JPH0689473B2 - Anti-corrosion steel plate with excellent corrosion resistance - Google Patents
Anti-corrosion steel plate with excellent corrosion resistanceInfo
- Publication number
- JPH0689473B2 JPH0689473B2 JP2107338A JP10733890A JPH0689473B2 JP H0689473 B2 JPH0689473 B2 JP H0689473B2 JP 2107338 A JP2107338 A JP 2107338A JP 10733890 A JP10733890 A JP 10733890A JP H0689473 B2 JPH0689473 B2 JP H0689473B2
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- Prior art keywords
- chromium
- plating
- zinc
- corrosion
- layer
- Prior art date
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Description
【発明の詳細な説明】 （産業上の利用分野） 本発明は、自動車をはじめとする運輸車両用材料ならび
に建築用材料、電気機器用材料等に使用される耐食性に
優れた防錆鋼板に関するものである。Description: TECHNICAL FIELD The present invention relates to a corrosion-resistant steel sheet having excellent corrosion resistance, which is used as materials for transportation vehicles including automobiles, materials for construction, materials for electric devices, and the like. Is.
（従来の技術） 従来亜鉛または亜鉛を主体とする合金をめっきした鋼板
が防錆用途に広く用いられているが、これは亜鉛のもつ
犠牲防食作用が基本となっている。しかしながら亜鉛ま
たは亜鉛を主体とする合金をめっきした鋼板は、腐食環
境下、特に塩分の存在する条件下では亜鉛の溶出はかな
り速く、長期にわたって鋼板の防錆効果を維持すること
ができない。(Prior Art) Conventionally, a steel sheet plated with zinc or an alloy mainly containing zinc has been widely used for rust prevention applications, but this is based on the sacrificial anticorrosion action of zinc. However, in a steel sheet plated with zinc or an alloy mainly containing zinc, zinc is considerably eluted in a corrosive environment, particularly under a condition where salt is present, and the rust preventive effect of the steel sheet cannot be maintained for a long period of time.
その理由は、第一亜鉛は鉄にくらべて電気化学的にかな
り卑であるため、鉄とのカップリング電流が過剰に流
れ、そのために亜鉛の溶失速度が大きいこと、第二に亜
鉛の腐食生成物質は比較的腐食電流が流れやすく、腐食
生成物質自体の皮膜も溶損しやすいことが考えられる。The reason is that zinc is electrochemically much less base than iron, so the coupling current with iron flows excessively, which causes a high rate of zinc dissolution, and secondly, corrosion of zinc. It is conceivable that a corrosion current easily flows in the produced substance, and the coating film of the corrosion produced substance itself is easily damaged.
これを改善するために現在行なわれているほうほうの主
流は、鉄またはニッケルを亜鉛に合金させた皮膜を用い
ることである。これによりめっき皮膜の電位が純亜鉛よ
りも貴になり、鉄との電位差が縮まって過剰な腐食電流
が流れることを抑制し、めっき皮膜の寿命を延長せしめ
るものである。The current mainstream approach to remedy this is to use iron or nickel alloyed zinc coatings. As a result, the potential of the plating film becomes nobler than that of pure zinc, the potential difference with iron is reduced, and an excessive corrosion current is prevented from flowing, thereby extending the life of the plating film.
（発明が解決しようとする問題点） しかしながら、鉄との電位差が小さくなれば、犠牲防食
作用の効果も低減するので、赤錆が発生しやすくなる不
利益を伴う。(Problems to be Solved by the Invention) However, if the potential difference from iron is reduced, the effect of sacrificial anticorrosion action is also reduced, so that there is a disadvantage that red rust is likely to occur.
而して特開昭59−170288号公報には、鋼板中に耐食性金
属としてCr,Mo,Ti,Cuなど１種または２種以上を添加し
て耐食性をもたせた鋼板表面に、Znを主体としてNi,Co,
Fe,Cr,Moの１種又は２種以上を添加しためっきを施すこ
とが開示されている。しかし、その実施例においては、
めっき中のCrは0.5〜1.0％添加されるに止まっており、
その耐食性は耐食性鋼板との相乗効果によるものであ
り、該めっき層自体によって複合腐食環境（例えば乾湿
交番腐食環境）に耐えられるようなものではなく、コス
ト上問題がある。Thus, in JP-A-59-170288, Zn is mainly contained on the surface of a steel sheet having corrosion resistance by adding one or more of corrosion-resistant metals such as Cr, Mo, Ti, Cu into the steel sheet. Ni, Co,
It is disclosed to perform plating with addition of one or more of Fe, Cr and Mo. However, in that example,
Cr in plating is only added to 0.5-1.0%,
The corrosion resistance is due to a synergistic effect with the corrosion-resistant steel plate, and the plating layer itself cannot withstand a complex corrosion environment (for example, a dry-wet alternating corrosion environment) and has a problem in cost.
