JPH0443994B2 - - Google Patents
Info
- Publication number
- JPH0443994B2 JPH0443994B2 JP61194043A JP19404386A JPH0443994B2 JP H0443994 B2 JPH0443994 B2 JP H0443994B2 JP 61194043 A JP61194043 A JP 61194043A JP 19404386 A JP19404386 A JP 19404386A JP H0443994 B2 JPH0443994 B2 JP H0443994B2
- Authority
- JP
- Japan
- Prior art keywords
- stainless steel
- corrosion resistance
- metallic luster
- electrode
- aqueous solution
- 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
- 229910001220 stainless steel Inorganic materials 0.000 claims description 43
- 239000010935 stainless steel Substances 0.000 claims description 42
- 230000007797 corrosion Effects 0.000 claims description 27
- 238000005260 corrosion Methods 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 21
- 239000002932 luster Substances 0.000 claims description 17
- 239000007864 aqueous solution Substances 0.000 claims description 13
- 239000003792 electrolyte Substances 0.000 claims description 8
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 6
- 229910017604 nitric acid Inorganic materials 0.000 claims description 6
- 230000001681 protective effect Effects 0.000 claims description 6
- 229910002651 NO3 Inorganic materials 0.000 claims description 3
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 2
- 239000008151 electrolyte solution Substances 0.000 claims 1
- 239000000463 material Substances 0.000 description 33
- 239000011651 chromium Substances 0.000 description 11
- 229910000831 Steel Inorganic materials 0.000 description 9
- 238000000137 annealing Methods 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 9
- 239000010959 steel Substances 0.000 description 9
- 229910052804 chromium Inorganic materials 0.000 description 7
- 238000005554 pickling Methods 0.000 description 7
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 5
- 230000007547 defect Effects 0.000 description 4
- 230000006698 induction Effects 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 239000002253 acid Substances 0.000 description 3
