JPS63250496A - Chromated zinc or zinc alloy plated steel sheet having superior resistance to blackening on standing and production thereof - Google Patents
Chromated zinc or zinc alloy plated steel sheet having superior resistance to blackening on standing and production thereofInfo
- Publication number
- JPS63250496A JPS63250496A JP8284387A JP8284387A JPS63250496A JP S63250496 A JPS63250496 A JP S63250496A JP 8284387 A JP8284387 A JP 8284387A JP 8284387 A JP8284387 A JP 8284387A JP S63250496 A JPS63250496 A JP S63250496A
- Authority
- JP
- Japan
- Prior art keywords
- zinc
- blackening
- steel sheet
- chromate
- ratio
- 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.)
- Granted
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 26
- 239000010959 steel Substances 0.000 title claims abstract description 26
- 239000011701 zinc Substances 0.000 title claims description 13
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 title claims description 11
- 229910052725 zinc Inorganic materials 0.000 title claims description 11
- 238000004519 manufacturing process Methods 0.000 title claims description 3
- 229910001297 Zn alloy Inorganic materials 0.000 title claims 3
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 claims abstract description 38
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 10
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 9
- 239000000956 alloy Substances 0.000 claims abstract description 9
- 239000011651 chromium Substances 0.000 claims description 31
- 238000000034 method Methods 0.000 claims description 20
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 9
- 230000008021 deposition Effects 0.000 claims description 4
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 abstract description 6
- 229910052759 nickel Inorganic materials 0.000 abstract description 2
- 229910052760 oxygen Inorganic materials 0.000 abstract description 2
- 239000002659 electrodeposit Substances 0.000 abstract 1
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 238000007747 plating Methods 0.000 description 17
- 230000000694 effects Effects 0.000 description 15
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 12
- 238000005260 corrosion Methods 0.000 description 10
- 230000007797 corrosion Effects 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 8
- 239000007788 liquid Substances 0.000 description 8
- 229910001335 Galvanized steel Inorganic materials 0.000 description 7
- 239000008397 galvanized steel Substances 0.000 description 7
- 150000002500 ions Chemical class 0.000 description 7
- 230000004888 barrier function Effects 0.000 description 6
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 5
- 238000002161 passivation Methods 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 229910000805 Pig iron Inorganic materials 0.000 description 4
- 229910000611 Zinc aluminium Inorganic materials 0.000 description 4
- HXFVOUUOTHJFPX-UHFFFAOYSA-N alumane;zinc Chemical compound [AlH3].[Zn] HXFVOUUOTHJFPX-UHFFFAOYSA-N 0.000 description 4
- 239000004327 boric acid Substances 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 150000001450 anions Chemical class 0.000 description 2
- 239000004566 building material Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000002845 discoloration Methods 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 2
- 241000272525 Anas platyrhynchos Species 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 229910001096 P alloy Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 1
- ABXXWVKOBZHNNF-UHFFFAOYSA-N chromium(3+);dioxido(dioxo)chromium Chemical compound [Cr+3].[Cr+3].[O-][Cr]([O-])(=O)=O.[O-][Cr]([O-])(=O)=O.[O-][Cr]([O-])(=O)=O ABXXWVKOBZHNNF-UHFFFAOYSA-N 0.000 description 1
- 230000002301 combined effect Effects 0.000 description 1
