JPH0520514B2 - - Google Patents
Info
- Publication number
- JPH0520514B2 JPH0520514B2 JP24082884A JP24082884A JPH0520514B2 JP H0520514 B2 JPH0520514 B2 JP H0520514B2 JP 24082884 A JP24082884 A JP 24082884A JP 24082884 A JP24082884 A JP 24082884A JP H0520514 B2 JPH0520514 B2 JP H0520514B2
- Authority
- JP
- Japan
- Prior art keywords
- corrosion resistance
- corrosion
- zinc
- plating
- steel
- 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
- 238000005260 corrosion Methods 0.000 claims description 85
- 230000007797 corrosion Effects 0.000 claims description 84
- 229910000831 Steel Inorganic materials 0.000 claims description 55
- 239000010959 steel Substances 0.000 claims description 55
- 229910045601 alloy Inorganic materials 0.000 claims description 38
- 239000000956 alloy Substances 0.000 claims description 38
- 239000011701 zinc Substances 0.000 claims description 38
- 238000009792 diffusion process Methods 0.000 claims description 22
- 238000000576 coating method Methods 0.000 claims description 21
- 239000011248 coating agent Substances 0.000 claims description 20
- 239000011247 coating layer Substances 0.000 claims description 20
- 229910052759 nickel Inorganic materials 0.000 claims description 15
- 229910052742 iron Inorganic materials 0.000 claims description 10
- 229910017709 Ni Co Inorganic materials 0.000 claims description 9
- 229910003267 Ni-Co Inorganic materials 0.000 claims description 9
- 229910003262 Ni‐Co Inorganic materials 0.000 claims description 9
- 229910052758 niobium Inorganic materials 0.000 claims description 6
- 229910052719 titanium Inorganic materials 0.000 claims description 6
- 229910001297 Zn alloy Inorganic materials 0.000 claims description 5
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- 229910052726 zirconium Inorganic materials 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 3
- 238000007747 plating Methods 0.000 description 54
- 239000010410 layer Substances 0.000 description 36
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 28
- 229910052725 zinc Inorganic materials 0.000 description 28
- 230000000694 effects Effects 0.000 description 20
- 239000000463 material Substances 0.000 description 19
- 238000011282 treatment Methods 0.000 description 16
- 239000011651 chromium Substances 0.000 description 14
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 14
- 238000011156 evaluation Methods 0.000 description 12
- 238000012360 testing method Methods 0.000 description 9
- 238000000227 grinding Methods 0.000 description 7
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 7
- 239000003973 paint Substances 0.000 description 7
- 239000007864 aqueous solution Substances 0.000 description 6
- 230000007547 defect Effects 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 150000003839 salts Chemical class 0.000 description 6
- 229910001335 Galvanized steel Inorganic materials 0.000 description 5
- 239000008397 galvanized steel Substances 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 238000003466 welding Methods 0.000 description 5
- 238000005275 alloying Methods 0.000 description 4
- 238000000137 annealing Methods 0.000 description 4
- 125000002091 cationic group Chemical group 0.000 description 4
- 239000010960 cold rolled steel Substances 0.000 description 4
- 238000004070 electrodeposition Methods 0.000 description 4
- 238000000465 moulding Methods 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 229910019142 PO4 Inorganic materials 0.000 description 3
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 3
- 239000004327 boric acid Substances 0.000 description 3
- 125000004122 cyclic group Chemical group 0.000 description 3
- 238000009713 electroplating Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 3
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 3
- 238000010422 painting Methods 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 3