- 230000002950 deficient Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 229910044991 metal oxide Inorganic materials 0.000 description 3
- 150000004706 metal oxides Chemical class 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000002436 steel type Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 229940077449 dichromate ion Drugs 0.000 description 1
- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000004807 localization Effects 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- -1 nitrate ions Chemical class 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Description
〈産業上の利用分野〉
この発明は、2B又はBA仕上げした金属光沢を
有するステンレス鋼の表面を電気化学的に調整
し、その耐食性を向上させる方法に関するもので
ある。
〈背景技術〉
現在、各方面に幅広く使用されているステンレ
ス鋼板は、一般的には所望板厚にまで冷間圧延し
た冷延板を加熱炉で焼鈍して製造されている。
ところが、通常、焼鈍雰囲気には多量の“O2”
や“燃料の燃焼によつて生じたH2Ｏ”が含まれ
ているので焼鈍後のステンレス鋼表面は厚い酸化
スケールに覆われてしまい、そのため焼鈍終了後
に溶融塩浴処理と酸洗とによりステンレス鋼表面
の酸化スケールを除去する工程が必須となつてい
た。しかし一方で、このようなスケール除去処理
を施すとステンレス鋼が有する特有の表面光沢が
損なわれてしまい、ステンレス鋼材に期待されて
いる金属的外観が得られなくなつてしまうと言う
問題もあつた。
そこで、ステンレス鋼特有の優れた金属光沢を
保持した材料が必要な場合には2B仕様やBA処理
等の手段が採用されている。
上記2B仕様は、酸洗後のステンレス鋼板を再
度調質圧延して表面光沢を付与する処理である
が、この場合でも酸洗を十分に行つてスケール除
去を完全ならしめようとするとステンレス鋼表面
の荒れが目立つようになり、調質圧延によつても
十分な光沢が得られなくなる。そのため、光沢を
より重視するときには酸洗を弱目に実施すること
もあると言われているが、この場合には所謂“ク
ロム欠乏層（焼鈍時のクロムの優先酸化によつて
生じた耐食性劣化層）”が十分に除去し切れない
ので鋼材の耐食性が不満足なものとなる恐れがあ
つた。
他方、BA（光輝焼鈍）処理は“焼鈍”をアン
モニア分解ガス（H2：N2＝３：１）等の不活性
ガス中で実施する方法であり、酸化スケールが生
成しないので酸洗が不要となつて優れた表面光沢
を維持した製品がそのままで得られるものであ
る。しかし、厳密に見れば上記不活性雰囲気中に
も微量のH2ＯやO2は存在しており、このため焼
鈍時に極く薄い酸化膜がステンレス鋼表面に形成
されるのを防止することはできない（ステンレス
鋼を構成する成分の中ではSi，Mn，Cr等が比較
的酸化し易いため成形される酸化膜の中にはこれ
らの元素が多く含まれるが、焼鈍条件によつては
雰囲気中のN2ガスと反応して窒化物ができる場
合もあると言われている）。このようなBA処理
によつてステンレス鋼表面に生成した表面皮膜は
焼鈍時の温度、時間、雰囲気ガス組成等により性
質が大きく異なり、所謂不働態皮膜のように保護
性の強いものができる場合もあれば、逆に非常に
保護性が弱く、むしろステンレス鋼表面の不働態
化を防げるような皮膜を形成する場合もある。従
つて、ステンレス鋼BA材の耐食性はBA条件に
よつて大きく異なるのが普通であるが、BA条件
と耐食性との関係は未だ十分に解明されていない
のが現状である。
上述の如く、市販のステンレス鋼2B仕様材や
BA処理材のように表面光沢の優れたステンレス
鋼は、同じ鋼種或いは同じ表面仕様のものであつ
ても製造工程の微妙な差により耐食性はかなり大
きく異なるものであり、しかも表面には比較的耐
食性に劣る層が多かれ少なかれ存在する。もつと
も、これらの材料の最表面は大気中のO2等の作
用によつて不働態化しているため一応はステンレ
ス鋼としての耐食性を保つているが、何らかの理
由（例えば疵付きや酸の付着等）によつて前記最
表面が除去されると、孔食等の局部腐食により発
銹することが多くなる。なお、これらの材料を硝