- 239000013065 commercial product Substances 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000004453 electron probe microanalysis Methods 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 150000002815 nickel Chemical class 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 238000004445 quantitative analysis Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
Abstract
Description
（産業上の利用分野）
家電及び建材分野における未塗装外板用途において亜鉛
めっき鋼板または亜鉛−アルミニウム系合金めっき鋼板
の経時による表面外観の安定性が要求される用途に対し
て広く利用できる。
（従来技術）
家電および建材分野において最も多くの需要を誇る表面
処理鋼板として亜鉛めっき鋼板（溶融めっき、電気めっ
き）又は亜鉛−アルミニウム系溶融合金めっき鋼板（以
下単ｌ二亜鉛系めっき鋼板という。）がある。ところが
、これらの亜鉛系めっき鋼板が未塗装下で外板使用され
る際、在庫又は曝露中にめっき表面が経時変色し黒変化
（以下、単に黒変という。）して、商品価値を大きく損
なう問題がある。
この黒変現象は、めっき界面での腐食初期に現われる現
象で特に高温多湿雰囲気の下では刀口速される。また、
高耐食性化を図った亜鉛−アルミニウム溶融合金めっき
鋼板において黒変は加速されるようである。更には、こ
の生成黒色皮膜はＺｎＯ又はＺｎＯ，Ｚｎ（ＯＲ）２Ｚ
ｎＣＯ１シ、ｒ）（２ｏで成り、針状結晶のために可視
光を吸収し易く、光学的に黒く見えるものと考えられて
いる。また、めっき層自身にも大きな原因があり、めっ
き層にＭ又はＡｌ、、Ｏ３或いはＰｂ、Ｓｎ、Ｃｄ
などの不純物が共存し、これとカップリングして亜鉛を
アノード（酸化反応）化する特注があり、亜鉛−アルミ
ニウムの如き高耐食性のめっき界面では、この反応が顕
著に認められ的規模において明確ではないが、研究的レ
ベルでは以下のようなものがある。
無水クロム酸又はそれにシリカゾルを含む処理浴で陰極
電解したのち水洗せずにそのまま過剰の付着液を絞って
なることを特徴とした重層クロメート処理鋼板として特
公昭５３−０３５７７９号がある。また、シリカゾル含
有の無水クロム酸浴に少量のＴｉ 、 Ｍｇ、 Ｎｉ
、 Ｃｏを添加し塗布することを特徴とする特願昭６１
−・５１９３号がある。以上は、下地のめつき界面の不
働態化或いはバリアー効果を狙いとした防止策であるが
、これらは４ｊξ単純亜鉛めっき鋼板には有効であるが
、亜鉛−アルミニウム系合金めっき鋼板に対する黒変防
止効果は小さいなど鉛の亜鉛系めっき鋼板の黒変防止策
としては汎用的でない。
また、亜鉛系めっき鋼板の上に異種金属をフラッシュめ
っきし、その上層にクロメート処理を施してなることを
特徴とする黒変防止対策としては、Ｎ１又はＣｏをフラ
ッシュめっきすることを特徴とする特開昭５９−１７７
３８１号があり、また、Ｎ１−Ｐ合金をフラッシュめっ
きすることを％徴とした特開昭６１−２５３３７８号が
ある。
これらは屋内での比較的低温多湿雰囲気の腐食環境下（
二おいて黒変防止効果としてはすぐれた汎用性を示すが
、屋外又は５０”Ｃ以上の高温多湿雰囲気の下では十分
な黒変防止機能を期待することは難しい。また、処理工
程の増による作業の繁雑化或いは処理コストの高騰など
生産性に不安が残る。
（間赴＾イｅ吠ｊ−ｆλ）了め間；１点）このような従
来技術の欠点を解消し、且つ、腐食環境の如何に左右さ
れない長期寿命をもつ黒変防止法として、本発明者等は
鋭意研究した結果、本願を発明するに至ったものである
。
本願発明は亜鉛めっき鋼板（溶融亜鉛−アルミニウム合
金めっき鋼板、溶融亜鉛めっき鋼板、電気亜鉛めっき鋼
板）が大気中での長期在庫又は高温多湿雰囲気（７０℃
、ＲＨ）９５％）の下で生じるめっき層の亜鉛の初期選
択腐食を長期にわたって抑制することにより、めっき表
面外観の黒変化を防止する点にある。
以下に本願発明の構成について記述する。
本願発明の構成入の・１は元素比として〔Ｎｉ〕／〔Ｎ
ｉ〕＋〔Ｃｒ〕＋(Industrial Application Fields) The present invention can be widely used for unpainted exterior panels in the fields of home appliances and building materials that require stability of the surface appearance of galvanized steel sheets or zinc-aluminum alloy coated steel sheets over time. (Prior art) Galvanized steel sheets (hot-dip plating, electroplating) or zinc-aluminum hot alloy coated steel sheets (hereinafter referred to as single liter di-zinc-plated steel sheets) are the surface-treated steel sheets that are most in demand in the fields of home appliances and building materials. There is. However, when these galvanized steel sheets are used as exterior panels without coating, the plating surface discolors over time and turns black (hereinafter simply referred to as black discoloration) during storage or exposure, which significantly reduces the product value. There's a problem. This blackening phenomenon occurs at the initial stage of corrosion at the plating interface, and is especially rapid in a high temperature and humid atmosphere. Also,
Blackening appears to be accelerated in zinc-aluminum hot alloy coated steel sheets designed to provide high corrosion resistance. Furthermore, this produced black film is composed of ZnO or ZnO, Zn(OR)2Z
It is composed of nCO1, r) (2o, and is considered to be a needle-shaped crystal that easily absorbs visible light and appears optically black.Also, the plating layer itself is also a major cause, and the plating layer M or Al, , O3 or Pb, Sn, Cd
There is a special order in which impurities, such as However, at the research level, there are the following. Japanese Patent Publication No. 53-035779 is a multilayer chromate-treated steel sheet characterized by cathodic electrolysis in a treatment bath containing chromic anhydride or silica sol, and then squeezing out excess adhering liquid without washing with water. In addition, small amounts of Ti, Mg, and Ni were added to the chromic acid anhydride bath containing silica sol.
, a patent application filed in 1983, characterized in that Co is added and applied.
