JP5398310B2

JP5398310B2 - Painted steel sheet and exterior member

Info

Publication number: JP5398310B2
Application number: JP2009054499A
Authority: JP
Inventors: 史城公文; 郷史山本; 矢野　　宏和
Original assignee: Nippon Steel Nisshin Co Ltd
Current assignee: Nippon Steel Nisshin Co Ltd
Priority date: 2009-03-09
Filing date: 2009-03-09
Publication date: 2014-01-29
Anticipated expiration: 2029-03-09
Also published as: JP2010208067A

Description

本発明は、溶融Ｚｎ−Ａｌ系めっき鋼板または溶融Ａｌ系めっき鋼板を原板とする塗装鋼板であって、切断端面や曲げ加工部などの金属露出部における耐食性、特に屋外暴露特性を改善した塗装鋼板、およびそれを用いた建築物の外装部材に関する。 The present invention is a coated steel sheet using a molten Zn-Al-based plated steel sheet or a molten Al-based plated steel sheet as a base plate, and the coated steel sheet having improved corrosion resistance, particularly outdoor exposure characteristics in exposed metal parts such as a cut end face and a bent part. And an exterior member of a building using the same.

塗装鋼板の原板としては従来から耐食性の良好な溶融亜鉛めっき鋼板が多用されている。最近では建築物の外装用途を中心に、更に耐食性が良好な溶融Ｚｎ−Ａｌ系めっき鋼板や溶融Ａｌ系めっき鋼板を塗装原板に用いることが多くなってきた。しかし、これらの高耐食性めっき鋼板を用いた場合でも、塗装鋼板の切断端面には金属（めっき層および鋼素地）が露出し、その部分での腐食が問題となることがある。また曲げ加工部では塗膜およびめっき層に不可避的にクラックが発生することがあり、その部分でも金属が露出して腐食が問題となることがある。このような腐食は、クロメート系の化成処理層を形成させたり、クロム酸系の防錆顔料を使用したりすることにより効果的に防止することができる。しかし、環境問題から最近ではクロムイオンの溶出が生じない材料が求められている。 Conventionally, hot-dip galvanized steel sheets with good corrosion resistance have been frequently used as the original sheets of coated steel sheets. Recently, mainly for exterior use of buildings, a hot-dip zinc-aluminum-plated steel sheet and a molten-aluminum-plated steel sheet, which have better corrosion resistance, are increasingly used as a coating original sheet. However, even when these highly corrosion-resistant plated steel sheets are used, metal (plated layer and steel base) is exposed on the cut end face of the coated steel sheet, and corrosion at that portion may be a problem. Moreover, in a bending process part, a crack may inevitably generate | occur | produce in a coating film and a plating layer, A metal may be exposed also in the part and corrosion may become a problem. Such corrosion can be effectively prevented by forming a chromate-based chemical conversion treatment layer or using a chromic acid-based rust preventive pigment. However, due to environmental problems, materials that do not cause elution of chromium ions have recently been demanded.

特許文献１、２には、溶融Ｚｎ−Ａｌ系めっき鋼板または溶融Ａｌ系めっき鋼板を原板とする塗装鋼板について、曲げ加工部の金属露出部における耐食性を改善する技術として、塗膜の中にマグネシウム塩およびリン酸塩を配合させる手法が開示されている。この場合、化成処理皮膜や塗膜にクロム成分を含まないので、環境には優しい。 In Patent Documents 1 and 2, as a technique for improving corrosion resistance in a metal exposed portion of a bent portion, a coating film containing magnesium is used as a coating steel plate using a molten Zn-Al-based plated steel plate or a molten Al-based plated steel plate as an original plate. A technique for blending salt and phosphate is disclosed. In this case, since the chemical conversion treatment film or coating film does not contain a chromium component, it is environmentally friendly.

特開２００５−１６９７６５号公報JP 2005-169765 A 特開２００５−２６２５２６号公報JP 2005-262526 A

特許文献１、２の技術によれば、屋外で雨水に曝された曲げ加工部のクラック発生箇所において、塗膜に配合されたマグネシウム成分およびリン酸成分が溶出し、これらの溶出成分とめっき層から溶出したＡｌイオン、Ｚｎイオンなどが難溶性腐食生成物を形成する。この腐食生成物はめっき層および鋼素地が露出している部分に保護皮膜を形成し、耐食性が確保される。 According to the techniques of Patent Documents 1 and 2, the magnesium component and the phosphoric acid component blended in the coating film are eluted at the cracked portion of the bent portion exposed to rainwater outdoors, and these eluted components and the plating layer Al ions, Zn ions, and the like eluted from the solution form hardly soluble corrosion products. This corrosion product forms a protective film on the exposed portions of the plating layer and the steel substrate, and ensures corrosion resistance.