- 239000010452 phosphate Substances 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 230000001603 reducing effect Effects 0.000 description 3
- 239000007921 spray Substances 0.000 description 3
- 229910020598 Co Fe Inorganic materials 0.000 description 2
- 229910002519 Co-Fe Inorganic materials 0.000 description 2
- 229910001030 Iron–nickel alloy Inorganic materials 0.000 description 2
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 239000010953 base metal Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- GVEHJMMRQRRJPM-UHFFFAOYSA-N chromium(2+);methanidylidynechromium Chemical compound [Cr+2].[Cr]#[C-].[Cr]#[C-] GVEHJMMRQRRJPM-UHFFFAOYSA-N 0.000 description 2
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 description 2
- 229910000361 cobalt sulfate Inorganic materials 0.000 description 2
- 229940044175 cobalt sulfate Drugs 0.000 description 2
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 description 2
- 238000005238 degreasing Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 238000004080 punching Methods 0.000 description 2
- 239000004575 stone Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910003470 tongbaite Inorganic materials 0.000 description 2
- 230000037303 wrinkles Effects 0.000 description 2
- 229910000531 Co alloy Inorganic materials 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 229910017061 Fe Co Inorganic materials 0.000 description 1
- 229910017060 Fe Cr Inorganic materials 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 229910002544 Fe-Cr Inorganic materials 0.000 description 1
- 229910003271 Ni-Fe Inorganic materials 0.000 description 1
- 229910007567 Zn-Ni Inorganic materials 0.000 description 1
- 229910007614 Zn—Ni Inorganic materials 0.000 description 1
- 238000005219 brazing Methods 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000001568 sexual effect Effects 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
- C23C28/021—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material including at least one metal alloy layer
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
- C23C28/023—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only
- C23C28/025—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only with at least one zinc-based layer
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electroplating Methods And Accessories (AREA)
- Coating With Molten Metal (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Description
（産業上の利用分野）
本発明はNaCl，CaCl2等の水溶液が存在する
苛酷な腐食環境に曝される場合の耐食性、塗膜性
能特に自動車用鋼板に使用される場合の孔食に対
して優れた性能を有する亜鉛系電気合金メツキ鋼
板に関する。
（従来の技術及びその問題点）
従来から自動車用鋼板には防錆被覆層が施され
ていない、いわゆる冷延鋼板が使われて来た。こ
の冷延鋼板は、自動車会社で自動車の各種部材に
加工され、組立てられた後、燐酸塩処理を施し、
次いで塗装される。即ち自動車に使用されている
冷延鋼板は、塗膜によつて腐食から保護されてい
る。しかし近年になつて自動車の耐久性向上、特
に腐食に基因する耐久性向上の要求が高くなり、
従来の塗装のみではこの要求に必ずしも対処出来
なくなつた。例えば、冬期、道路の凍結を防止す
るため塩を散布するカナダにおいては、1985年の
自動車の車体腐食に関するガイドラインとして
“10年間孔あきなし”及び“５年間錆発生なし”
を目標にしている。このガイドラインは“カナダ
コード”として知られ、このため車体防錆に対す
る目標として各種対策が採られつつある。
現在、冷延鋼板の耐食性、塗装後の耐食性を向
上し、かつ加工性を損なわずに量産可能なものと
して、電気亜鉛メツキ鋼板が広く使われている。
しかし、亜鉛メツキ鋼板は、亜鉛が地鉄よりアノ
ーデイツク（Anodic）であるため、一般的な腐
食環境では良好な耐食性を示すが、前述の様に塩
類（NaCl，CaCl2等）を散布する苛酷な腐食環
境では亜鉛の腐食速度が大きく、短期間で亜鉛の
犠牲防食作用が失なわれ長期間の防食効果が得ら
れない。
耐食性の向上にはメツキ量を増す事が最も簡単
な方法である。しかし、メツキ量の増加は電気メ
ツキでは著るしい生産性の低下とコスト上昇をも
たらし、経済的に望ましくないばかりでなく、加
工性、溶接性等の面でも次の様な問題がある。
即ち、メツキ鋼板を自動車部品に加工する際、
特に絞り加工において、メツキ層が剥離したり、
又その一部が削り取られて（所謂パウダリング）
プレス金型に堆積し、成品に疵を生じる現象があ
る。この様なパウダリングを起すと、金型の手入
れで生産性が著るしく落ちるばかりでなく、成品
の性能にも悪影響がある所から、メツキ量を少な
くする必要がある。一方加工された各種部材の組
立ては、殆んど抵抗溶接（スポツト溶接）が使わ
れ、溶接性の良悪が重視されている。溶接性に
は、メツキ量が大きく影響し、メツキ量がある程
度以上に増えると、溶接部の強度不足、外観不良
等の欠陥を生じ易くなり、更には溶接電極寿命の
著るしい低下が生じる。従つて、加工性、溶接性
の見地からすると、出来るだけ低メツキ量である
事が望ましい。更に、自動車用亜鉛メツキ鋼板は
最終的には塗装されるが、塗膜を浸透した腐食性
水溶液に亜鉛が腐食され易いために、塗膜面“ふ
くれ”（所謂ブリスター）を発生し、塗膜が素地
から浮き上り剥離するという欠点がある。又、自
動車が走行中、飛石等により塗膜欠陥が生じる
と、その部分から塗膜下の腐食が広がり、塗膜剥
離を生じ易い。
かかる亜鉛メツキ鋼板の欠点の解消を目的に、