-・There is No. 5193. The above measures are aimed at passivating the underlying plating interface or creating a barrier effect. Although these are effective for 4jξ simple galvanized steel sheets, they are effective for preventing blackening on zinc-aluminum alloy coated steel sheets. It is not a general-purpose method for preventing blackening of lead-zinc-plated steel sheets, as the effect is small. Further, as a countermeasure against blackening, which is characterized by flash plating a different metal on a zinc-based plated steel sheet and applying chromate treatment to the upper layer, there is a special method characterized by flash plating N1 or Co. Kaisho 59-177
There is No. 381, and there is also JP-A-61-253378, which features flash plating of N1-P alloy. These are used indoors in a corrosive environment with relatively low temperature and high humidity (
Secondly, it shows excellent versatility as a blackening prevention effect, but it is difficult to expect a sufficient blackening prevention function outdoors or in a high temperature and humid atmosphere of 50"C or more. Concerns about productivity remain, such as the complexity of work or the rise in processing costs. As a result of intensive research, the present inventors have arrived at the invention of the present application as a method for preventing blackening that has a long service life regardless of the , hot-dip galvanized steel sheets, electrogalvanized steel sheets) in long-term storage in the atmosphere or in high-temperature and humid atmospheres (70℃
The purpose of this method is to prevent the appearance of the plating surface from turning black by suppressing the initial selective corrosion of zinc in the plating layer that occurs under conditions (RH) of 95%) over a long period of time. The configuration of the present invention will be described below.・1 in the composition of the present invention is [Ni]/[N
i〕+〔Cr〕+
〔０〕から算出されるＮ１共析率が３
０〜６ｏｗｔ％を含有したクロメート皮膜が総クロム付
着量として片面５０〜１５０■／Ｒ電析させてなること
を特徴とした耐黒変性にすぐれた亜鉛系めっき鋼板であ
る。
また、その構成Ｎｃｏ−ＬハＣｒ６＋ ５〜５ Ｑ ｔ
／ｌ 。
Ｎ３ ＢＯ２５〜５０ ｆ／／ｌ＋ ｐＨ１−５〜５！
ＯＮ１”／Ｃｒ”比０．５〜２．０、陰極電流密度１
０〜ｌ ＯＯＡ／ｄイ、浴温４０〜６０℃でなることを
特徴とする耐黒変性にすぐれた。亜鉛系めっき鋼板の、
電、解〜クロム醗処双方法である。
すなわち、本発明の骨子は、蒔にＳＯ１′−の如き還元
性アニオンを含有しないクロム酸浴を基本浴とし、これ
に還元性アニオ゛ンを有しないカチオンとしてＮｉ２＋
を特定の比（Ｎｉ”’／Ｃｒ” ）に共存させることに