尤も、該公報には、Zn中にNi,Co,Fe,Cr,Moの１または２
種以上を含有するめっき層は、塩水噴霧と潤滑環境で耐
食性がある旨開示されている。しかし、実際の自動車、
建築構造物等が曝される腐食環境は、濡れた状態のみで
はなく、乾いた状態との交番環境にあり、このような乾
湿複合環境では腐食が更に酷しくなり、特にめっき層の
受ける腐食メカニズムは、濡れた状態だけの場合とは大
きく異なる。However, in the publication, Zn, Ni, Co, Fe, Cr, Mo 1 or 2 of
It is disclosed that the plating layer containing more than one species is corrosion resistant in salt spray and lubricated environment. But a real car,
The corrosive environment to which building structures are exposed is not only in a wet state, but also in an alternating environment with a dry state. Corrosion becomes even more severe in such a dry-wet complex environment, especially the corrosion mechanism that the plating layer receives. Is very different from the wet state alone.
即ち、乾燥条件が加わると、 めっき層の腐食速度が加速される。なぜならば、濡れ
た状態では表面に水膜が存在し、酸素の拡散速度が律速
となるが、乾燥時には酸素が容易に供給されるからであ
る。That is, when the drying condition is added, the corrosion rate of the plating layer is accelerated. This is because a water film is present on the surface in a wet state and the diffusion rate of oxygen is rate-determining, but oxygen is easily supplied during drying.
めっき層の犠牲防食作用の及ぶ範囲が狭くなり、素地
鋼板が侵食され、赤錆が発生し易くなる。The range of the sacrificial anticorrosive action of the plating layer is narrowed, the base steel sheet is corroded, and red rust is easily generated.
めっき層からの腐食生成物が表面から流出せず、腐食
サイトに沈積して皮膜化する傾向が出現する。従って、
めっき金属によっては腐食生成物そのものが、耐食性を
有し、その後の腐食の進行を抑制する働きを示すものが
あり得る。Corrosion products from the plating layer do not flow out from the surface, but tend to deposit on the corrosion site and form a film. Therefore,
Depending on the plating metal, the corrosion product itself may have corrosion resistance and exhibit a function of suppressing the subsequent progress of corrosion.
前記公報はNi,Co,Fe,Cr,Moを列挙して、濡れた環境での
耐食効果を述べているが、上述したように、乾湿複合環
境では合金元素の耐食挙動は全く異なるのである。The above-mentioned publication lists Ni, Co, Fe, Cr and Mo and describes the corrosion resistance effect in a wet environment, but as described above, the corrosion resistance behavior of alloy elements is completely different in a wet-dry composite environment.
特に、防錆鋼板の端面は素地鋼板が露出してめっき層と
隣接しているので、腐食を受けやすい部位であるが、最
近、自動車等では端面からの赤錆の吹き出しが車の見栄
えを損ねるので、端面の耐赤錆性の優れた防錆鋼板が要
求されるようになった。In particular, the end face of the rust-proof steel plate is exposed to the base steel plate and is adjacent to the plating layer, so it is a site susceptible to corrosion, but recently, in automobiles etc., the blowing of red rust from the end face impairs the appearance of the car. , Rust-preventing steel plate with excellent red rust resistance on the end face has been required.
本発明はこのような観点で開発されたものであり、亜鉛
とクロムの共析めっき層を有することを骨子とする乾湿
交番環境にすぐれた防錆鋼板を提供する。The present invention has been developed from such a point of view, and provides a rust-preventing steel sheet excellent in a dry-wet alternating environment, which has as its essence a zinc-chromium eutectoid plating layer.
（問題を解決するための手段） 本発明によって得られる防錆鋼板は、クロムを５重量％
超えから40重量％含む亜鉛とクロムを主体とする共析め
っき層中に、さらにFe,Ni、Co,Mn,Mo,Cu,Pb,Sn,Sb,Pか
ら選ばれた１種又は２種以上の元素を総量で亜鉛、クロ
ムのいづれの重量含有率よりも小さい範囲で含有せしめ
た亜鉛とクロムを主体とする共析めっき層と、Znめっき
層またはZnとFe,Ni,Co,Mn,Cr,Al,Mg,Si,Mo,Cu,Pb,Sn,T
i,Sb,Pから選ばれた１種または２種以上の元素のめっき
層とからなる複層めっきを有するものである。(Means for Solving the Problem) The rustproof steel sheet obtained by the present invention contains 5% by weight of chromium.
One or more selected from Fe, Ni, Co, Mn, Mo, Cu, Pb, Sn, Sb, P in the eutectoid plating layer mainly containing zinc and chromium in an amount of more than 40% by weight. The total amount of the elements of zinc and chromium in a range smaller than the weight content of either zinc or chromium, the eutectoid plating layer mainly composed of zinc and chromium, and the Zn plating layer or Zn and Fe, Ni, Co, Mn, Cr , Al, Mg, Si, Mo, Cu, Pb, Sn, T
It has a multi-layer plating including a plating layer of one or more elements selected from i, Sb and P.