酸等の酸化性の酸に浸漬しても不働態皮膜（酸化
膜）は強化されるが、この場合でもクロム欠乏層
はなかなか除去されないため耐孔食性はあまり改
善されない。
勿論、これら市販の2B仕様材やBA処理材を
“硝酸とフツ化水素酸との混合水溶液”で酸洗し、
表面の耐食性が劣る部分を完全に除去すれば地金
本来の優れた耐食性を得ることは可能であるが、
この場合には表面の光沢がなくなつて鏡面仕様材
としての商品価値は失われてしまう。
このようなことから、ステンレス鋼BA処理材
の耐食性改善手段として、材料を硝酸等の水溶液
中で陽極電解又は交番電流電解した後、更に必要
に応じて酸化性酸（硝酸等）に浸漬して不働態化
処理する方法も提案された（特開昭54−142140
号、特開昭54−142142号、特開昭59−6398号、特
開昭59−23882号等）。
しかしながら、これらの方法は、何れも被処理
ステンレス鋼材にリード線を直接接続し電流を通
じて行う電解処理によつて耐食性を向上させよう
とするものであり、実験的なビーカーテストにお
いては容易に実施することが可能かも知れない
が、例えば連続鋼帯を工業的規模で処理しようと
する場合には移動する鋼帯に電流を通じるための
特別な工夫が必要である上、ややもするとスパー
ク疵が発生する恐れがあつて（移動する被処理物
に直接電気を接続するとスパークが生じ易い）、
表面外観に格別な気配りが必要な上記“金属光沢
を有するステンレス鋼材”の処理手段としては決
して好ましいものではなかつた。
〈問題点を解決するための手段〉
この発明は、上述のような観点から、例え処理
対象材が連続的に走行する鋼帯のようなもので
も、或いは極く小さな単品であつたとしても、表
面にスパーク疵等のような欠陥を発生させる懸念
なく簡単容易に実施できるところの“2B又はBA
仕上げした金属光沢を有するステンレス鋼の耐食
性改善方法”を提供すべくなされた本発明者等の
研究によつて完成されたものであり、
例えば第１図に示すように、2B又はBA仕上げ
した金属光沢を有するステンレス鋼１を電解質水
溶液２に浸漬すると共に、その近傍に位置せしめ
た電極３の作用によつて前記ステンレス鋼表面に
正と負の電荷の局在化を生ぜしめることにより、
被処理ステンレス鋼１に直接的に電流を通じるこ
となくその表面に保護性の強い、しかも光沢に影
響を与えることのない酸化皮膜を形成せしめて耐
食性を改善する点、に特徴を有するものである。
つまり、電解質水溶液２の中に浸漬した2B又
はBA仕上げした金属光沢を有するステンレス鋼
１に例えば負に帯電した電極３を近づけると、ス
テンレス鋼１と対向面に正の電荷が集まつて局在
化し（静電誘導作用）、
Me＋2OH-→MeO＋H2Ｏ＋2e ……(1)
（金属） （金属酸化物）
或いは
Me＋NO3 -→MeO＋NO2＋ｅ ……(2)
（金属） （金属酸化物）
等の反応によつてステンレス鋼１の表面に保護性
が強くかつ金属光沢を害することのないCrリツ
チで緻密な金属酸化膜（不働態皮膜）が生成し、
ステンレス鋼１の耐食性を十分に向上する。ま
た、2B仕様材やBA処理材の表面には素地よりも
クロム含有量の少ない耐食性に劣る層（クロム欠
乏層）が存在することがあるが、この場合に前記
処理（電解質中で電極を近づける処理）を行うと
正の電荷が局在した側では
Me→Mn+＋ne- ……(3)
の反応によつてFeが溶解すると同時に、Crが上
記(1)式あるいは(2)式の反応により酸化物となつて
Crリツチの緻密な酸化膜（不働態皮膜）が形成
される。なお、このとき負の電荷が局在している
ところでは
2H+＋2e→H2 ……(4)
なる反応が起きて水素ガスが生じ、もしも酸化
スケール等が存在しているようなものではその剥
離が促進される。
このように、この発明の方法では、静電誘導作
用によつて生じた電荷がステンレス鋼表面の溶
解、酸化、若しくは還元を促進して速やかに金属
光沢を有するステンレス鋼の耐食性を向上させる
ので、例え僅かなクロム欠乏層が存在していたと
しても十分に耐食性に優れた表面状態を得ること
ができる。
以上の説明からも明らかなように、ステンレス
鋼の不働態皮膜生成のためには正の電荷が有効な
作用〔前記(1)式、(2)式又は(3)式の反応を促進す
る〕をするのに対して負の電荷は直接的に有効な
働きをしないが、静電誘導の場合にはある部分に
電荷が集まれば別の部分には必ず負の電荷が集ま
るので、これを効率良く行うためには、第２図に
示すように正と負の電極を相対して接近させるの
も良い。
また、このとき電極の電位を経時変化させるこ
とは処理材表面の処理効果を均一化する上で好ま
しいことである。そして、電極電位の経時変化は
“交番電圧を加える（交流電流を使用する）”こと
によつて容易に実現されるが、その波形は通常の