より、得られるクロメート皮膜中にＮ１を特定量含有さ
せ、これによってめっき界面の不働態化とバリアー効果
との複合作用により亜鉛系めっき層を腐食環境から遮断
する点にある。
（作用）
３０〜６０チと限定した理由及びクロム皮膜の付着量を
片面５０〜１５０ ｍ９／ｒｒ？ と限定した理由に
ついて説明する。
〔イ〕総クロム付着量
本発明によるクロメート付着量は仕上り外観、耐黒変性
及び裸耐食性など商品提供上基本性能を左右する上で重
要な因子である。
総クロメート付着量が総クロム量として片面３０ｍ９β
未、満においては耐黒変性に対して十分なバリアー効果
又は不働態化作用が現われず、また、採板の耐食性にお
いても十分でない。
従って好ましい下限付着量としては５０ ｍｃ）／ｒｒ
？以上がよい。また１ ５０ ｍ９７ｍ″超ではクロメ
ート皮膜が厚すぎて脆く凝集破壊し易いため商品価値の
低下を招き好ましくない。
従って好ましいクロム付着量の上限としては１００ｎ９
／ｒｒｌ がよい。
〔口） Ｎｉ含有率
本発明法でいうＮ１含有率はクロメート皮膜が元素とし
て（Ｎｉ） 、 （Ｃｒ） 、 Ｃｏ）でなると定義し
、その三成分中の〔Ｎｉ〕の占める割り合いを示したも
のである。このＮ１含有率は、クロメート皮膜の付着量
にもよるが、すぐれた耐黒変性を示すための不可欠因子
である。
クロメート皮膜中のＮ１含有率が３０チ未満ではたとえ
総クロム付着量が所定量生成しても満足する耐黒変性は
得られない。またＮ１含有率がａｏ％を超えては、耐食
性に不安を招くため、余り好ましくない。このため、好
ましいクロメート皮膜中作用と限定範囲について詳述す
る。
［イ］ Ｃｒ’＋イオン濃度
本発明法の基本浴成分であるＣｒ６＋は、無水クロム酸
または、その塩のいづれかまたはその組み合せで用いら
れてよい。
Ｃｒ が５９／を未満では、品質面でクロメート皮膜
中のＮｉ共析率が高くなり過ぎ耐食性の低下を招き易く
また、作業面で処理浴の液抵抗が高く耐黒変性に対する
適正電流密度範囲が狭くなり、生産の安定性に欠ける。
このためＣｒ’＋ イオン濃度としては１０９７１以上
が好ましい。
また、Ｃｒ ５０ ｆ／／Ｌを超えては、性能に与え
る影響は特にないものの鋼板による処理液の持ち出し量
が増し又、その後の水洗水の汚染度、排水処理が繁雑化
し処理コストの増を伴なうため余り好ましくない。この
ため上限Ｃｒ’＋ イオン濃度としては２５ ｙ／ｌが
好ましい。
〔口）Ｎ１ ／Ｃｒ 比
この比は、本願発明の構成にあたって最も重要な因子で
ある。Ｎｉ”＋ イオンは析出クロメート皮膜中に共析
し、大気中の腐食性因子（水分酸素など）の亜鉛めっき
層への透過を遮断することによって亜鉛系めっき表面で
の界面腐食反応を抑制する一種のバリアー効果と更には
、Ｃｒ によるセルフヒーリング作用によるめっき
表面の不働態化から亜鉛めっき表面の黒変現象を防止す
るための最も重要な因子の一つである。
本発明法で用いるＮｉ”＋ イオンの供給は炭酸塩、水
酸化物又は、これらの複合塩の何れを用いてもよい。
Ｎｉ”／Ｃｒ’＋の比が０．５未満においては、生成り
ロメート皮膜中のＮｉ共析率が小さいため、これによる
めっきの界面腐食反応を抑制することは難しく従って、
耐黒変性を向上させることは難しい。
これは１本発明によるクロメート皮膜構造がＣｒ３＋主
体のクロミッククロメート型（Ｃｒｙ、・Ｃｒ２Ｏ，・
Ｎ２０）からＣ’ｒ−Ｎｉ−０で成る皮膜構造（例えば
ＮｉＣｒＯ４など）へと変化したものであり、この改質
が耐黒変性向上に有効に働くものと考えられる。従って
、クロメート皮膜中のＮ１含有率によって、皮膜のもつ
バリアー効果或いは不働態化作用は異なり、Ｎ１含有率
の小さいクロメート皮膜にはすぐれた耐黒変性を期待す
ることは難しい。このため、Ｎ１２＋／Ｃｒ 比の
下限は０．８以上が好ましい。
−万、Ｎｉ ／Ｃｒ 比か２．０超においては耐黒変
性或いは密着性に乏しいポーラスなりロメート皮膜しか
生成せず商品価値を損なうため好ましくない。
このため、Ｎ１／Ｃｒ 比の上限は１．５が好ましい
。
〔ハ）Ｈ，ＢＯ。
本発明でのホウ酸の役割は陰極界面でのｐＨ変動を抑制
し、均質なりロメート皮膜の生成を助け、均一外観を得
るためにある。ホウ酸が５ ｆ／を未満においては、均
一外観が得られにくく、また５０２μ超では品質上の問
題はないものの処理コストの上昇を招く。
従って好ましいホウ酸濃度としては１０〜３０り／ｌが
よい。
〔二） ｐＨ
本発明法でいう処理浴のｐＨは、供給するニッケル塩に
よって左右されるが、クロメート皮膜の安定した仕上り
外観を維持させるための重要な因子である。
ｐＨが１．５未満では、クロメート皮膜としてすぐれた
耐黒変ｉ生金示すほどにＮ１含有率を高めることが難し
い。これは一度生成したゲル状のクロメート皮膜が遊離
酸によって再溶解するためと考えられる。
このため、好ましい下限ｐＨとしては２．０以上がよい
。
またｐＨが５．０を超えては、耐黒変性に対しすぐれた
バリアー効果或いは不働態化作用を発揮させるためのク
ロメート皮膜中のＮ１含有率は飽和状態にあり、これ以
上高ｐＨ化させる利点は品質上特になく、返って密着性
を損う。更には、処理液の中性化に伴なう液抵抗の上昇
から電力コストの高騰を招き経済的でない。