亜鉛よりも電位が貴（cathodic）、かつ地鉄より
は卑（Anodic）で、地鉄に対して陽極防食効果
があり、塩類による腐食速度が小さく、更に、塗
装性能（特に塗装後耐食性、二次塗料密着性……
塗装部が腐食環境に曝された時の塗膜の密着性の
劣化）、加工性、溶接性に優れるという考え方に
基づいて、例えばZn−Fe系、Zn−Ni系、Zn−
Fe−Ni系、Zn−Ni−Co系、Zn−Fe−Cr系等、
更には、それ等を組合せた複層メツキ等特開昭55
−110793号公報、特開昭57−51284号公報、特開
昭57−149483号公報のように多くの亜鉛系合金メ
ツキ鋼板が開発されている。これ等の亜鉛系合金
メツキ鋼板は、全般的に亜鉛メツキ鋼板に比して
優れた性能を有しているものの、耐食性、特に、
前述の塩類が散布される苛酷な腐食環境での孔食
（Pitting Corrosion）については、更に一段の向
上が望まれている。
耐食性の向上は、メツキ量の増加により最も簡
単に達成されるが、しかし既に亜鉛メツキ鋼板に
ついて述べたように、Zn系合金メツキ鋼板の場
合においても、メツキコストの上昇、加工時のパ
ウダリング、溶接性の劣化等の問題を生じるた
め、出来るだけ低メツキ量である事が望ましい。
（問題点を解決するための手段、作用）
以上の諸点に鑑み、本発明者等は、耐食性、塗
装性能のみではなく、加工時のパウダリング性、
溶接性等自動車用防錆鋼板に求められている諸性
能に優れた自動車用防錆鋼板として、最適な亜鉛
系合金メツキ鋼板を得る事を目的に種々の検討を
行なつた。
その結果、メツキ層自体の耐食性を向上させる
ために、電位的にZnよりカソーデイツク化され
た亜鉛系合金メツキ層は、Cl-イオン等を含有す
る腐食環境では腐食速度が小さくなるが、腐食が
進行するにつれて合金メツキ層中のZnが優先腐
食され、残存した貴な合金化元素Ni，Fe，Co等
の影響により、鋼板との電位差が小さくなり、孔
食９を発生する原因となつたり或いは端面の犠牲
防食能等を劣化し、耐食性能、特に耐食寿命を劣
化する原因になつていることが判つた。従つて、
これらの亜鉛系合金メツキ層と鋼板の間の電位差
を拡大して、犠牲防食能を確保すると共に、鋼板
自体の耐孔食性能を改良する事によつて、腐食環
境における腐食速度の小さい亜鉛系合金メツキ層
の良好な耐食性との相剰効果により、低メツキ量
で耐食性、特に耐食寿命がすぐれ、また上記の如
き各特性のすぐれた亜鉛系合金メツキ鋼板を得る
事ができた。
而して、その要旨とするところは、Ｃ：0.02％
以下、solAl：0.005〜0.08％、Cr：0.2〜10％ある
いは必要に応じてTi，Nb，Ｖ，Zrの１種又は２
種以上をそれぞれ0.03〜0.5％含有して残部がFe
および不可避的不純物からなる鋼板にNi，Co，
Ni−Co合金からなる拡散下地被覆層とZnに対し
てNi，Fe，Co，Moの１種又は２種以上を含有
せしめたZn合金系被覆を施した高耐食性Zn系合
金メツキ鋼板である。
以下に本発明について詳細に説明する。
転炉、電気炉等の溶解された溶鋼を連続鋳造法
または造塊、分塊法を経てスラブとし熱間圧延、
冷間圧延あるいはさらに焼鈍工程を経てＣ：0.10
％以下、solAl：0.005〜0.08％、Cr：0.2〜10％を
含有して残部が実質的にFeからなるメツキ原液
を製造する。Ｃは含有量の増加に鋼板の加工性を
劣化し、鋼板表面に点在して析出した多量のセメ
ンタイトが、Ni，Co，Ni−Co合金等の下地被覆
処理後或いは亜鉛系合金メツキ後に多くのピンホ
ールを発生させる原因となる。したがつてＣ成分
は耐食性を劣化する有害元素として少ない方が好
ましく、その上限を0.10％とした。好ましいのは
0.01％以下である。Alは溶鋼の脱酸元素である
が、製造された鋼板中に残存するsolAl量が0.005
％未満では酸素ガスによる表面欠陥の発生率を著
しく高め、下地処理面或いは亜鉛系合金メツキ面
に多量のピンホールが発生し耐食性を劣化する。
また0.08％を越える過剰なsolAlはAl系酸化物
を鋼表面に多く点在せしめ、不メツキ部分あるい
はピンホールを発生してメツキの健全性を失い、
耐食性を劣化する。したがつて鋼中に含有される
solAlは、耐食性が安定して確保できる量として
0.005〜0.08％に限定した。
Crの添加は、腐食環境に曝された鋼板の電位
を貴な方向に近づけ、鋼板自体の耐食性を向上せ
しめるとともに、鋼板表面に施されるNi，Co，
Ni−Co合金の下地被覆、拡散層とあいまつて、
Cl-イオンを含有する腐食環境における耐孔食性
能の向上と、亜鉛系合金メツキ層との電位差拡大
による亜鉛系合金メツキ層の犠牲防食能を腐食環
境に曝された後も確保する。
而して、Crの添加量が0.2％未満では上記の効
果が得られず、またCrの添加量が10％をこえる
と成形加工時にリジングが発生し、成形加工品の
外観及び板厚にも変動が生じるので耐食性能の点
からも好ましくない。従つて、Crの添加量は0.2
〜10％とし好ましくは0.5〜８％である。
又、本発明においては上記の鋼成分に対して、
Ti，Nb，Ｖ，Zrの１種又は２種以上それぞれ
0.03〜0.5％を添加する。これは、本発明が苛酷
な成形加工が要求される用途、例えば深絞り成形
形状が複残なクオーターパネル、リヤーフエンダ
ー、フロントフエンダー等のように、鋼板自体に
優れた成形加工性と耐食性を要求される場合、
Ti，Nb，Ｖ，Zrの１種又は２種以上を添加する
事によつて、鋼中のＣと結合せしめクロムカーバ
イドの析出を防止してCrの有効化を計り、良好
な成形加工性と、耐食性の向上が可能となる。こ
の場合のTi，Nbなどの鋼成分の含有量が0.03％
未満ではクロムカーバイドの析出を防止して、成
形加工性及び耐食性を向上せしめる効果が少な
く、またその含有量が0.50％を越えるとその効果
が飽和に達し経済的でなくなると共に、これら成
分の析出によつて素材の硬質化を起し、成形加工
性を劣化する傾向にある。特に、好ましくはこれ
ら元素の含有量が0.05〜0.30％の範囲である。
鋼中に含有される不可避的不純物のＰ，Ｓ等は
結晶粒界にの析出して結晶粒界をぜい化するため
少ない程よい。尚、本発明においては、その用途
によつては、Ti，Nb等を添加した鋼板に対して
は、0.0001〜0.003％のＢを添加してもよい。Ｂ
は結晶粒界に析出するので、溶接或いはロウ付け
作業等の高熱操作を受ける場合に、これら熱影響
部での結晶粒の成長、粗大化を防止する有効な成
分である。
上記のように成分組成に構成されたメツキ原板
は、脱脂、酸洗等のメツキ前処理工程を経て、
Ni，Co，Ni−Co合金メツキのいずれかの一層か
らなる拡散層の下地被覆処理が施される。これら
の下地被覆処理方法は、メツキ浴組成、メツキ条
件等は特に規定されるものではないが、大体電流
密度３〜300A／ｄm2，メツキ温度80℃以下がよ
い。メツキ浴組成の一例及びメツキ条件の一例を
あげれば下記の如くである。
(1) Niメツキ浴
硫酸ニツケル 240g／
塩化ニツケル 45g／
ほう酸 30g／
電流密度 15A／ｄm2
(2) Coメツキ浴
硫酸コバルト 300g／
塩化コバルト 50g／
ほう酸 30g／
電流密度 10A／ｄm2
(3) Ni−Co合金メツキ浴
硫酸ニツケル 150g／
硫酸コバルト 120g／
塩化ニツケル 30g／
塩化コバルト 24g／
ホウ酸 40g／
電流密度 7.5A／ｄm2
などを用いて、電気メツキを行なえばよい。
又、これらの電気メツキによる下地前処理後或
いはこれらの金属イオンを含有する水溶液、例え
ばさく酸ニツケル（100g／）−界面活性剤系の
水溶液を塗布乾燥後に、各々非酸化性或いは還元
性或いは還元性雰囲気で、600〜850℃で20〜180
秒の加熱拡散処理を行ない、Ni−Fe，Co−Fe，
Ni−Co−Fe等からなる拡散処理層を形成する。
尚、この場合、下地被覆層の一部がNi，Co，
Ni−Coの形態のままで残存してもよい。さらに、
この下地被覆処理層の付与及び加熱拡散処理を施
すにあたり、これらの処理は冷間圧延材（As
Cold材）或いは冷間圧延後に焼鈍した素材のい
ずれに適用してもよい。しかしながら、冷間圧延
材にこれらの下地被覆処理を施し、材質の焼鈍を
兼ねて拡散処理を行なうのが好ましい。
すなわち、冷間圧延材（As Cold材）の加工歪
によつて、下地被覆層と鋼板の相互拡散が促進さ
れる傾向が大きいため、短時間の加熱処理で目的
の拡散被覆層を得る事ができる。また、同時に、
Cr含有量が2.5％以上になると酸化され易い傾向
にあるので、加熱焼鈍雰囲気を調整する必要があ
るが、上記の如く焼鈍と拡散処理を同時に行なう
場合は、下地被覆層のいんぺい効果によつて、そ
の酸化を防止できるので、加熱雰囲気の調整が容
易になる利点もある。
拡散下地被覆層は、Cr含有鋼板の表面を改質