正弦波のみではなく矩形波や三角波等をも適用す
ることができ、また周波数も50〜60Hzに限られる
ものではなく、例えば１〜300Hz等においても十
分に効果が得られることからみて格別に制限され
るものではない。
なお、電極の電位を変化させずに電極近傍に被
処理材を連続的に通過させても、上記と同様に処
理効果の均一化を図ることができる。
この発明の方法で使用する電解質水溶液として
は硝酸又は硝酸塩を含む水溶液（硝酸イオンを含
む水溶液）が価格面からみても好適であるが、例
えば酸化力のあるクロム酸イオン（CrO4 2-）や
重クロム酸イオン（CrO2O7 2-）等を含むものを
採用するのも良い。
ところで、この発明に係る処理は「電解酸洗」
に類似しているようにも見えるが、電解酸洗では
大きな電流を流して前記(3)式及び(4)式の反応を主
として行わしめることが欠かせないので、当然被
処理材の表面は肌荒れして光沢が失われる。これ
に対してこの発明に係る処理では、被処理材が酸
化スケールの無い2B又はBA仕上げをして光沢の
あるステンレス鋼であり、前記(1)式又は(2)式の反
応で金属の酸化を行わしめて不働態皮膜を形成さ
せるもので、電解酸洗とは全く異なるものであ
る。この場合、前記(3)式の反応により金属の溶解
が起きるか、或いは前記(1)式又は(2)式の反応によ
り酸化が起きるかは負電荷の強さ（量）、電極と
被処理材との距離、電解質濃度或いは電極の電気
抵抗等に依存するが、これらのコントロールによ
つて｛具体的には電解質濃度を比較的薄くし、電
極としては比較的電気抵抗の大きいものを用いて
電位をより正側に持つて行けば前記(3)式の溶解が
抑えられて(1)式の酸化反応が促進される｝表面に
Cr含有率が高く、保護性の強い酸化皮膜が生じ
る。
この発明の方法にて連続鋼帯を工業的規模で処
理するには、例えば第３〜５図のような装置を使
用すれば良い。即ち、第３図は２枚の電極板４，
４に交番電圧を印加し、その間を連続鋼帯５が通
過するように構成された例である。また第４図は
極性の異なる電極板が別の槽に配置された構成の
ものを示していて、電流ロスが無く処理効率が極
めて良いものである。そして、第５図は極性の異
なる電極板を横に並べたものの例であるが、これ
は電流効率に劣るが設備費が安くて済むものであ
る。
上記説明からも、この発明の方法では被処理材
に直接リード線等を接触させて電流を供給する必
要が無いのでスパークを発生する恐れは無く、従
つてスパーク疵による外観不良品を懸念する必要
の無いことが明らかであろう。
続いて、この発明の効果を実施例により具体的
に説明する。
〈実施例〉
第６図に示す如くに、SUS430ステンレス鋼
（16.5％Crフエライト系ステンレス鋼）のBA処理
材から切り出した試験片６を挟んで２枚の電極板
（陽極酸化したチタンに特殊コーテイングしたも
の）４，４を配置し（各電極板と試験片面との距
離：３mm）、これらを浴温50℃の10％HNO3水溶
液７に浸漬した。
次いで、上記電極４，４に50Hzの交番電流を10
〜60秒間印加した後試験片を取り出し、水洗・乾
燥してからその光沢保持率：
処理後の光沢／処理前の光沢×100
と耐食性とを調査した。
得られた結果を処理条件の一部と共に第１表に
示す。
第１表に示される結果からも明らかなように、
この発明の処理によつてステンレス鋼の耐食性が
表面光沢の低下を殆ど来さずに著しく改善さるこ
とか分かる。また、該処理によつて光沢がやや低
下した場合でも、その後に軽度の調質圧延を施す
のみで十分に光沢を回復することができること
<Industrial Application Field> The present invention relates to a method for electrochemically adjusting the surface of stainless steel having a metallic luster that has been finished with 2B or BA to improve its corrosion resistance. <Background Art> Stainless steel plates, which are currently widely used in various fields, are generally manufactured by cold-rolling a cold-rolled plate to a desired thickness and annealing it in a heating furnace. However, there is usually a large amount of “O 2 ” in the annealing atmosphere.