金属クロムは周知のように酸素の存在下では不動態化
し、希酸中でも腐食されない極めて耐食性のある材料で
ある。ところがクロムは亜鉛と接触していれば、電気化
学的に亜鉛に近い卑な状態となり、鋼素地に対して充分
な犠牲防食作用をもつ。As is well known, metallic chromium is an extremely corrosion resistant material that is passivated in the presence of oxygen and is not corroded even in dilute acid. However, when chromium is in contact with zinc, it is electrochemically in a base state close to that of zinc and has a sufficient sacrificial anticorrosive action on the steel substrate.
CrはNi,Co,Fe,Mo等とは異なり、Znとの合金状態で腐食
電位を卑に維持するので乾湿交番環境でも十分な犠牲防
食作用をもち、後述するように特に端面の耐赤錆性を向
上できる。Unlike Ni, Co, Fe, Mo, etc., Cr keeps the corrosion potential base in the alloy state with Zn, so it has sufficient sacrificial anticorrosive action even in a wet and dry alternating environment. Can be improved.
乾湿交番環境（複合腐食環境）下での腐食生成物は三価
クロムの塩基性塩化物と推定されるが、極めて難溶性の
多核錯体の一種と認められる。これが表面に沈積して保
護皮膜となるのでZn−Crめっき層自身の腐食速度が極め
て小さくなり、長期間の犠牲防食作用を維持できる。Corrosion products in a dry-wet alternating environment (composite corrosion environment) are presumed to be basic chlorides of trivalent chromium, but they are recognized as a kind of extremely insoluble polynuclear complex. Since this deposits on the surface to form a protective film, the corrosion rate of the Zn-Cr plated layer itself becomes extremely low, and a long-term sacrificial anticorrosive action can be maintained.
金属クロムを亜鉛系めっきに適用する態様として、耐食
性に寄与するに足る十分な、たとえば５重量％超のクロ
ム含有量を確保した亜鉛−クロム主体合金めっきを得る
ことは、従来技術では電気めっき法、溶融めっき法いず
れにおいても事実上不可能であった。As a mode of applying metallic chromium to zinc-based plating, to obtain a zinc-chromium-based alloy plating that secures a chromium content sufficient to contribute to corrosion resistance, for example, more than 5% by weight, is a conventional technique. However, it was virtually impossible in any of the hot dip plating methods.
他の態様として、酸化クロムまたは金属クロムもしくは
これら両者を亜鉛めっき層の表面に被覆しためっき鋼板
が提案されているが、表面皮膜が腐食環境で溶解し尽く
せば、耐食性に寄与しない難点がある。本発明者らは、
三価クロムイオンによるクロムめっき浴に亜鉛イオンを
添加することにより、この浴からの電気めっきにより、
金属亜鉛と金属クロムを共析させることを可能にした。
用いるめっき浴は、例えば亜鉛イオンとクロムイオンの
合計が0.2〜1.2モル／リットル、アニオンは硫酸イオ
ン、ハロゲンイオンのうち１種または２種以上、三価ク
ロムイオンの錯イオン形成剤ならびに酸化防止安定剤と
してぎ酸、ぎ酸塩、アミノ基をもつ化合物例えばグリシ
ンをはじめとする各種アミノ酸、尿素、アミン、アミド
等のうち１種または２種以上を総量で0.2〜5.0モル／リ
ットルを加えたもの用いる。なお、この浴には更に電導
度助剤として、硼酸アンモニウム、塩化アンモニウム、
臭化アンモニウム、その他のハロゲン化アンモニウム、
アルカリ金属のハロゲン化物、アルカリ金属の硫酸塩の
うち１種または２種以上を総量で４モル／リットルを超
えない範囲で加えることができる。またpH緩衝剤とし
て、硝酸、りん酸等の各種酸の１種または２種以上を加
えることも可能であり、さらにこれらの酸のアルカリ金
属塩ないしアンモニウム塩のうち１種または２種以上を
加えることも可能である。As another embodiment, a plated steel sheet in which the surface of a galvanized layer is coated with chromium oxide, metallic chromium or both of them has been proposed, but there is a drawback that if the surface coating is completely dissolved in a corrosive environment, it will not contribute to corrosion resistance. We have
By adding zinc ions to the chromium plating bath with trivalent chromium ions, by electroplating from this bath,
It was possible to co-deposit metallic zinc and metallic chromium.
The plating bath used is, for example, a total of 0.2 to 1.2 mol / liter of zinc ions and chromium ions, the anion is one or more of sulfate ions and halogen ions, a complex ion forming agent of trivalent chromium ions, and antioxidant stability. Formic acid, formate, compounds having amino groups such as glycine, various amino acids, urea, amine, amide, etc., to which one or two or more of them are added in a total amount of 0.2 to 5.0 mol / liter To use. In this bath, as a conductivity aid, ammonium borate, ammonium chloride,
Ammonium bromide, other ammonium halides,
One kind or two or more kinds of alkali metal halides and alkali metal sulfates can be added in a total amount of 4 mol / liter or less. It is also possible to add one or more kinds of various acids such as nitric acid and phosphoric acid as a pH buffer, and further add one or more kinds of alkali metal salts or ammonium salts of these acids. It is also possible.