して、耐食性、耐孔食性を向上せしめるととも
に、Zn系合金メツキ層との電位差を大きくして、
その犠牲防食効果を確保するために設けられるも
ので、その厚さは、0.01〜1.5μで使用するとよ
い。
下地被覆層の厚さが0.01μ未満では原板の拡散
処理によつて均一な拡散被覆層が得られないた
め、下地被覆層の欠陥部が多く生成されない場合
もある。一方、その下地被覆層の厚さが1.5μをこ
える場合には、拡散被覆層の目的とする効果が飽
和するとともに、拡散下地被覆層の表面に下地被
覆層の形態のままで多くのNi，Co，Ni−Co合金
が残り、成形加工性を劣化する場合もある。従つ
て、拡散下地被覆層の厚さは、下地被覆層として
0.01〜1.5μが好ましい。
次に、これらの拡散下地被覆層の上層にZnに
対してNi，Fe，Co，Mo1種又は２種以上を含有
した亜鉛系合金メツキを施す。
以上に説明したようにCr含有鋼板に拡散下地
被覆層を施した鋼板は、従来の鋼板に比して耐食
性が優れているものの、自動車用防錆鋼板として
の耐食性が十分でなく、また赤錆の発生が認めら
れる。したがつて前記の亜鉛系合金メツキ層を施
す必要がある。
亜鉛系合金メツキ層は、その腐食速度が小さ
く、又塗装性能のすぐれたものとして、Znに対
してNi，Fe，Co，Moの１種又は２種以上を含
有したものを使用する。この場合該被覆層中の
Ni，Feなどの合金化成分が7.5％未満では、亜鉛
系合金メツキ層の塗膜を通つて侵入する腐食水溶
液によつてメツキ層が溶解され、その腐食生成物
によつて塗膜に微小なフクレ（ブリスター）を生
じるなど塗装後の耐食性が充分でない。又、合金
化元素が30％をこえる場合は、合金メツキ層のピ
ンホール生成量が多くなつて耐食性向上効果が期
待できず、またメツキ層がもろくなるため成形加
工性が劣化（成形加工時にパウダリングが発生し
易くなる）するので好ましくない。さらに、これ
らの亜鉛系合金メツキ層は、耐食性確保の点から
1.5μ以上メツキまた溶接性、成形加工性、特にパ
ウダリング防止から8μ以下がよい。
さらに、本発明においては、亜鉛系合金メツキ
層の化成処理性、溶接性の向上、カチオン電着塗
装時のクレーター発生防止のために、60％以上の
Feを主成分とする厚さ1μ以下のZn−Fe系合金
（Zn−Fe，Zn−Fe−Ni，Zn−Fe−Co，Zn−Fe
−Ｐ）、及び0.5μ厚さ以下のFe系合金（Fe−Ｐ，
Fe−Ni，Fe−Co）等を前記亜鉛系合金被覆層を
施してもよい。この場合、各々の厚さがその上限
をこえると、パウダリング性が劣化する事及び腐
食環境に曝された場合Feの腐食生成物である赤
錆生成量が多くなり、赤錆付着下での〓間腐食に
よる孔食を発生し易い等の欠点が生じる。
（発明の効果）
以上の如く、Cr含有鋼成分及び拡散下地被覆
層に亜鉛系合金メツキ層を施した本発明の耐食性
鋼板は、腐食環境において腐食水溶液に曝された
時、メツキ層自体の耐食性が優れているため、長
期にわたつて下地鋼板に対する防食効果が持続す
る事及び合金メツキ層にピンホール、成形加工時
の地鉄に達する傷つき等の欠陥部、特にメツキ層
の腐食が進行してZnの優先溶解が生じて合金化
元素の残存が多くなつた場合におけるこれら欠陥
部或いは鋼板の端面部等におけるFe露出部分に
対して、亜鉛系合金メツキ層の鋼板に対する犠牲
防食効果が維持される事によつて、これらの部分
からの穿孔腐食が防止しうるので、その耐食寿命
の向上効果が著しい。
また、これら亜鉛系合金メツキ層の防食効果が
なくなつた場合にも、鋼板自体のCrが含有され
た効果及び耐食性にすぐれたNi，Co，Ni−Co合
金等の拡散被覆層を生成せしめた効果と相まつ
て、メツキ原板の耐食性向上による孔食の進行を
抑制する効果が得られる。
このように、亜鉛系合金メツキ層と下地鋼板、
その表面の拡散被覆層との相剰効果で極めて優れ
た耐食性、耐食寿命が得られる所からメツキ量の
低減が可能となり、溶接性、パウダリング性がそ
の結果として良好であり、またメツキ層自体の優
れた化成処理性、塗装性能と相まつて、極めてす
ぐれた高耐食性、防錆鋼板が得られる。
（実施例）
次に、本発明の実施例を述べる。
冷間圧延された0.8mm板厚のCr含有鋼板（As
Cold材）を脱脂後、第１表に示す各種の下地被
覆層を電気メツキ後に水系含有還元性雰囲気で加
熱拡散処理を行なつて拡散下地被覆層を設けた。
該素材に亜鉛系合金メツキ層を設けてその性能評
価試験を行なつた。第２表にその性能評価結果を
示す。尚、評価試験は以下に示す条件で実施し
た。
無塗装材の塩水噴霧試験後の耐食性
評価材に対して地鉄に達するスクラツチ傷を入
れ、塩水噴霧試験500時間後の孔食深さにより、
その耐食性を評価した。尚、評価基準は以下の通
りである。
◎…板厚減少量0.25mm以下の場合
○… 〃 0.35mm以下 〃
△… 〃 0.50mm以下 〃
×… 〃 0.50mmこえる場合
無塗装材のサイクリツクコロジヨンテストに
よる耐食性評価
延び率10％のバルジ加工を行なつた評価材に対
して、直径７〜10mmの細石を圧力3.5Kg／cm2で10
秒間、１cm2当り2.5gが衝突するようにチツピング
させてから、第１図に示す条件のサイクリツクコ
ロジヨンテストを120サイクル行ない、赤錆発生
部分の板厚減少量を測定して、その耐食性を評価
した。尚、評価は以下の基準によつた。
◎…板厚減少量0.5mm以下
○… 〃 0.6mm以下
△…穿孔腐食の発生３ケ以下
×…穿孔腐食が３ケより多く、多数発生
カチオン電着塗装後の耐食性
評価材に対して、付着量約2.3〜2.8g／m2（片
面当り）の燐酸塩処理を施した後、厚さ20μのカ
チオン電着塗装を施した。次いで、該評価材に対
して地鉄に達するスクラツチ傷を入れ、塩水噴霧
試験1000時間を行ない、その板厚減少量よりその
耐食性評価を行なつた。
◎…板厚減少量0.3mm以下
○… 〃 0.4mm 〃
△…板厚減少量0.5mm以下
×… 〃 0.5mmをこえるか孔食発生
3Coat材の耐食性
ブランクサイズ0.8×500×500mm、潤滑油塗油
後しわ押え圧力20Tで150×150mm角のポンチで
100mm深さの角筒絞りを行なつた場合の四辺の側
壁部から試料を切り出し評価材とした。該素材に
ついて、燐酸塩処理後（2.3〜2.8g／m2付着量）、
カチオン電着15μ塗装、中塗り30μ、上塗り35μ塗
装後にと同様のグラベロチツピングテスト後
に、と同一条件のサイクリツクコロジヨンテス
トを150サイクル実施した。その後に、赤錆発生
部の穿孔腐食部分の板厚減少量よりその耐食性を
評価した。
◎…板厚減少量0.5mm以下
○… 〃 0.7mm以下
△…穿孔腐食、数点発生（10ケ未満）
×…穿孔腐食10数点以上発生（10ケ以上発生）
成形加工性
ブランクサイズ0.8×500×500mm、潤滑油塗布
後、しわ押え圧力30Tの条件で150×150mm角のポ
ンチで角筒絞りを行ない、絞り深さの限界と角筒
絞り材外面のカジリの発生状況より評価した。
◎…成形加工性極めて良好
○…成形加工性比較的良好
△…成形加工によるメツキ層のカジリ可成り発
生
×…成形加工不可
(Industrial Application Field) The present invention improves corrosion resistance and coating performance when exposed to severe corrosive environments where aqueous solutions such as NaCl and CaCl 2 are present, particularly against pitting corrosion when used on automotive steel sheets. This invention relates to zinc-based electrical alloy plated steel sheets with excellent performance. (Prior Art and its Problems) Conventionally, so-called cold-rolled steel sheets without a rust-preventing coating layer have been used as steel sheets for automobiles. This cold-rolled steel sheet is processed and assembled into various parts of automobiles at automobile companies, and then subjected to phosphate treatment.