The stainless steel surface after annealing is covered with a thick oxide scale because it contains H 2 O produced by combustion of fuel. A process to remove oxidized scale from the steel surface was essential. On the other hand, however, there was the problem that when such scale removal treatment was applied, the characteristic surface luster of stainless steel was lost, making it impossible to obtain the metallic appearance expected of stainless steel materials. . Therefore, when a material that retains the excellent metallic luster characteristic of stainless steel is required, methods such as 2B specifications and BA treatment are adopted. The above 2B specification is a treatment in which the stainless steel plate is heat-rolled again after pickling to give it surface gloss, but even in this case, if you try to remove scale completely by carrying out sufficient pickling, the stainless steel surface The roughness becomes noticeable, and sufficient gloss cannot be obtained even by temper rolling. Therefore, it is said that pickling may be carried out weakly when gloss is more important, but in this case, the so-called "chromium-deficient layer" (deterioration of corrosion resistance caused by preferential oxidation of chromium during annealing) There was a risk that the corrosion resistance of the steel material would be unsatisfactory because the "layer)" could not be sufficiently removed. On the other hand, BA (bright annealing) treatment is a method in which "annealing" is performed in an inert gas such as ammonia decomposition gas (H 2 : N 2 = 3:1), and no pickling is required as oxide scale is not generated. As a result, a product that maintains excellent surface gloss can be obtained as is. However, strictly speaking, trace amounts of H 2 O and O 2 are present even in the above-mentioned inert atmosphere, so it is impossible to prevent the formation of a very thin oxide film on the stainless steel surface during annealing. (Among the components that make up stainless steel, Si, Mn, Cr, etc. are relatively easy to oxidize, so the formed oxide film contains many of these elements, but depending on the annealing conditions, they may oxidize in the atmosphere.) (It is said that nitrides may be formed by reacting with N2 gas). The properties of the surface film formed on the stainless steel surface by BA treatment vary greatly depending on the temperature, time, atmosphere gas composition, etc. during annealing, and in some cases, a highly protective film such as a so-called passive film is formed. If present, it may form a film that has very weak protective properties and may actually prevent the stainless steel surface from becoming passivated. Therefore, the corrosion resistance of stainless steel BA materials usually varies greatly depending on the BA conditions, but the relationship between BA conditions and corrosion resistance has not yet been fully elucidated. As mentioned above, commercially available stainless steel 2B specification materials and
Stainless steels with excellent surface gloss, such as BA-treated materials, have very large differences in corrosion resistance even if they are of the same steel type or have the same surface specifications due to subtle differences in the manufacturing process. There are more or less inferior classes. Of course, the outermost surface of these materials is made passivated by the action of O 2 in the atmosphere, so they maintain the corrosion resistance of stainless steel, but for some reason (for example, scratches, acid adhesion, etc.) ), when the outermost surface is removed, rusting often occurs due to localized corrosion such as pitting corrosion. Note that even if these materials are immersed in an oxidizing acid such as nitric acid, the passive film (oxide film) is strengthened, but even in this case, the chromium-deficient layer is not easily removed, so pitting corrosion resistance is not improved much. Of course, these commercially available 2B specification materials and BA treated materials are pickled with a mixed aqueous solution of nitric acid and hydrofluoric acid.
It is possible to obtain the excellent corrosion resistance inherent to bare metal by completely removing the parts of the surface with poor corrosion resistance.
In this case, the surface loses its luster and its commercial value as a mirror finish material is lost. For this reason, as a means to improve the corrosion resistance of stainless steel BA-treated materials, the material is subjected to anodic electrolysis or alternating current electrolysis in an aqueous solution such as nitric acid, and then further immersed in an oxidizing acid (nitric acid, etc.) as necessary. A method of passivation treatment was also proposed (Japanese Patent Application Laid-open No. 142140-1983).
(Japanese Patent Publication No. 54-142142, Japanese Patent Application Publication No. 59-6398, Japanese Patent Application Publication No. 59-23882, etc.). However, all of these methods attempt to improve corrosion resistance through electrolytic treatment, which is performed by directly connecting lead wires to the stainless steel material to be treated and passing an electric current through it, which is easily carried out in experimental beaker tests. However, if continuous steel strips are to be processed on an industrial scale, special measures are needed to pass current through the moving steel strips, and spark defects may occur. (sparks are likely to occur when electricity is connected directly to a moving workpiece),
This method was by no means preferable as a treatment means for the above-mentioned "stainless steel material with metallic luster" which requires special attention to the surface appearance. <Means for Solving the Problems> From the above-mentioned viewpoints, the present invention provides a method for treating even if the material to be treated is a continuously running steel strip or an extremely small single item. 2B or BA, which can be easily performed without worrying about creating defects such as spark scratches on the surface.