めっき浴の濃度範囲については、亜鉛イオンとクロムイ
オンの合計が0.2モル／リットル未満ではめっき効率が
低く、1.2モル／リットル超えではめっき浴が飽和して
適用できなくなる。ぎ酸、ぎ酸塩、アミノ基をもつ化合
物（グリシンをはじめとする各種アミノ酸、尿素、アミ
ン、アミド等）のうち１種または２種以上の総量が0.2
モル／リットル未満では、三価クロムイオンの錯イオン
形成作用ならびに酸化防止作用が不十分であり、5.0モ
ル／リットル超えでは飽和に達する。電導度助剤濃度は
総量で４モル／リットルを超えると浴の飽和が起こる。Regarding the concentration range of the plating bath, if the total of zinc ions and chromium ions is less than 0.2 mol / liter, the plating efficiency is low, and if it exceeds 1.2 mol / liter, the plating bath is saturated and cannot be applied. The total amount of one or more of formic acid, formate, and compounds having amino groups (amino acids including glycine, urea, amine, amide, etc.) is 0.2 or more.
If it is less than mol / liter, the complex ion forming action of trivalent chromium ions and the antioxidant action are insufficient, and if it exceeds 5.0 mol / liter, saturation is reached. If the total concentration of the conductivity aid exceeds 4 mol / liter, the bath will be saturated.
めっき電流密度は、10A/dm2〜300A/dm2が好ましい。10A
/dm2未満では、工業的な生産性が著しく悪く現実的でな
い。一方300A/dm2を超える領域では、めっき界面へのク
ロムイオンの拡散が追随できなくなり、まためっき界面
にて水素イオンの放電が著しく、それに伴うpH上昇によ
りpH緩衝剤の効果がもはや及ばなくなって、正常なめっ
きが不可能になる。The plating current density is preferably 10 A / dm 2 to 300 A / dm 2 . 10A
If it is less than / dm 2 , the industrial productivity is remarkably poor and it is not practical. On the other hand, in the area exceeding 300 A / dm 2 , the diffusion of chromium ions to the plating interface cannot follow, and the discharge of hydrogen ions at the plating interface is remarkable, and the pH increase accompanying this causes the effect of the pH buffering agent to cease to exist. , Normal plating becomes impossible.
めっき液流速は静止から150cm/秒まで適用できる。流速
上昇に共なって境膜厚の減少がおこると、電析中間体例
えばCr2+、配位子を失ったZn2+等が沖合に流失しやすく
なって、めっき効率が低下するが、前述した各種助剤の
濃度を適切に選択することにより、好ましいめっき皮膜
生成が可能である。The plating solution flow rate can be applied from static to 150 cm / sec. When the boundary film thickness decreases with an increase in the flow velocity, the electrodeposition intermediates such as Cr 2+ and the ligand-depleted Zn 2+ are easily washed offshore, and the plating efficiency is reduced. Appropriate selection of the concentrations of the various auxiliaries described above makes it possible to produce a preferable plating film.
めっき浴温は20〜70℃が好ましい。20℃未満では液の粘
性が高く、イオンの充分な拡散が抑制されてめっき効率
が低くなり、好ましくない。逆に70℃より高温では、ク
ロム錯イオンの配位子開離のために正常なめっきが不可
能になる。The plating bath temperature is preferably 20 to 70 ° C. If the temperature is lower than 20 ° C, the viscosity of the solution is high, the sufficient diffusion of ions is suppressed, and the plating efficiency is lowered, which is not preferable. On the other hand, at a temperature higher than 70 ° C, normal plating becomes impossible due to the ligand cleavage of the chromium complex ion.
本発明は上記の如く亜鉛とクロムを主体とし、且つFe,N
i,Co,Mn,Mo,Cu,Pb,Sn,Sb,Pから選ばれた１種または２種
以上の元素を、総量で亜鉛、クロムのいずれの重量含有
率よりも小さい範囲で含有せしめた亜鉛とクロムを主体
とする共析めっき層を析出させるためのめっき浴は、上
述した亜鉛とクロムの共析めっき浴組成に加えて、Fe,N
i,Co,Mn,Mo,Cu,Pb,Sn,Sb,Pから選ばれた１種または２種
以上の元素を、金属イオンもしくは酸化物イオンもしく
は錯イオンの形態で、総量が0.5モル／リットルを超え
ない範囲で含む浴を用いることができる。Fe,Ni,Co,Mn,
Mo,Cu,Pb,Sn,Sb,Pから選ばれた１種または２種以上の元
素からなるイオンの総量が0.5モル／リットルを超える
と、本来クロムの電析に必要な浴成分すなわち三価クロ
ムイオンの錯イオン形成剤ならびに酸化防止安定剤とし
てのぎ酸、ぎ酸塩、アミノ基をもつ化合物（グリシンを
はじめとする各種アミノ酸、尿素、アミン、アミド等）
のうち１種または２種以上がFe,Ni,Co,Mn,Mo,Cu,Pb,Sn,
Sbの錯イオン形成に消費されるために、クロムの電析に
とって不利になる。The present invention is mainly composed of zinc and chromium as described above, and Fe, N
One or more elements selected from i, Co, Mn, Mo, Cu, Pb, Sn, Sb, P were contained in a total amount smaller than the weight content ratio of zinc or chromium. The plating bath for depositing the eutectoid plating layer mainly composed of zinc and chromium is composed of Fe, N and
i, Co, Mn, Mo, Cu, Pb, Sn, Sb, P, one or more elements selected in the form of metal ions, oxide ions, or complex ions in a total amount of 0.5 mol / liter It is possible to use a bath containing it within a range not exceeding. Fe, Ni, Co, Mn,
If the total amount of ions consisting of one or more elements selected from Mo, Cu, Pb, Sn, Sb, and P exceeds 0.5 mol / liter, the bath components originally required for electrodeposition of chromium, namely trivalent Formic acid, formate, and compounds with amino groups as complex ion formers and antioxidant stabilizers for chromium ions (various amino acids such as glycine, urea, amine, amide, etc.)