ところが発明者らの詳細な調査によれば、特許文献１、２に開示の塗装鋼板では、屋外暴露のような比較的マイルドな環境で保持すると、比較的短期から切断端面や曲げ加工部においてめっき層あるいは鋼素地の腐食が観測される場合があることがわかった。特に切断端面では、めっき層の腐食が進行することにより塗膜に膨れが生じる「エッジクリープ」と呼ばれる現象が目立ちやすい。種々検討の結果、特許文献１、２の手法では腐食生成物による安定な保護皮膜が形成されるまでに長時間を要する場合があり、腐食環境によってはそれまでの期間に金属の腐食が進行してしまうものと考えられた。既に発生したエッジクリープは、その後、保護皮膜が形成された後も修復不可能であることから、できるだけ早期に腐食の進行を食い止めることが望まれる。 However, according to detailed investigations by the inventors, the coated steel sheets disclosed in Patent Documents 1 and 2 can be plated on a cut end face or a bent portion from a relatively short time when held in a relatively mild environment such as outdoor exposure. It was found that corrosion of the layer or the steel substrate may be observed. In particular, a phenomenon called “edge creep” in which the coating film swells due to the progress of corrosion of the plating layer is easily noticeable on the cut end face. As a result of various studies, in the methods of Patent Documents 1 and 2, it may take a long time to form a stable protective film due to the corrosion products, and depending on the corrosive environment, the corrosion of the metal progresses until that time. It was thought that it would end up. Since the edge creep that has already occurred cannot be repaired after the protective film is formed, it is desired to stop the progress of corrosion as soon as possible.

本発明はこのような現状に鑑み、本来耐食性に優れる溶融Ｚｎ−Ａｌ系めっき鋼板または溶融Ａｌ系めっき鋼板を原板とする塗装鋼板において、切断端面や曲げ加工部の耐食性に関し、クロムイオンの溶出による環境問題を生じること無く、従来一般的な促進試験条件下での耐食性を確保するとともに、特に屋外暴露環境での耐食性を改善することを目的とする。 In view of such a current situation, the present invention relates to the corrosion resistance of a cut end face and a bent portion in a coated steel sheet using a molten Zn-Al-based plated steel sheet or a molten Al-based plated steel sheet that is originally excellent in corrosion resistance, by elution of chromium ions. The objective is to ensure corrosion resistance under conventional accelerated test conditions without causing environmental problems, and to improve corrosion resistance especially in outdoor exposure environments.

上記目的は、質量％で、Ａｌ：５〜９５％を含有し、残部元素としてＺｎ：９５％以下、Ｍｇ：１０％以下：Ｓｉ：１２％以下の１種以上を含有し、Ａｌ、Ｚｎ、Ｍｇ、Ｓｉ以外の元素の合計含有量が３％以下（０％を含む）である溶融めっき浴を用いてＡｌ含有めっき層を形成しためっき鋼板の、当該めっき層の上に、化成処理皮膜、下塗り塗膜、上塗り塗膜を有する塗装鋼板において、前記下塗り塗膜中に顔料としてリン酸マンガン、亜リン酸マンガンの１種以上が合計１０〜３５質量％含有されていることを特徴とする塗装鋼板によって達成される。下塗り塗膜の平均厚さ（乾燥後、鋼板片面あたり）は２〜２５μｍの範囲とすることが望ましい。また本発明では上記塗装鋼板を素材として成形され、切断端面の金属露出部および曲げ加工部の金属露出部の少なくとも一方を持つ建築物の外装部材が提供される。ここで外装部材は、屋根材料、外壁材料など、屋外の大気環境に曝される建築部材である。 The purpose is to contain at least 5% by mass of Al: 5 to 95%, with the balance being one or more of Zn: 95% or less, Mg: 10% or less: Si: 12% or less, Al, Zn, On the plating layer of the plated steel sheet in which the Al-containing plating layer is formed using a hot dipping bath having a total content of elements other than Mg and Si of 3% or less (including 0%), a chemical conversion treatment film, A coated steel sheet having an undercoat film and an overcoat film, wherein the undercoat film contains a total of 10 to 35% by mass of one or more of manganese phosphate and manganese phosphite as pigments. Achieved with steel sheet. The average thickness of the undercoat coating film (after drying, per one side of the steel sheet) is desirably in the range of 2 to 25 μm. Moreover, in this invention, the exterior member of a building which is shape | molded using the said coated steel plate as a raw material, and has at least one of the metal exposed part of a cut end surface, and the metal exposed part of a bending process part is provided. Here, the exterior member is a building member that is exposed to an outdoor atmospheric environment, such as a roof material and an outer wall material.