This was completed through research conducted by the present inventors to provide a method for improving the corrosion resistance of finished stainless steel with metallic luster. For example, as shown in Figure 1, 2B or BA finished metal By immersing a shiny stainless steel 1 in an electrolyte aqueous solution 2 and causing localization of positive and negative charges on the surface of the stainless steel by the action of an electrode 3 placed in the vicinity,
It is characterized in that it improves corrosion resistance by forming a highly protective oxide film on the surface of the stainless steel to be treated 1 without directly passing an electric current through it, and which does not affect the gloss. . In other words, when, for example, a negatively charged electrode 3 is brought close to a 2B or BA-finished stainless steel 1 that has been immersed in an electrolyte aqueous solution 2 and has a metallic luster, positive charges will gather and localize on the surface facing the stainless steel 1. (electrostatic induction effect), Me+2OH - →MeO+H 2 O+2e ...(1) (metal) (metal oxide) or Me+NO 3 - →MeO+NO 2 +e ...(2) (metal) (metal oxide), etc. Through the reaction, a dense Cr-rich metal oxide film (passive film) is formed on the surface of stainless steel 1, which has strong protective properties and does not impair the metallic luster.
To sufficiently improve the corrosion resistance of stainless steel 1. In addition, there may be a layer (chromium-deficient layer) with lower chromium content and poorer corrosion resistance than the base material on the surface of 2B specification materials or BA-treated materials. treatment), on the side where positive charges are localized, Fe is dissolved by the reaction of Me→M n+ +ne - ...(3), and at the same time, Cr is dissolved by the reaction of equation (1) or (2) above. becomes an oxide
A dense Cr-rich oxide film (passive film) is formed. In addition, at this time, where negative charges are localized, the following reaction occurs, 2H + +2e→H 2 ...(4), and hydrogen gas is generated. Peeling is promoted. As described above, in the method of the present invention, the electric charge generated by the electrostatic induction action promotes dissolution, oxidation, or reduction of the stainless steel surface and quickly improves the corrosion resistance of stainless steel with metallic luster. Even if a slight chromium-depleted layer exists, a surface condition with sufficiently excellent corrosion resistance can be obtained. As is clear from the above explanation, positive charge is an effective action for generating a passive film on stainless steel [promoting the reaction of formula (1), (2), or (3)]. However, in the case of electrostatic induction, if a charge collects in one part, negative charge will always collect in another part, so this can be used efficiently. For good results, it is also good to place the positive and negative electrodes close to each other as shown in FIG. Further, at this time, it is preferable to change the potential of the electrode over time in order to equalize the treatment effect on the surface of the treatment material. Changes in electrode potential over time can be easily realized by "applying an alternating voltage (using alternating current)," but the waveform can be not only a normal sine wave but also a square wave, triangular wave, etc. Furthermore, the frequency is not limited to 50 to 60 Hz, and sufficient effects can be obtained even at, for example, 1 to 300 Hz, so there is no particular restriction. Note that even if the material to be treated is continuously passed near the electrode without changing the potential of the electrode, the treatment effect can be made uniform in the same way as described above. As the electrolyte aqueous solution used in the method of this invention, an aqueous solution containing nitric acid or a nitrate (an aqueous solution containing nitrate ions) is preferable from a cost standpoint. It is also good to use a material containing dichromate ion (CrO 2 O 7 2- ) or the like. By the way, the treatment according to this invention is "electrolytic pickling"
However, in electrolytic pickling, it is essential to apply a large current to mainly carry out the reactions of equations (3) and (4), so naturally the surface of the material to be treated is The skin becomes rough and loses its luster. On the other hand, in the treatment according to the present invention, the material to be treated is shiny stainless steel with a 2B or BA finish without oxidation scale, and the metal is oxidized by the reaction of formula (1) or formula (2) above. This process is completely different from electrolytic pickling, as it forms a passive film. In this case, whether metal dissolution occurs due to the reaction of formula (3) above, or oxidation occurs due to the reaction of formula (1) or (2) above, depends on the strength (amount) of the negative charge, the electrode and the treated object. It depends on the distance to the material, the electrolyte concentration, the electrical resistance of the electrode, etc., but by controlling these things {specifically, by keeping the electrolyte concentration relatively thin and using an electrode with relatively high electrical resistance. If the potential is brought to a more positive side, the dissolution of formula (3) above is suppressed and the oxidation reaction of formula (1) is promoted.