It is then painted. That is, cold-rolled steel sheets used in automobiles are protected from corrosion by a coating film. However, in recent years, there has been a growing demand for improved durability of automobiles, especially for durability caused by corrosion.
Conventional coatings alone are no longer able to meet these demands. For example, in Canada, where salt is sprayed to prevent roads from freezing in the winter, the 1985 guidelines for car body corrosion include "no holes for 10 years" and "no rust for 5 years".
is the goal. These guidelines are known as the "Canadian Code," and for this reason, various measures are being taken as goals for car body rust prevention. Currently, electrogalvanized steel sheets are widely used because they improve the corrosion resistance of cold-rolled steel sheets and the corrosion resistance after painting, and can be mass-produced without impairing workability.
However, galvanized steel sheets have good corrosion resistance in general corrosive environments because the zinc is more anodic than base steel. In a corrosive environment, the corrosion rate of zinc is high, and the sacrificial anticorrosion effect of zinc is lost in a short period of time, making it impossible to obtain a long-term anticorrosion effect. The easiest way to improve corrosion resistance is to increase the amount of plating. However, in electroplating, an increase in the amount of plating causes a significant decrease in productivity and an increase in cost, which is not only economically undesirable, but also poses the following problems in terms of workability, weldability, etc. In other words, when processing plated steel sheets into automobile parts,
Especially during drawing process, the plating layer may peel off,
Also, part of it is scraped off (so-called powdering).
There is a phenomenon in which it accumulates on press molds and causes defects on finished products. When such powdering occurs, it is necessary to reduce the amount of plating because not only does the productivity drop significantly due to maintenance of the mold, but it also has a negative effect on the performance of the finished product. On the other hand, resistance welding (spot welding) is mostly used to assemble various processed parts, and importance is placed on the quality of weldability. Weldability is greatly affected by the amount of plating, and if the amount of plating increases beyond a certain level, defects such as insufficient strength of the weld and poor appearance are likely to occur, and furthermore, the life of the welding electrode will be significantly reduced. Therefore, from the viewpoint of workability and weldability, it is desirable that the amount of plating be as low as possible. Furthermore, galvanized steel sheets for automobiles are eventually painted, but since the zinc is easily corroded by the corrosive aqueous solution that has penetrated the paint film, the paint film surface ``blisters'' (so-called blisters) occur, causing the paint film to deteriorate. It has the disadvantage that it lifts up from the substrate and peels off. Furthermore, if a paint film defect occurs due to a flying stone or the like while the vehicle is running, corrosion under the paint film spreads from that area, which tends to cause the paint film to peel off. In order to eliminate the drawbacks of such galvanized steel sheets,
The potential is more noble (cathodic) than that of zinc, and more base (anodic) than that of base steel, which has an anodic corrosion protection effect on base steel, has a low corrosion rate due to salts, and has excellent coating performance (especially post-painting corrosion resistance, secondary Next Paint adhesion...
For example, Zn-Fe type, Zn-Ni type, Zn-
Fe-Ni system, Zn-Ni-Co system, Zn-Fe-Cr system, etc.
Furthermore, multi-layer plating, etc. that combines these, etc.