One or more of these are Fe, Ni, Co, Mn, Mo, Cu, Pb, Sn,
It is disadvantageous for the deposition of chromium because it is consumed in the formation of Sb complex ions.
なお、これらのめっき被膜の製造例のいくつかを第２表
にした。In addition, some of the production examples of these plating films are shown in Table 2.
亜鉛−クロム共析めっき層または亜鉛とクロムを主体と
する共析めっき層のめっき組成は、クロムが５重量％超
〜40重量％が適切である。５重量％以下では、クロムが
耐食性に及ぼす良好な効果がほとんど得られず、反対に
40重量％超ではクロムの不動態化が顕著になるために電
位が貴になり、鋼素地に対する犠牲防食作用が期待し得
ない。またこのようなクロム比率の高い組成のめっきは
めっき層が脆く、めっき電流効率が低いため実用的でな
い。The plating composition of the zinc-chromium eutectoid plating layer or the eutectoid plating layer containing zinc and chromium as a main component is preferably more than 5% by weight and 40% by weight of chromium. If it is less than 5% by weight, the good effect of chromium on the corrosion resistance is hardly obtained.
If it exceeds 40% by weight, the passivation of chromium becomes remarkable, so the potential becomes noble, and the sacrificial anticorrosive action on the steel base cannot be expected. Further, such a plating having a high chromium ratio is not practical because the plating layer is brittle and the plating current efficiency is low.
また亜鉛とクロムを主体とする共析めっき層の場合、第
三成分以下の元素即ちFe,Ni,Co,Mn,Mo,Cu,Pb,Sn,Sb,Pか
ら選ばれた１種または２種以上の元素の総量が、亜鉛、
クロムの何れの重量含有率よりも小さい範囲であること
が必要である。第三成分以下の元素の総量が、亜鉛、ク
ロムの何れかの重量含有率以上になると、亜鉛の犠牲防
食作用およびクロムの難溶性腐食生成物の成形が充分で
なくなるため、本発明の効果が減少する、これら第三成
分はめっき層の化成処理性や溶接性を改善するために添
加される場合がある。In the case of eutectoid plating layer consisting mainly of zinc and chromium, one or two elements selected from the elements below the third component, namely Fe, Ni, Co, Mn, Mo, Cu, Pb, Sn, Sb, P The total amount of the above elements is zinc,
It must be in the range smaller than any weight content of chromium. When the total amount of the elements of the third component or less is zinc or more than the weight content of any of chromium, the sacrificial anticorrosive action of zinc and the formation of a poorly soluble corrosion product of chromium are not sufficient, so that the effect of the present invention is obtained. These third components, which decrease, may be added to improve the chemical conversion treatability and weldability of the plated layer.
めっき皮膜層は1g/m2以上が好ましい。1g/m2未満では耐
食性が充分に得られない。上限は用途によって異なる
が、製造コストの点から50g/m2、好ましくは30g/m2であ
る。The plating film layer is preferably 1 g / m 2 or more. If it is less than 1 g / m 2 , sufficient corrosion resistance cannot be obtained. The upper limit is varied depending on the use, 50 g / m 2 from the viewpoint of production cost, it is preferably 30 g / m 2.
（作用） 亜鉛−クロム主体共析めっきの構造は、Ｘ線回折によれ
ば、2.13〜2.14オングストローム、1.50オングストロー
ム、1.22〜1.23オングストローム程度の格子面間隔
（ｄ）をもつ、これはクロムの結晶格子定数が亜鉛原子
の固溶によってシフトしたものとみられる。ただし亜鉛
組成の多い場合は、これのみならず、η相（純亜鉛）の
回析ピークを伴う。(Function) According to X-ray diffraction, the structure of zinc-chromium-based eutectoid plating has a lattice spacing (d) of about 2.13 to 2.14 angstroms, 1.50 angstroms, 1.22 to 1.23 angstroms, which is a crystal lattice of chromium. It seems that the constant was shifted by the solid solution of zinc atoms. However, when the zinc composition is large, not only this but also the diffraction peak of the η phase (pure zinc) is involved.