このため、好ましい上限ｐＨとしては５．０以下にした
方がよい。
〔ホ〕陰極電流密度
本発明法による陰極電流密度は、適正Ｃｒ 濃度或い
はＮｉ”／Ｃｒ’＋ 比に対する適応範囲を拡げ、高生
産性ライン化で生産性よく短時間処理化を図る上で重要
な因子である。
電流密度が１０Ａ／ｄｍ’未満では、Ｃｒ６＋濃度或い
はＮ１２＋／Ｃｒ６＋ 比に対しすぐれた耐黒変性を示
すクロメート皮膜を得るための適正作業範囲が狭く、ま
た、クロメート皮膜中のＮ］含有率が高められないこと
もあって作業性、品質ともに満足のいくクロメート皮膜
は得にくい。
このため、電流密度の下限としては２０Ａ／ｄｉ以上が
好ましい。また、電流密度の上限が１００Ａ／ｄ−を超
えては処理浴の限界電流密度を超えるため、いわゆる”
ヤケ″現象を伴ない処理外観をはじめとする性能の低下
が著るしく商品にならない。
このため、電流密度の上限としては５０Ａ／ｄｙｙＩ″
が好ましい。
〔へ〕浴温
本発明法における浴温は、液抵抗を下げ電力コストの低
減化を図って生産性よく短時間で所望のクロメート皮膜
を得るために必要とされる因子である。
浴温か３０℃未満では、液抵抗が比較的大きく水の電気
分解が生じてクロメートの還元効率が低下し生産性の１
氏下を招き易い。また、電解熱により液温制御に設備投
資を要し、余り得策でない。従って好ましい浴温の下限
としては４０℃がよい。また、浴温か６０′Ｃを超えて
は、浴の水分蒸発が激しく、処理浴の濃度制御に多量の
水の投入を要し経済的でない。従って、浴温の上限は５
０°Ｃが好ましい。
（実施例）
以下に実施例を挙げ、本発明の効果について具体的に説
明する。
素材めっき鋼板として所定のめつき付着量をもった微細
スパングルの溶融Ｚｎ−ｋｌ系合金めっき鋼板および溶
融亜鉛めっき鋼板或いは電気亜鉛めっき鋼板に対し本発
明法を）商用したクロメート処理鋼板の耐黒変性をはじ
めとする諸性能について比較例と共に第１表にまとめて
示す。
まず適正クロメート処理浴組成に関し、本発明法による
実施例Ｎ［Ｌｌ−Ｎａ５にはクロメート処理浴中のＯｒ
’＋ イオン濃度の適正範囲について示し、その比較例
を醜３４に示す。また本発明法の実施例Ｎａ６〜随９に
は、ホウ酸の適正濃度範囲において示しその比較例をＮ
１１３５に示す。更にはＮｔ ／Ｃｒ比の適正範囲につ
いては本発明法の実施例Ｎα１Ｏ−Ｎａ１３に示しその
比較例を随３６〜３７に示す。
次にクロメートの適正処理条件としてｐＨ適正範囲につ
いて本発明法の実施例は１４−Ｎａ １．８に示し、そ
の比較例を随３８〜醜３９に示す。また適正電流密度の
範囲については本発明法の実施例１１１［１１９〜随２
３に示し、その比較例を随４０〜階４１に示す。また適
正処理浴温については本発明法の実施例Ｎａ２４〜随２
５と階３に示し、その比較例をＮａ４２に示す。
次に、クロメート皮膜の適正構成については本発明法の
実施例Ｍａｌ〜随３１に示し、その比較例については総
クロム付着量の比較例はＮ［１４３〜ＮＩ１４４に示し
、Ｎｌ共析率については随３６．ＮＦＬ３８゜８ａ４０
に順次示す。
＊Ｉ
ＧＡ：Ｚｎ−ｋｌ、系溶融合金めっき鋼板、めっき付着
量Ｚ２７、無処理後スキンパス材
Ｇ： 溶融Ｚｎめつき鋼板、めっき付着量Ｚ２’７、無
処理後スキンパス材
Ｅ ： 電気Ｚｎめっき鋼板、めっき付着量２０ｆ／ｒ
ｒ？、無処理材
＊２
Ｃｒ” ： Ｃｒｙ、或いはＮａ２ Ｃｒ ２０７の
単独又は併用用
＊３
総クロム付着量：螢光Ｘ線にて測定
Ｎｌ共 折率： ＥＰＭＡスポット定量分析による。
＊４
（１）耐黒変性
冷蔵庫による結露スタック梱包後、７０′Ｃ１ＲＨ）
９５ ％雰囲気中に１６８時間放置しめつき表面の黒色
化を目視判定。
◎全く黒変せず、Ｏ極く僅かに変色、６部分的に黒変、
×全面黒変
（２）耐食性
無塗装、平板での塩水噴霧試験（ＪＩＳＺ−２３７１）
◎白銑ごく僅か発生、○白銑５ｑ６以内、Δ白銑３０チ
未満、×白銑３０％以上又は一部赤銹発生
（３）密着性
エリクセン押出し５鴨後テープ剥離
◎全く剥離せず、Ｏごく僅か剥離、Δかなり剥離、×全
面剥離
（４）外観均一性
目視判定
◎全面均一色調、○ごく僅かムラ模様、Δ部分的色調ム
ラ、×全面不拘−色調
（発明の効果）
これら本発明法の実施例より明らかなように、クロメー
ト皮膜中に適量のＮ１を共析させることによりクロメー
ト皮膜の皮膜構造が改質され、これによる不働態化作用
又はバリアー効果の複合作用によって下地亜鉛系めっき
層の耐経時黒変性は大きく改善されることが分る。The N1 eutectoid rate calculated from [0] is 3
This is a zinc-based plated steel sheet with excellent blackening resistance characterized by a chromate film containing 0 to 6 wt% deposited on one side with a total chromium deposition amount of 50 to 150 μ/R. Also, its composition Nco-L Cr6+ 5~5 Q t
/l. N3 BO25~50 f//l+ pH1-5~5!