Many zinc-based alloy plated steel sheets have been developed, as disclosed in Japanese Patent Application Laid-open No. 110793, Japanese Patent Application Laid-Open No. 57-51284, and Japanese Patent Application Laid-open No. 149483-1983. Although these zinc-based alloy plated steel sheets generally have superior performance compared to galvanized steel sheets, they have poor corrosion resistance, especially
Further improvements in pitting corrosion in the harsh corrosive environment where salts are sprayed are desired. Improvement in corrosion resistance is most easily achieved by increasing the amount of plating, but as already mentioned for galvanized steel sheets, even in the case of Zn-based alloy plated steel sheets, there are problems such as increased plating costs, powdering during processing, and welding. It is desirable that the amount of plating be as low as possible, as this may cause problems such as deterioration of properties. (Means and effects for solving the problems) In view of the above points, the present inventors have developed not only corrosion resistance and coating performance, but also powdering property during processing,
Various studies were conducted with the aim of obtaining an optimal zinc-based alloy plated steel sheet as an automotive rust-proofing steel sheet that has excellent weldability and other properties required for automotive rust-proofing steel sheets. As a result, in order to improve the corrosion resistance of the plating layer itself, the zinc-based alloy plating layer, which has been made more cathodic than Zn in terms of potential, has a lower corrosion rate in a corrosive environment containing Cl - ions, etc., but corrosion progresses. As the process progresses, Zn in the alloy plating layer is preferentially corroded, and due to the influence of the remaining noble alloying elements Ni, Fe, Co, etc., the potential difference with the steel plate becomes smaller, causing pitting corrosion 9 or the end surface. It was found that the sacrificial anti-corrosion ability of the steel deteriorated, and this caused the deterioration of the corrosion resistance performance, especially the corrosion resistance life. Therefore,
By expanding the potential difference between these zinc-based alloy plating layers and the steel plate to ensure sacrificial corrosion protection, and by improving the pitting corrosion resistance of the steel plate itself, we have developed zinc-based alloys that have a low corrosion rate in corrosive environments. Due to the mutual effect of the good corrosion resistance of the alloy plating layer, it was possible to obtain a zinc-based alloy plated steel sheet that had excellent corrosion resistance, especially corrosion resistance life, with a low plating amount and also had excellent properties as described above. Therefore, the gist is that C: 0.02%
Below, solAl: 0.005 to 0.08%, Cr: 0.2 to 10%, or one or two of Ti, Nb, V, and Zr as necessary.
Contains 0.03 to 0.5% of each species and the balance is Fe.
Ni, Co,
This is a highly corrosion-resistant Zn-based alloy plated steel sheet with a diffusion base coating layer made of a Ni-Co alloy and a Zn alloy-based coating containing one or more of Ni, Fe, Co, and Mo for Zn. The present invention will be explained in detail below. Molten steel melted in a converter, electric furnace, etc. is converted into a slab through continuous casting, ingot making, or blooming, followed by hot rolling.
C: 0.10 after cold rolling or further annealing process
%, solAl: 0.005 to 0.08%, Cr: 0.2 to 10%, and the remainder is substantially Fe. As C content increases, the workability of the steel sheet deteriorates, and a large amount of cementite precipitates scattered on the surface of the steel sheet. This causes pinholes to occur. Therefore, as the C component is a harmful element that deteriorates corrosion resistance, it is preferable to have a small amount, and the upper limit thereof is set at 0.10%. What is preferable is
Less than 0.01%. Al is a deoxidizing element for molten steel, but the amount of solAl remaining in manufactured steel sheets is 0.005
If it is less than %, the rate of occurrence of surface defects due to oxygen gas will be significantly increased, and a large number of pinholes will be generated on the base treatment surface or the zinc-based alloy plating surface, deteriorating the corrosion resistance. In addition, excessive solAl exceeding 0.08% causes many Al-based oxides to be scattered on the steel surface, causing unplated areas or pinholes, and losing the integrity of the plating.
Deteriorates corrosion resistance. Therefore, it is contained in steel.
solAl is the amount that can stably ensure corrosion resistance.
Limited to 0.005-0.08%. The addition of Cr brings the electric potential of a steel plate exposed to a corrosive environment closer to the noble direction, improving the corrosion resistance of the steel plate itself, and also increases the corrosion resistance of Ni, Co, and
Together with the Ni-Co alloy base coating and diffusion layer,
It improves pitting corrosion resistance in a corrosive environment containing Cl - ions, and maintains the sacrificial corrosion protection ability of the zinc-based alloy plating layer by increasing the potential difference with the zinc-based alloy plating layer even after exposure to the corrosive environment. Therefore, if the amount of Cr added is less than 0.2%, the above effects cannot be obtained, and if the amount of Cr added exceeds 10%, ridging will occur during molding, and the appearance and thickness of the molded product will be affected. This is not preferable from the viewpoint of corrosion resistance as it causes fluctuations. Therefore, the amount of Cr added is 0.2
-10%, preferably 0.5-8%. In addition, in the present invention, for the above steel components,
One or more of Ti, Nb, V, and Zr
Add 0.03-0.5%. This is because the present invention is suitable for applications that require severe forming processes, such as quarter panels, rear fenders, front fenders, etc., which have multiple deep drawing shapes, which require excellent formability and corrosion resistance of the steel sheet itself. If
By adding one or more of Ti, Nb, V, and Zr, it combines with C in the steel, prevents the precipitation of chromium carbide, and makes Cr more effective, resulting in good formability and , it is possible to improve corrosion resistance. In this case, the content of steel components such as Ti and Nb is 0.03%
If the content is less than 0.50%, the effect of preventing the precipitation of chromium carbide and improving formability and corrosion resistance will be small, and if the content exceeds 0.50%, the effect will reach saturation and become uneconomical. As a result, the material tends to become hard and its moldability deteriorates. Particularly preferably, the content of these elements is in the range of 0.05 to 0.30%. Unavoidable impurities such as P and S contained in steel precipitate at grain boundaries and embrittle the grain boundaries, so the smaller the better. In the present invention, depending on the application, 0.0001 to 0.003% of B may be added to a steel sheet to which Ti, Nb, etc. are added. B
Since it precipitates at grain boundaries, it is an effective component for preventing the growth and coarsening of grains in these heat-affected zones when subjected to high-temperature operations such as welding or brazing operations. The plating original plate with the above-mentioned composition is subjected to pre-plating processes such as degreasing and pickling.