It has a high Cr content and forms a highly protective oxide film. In order to process a continuous steel strip on an industrial scale using the method of the present invention, it is sufficient to use, for example, an apparatus as shown in FIGS. 3 to 5. That is, FIG. 3 shows two electrode plates 4,
In this example, an alternating voltage is applied to 4, and a continuous steel strip 5 passes between them. Further, FIG. 4 shows a structure in which electrode plates of different polarities are arranged in different tanks, and there is no current loss and the processing efficiency is extremely high. FIG. 5 shows an example in which electrode plates of different polarities are arranged side by side, which is inferior in current efficiency but requires less equipment cost. As can be seen from the above explanation, the method of this invention does not require direct contact of lead wires etc. to the material to be treated to supply current, so there is no risk of generating sparks, and therefore there is no need to worry about products with poor appearance due to spark defects. It is clear that there is no such thing. Next, the effects of the present invention will be specifically explained with reference to Examples. <Example> As shown in Fig. 6, two electrode plates (anodized titanium with special coating (distance between each electrode plate and the surface of the test piece: 3 mm), and these were immersed in a 10% HNO 3 aqueous solution 7 with a bath temperature of 50°C. Next, a 50Hz alternating current is applied to the electrodes 4, 4 for 10 minutes.
After application for ~60 seconds, the test piece was taken out, washed with water and dried, and its gloss retention rate: gloss after treatment/gloss before treatment x 100 and corrosion resistance were investigated. The results obtained are shown in Table 1 along with some of the processing conditions. As is clear from the results shown in Table 1,
It can be seen that the treatment of this invention significantly improves the corrosion resistance of stainless steel with almost no reduction in surface gloss. In addition, even if the gloss is slightly reduced due to the treatment, the gloss can be sufficiently restored by simply applying mild temper rolling afterwards.
【表】
も明瞭である。
なお、この実施例ではSUS430ステンレス鋼の
BA処理材に対する処理例だけを示したが、この
発明の方法の適用材はこれに限られるものではな
く、別鋼種の材料であつても、また2B仕様材で
あつても適用できることは言うまでもない。
以上に説明した如く、この発明によれば、金属
光沢を有したステンレス鋼の2B仕様材やBA処理
材の耐食性を、該金属光沢を劣化させることなく
かつ表面にスパーク疵等の欠陥を生じさせること
なく顕著に改善することができ、ステンレス鋼の
適用分野が一層拡大されるなど、産業上極めて有
用な効果がもたらされるのである。[Table] is also clear. In addition, in this example, SUS430 stainless steel is used.
Although only an example of treatment for BA-treated material is shown, the material to which the method of this invention can be applied is not limited to this, and it goes without saying that it can also be applied to materials of different steel types or 2B specification materials. . As explained above, according to the present invention, the corrosion resistance of 2B specification stainless steel materials and BA treated materials with metallic luster can be improved without deteriorating the metallic luster and causing defects such as spark scratches on the surface. This results in extremely useful industrial effects, such as further expanding the fields of application of stainless steel.