亜鉛−クロム主体共析めっきの腐食電位は、亜鉛めっき
の場合−1000mVvs.S.C.E.程度であるのに対し、クロム
組成の増大に伴って貴の方向にやや移行するが、Cr含有
量40％でも−900mVvs.S.C.E.程度の比較的卑な電位を保
つ。この水準の電位は、鉄のそれより明らかに卑である
ため、本発明の亜鉛−クロム主体共析めっきは素地鉄を
充分犠牲防食できる。なお、Znと他の金属、例えばNi,C
o,Fe,Mo等との合金系では合金組成とともに電位が貴方
向に急上昇するので、犠牲防食作用が弱くなることがZn
−Cr合金系との相異である。また、皮膜成分中のクロム
めっき表面にて強固かつ化学的に安定で電気抵抗に高い
腐食生成物皮膜を形成する。これが下地に残存している
めっき層および素地鉄への水、酸素、各種イオンの侵入
ならびに腐食電流を強く防げるため、本発明は鋼板の長
期防錆に最適である。なお、純Znはめっき層自身の腐食
速度が比較的高いので長期防錆力が不足する。The corrosion potential of zinc-chromium-based eutectoid plating is about -1000 mVvs.SCE in the case of zinc plating, whereas it slightly shifts toward the noble direction as the chromium composition increases, but even with a Cr content of 40%- Maintain a relatively low potential of about 900 mV vs. SCE. Since this level of potential is obviously lower than that of iron, the zinc-chromium-based eutectoid plating of the present invention can sufficiently sacrifice and protect the base iron. In addition, Zn and other metals such as Ni, C
In an alloy system with o, Fe, Mo, etc., the potential rises in the noble direction along with the alloy composition.
-It is different from the Cr alloy system. Further, a corrosion product film which is strong and chemically stable and has high electric resistance is formed on the surface of the chromium plating in the film components. The present invention is most suitable for long-term rust prevention of steel sheets, because it can strongly prevent invasion of water, oxygen and various ions into the plating layer remaining on the base and the base iron and corrosion current. Since pure Zn has a relatively high corrosion rate of the plating layer itself, it lacks long-term rust preventive power.
次に端面耐食性について述べる。通常塗装後の耐赤錆性
は塗装板の上から素地鋼板に達するナイフカットを入れ
て塩水噴霧試験等の腐食試験をするが、このような試験
では条件がおだやかであって、市場で問題となるような
端面の耐赤錆性の評価として適当ではない。端面は、例
えば板厚0.8mmの鋼板と、３μｍのめっき層が隣接して
おり、塗膜下で大面積のカソードと小面積のアノードの
腐食電池が形成される。従って、鋼板からの赤錆を抑制
するには、鋼板をあまねく貴な電位に維持するカソード
防食作用の遠達力が必要であって、この意味でめっき層
の電位は十分卑でなければならない。更に、小面積アノ
ードとなるめっき層に腐食電流が集中するので、めっき
層自身の耐食性が必要である。Zn−Cr共析めっきは上述
の両条件を満たしているので、端面の赤錆を抑制し得る
好適なめっき層である。Next, the end surface corrosion resistance will be described. Normally, the red rust resistance after painting is subjected to a corrosion test such as a salt spray test by inserting a knife cut that reaches the base steel plate from the top of the painted plate, but in such a test the conditions are mild and become a problem in the market. It is not suitable for evaluating the red rust resistance of such end faces. For example, a steel plate having a plate thickness of 0.8 mm and a 3 μm-plated layer are adjacent to each other on the end face, and a corrosion battery having a large-area cathode and a small-area anode is formed under the coating film. Therefore, in order to suppress the red rust from the steel sheet, it is necessary to have a long-lasting ability of cathodic protection for maintaining the steel sheet at a generally noble potential, and in this sense, the potential of the plating layer must be sufficiently base. Further, since the corrosion current concentrates on the plating layer which becomes the small area anode, the corrosion resistance of the plating layer itself is required. Since Zn-Cr eutectoid plating satisfies both of the above conditions, it is a suitable plating layer capable of suppressing red rust on the end surface.
端面の鋭角コーナー部は通常塗膜が薄いので、ナイフカ
ットを入れなくとも腐食の起点となる。ここから塗膜下
腐食が進行するが、乾湿交番環境ではカソード防食の及
ぶ距離が制限されるので、塩水噴霧試験等よりも赤錆の
発生が促進される。このような過酷な条件下では、従来
のZn系めっき鋼板は耐赤錆性が十分でなく、Zn−Cr共析
めっきに、極めて優れた腐食性のあることが見出された
のである。Since the coating film is usually thin at the sharp corners of the end faces, it can be the starting point of corrosion even without knife cutting. Although the under-coating corrosion progresses from here, the distance over which cathodic protection extends is limited in a dry and wet alternating environment, so that the generation of red rust is promoted more than in a salt spray test or the like. Under such harsh conditions, the conventional Zn-based plated steel sheet does not have sufficient red rust resistance, and it has been found that Zn-Cr eutectoid plating has extremely excellent corrosion resistance.