An undercoat treatment for a diffusion layer consisting of one layer of Ni, Co, or Ni-Co alloy plating is performed. Although the plating bath composition, plating conditions, etc. of these base coating treatment methods are not particularly specified, it is preferable that the current density be approximately 3 to 300 A/dm 2 and the plating temperature be 80° C. or less. An example of the plating bath composition and plating conditions are as follows. (1) Ni plating bath Nickel sulfate 240g / Nickel chloride 45g / Boric acid 30g / Current density 15A/dm 2 (2) Co plating bath Cobalt sulfate 300g / Cobalt chloride 50g / Boric acid 30g / Current density 10A/dm 2 (3) Ni -Co alloy plating bath Nickel sulfate 150g/cobalt sulfate 120g/nickel chloride 30g/cobalt chloride 24g/boric acid 40g/current density 7.5A/dm2, etc. may be used for electroplating. In addition, after pre-treatment of the base by electroplating, or after coating and drying an aqueous solution containing these metal ions, such as a nickel sulfate (100 g/) - surfactant-based aqueous solution, non-oxidizing, reducing or reducing properties can be prepared, respectively. 20-180 at 600-850℃ in a sexual atmosphere
Ni−Fe, Co−Fe,
A diffusion treatment layer made of Ni-Co-Fe or the like is formed. In this case, part of the base coating layer is made of Ni, Co,
It may remain in the form of Ni-Co. moreover,
When applying this base coating treatment layer and performing heating diffusion treatment, these treatments are carried out on cold-rolled materials (As
It may be applied to either cold-rolled and annealed materials. However, it is preferable to subject the cold-rolled material to these base coating treatments and to perform a diffusion treatment which also serves as annealing of the material. In other words, the processing strain of the cold-rolled material (As Cold material) has a strong tendency to promote mutual diffusion between the base coating layer and the steel plate, so it is difficult to obtain the desired diffusion coating layer with a short heat treatment. can. Also, at the same time,
When the Cr content exceeds 2.5%, it tends to be easily oxidized, so it is necessary to adjust the heating annealing atmosphere. However, when annealing and diffusion treatment are performed simultaneously as described above, the Cr content is more likely to be oxidized. Since its oxidation can be prevented, there is also the advantage that the heating atmosphere can be easily adjusted. The diffusion base coating layer modifies the surface of the Cr-containing steel sheet to improve corrosion resistance and pitting resistance, and increases the potential difference with the Zn-based alloy plating layer.
It is provided to ensure the sacrificial anticorrosion effect, and its thickness is preferably 0.01 to 1.5μ. If the thickness of the base coating layer is less than 0.01 μm, a uniform diffusion coating layer cannot be obtained by diffusion treatment of the original plate, and therefore, many defects may not be generated in the base coating layer. On the other hand, if the thickness of the base coating layer exceeds 1.5μ, the desired effect of the diffusion coating layer will be saturated, and a large amount of Ni, Co, Ni-Co alloys may remain and may deteriorate formability. Therefore, the thickness of the diffusion base coating layer is as follows:
0.01-1.5μ is preferable. Next, a zinc-based alloy plating containing one or more of Ni, Fe, Co, and Mo to Zn is applied to the upper layer of these diffusion base coating layers. As explained above, a steel sheet made of a Cr-containing steel sheet with a diffusion undercoating layer has superior corrosion resistance compared to conventional steel sheets, but it does not have sufficient corrosion resistance as a rust-preventing steel sheet for automobiles, and it also suffers from red rust. Occurrence is recognized. Therefore, it is necessary to apply the aforementioned zinc-based alloy plating layer. The zinc-based alloy plating layer contains one or more of Ni, Fe, Co, and Mo with respect to Zn because its corrosion rate is low and the coating performance is excellent. In this case, in the coating layer
If the alloying components such as Ni and Fe are less than 7.5%, the zinc-based alloy plating layer will be dissolved by the corrosive aqueous solution that penetrates through the coating film, and the corrosion products will cause minute damage to the coating film. Corrosion resistance after painting is insufficient, such as causing blisters. In addition, if the alloying element exceeds 30%, the amount of pinholes formed in the alloy plating layer will increase, making it impossible to expect the effect of improving corrosion resistance, and the plating layer will become brittle, resulting in poor formability (powder formation during forming). This is undesirable because it causes rings to occur more easily. Furthermore, these zinc-based alloy plating layers are suitable for ensuring corrosion resistance.
Plating of 1.5μ or more, and 8μ or less is recommended for weldability, moldability, and especially to prevent powdering. Furthermore, in the present invention, in order to improve the chemical conversion treatability and weldability of the zinc-based alloy plating layer, and to prevent the generation of craters during cationic electrodeposition coating, a
Zn-Fe alloys (Zn-Fe, Zn-Fe-Ni, Zn-Fe-Co, Zn-Fe
-P), and Fe-based alloys (Fe-P,
The zinc-based alloy coating layer may be formed of a material such as Fe--Ni, Fe--Co), etc. In this case, if each thickness exceeds the upper limit, the powdering property will deteriorate, and when exposed to a corrosive environment, the amount of red rust that is a corrosion product of Fe will increase, and the There are disadvantages such as easy occurrence of pitting due to corrosion. (Effects of the Invention) As described above, the corrosion-resistant steel sheet of the present invention, in which a zinc-based alloy plating layer is applied to a Cr-containing steel component and a diffusion base coating layer, exhibits corrosion resistance of the plating layer itself when exposed to a corrosive aqueous solution in a corrosive environment. Because of its excellent corrosion resistance, it maintains its anticorrosion effect on the base steel plate over a long period of time, and prevents defects such as pinholes in the alloy plating layer and scratches that reach the base steel during forming, especially corrosion of the plating layer. When preferential dissolution of Zn occurs and a large amount of alloying elements remain, the sacrificial corrosion protection effect of the zinc-based alloy plating layer on the steel sheet is maintained for these defective areas or exposed Fe parts at the edge of the steel sheet. As a result, drilling corrosion from these parts can be prevented, which significantly improves the corrosion resistance life. In addition, even when the anticorrosion effect of these zinc-based alloy plating layers disappears, the effect of containing Cr in the steel sheet itself and the formation of a diffusion coating layer of Ni, Co, Ni-Co alloy, etc., which has excellent corrosion resistance. Coupled with this effect, it is possible to obtain the effect of suppressing the progress of pitting corrosion by improving the corrosion resistance of the plating original plate. In this way, the zinc-based alloy plating layer and the base steel plate,
Due to the mutual effect with the diffusion coating layer on the surface, extremely excellent corrosion resistance and corrosion-resistant life can be obtained, which makes it possible to reduce the amount of plating, resulting in good weldability and powdering properties, and the plating layer itself Coupled with the excellent chemical conversion treatment properties and coating performance, extremely high corrosion resistance and rust prevention steel sheets can be obtained. (Example) Next, an example of the present invention will be described. Cold-rolled 0.8mm thick Cr-containing steel plate (As
After degreasing the various undercoating layers shown in Table 1, a diffusion undercoating layer was provided by performing a heating diffusion treatment in a reducing atmosphere containing an aqueous system.
A zinc-based alloy plating layer was provided on the material and a performance evaluation test was conducted. Table 2 shows the performance evaluation results. The evaluation test was conducted under the conditions shown below. Corrosion resistance after salt spray test of unpainted materials Scratches reaching the base metal were made on the evaluation material, and the depth of pitting corrosion after 500 hours of salt spray test was determined.
