度は、特に限定はしないが、夏場を考慮した温度制御の容易化の観点からは、40℃以上とすることが好ましい。さらに、前記めっき浴の温度が65℃を超えると蒸発量が増加するため、温度は40〜65℃の範囲とすることがより好適である。 The temperature of the plating bath is not particularly limited, but is preferably 40 ° C. or higher from the viewpoint of facilitating temperature control in consideration of summer. Furthermore, since the amount of evaporation increases when the temperature of the plating bath exceeds 65 ° C, the temperature is more preferably in the range of 40 to 65 ° C.
さらに、前記亜鉛系複合電気めっきにおける電解は、その電流密度が30A／dm2以上であることが好ましい。電流密度を30A／dm2以上とすると、めっき速度が速く、生産性が低下しないからである。なお、電流密度の上限は特に限定しない。Znイオン濃度及び相対流速を高くすることにより、例えば200A／dm2以上の高電流密度でもめっき可能だからである。 Further, the electrolysis in the zinc-based composite electroplating preferably has a current density of 30 A / dm 2 or more. This is because when the current density is 30 A / dm 2 or more, the plating rate is high and productivity does not decrease. The upper limit of the current density is not particularly limited. This is because, by increasing the Zn ion concentration and the relative flow rate, for example, plating can be performed even at a high current density of 200 A / dm 2 or more.
上述したところは、この発明の実施形態の一例を示したにすぎず、請求の範囲において種々の変更を加えることができる。 The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.
本発明の実施例について説明する。
（サンプル１〜６０）
素材鋼板である冷延鋼板の片面に対して、脱脂処理、酸洗処理を行った後、所定の亜鉛含有めっき浴中で、素材鋼板を陰極として電解することで、前記素材鋼板の表面に亜鉛系複合電気めっき層を形成し、サンプルとなる亜鉛系複合電気めっき鋼板を製造した。
なお、めっき浴の条件（亜鉛イオン濃度、亜鉛イオン源、金属イオンの種類（Al、Sc、Y、La、Ce、Nd、Zr、V）、金属イオン濃度、金属イオン源、硝酸イオン濃度、硝酸イオン源、めっき浴のpH及びめっき浴温度）、並びに、めっき条件（素材鋼板に対するのめっき液の相対流速及び電流密度）の詳細については、表１に示す。
Examples of the present invention will be described.
(Samples 1-60)
After performing a degreasing treatment and a pickling treatment on one side of a cold-rolled steel plate that is a raw steel plate, electrolysis is performed on the surface of the raw steel plate as a cathode in a predetermined zinc-containing plating bath. A system composite electroplating layer was formed to produce a zinc system composite electroplated steel sheet as a sample.
In addition, plating bath conditions (zinc ion concentration, zinc ion source, metal ion type (Al, Sc, Y, La, Ce, Nd, Zr, V), metal ion concentration, metal ion source, nitrate ion concentration, nitric acid The details of the ion source, the pH of the plating bath and the plating bath temperature) and the plating conditions (the relative flow rate and current density of the plating solution with respect to the material steel plate) are shown in Table 1.
（サンプル６１〜６４）
めっき浴の条件として、めっき浴中に、所定の金属イオン（Al、Sc、Y、La、Ce、Nd、Zr、V）を含有しないこと以外は、サンプル１〜６０と同様の条件によって、サンプルとなる亜鉛電気めっき鋼板を製造した。
なお、めっき浴の条件（亜鉛イオン濃度、亜鉛イオン源、硝酸イオン濃度、硝酸イオン源、めっき浴のpH及びめっき浴温度）、並びに、めっき条件（素材鋼板に対するのめっき液の相対流速及び電流密度）の詳細については、表１に示す。
(Samples 61-64)
As a condition of the plating bath, the sample is subjected to the same conditions as those of Samples 1 to 60 except that the plating bath does not contain a predetermined metal ion (Al, Sc, Y, La, Ce, Nd, Zr, V). A zinc electroplated steel sheet was produced.
The plating bath conditions (zinc ion concentration, zinc ion source, nitrate ion concentration, nitrate ion source, plating bath pH and plating bath temperature), and plating conditions (relative flow rate and current density of the plating solution with respect to the material steel plate) The details of) are shown in Table 1.
以上のようにして得られた各亜鉛系複合電気めっき鋼板又は亜鉛電気めっき鋼板のサンプル１〜６４について評価を行った。評価方法を以下に示す。 Evaluation was performed on samples 1 to 64 of each zinc-based composite electroplated steel sheet or zinc electroplated steel sheet obtained as described above. The evaluation method is shown below.
（評価方法）
（１）耐食性
各サンプル（サイズ：55mm×70mm）について、裏面と端面をシールした状態で、図１に示す腐食促進試験を行った。７日経過ごとに目視観察し、素材鋼板である冷延鋼板に発生した腐食（赤錆）の面積率が、評価面積（45mm×60mm）の5％以上となるまでに要する日数（日）計測することで、耐食性の評価を行った。結果を表１に示す。なお、計測した日数は、長くなるほど耐食性が高く優れた結果である。
また、後述する（２）外観均一性の評価が「×」であるサンプル１３〜１６、３１、３２、４７及び４８については、耐食性の評価を行わなかった。
(Evaluation methods)
(1) Corrosion resistance Each sample (size: 55 mm x 70 mm) was subjected to the corrosion promotion test shown in Fig. 1 in a state where the back surface and the end surface were sealed. Visually observe every 7 days, and measure the number of days (days) required for the area ratio of corrosion (red rust) occurring on the cold-rolled steel sheet, which is the material steel sheet, to be 5% or more of the evaluation area (45 mm x 60 mm). Thus, the corrosion resistance was evaluated. The results are shown in Table 1. Note that the longer the measured number of days, the higher the corrosion resistance and the better.