ON1”/Cr” ratio 0.5-2.0, cathode current density 1
Excellent blackening resistance characterized by 0-1 OOA/d and bath temperature of 40-60°C. galvanized steel sheet,
There are two methods: electricity, solution and chromium alcohol. That is, the gist of the present invention is to use a chromic acid bath that does not contain reducing anions such as SO1'- as a basic bath, and to add Ni2+ as a cation that does not have reducing anions.
By making N1 coexist in a specific ratio (Ni"'/Cr"), a specific amount of N1 is contained in the resulting chromate film. The point is to isolate the layer from the corrosive environment. (Function) Why was it limited to 30 to 60 inches and the amount of chromium film attached to one side was 50 to 150 m9/rr? The reason for this limitation will be explained. [B] Total amount of chromate deposited The amount of chromate deposited according to the present invention is an important factor in determining the basic performance of products, such as finished appearance, blackening resistance, and bare corrosion resistance. The total amount of chromate deposited is 30m9β on one side as the total amount of chromium.
At lower and higher temperatures, sufficient barrier effect or passivation effect against blackening resistance does not appear, and the corrosion resistance of the plate is also insufficient. Therefore, the preferable lower limit of adhesion amount is 50 mc)/rr
? The above is good. In addition, if it exceeds 150 m97 m, the chromate film is too thick and becomes brittle and prone to cohesive failure, resulting in a decrease in commercial value, which is undesirable. Therefore, the preferred upper limit for the amount of chromium deposited is 100 n9.
/rrl is better. [Note] Ni content rate The N1 content rate in the method of the present invention is defined as the chromate film consisting of (Ni), (Cr), Co) as elements, and indicates the proportion of [Ni] among the three components. It is something. This N1 content is an essential factor for exhibiting excellent blackening resistance, although it depends on the amount of chromate film deposited. If the N1 content in the chromate film is less than 30 inches, satisfactory blackening resistance cannot be obtained even if a predetermined amount of total chromium is deposited. Furthermore, if the N1 content exceeds ao%, this is not very preferable because it may lead to concerns about corrosion resistance. For this reason, the preferred action in the chromate film and its limited range will be explained in detail. [A] Cr'+ ion concentration Cr6+, which is the basic bath component of the method of the present invention, may be used in the form of chromic anhydride, a salt thereof, or a combination thereof. If Cr is less than 59/, the Ni eutectoid rate in the chromate film becomes too high in terms of quality, which tends to lead to a decrease in corrosion resistance.In addition, the liquid resistance of the treatment bath is high on the working surface, and the appropriate current density range for blackening resistance is It becomes narrow and production stability is lacking. Therefore, the Cr'+ ion concentration is preferably 10971 or higher. In addition, if Cr exceeds 50 f//L, there is no particular effect on performance, but the amount of treatment liquid taken out by the steel plate increases, the degree of contamination of the subsequent flushing water, and the complexity of wastewater treatment, which increases the treatment cost. It is not very desirable because it is accompanied by Therefore, the upper limit of Cr'+ ion concentration is preferably 25 y/l. [Example] N1/Cr ratio This ratio is the most important factor in constructing the present invention. Ni”+ ions are eutectoid in the precipitated chromate film, and are a type of ion that suppresses interfacial corrosion reactions on the zinc-based plating surface by blocking the permeation of corrosive factors in the atmosphere (moisture, oxygen, etc.) to the galvanized layer. This is one of the most important factors for preventing the blackening phenomenon of the zinc plating surface due to the barrier effect of Cr and furthermore, the passivation of the plating surface due to the self-healing effect of Cr. For supplying ions, carbonate, hydroxide, or a complex salt thereof may be used. When the ratio of Ni''/Cr'+ is less than 0.5, the Ni eutectoid rate in the formed romate film is small, so it is difficult to suppress the interfacial corrosion reaction of the plating due to this.