Its corrosion resistance was evaluated. The evaluation criteria are as follows. ◎...If the plate thickness reduction is 0.25mm or less ○... 〃 0.35mm or less 〃 △... 〃 0.50mm or less 〃 ×... 〃 If it exceeds 0.50mm Corrosion resistance evaluation by cyclic corrosion test of unpainted material Bulge with elongation rate of 10% For the processed evaluation material, fine stones with a diameter of 7 to 10 mm were placed at a pressure of 3.5 kg/cm 2 for 10 minutes.
After chipping at a rate of 2.5g per cm2 per second, a cyclic corrosion test was performed under the conditions shown in Figure 1 for 120 cycles, and the amount of reduction in plate thickness at the area where red rust occurred was measured to evaluate its corrosion resistance. evaluated. The evaluation was based on the following criteria. ◎…Plate thickness reduction 0.5mm or less ○…〃 0.6mm or less △…3 or less occurrences of perforation corrosion ×…more than 3 occurrences of perforation corrosion Corrosion resistance after cationic electrodeposition coating Adhesion to evaluation materials After a phosphate treatment with an amount of about 2.3-2.8 g/m 2 (per side), a cationic electrodeposition coating with a thickness of 20 μm was applied. Next, scratches reaching the base metal were made on the evaluation material, and a salt spray test was conducted for 1000 hours, and the corrosion resistance was evaluated based on the amount of reduction in plate thickness. ◎…Plate thickness reduction 0.3mm or less ○… 〃 0.4mm 〃 △…Plate thickness reduction 0.5mm or less ×… 〃 Exceeds 0.5mm or pitting corrosion occurs Corrosion resistance of 3-coat material Blank size 0.8 x 500 x 500 mm, lubricated oil coating After applying oil, use a 150 x 150 mm square punch with a wrinkle presser pressure of 20 T.
Samples were cut out from the side walls of the four sides of the rectangular tube drawn to a depth of 100 mm and used as evaluation materials. For the material, after phosphate treatment (2.3-2.8 g/m 2 coverage),
After applying a 15μ cationic electrodeposition coating, a 30μ intermediate coat, and a 35μ topcoat, a gravel chipping test was performed, followed by a cyclic colloidal test under the same conditions for 150 cycles. Thereafter, the corrosion resistance was evaluated based on the amount of plate thickness reduction in the corroded area where red rust occurred. ◎…Plate thickness reduction 0.5mm or less ○…〃 0.7mm or less △…Punching corrosion, several points occurred (less than 10) ×…Punching corrosion occurred in 10 or more points (more than 10 occurred) Forming workability Blank size 0.8× 500 x 500 mm, after applying lubricating oil, square tube drawing was performed using a 150 x 150 mm square punch under the conditions of wrinkle pressing pressure of 30T, and evaluation was made based on the limit of drawing depth and the occurrence of galling on the outer surface of the square tube drawing material. ◎…Very good molding processability ○…Comparatively good molding processability △…Significant galling of the plating layer due to molding ×…Cannot be molded
【表】【table】
【表】【table】
【表】【table】
第１図は本発明の実施例における耐食性を評価
する際の１サイクルを示す図である。
FIG. 1 is a diagram showing one cycle when evaluating corrosion resistance in an example of the present invention.
Claims (1)
なる鋼板に、Ni，Co，Ni−Co合金からなる拡散
下地被覆層、さらにZnに対してNi，Fe，Co，
Moの１種又は２種以上を含有せしめたZn合金系
被覆層を施した事を特徴とする高耐食性亜鉛系合
金メツキ鋼板。 ２ Ｃ：0.02％以下 solAl：0.005〜0.08％ Cr：0.2〜10％ Ti，Nb，Ｖ，Zrの１種又は２種以上をそれぞれ
0.03〜0.5％を含有して残部がFeおよび不可避的
不純物からなる鋼板にNi，Co，Ni−Co合金から
なる拡散下地被覆層、さらにZnに対してNi，
Fe，Co，Moの１種又は２種以上を含有せしめた
Zn合金系被覆を施した事を特徴とする高耐食性
亜鉛系合金メツキ鋼板。[Claims] 1 A steel plate containing C: 0.10% or less, solAl: 0.005 to 0.08%, and Cr: 0.2 to 10%, with the balance consisting of Fe and unavoidable impurities, and a steel plate made of Ni, Co, and Ni-Co alloy. Ni, Fe, Co,
A highly corrosion-resistant zinc alloy plated steel sheet characterized by being coated with a Zn alloy coating layer containing one or more types of Mo. 2 C: 0.02% or less solAl: 0.005 to 0.08% Cr: 0.2 to 10% One or more of Ti, Nb, V, and Zr, respectively
A steel plate containing 0.03 to 0.5% of Zn with the remainder consisting of Fe and unavoidable impurities is coated with a diffusion base coating layer of Ni, Co, and Ni-Co alloy, and further Ni,
Contains one or more of Fe, Co, and Mo
A highly corrosion-resistant zinc alloy plated steel sheet featuring a Zn alloy coating.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24082884A JPS61119679A (en) | 1984-11-16 | 1984-11-16 | Zinc alloy plated steel sheet of high corrosion resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24082884A JPS61119679A (en) | 1984-11-16 | 1984-11-16 | Zinc alloy plated steel sheet of high corrosion resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61119679A JPS61119679A (en) | 1986-06-06 |
| JPH0520514B2 true JPH0520514B2 (en) | 1993-03-19 |
Family
ID=17065296
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP24082884A Granted JPS61119679A (en) | 1984-11-16 | 1984-11-16 | Zinc alloy plated steel sheet of high corrosion resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61119679A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6756134B2 (en) * | 2002-09-23 | 2004-06-29 | United Technologies Corporation | Zinc-diffused alloy coating for corrosion/heat protection |
| JP5217637B2 (en) * | 2007-10-12 | 2013-06-19 | Ｊｆｅスチール株式会社 | Method for evaluating corrosion resistance of surface-treated steel sheets |
| WO2016178372A1 (en) | 2015-05-07 | 2016-11-10 | 株式会社日立製作所 | Laminated body having corrosion-resistant coating, and method for manufacturing same |
-
1984
- 1984-11-16 JP JP24082884A patent/JPS61119679A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61119679A (en) | 1986-06-06 |
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