第１図及び第２図は、それぞれ本発明の処理時
に起きる“静電誘導作用による被処理材表面の電
荷分布”を説明した概略模式図、第３図、第４図
及び第５図は、それぞれ連続鋼帯に工業的規模で
本発明に係る方法を適用する場合の仕様装置例を
示す概略模式図、第６図は、実施例で採用したビ
ーカーテストの手法を説明する概略模式図であ
る。
図面において、１……ステンレス鋼、２……電
解質水溶液、３……電極、４……電極板、５……
連続鋼帯、６……試験片、７……10％HNO3水溶
液。
Figures 1 and 2 are schematic diagrams illustrating the "charge distribution on the surface of the treated material due to electrostatic induction" that occurs during the treatment of the present invention, and Figures 3, 4, and 5 are FIG. 6 is a schematic diagram illustrating an example of specification equipment when applying the method according to the present invention to a continuous steel strip on an industrial scale, and FIG. 6 is a schematic diagram illustrating the beaker test method adopted in the example. . In the drawings, 1... Stainless steel, 2... Electrolyte aqueous solution, 3... Electrode, 4... Electrode plate, 5...
Continuous steel strip, 6... Test piece, 7... 10% HNO 3 aqueous solution.
Claims (1)
ンレス鋼を電解質水溶液に浸漬すると共に、その
近傍に位置せしめた電極の作用により前記ステン
レス鋼表面に正と負の電荷の局在化を生ぜしめて
保護酸化皮膜を形成することを特徴とする、金属
光沢を有したステンレス鋼の耐食性改善方法。 ２ 電解質水溶液が硝酸又は硝酸塩を含む水溶液
である、特許請求の範囲第１項記載の金属光沢を
有したステンレス鋼の耐食性改善方法。 ３ 電極電位を経時変化させる、特許請求の範囲
第１項又は第２項記載の金属光沢を有したステン
レス鋼の耐食性改善方法。 ４ 電極電位を経時変化させることなく、電極近
傍にステンレス鋼を連続的に通過させる、特許請
求の範囲第１項又は第２項記載の金属光沢を有し
たステンレス鋼の耐食性改善方法。[Claims] 1. A stainless steel with a metallic luster that has been finished with 2B or BA is immersed in an electrolyte aqueous solution, and positive and negative charges are localized on the surface of the stainless steel by the action of an electrode placed near the electrolyte solution. 1. A method for improving the corrosion resistance of stainless steel with metallic luster, characterized by forming a protective oxide film. 2. The method for improving corrosion resistance of stainless steel with metallic luster according to claim 1, wherein the electrolyte aqueous solution is an aqueous solution containing nitric acid or nitrate. 3. A method for improving the corrosion resistance of stainless steel with metallic luster according to claim 1 or 2, which comprises changing the electrode potential over time. 4. A method for improving the corrosion resistance of stainless steel with metallic luster according to claim 1 or 2, which comprises continuously passing the stainless steel near the electrode without changing the electrode potential over time.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19404386A JPS6350498A (en) | 1986-08-21 | 1986-08-21 | Improvement of corrosion resistance of stainless steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19404386A JPS6350498A (en) | 1986-08-21 | 1986-08-21 | Improvement of corrosion resistance of stainless steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6350498A JPS6350498A (en) | 1988-03-03 |
| JPH0443994B2 true JPH0443994B2 (en) | 1992-07-20 |
Family
ID=16317985
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP19404386A Granted JPS6350498A (en) | 1986-08-21 | 1986-08-21 | Improvement of corrosion resistance of stainless steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6350498A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH089798B2 (en) * | 1989-06-26 | 1996-01-31 | 株式会社ケミカル山本 | Surface treatment method for stainless steel |
| CN109137045B (en) * | 2018-09-13 | 2019-10-25 | 湖北大学 | A method of colour super-hydrophobic stainless steel is prepared based on alkali electrochemical coloring |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5959899A (en) * | 1982-09-29 | 1984-04-05 | Kawasaki Steel Corp | Method for electrolytic descaling of stainless steel strip |
-
1986
- 1986-08-21 JP JP19404386A patent/JPS6350498A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5959899A (en) * | 1982-09-29 | 1984-04-05 | Kawasaki Steel Corp | Method for electrolytic descaling of stainless steel strip |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6350498A (en) | 1988-03-03 |
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