It is difficult to improve blackening resistance. This is because the chromate film structure according to the present invention is a chromic chromate type (Cry, ・Cr2O, ・
N20) to a film structure composed of C'r-Ni-0 (for example, NiCrO4), and this modification is thought to be effective in improving blackening resistance. Therefore, the barrier effect or passivation effect of the film varies depending on the N1 content in the chromate film, and it is difficult to expect excellent blackening resistance from a chromate film with a low N1 content. Therefore, the lower limit of the N12+/Cr ratio is preferably 0.8 or more. If the Ni/Cr ratio exceeds 2.0, only a porous or romate film with poor blackening resistance or adhesion is formed, which impairs commercial value, which is undesirable. Therefore, the upper limit of the N1/Cr ratio is preferably 1.5. [C) H, BO. The role of boric acid in the present invention is to suppress pH fluctuations at the cathode interface, assist in the formation of a homogeneous romate film, and obtain a uniform appearance. If the boric acid content is less than 5 f/, it is difficult to obtain a uniform appearance, and if it exceeds 502 μ, there is no quality problem, but the processing cost increases. Therefore, the preferred concentration of boric acid is 10 to 30 l/l. [2) pH The pH of the treatment bath in the method of the present invention depends on the nickel salt supplied, but is an important factor for maintaining a stable finished appearance of the chromate film. If the pH is less than 1.5, it is difficult to increase the N1 content to the extent that the raw metal exhibits excellent blackening resistance as a chromate film. This is thought to be because the gel-like chromate film once formed is redissolved by the free acid. Therefore, the preferable lower limit pH is 2.0 or more. In addition, when the pH exceeds 5.0, the N1 content in the chromate film, which exerts an excellent barrier effect or passivation effect against blackening resistance, is saturated, and there is no advantage to increasing the pH further. This is not particularly important in terms of quality and actually impairs adhesion. Furthermore, the increase in liquid resistance due to the neutralization of the processing liquid causes a rise in electricity costs, making it uneconomical. Therefore, the preferred upper limit pH is preferably 5.0 or less. [E] Cathode current density The cathode current density according to the method of the present invention is important in expanding the range of application to the appropriate Cr concentration or Ni''/Cr'+ ratio, and achieving high productivity and short processing time with a high productivity line. If the current density is less than 10 A/dm', the appropriate working range for obtaining a chromate film that exhibits excellent blackening resistance with respect to the Cr6+ concentration or N12+/Cr6+ ratio is narrow, and the N in the chromate film is ] Because the content cannot be increased, it is difficult to obtain a chromate film that is satisfactory in both workability and quality.For this reason, the lower limit of current density is preferably 20 A/di or more.Also, the upper limit of current density is 100 A/di. Exceeding d- exceeds the limiting current density of the treatment bath, so the so-called "
It cannot be used as a commercial product due to the significant deterioration in performance, including the appearance of the treatment, accompanied by the phenomenon of "burning".For this reason, the upper limit of the current density is 50A/dyyI".
is preferred. [F] Bath temperature The bath temperature in the method of the present invention is a factor required to lower the liquid resistance and reduce the power cost to obtain the desired chromate film with high productivity in a short time. If the bath temperature is less than 30°C, the liquid resistance is relatively large and water electrolysis occurs, reducing the chromate reduction efficiency and reducing productivity.
It is easy to invite subordinates. In addition, it requires capital investment to control the liquid temperature using electrolytic heat, which is not a good idea. Therefore, the lower limit of the bath temperature is preferably 40°C. Furthermore, if the bath temperature exceeds 60'C, the water in the bath will evaporate rapidly, and a large amount of water will have to be added to control the concentration of the treatment bath, which is not economical. Therefore, the upper limit of bath temperature is 5
0°C is preferred. (Example) Examples are given below to specifically explain the effects of the present invention. Resistance to blackening of chromate-treated steel sheets using the method of the present invention commercially applied to fine-spangled hot-dip Zn-kl alloy coated steel sheets, hot-dip galvanized steel sheets, or electrogalvanized steel sheets with a predetermined coating weight as raw material coated steel sheets The various performances including the following are summarized in Table 1 along with comparative examples. First, regarding the appropriate chromate treatment bath composition, Example N according to the method of the present invention [Ll-Na5 has Or in the chromate treatment bath.
The appropriate range of '+ ion concentration is shown, and a comparative example thereof is shown in Ugly 34. In addition, in Examples Na6 to No.9 of the method of the present invention, comparative examples are shown in the appropriate concentration range of boric acid.