本発明を複層めっきの形態で利用する場合、亜鉛−クロ
ム主体共析めっき層は、素地鋼板に直接接する最下層、
中間層、複層めっきの表面積すなわち最上層のいずれに
も用いることができる。亜鉛−クロム主体共析めっき層
を最下層または中間層に用いる場合、最上層めっきは化
成処理が可能なめっき層であればよい。具体的な好適例
の一つとして、最上層に鉄60重量％以上を含む鉄−亜鉛
合金めっき又は亜鉛めっきを1g/m2以上施したものを挙
げることができる。When the present invention is used in the form of multi-layer plating, the zinc-chromium-based eutectoid plating layer is the bottom layer that is in direct contact with the base steel sheet,
It can be used for both the intermediate layer and the surface area of multilayer plating, that is, the uppermost layer. When the zinc-chromium-based eutectoid plating layer is used as the lowermost layer or the intermediate layer, the uppermost layer plating may be a plating layer capable of chemical conversion treatment. As one of the specific preferred examples, an iron-zinc alloy plating containing 60% by weight or more of iron or zinc plating of 1 g / m 2 or more can be given as the uppermost layer.
次に亜鉛−クロム主体共析めっき層を中間層または最上
層に用いる場合、最下層めっきは亜鉛めっきまたは亜鉛
を60％以上含む合金めっきが好ましい。この際、亜鉛合
金とする金属としてはFe,Ni,Co,Mn,Al,Mg,Si,Mo,Cu,Sn,
Ti,Pなどの１種又は２種以上が該当する。Next, when the zinc-chromium-based eutectoid plating layer is used as the intermediate layer or the uppermost layer, the lowermost layer plating is preferably zinc plating or alloy plating containing 60% or more of zinc. At this time, as the zinc alloy metal, Fe, Ni, Co, Mn, Al, Mg, Si, Mo, Cu, Sn,
One or more types such as Ti and P are applicable.
第三に亜鉛−クロム主体共析めっき層をいずれの層に用
いようとも、その他のめっき層は亜鉛系のめっきに限定
されるわけではなく、めっき製品の用とに応じて鉛、ア
ルミニウム、錫、、クロム、ニッケル、マンガン等およ
びこれらを主体とする合金めっきが適用できる。Thirdly, whichever zinc-chromium-based eutectoid plating layer is used, the other plating layers are not limited to zinc-based plating, and lead, aluminum, tin depending on the purpose of the plated product. ,, chromium, nickel, manganese, etc., and alloy plating mainly composed of these are applicable.
また亜鉛とクロムの含有比率の異なる２層以上の亜鉛−
クロム主体共析めっき層をい有する態様も有効である。Also, two or more layers of zinc with different content ratios of zinc and chromium-
An embodiment having a chromium-based eutectoid plating layer is also effective.
亜鉛とクロムを主体とする共析めっきは、クロムの安定
な腐食生成物の形成を阻害する元素でない限り、副成分
として各種元素を含有していても、亜鉛とクロムの２成
分系の場合と同様の効果が得られる。The eutectoid plating mainly composed of zinc and chromium is different from the case of the two-component system of zinc and chromium even if it contains various elements as auxiliary components, as long as it is an element that does not inhibit the formation of stable corrosion products of chromium. The same effect can be obtained.
（実施例） 以下に本発明の実施例を比較例とともに挙げる。(Example) Below, the Example of this invention is given with a comparative example.
各々の裸耐食性試験結果を掲げた。耐食性試験として塩
水噴霧試験、乾湿交番環境（複合腐食環境）試験を行っ
た。なおめっき原板は連続鋳造アルミキルド箱焼鈍材
で、板厚0.8mmの冷延鋼板である。 The results of each bare corrosion resistance test are listed. As a corrosion resistance test, a salt spray test and a wet and dry alternating environment (composite corrosion environment) test were performed. The plating base plate is a continuous cast aluminum killed box annealed material, which is a cold-rolled steel plate with a plate thickness of 0.8 mm.
第２表にはこれらの製造例を挙げた。Table 2 lists these production examples.
《塩水噴霧試験》 塩水噴霧試験（JISZ2371に準拠）により、試験面積の50
％に赤錆が発生するまでの時間で評価した。《Salt spray test》 The salt spray test (according to JIS Z2371) shows 50
% Until the red rust occurred.
《腐食サイクル試験（乾湿交番環境試験）》 湿潤（50℃RH85％15.5時間）→乾燥（70℃３時間）→塩
水浸漬（50℃２時間）→室内放置（常温２時間）→塩水
噴霧試験（50℃1.5時間）を１サイクルとする腐食試験
を行い、30サイクル経過後の腐食減量と１dm2当たりの
素地鋼板の孔開き発生個数と、カチオン電着塗装20μ、
中塗り30μ、上塗り30μ後の端面耐食性（赤錆発生状況
を目視判断大、中、小）評価を行った。<< Corrosion cycle test (dry and wet alternating environment test) >> Wet (50 ° C RH85% 15.5 hours) → Drying (70 ° C 3 hours) → Saltwater immersion (50 ° C 2 hours) → Indoor exposure (room temperature 2 hours) → Salt spray test ( Corrosion test with 1 cycle of 50 ° C for 1.5 hours) was performed. Corrosion weight loss after 30 cycles, the number of holes perforated in the base steel sheet per 1 dm 2 , cation electrodeposition coating 20μ,
After 30μ of middle coating and 30μ of top coating, the end face corrosion resistance (red rust occurrence was visually judged large, medium and small) was evaluated.