Moreover, the corrosion resistance evaluation was not performed about the samples 13-16, 31, 32, 47 and 48 whose (2) external appearance uniformity evaluation mentioned later is "x".
（２）外観均一性
各サンプルについて、形成しためっき層のムラの有無及びムラの程度を中心に目視観察を行うことによって、外観均一性の評価を行った。評価は、以下の基準に従って行い、結果を表１に示す。
◎：外観ムラが観察されない
○：軽微な外観ムラ（製品として十分に用いることができる程度）が観察される
×：ひどい外観ムラ（製品として用いることができない程度）が観察される
(2) Appearance uniformity The appearance uniformity of each sample was evaluated by visual observation centered on the presence or absence of unevenness of the formed plating layer and the degree of unevenness. Evaluation is performed according to the following criteria, and the results are shown in Table 1.
◎: Appearance unevenness is not observed ○: Appearance of minor appearance unevenness (a level that can be used as a product is sufficient) X: Severe appearance unevenness (a level that cannot be used as a product) is observed
（３）めっき層の付着量
各サンプルについて、蛍光Ｘ線分析により、付着量が既知の標準板測定により、得られた検量線を用いて、亜鉛系複合電気めっき層又は亜鉛電気めっき層の片面当たりのZn付着量（g／m2）を測定した。測定結果を表１に示す。
なお、本発明では、めっきの付着量低減を目的としているが、付着量が8g／m2以下程度であれば、有効に付着量を低減できているといえる。
(3) Adhesion amount of plating layer For each sample, one side of a zinc-based composite electroplating layer or zinc electroplating layer using a calibration curve obtained by standard plate measurement with a known adhesion amount by fluorescent X-ray analysis The amount of Zn deposited per g (g / m 2 ) was measured. The measurement results are shown in Table 1.
In the present invention, the object is to reduce the adhesion amount of plating. However, if the adhesion amount is about 8 g / m 2 or less, it can be said that the adhesion amount can be effectively reduced.
表１の結果から、本発明の範囲である実施例の各サンプル（５〜１２、１７〜３０、３５〜４６、５０〜６０）の赤錆発生日数は、いずれも42日以上であり、28日以下である比較例のサンプル（１〜４、３３、３４、４９及び６１〜６４）に比べて、いずれも高い耐食性を有していることがわかる。さらに、実施例の各サンプルは、比較例のサンプル（１３〜１６、３１、３２、４７及び４８）に比べて、いずれも外観均一性が優れていることがわかる。よって、本発明に係る実施例のサンプルは、いずれも、高い耐食性及び外観均一性を有することがわかる。
さらに、実施例及び比較例の各サンプルは、いずれも、めっき層の付着量が8g／m2以下であり、有効にめっき層の付着量を低減できていることがわかる。
From the results of Table 1, the number of days of red rust on each sample (5-12, 17-30, 35-46, 50-60) of the examples within the scope of the present invention is 42 days or more, and 28 days. It turns out that all have high corrosion resistance compared with the sample (1-4, 33, 34, 49 and 61-64) of the comparative example which is the following. Furthermore, it can be seen that each sample of the example is superior in appearance uniformity as compared with the samples of the comparative examples (13 to 16, 31, 32, 47 and 48). Therefore, it can be seen that all the samples of the examples according to the present invention have high corrosion resistance and appearance uniformity.
Further, each sample of the example and the comparative example has an adhesion amount of the plating layer of 8 g / m 2 or less, which shows that the adhesion amount of the plating layer can be effectively reduced.
本発明によれば、めっき層の付着量を少なくした場合であっても、優れた耐食性及び外観均一性を有し、将来の亜鉛めっき付着量の減量化の要求に対応した亜鉛系複合電気めっき鋼板の製造方法の提供が可能となった。 According to the present invention, a zinc-based composite electroplating that has excellent corrosion resistance and appearance uniformity even in the case where the amount of plating layer deposited is reduced, and that meets the demand for reducing the amount of zinc coating deposited in the future. It has become possible to provide a method for manufacturing steel sheets.
Claims (4)
前記めっき浴は、0.2mol／L以上のZnイオンと、Al、Sc、Y、La、Ce、Nd、Zr及びVから選択される少なくとも一種の金属イオンと、0.0005〜0.1mol／Lの硝酸イオンとを含有し、前記素材鋼板に対する前記めっき浴中のめっき液の相対流速が0.6m／s以上であることを特徴とする亜鉛系複合電気めっき鋼板の製造方法。 A method for producing a zinc-based composite electroplated steel sheet in which a zinc-based composite electroplated layer is formed on the surface of the material steel sheet by electrolyzing the steel sheet as a cathode in a zinc-containing plating bath,
The plating bath includes 0.2 mol / L or more of Zn ions, at least one metal ion selected from Al, Sc, Y, La, Ce, Nd, Zr and V, and 0.0005 to 0.1 mol / L of nitrate ions. And a relative flow rate of the plating solution in the plating bath with respect to the material steel plate is 0.6 m / s or more.
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| JP2016069663A (en) * | 2014-09-26 | 2016-05-09 | Ｊｆｅスチール株式会社 | Manufacturing method of zinc-based electric plating steel sheet excellent in fingerprint resistance and whiteness |
| KR20180015133A (en) | 2015-06-09 | 2018-02-12 | 신닛테츠스미킨 카부시키카이샤 | Surface treated steel plate |
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