1135. Furthermore, the appropriate range of the Nt/Cr ratio is shown in Example Nα1O-Na13 of the method of the present invention, and comparative examples are shown in Figures 36 and 37. Next, an example of the method of the present invention is shown in 14-Na 1.8 regarding the appropriate pH range as the appropriate treatment condition for chromate, and comparative examples are shown in No. 38 to No. 39. Regarding the range of appropriate current density, Example 111 of the method of the present invention [119 to 2]
3, and comparative examples thereof are shown in floors 40 to 41. Regarding the appropriate processing bath temperature, Examples Na24 to No.2 of the method of the present invention
5 and 3, and a comparative example thereof is shown in Na42. Next, the appropriate structure of the chromate film is shown in Examples Mal to Volume 31 of the method of the present invention, and the comparative examples of the total chromium deposition amount are shown in N[143 to NI144, and the Nl eutectoid rate is shown in Part 36. NFL38°8a40
are shown in sequence. *I GA: Zn-kl, hot-dip alloy coated steel sheet, coating amount Z27, skin pass material after no treatment G: Hot dip Zn plated steel sheet, coating amount Z2'7, skin pass material E after no treatment: Electro Zn-plated steel sheet , plating amount 20f/r
r? , untreated material *2 Cr": Cry or Na2 Cr 207 used alone or in combination *3 Total chromium deposition amount: Measured with fluorescent X-ray Nl co-refraction index: Based on EPMA spot quantitative analysis *4 (1) After condensation stack packaging with blackening resistant refrigerator, 70'C1RH)
Leave it in a 95% atmosphere for 168 hours and visually check for blackening of the surface. ◎ No blackening at all, 0 Very slight discoloration, 6 Partial blackening,
×Full surface blackening (2) Corrosion resistance Unpainted, flat plate salt spray test (JISZ-2371)
◎ Very small amount of white pig iron generated, ○ Less than 5 q6 white pig iron, ∆ Less than 30 inches of white pig iron, × 30% or more of white pig iron or some red iron generated (3) Adhesion Erichsen extrusion 5 Tape peeled after duck ◎ No peeling at all, ○ Very slight peeling, Δ Considerable peeling, × Whole surface peeling (4) Visual judgment of appearance uniformity ◎ Uniform color tone throughout the entire surface, ○ Very slight uneven pattern, Δ Partial uneven color tone, × Whole surface unrestricted color tone (effects of the invention) These inventions As is clear from the examples of the method, the film structure of the chromate film is modified by eutectoiding an appropriate amount of N1 into the chromate film, and the combined effect of passivation or barrier effect improves the base zinc plating. It can be seen that the aging blackening of the layer is greatly improved.
Claims (2)
で〔Ｎｉ〕分を３０〜６０％含有したクロメート皮膜を
総クロム付着量として片面５０〜１５０ｍｇ／ｍ＾２電
析させてなることを特徴とする耐経時黒変性にすぐれた
クロメート処理亜鉛又は亜鉛系合金めつき鋼板。(1) A chromate film containing 30 to 60% of [Ni] in the elemental ratio of [Ni]/[Ni] + [Cr] + [O], with a total chromium deposition amount of 50 to 150 mg/m^2 on one side. A chromate-treated zinc or zinc-based alloy coated steel sheet with excellent resistance to blackening over time.
〜５０ｇ／ｌ、Ｎｉ＾２＾＋／Ｃｒ＾６＾＋比０．５〜
２．０ｐＨ１．５〜５．０の処理浴、陰極電流密度１０
〜１００Ａ／ｄｍ＾２、浴温３０〜６０℃にて亜鉛又は
亜鉛系合金めつき鋼板を電解処理することを特徴とした
耐黒変性にすぐれたクロメート処理亜鉛又は亜鉛系合金
めつき鋼板の製造方法。(2) Cr^6^+5~50g/l, H_3BO_35
~50g/l, Ni^2^+/Cr^6^+ ratio 0.5~
2.0 pH 1.5-5.0 treatment bath, cathode current density 10
Production of chromate-treated zinc or zinc alloy coated steel sheet with excellent blackening resistance, characterized by electrolytically treating the zinc or zinc alloy coated steel sheet at ~100 A/dm^2 and bath temperature of 30 to 60°C. Method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8284387A JPS63250496A (en) | 1987-04-06 | 1987-04-06 | Chromated zinc or zinc alloy plated steel sheet having superior resistance to blackening on standing and production thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8284387A JPS63250496A (en) | 1987-04-06 | 1987-04-06 | Chromated zinc or zinc alloy plated steel sheet having superior resistance to blackening on standing and production thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS63250496A true JPS63250496A (en) | 1988-10-18 |
| JPH0361759B2 JPH0361759B2 (en) | 1991-09-20 |
Family
ID=13785670
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8284387A Granted JPS63250496A (en) | 1987-04-06 | 1987-04-06 | Chromated zinc or zinc alloy plated steel sheet having superior resistance to blackening on standing and production thereof |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS63250496A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04304397A (en) * | 1991-03-29 | 1992-10-27 | Nkk Corp | Chromate treated zinc plated steel sheet excellent in corrosion resistance, finger print resistance and production thereof |
| US5496652A (en) * | 1992-04-30 | 1996-03-05 | Nkk Corporation | Zinc-plated steel plate having resin coating film |
-
1987
- 1987-04-06 JP JP8284387A patent/JPS63250496A/en active Granted
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04304397A (en) * | 1991-03-29 | 1992-10-27 | Nkk Corp | Chromate treated zinc plated steel sheet excellent in corrosion resistance, finger print resistance and production thereof |
| US5496652A (en) * | 1992-04-30 | 1996-03-05 | Nkk Corporation | Zinc-plated steel plate having resin coating film |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0361759B2 (en) | 1991-09-20 |
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