（発明の効果） 本発明によれば、薄目付のめっきにて鋼板の耐食性を著
しく向上させることができ、自動車をはじめとする運輸
車両用材料ならびに建築用材料電気機器用材料等に適用
することによって工業的に優れた効果が得られる。(Effect of the Invention) According to the present invention, the corrosion resistance of a steel sheet can be remarkably improved by plating with a light weight, and it can be applied to materials for transportation vehicles such as automobiles and materials for construction and materials for electrical equipment. The industrially excellent effect is obtained.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 新井 勝利 愛知県東海市東海町５―３ 新日本製鐵株 式会社名古屋製鐵所内 (56)参考文献 特開 昭58−141397（ＪＰ，Ａ) 特開 昭59−25992（ＪＰ，Ａ) ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoru Arai 5-3 Tokai-cho, Tokai City, Aichi Prefecture Nippon Steel Co., Ltd. Inside the Nagoya Works (56) References JP-A-58-141397 (JP, A) JP-A-59-25992 (JP, A)
Claims (1)
鉛とクロムを主体とする共析めっき層中に、さらにFe,N
i,Co,Mn,Mo,Cu,Pb,Sn,Sb,Pから選ばれた１種または２種
以上の元素を総量で亜鉛、クロムのいづれの重量含有率
よりも小さい範囲で含有せしめた亜鉛とクロムを主体と
する共析めっき層と、Znめっき層またはZnとFe,Ni,Co,M
n,Cr,Al,Mg,Si,Mo,Cu,Pb,Sn,Ti,Sb,Pから選ばれた１種
または２種以上のめっき層とからなる複層めっきを有す
る耐食性の優れた防錆鋼板。1. An eutectoid plating layer mainly containing zinc and chromium containing 5% to 40% by weight of chromium, and Fe, N
Zinc containing one or more elements selected from i, Co, Mn, Mo, Cu, Pb, Sn, Sb and P in a total amount smaller than the weight content ratio of zinc or chromium. And chromium, eutectoid plating layer, Zn plating layer or Zn and Fe, Ni, Co, M
Rust prevention with excellent corrosion resistance having a multi-layer plating consisting of one or more plating layers selected from n, Cr, Al, Mg, Si, Mo, Cu, Pb, Sn, Ti, Sb, P steel sheet.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2107338A JPH0689473B2 (en) | 1990-04-25 | 1990-04-25 | Anti-corrosion steel plate with excellent corrosion resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2107338A JPH0689473B2 (en) | 1990-04-25 | 1990-04-25 | Anti-corrosion steel plate with excellent corrosion resistance |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62079027A Division JPS63243295A (en) | 1987-03-31 | 1987-03-31 | Rust preventive steel sheet having superior corrosion resistance |
Related Child Applications (3)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2036346A Division JP2866697B2 (en) | 1990-02-19 | 1990-02-19 | Method of forming tough electrical insulation layer on copper material surface |
| JP2204134A Division JPH0791669B2 (en) | 1990-08-01 | 1990-08-01 | Anticorrosion steel plate with excellent corrosion resistance |
| JP2204135A Division JPH0781198B2 (en) | 1990-08-01 | 1990-08-01 | Rust-preventing steel plate with excellent dry-temperature alternation environment |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH03115594A JPH03115594A (en) | 1991-05-16 |
| JPH0689473B2 true JPH0689473B2 (en) | 1994-11-09 |
Family
ID=14456524
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2107338A Expired - Fee Related JPH0689473B2 (en) | 1990-04-25 | 1990-04-25 | Anti-corrosion steel plate with excellent corrosion resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0689473B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0751240B1 (en) * | 1994-12-08 | 1999-08-04 | Sumitomo Metal Industries, Ltd. | Surface-treated steel plate for fuel tanks |
| US20100084278A1 (en) * | 2008-10-02 | 2010-04-08 | Rowan Anthony J | Novel Cyanide-Free Electroplating Process for Zinc and Zinc Alloy Die-Cast Components |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5891163A (en) * | 1981-11-24 | 1983-05-31 | Kobe Steel Ltd | Manufacture of composite zinc plated steel plate with superior suitability to coating |
| JPS58141397A (en) * | 1982-02-12 | 1983-08-22 | Kawasaki Steel Corp | Surface-treated steel plate with high corrosion resistance and its manufacture |
| JPS5925992A (en) * | 1982-08-04 | 1984-02-10 | Kawasaki Steel Corp | Surface treated steel sheet having high corrosion resistance and its production |
-
1990
- 1990-04-25 JP JP2107338A patent/JPH0689473B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH03115594A (en) | 1991-05-16 |
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