本発明によれば、溶融Ｚｎ−Ａｌ系めっき鋼板または溶融Ａｌ系めっき鋼板を原板とする塗装鋼板において、切断端面などの金属露出部で問題となっていた屋外暴露環境での耐食性が改善された。すなわち、暴露開始後の比較的早期の段階で塗膜中の成分が迅速にめっき金属の溶出成分と結びついて保護性の高い皮膜を形成し、特にエッジクリープの発生量を顕著に抑制することが可能となる。 According to the present invention, in a coated steel sheet using a molten Zn-Al-based plated steel sheet or a molten Al-based plated steel sheet as a base plate, corrosion resistance in an outdoor exposure environment that has been a problem in exposed metal parts such as cut end faces has been improved. . In other words, at a relatively early stage after the start of exposure, the components in the coating quickly combine with the elution components of the plated metal to form a highly protective coating, particularly reducing the amount of edge creep. It becomes possible.

本発明の塗装鋼板における切断端面近傍の腐食形態を模式的に示した断面図。Sectional drawing which showed typically the corrosion form of the cutting end surface vicinity in the coated steel plate of this invention. 本発明の塗装鋼板における曲げ加工部の腐食形態を模式的に示した断面図。Sectional drawing which showed typically the corrosion form of the bending process part in the coated steel plate of this invention.

図１に、本発明の塗装鋼板の切断端面近傍における断面の腐食形態を模式的に示す。めっき原板である鋼素地１の上に溶融Ｚｎ−Ａｌ系めっきまたは溶融Ａｌ系めっきによって形成されためっき層２があり、その上に化成処理層３を介して下塗り塗膜４および上塗り塗膜５が形成されている。切断端面６においては鋼素地１とめっき層２が金属露出部を構成している。このような切断端面を持つ塗装鋼板が腐食環境に曝されると、めっき層は切断端面から腐食していき、腐食箇所１０が形成される。Ｚｎ−Ａｌ系めっきの場合は特にＺｎリッチ相が優先的に腐食する。腐食箇所１０の体積膨張に起因する膨れが上塗り塗膜５の表面にまで伝わり、エッジクリープ２０が発生する。切断端面６からエッジクリープ２０の最前線までの距離ｘを「エッジクリープ長さ」と呼ぶ。めっき層の腐食の進行に伴ってエッジクリープ長さは増大する。 In FIG. 1, the corrosion form of the cross section in the cutting end surface vicinity of the coated steel plate of this invention is shown typically. There is a plating layer 2 formed by hot-dip Zn-Al plating or hot Al plating on a steel substrate 1 which is a plating base plate, and an undercoat coating 4 and a topcoat coating 5 are formed thereon via a chemical conversion treatment layer 3. Is formed. On the cut end face 6, the steel substrate 1 and the plating layer 2 constitute a metal exposed portion. When the coated steel sheet having such a cut end face is exposed to a corrosive environment, the plating layer corrodes from the cut end face, and a corroded portion 10 is formed. In the case of Zn-Al plating, the Zn-rich phase corrodes preferentially. The blister due to the volume expansion of the corroded portion 10 is transmitted to the surface of the top coat film 5 and the edge creep 20 is generated. A distance x from the cut end face 6 to the forefront of the edge creep 20 is referred to as “edge creep length”. As the corrosion of the plating layer progresses, the edge creep length increases.

従来、下塗り塗膜４の中にリン酸マグネシウムやリン酸亜鉛等のリン酸塩を防錆顔料として含有させる手法が知られている（例えば特許文献１、２）。この場合、下塗り塗膜４から溶出したリン酸成分（ＰＯ₄ ^3-、ＰＯ₃ ^2-）や金属成分（Ｍｇ²⁺など）が、めっき層２の腐食によって生じた金属成分（Ａｌ³⁺、Ｚｎ²⁺など）とともに難溶性の腐食生成物を形成し、これがやがて保護皮膜１１となって切断端面６に付着する。保護皮膜１１によって端面が保護されるまでの期間にエッジクリープ２０が成長し、エッジクリープ長さｘが１ｍｍ以上となる場合がある。そうなると外装材の外観を損ね、好ましくない。 Conventionally, there has been known a technique in which a phosphate such as magnesium phosphate or zinc phosphate is contained in the undercoat coating 4 as a rust preventive pigment (for example, Patent Documents 1 and 2). In this case, phosphoric acid components (PO ₄ ³⁻ , PO ₃ ²⁻ ) and metal components (Mg ^2+, etc.) eluted from the undercoat coating 4 are metal components (Al ³⁺ , A slightly soluble corrosion product is formed together with Zn ^{2+ and the} like, which eventually becomes the protective film 11 and adheres to the cut end face 6. The edge creep 20 grows during the period until the end face is protected by the protective coating 11, and the edge creep length x may be 1 mm or more. If it becomes so, the external appearance of an exterior material will be impaired and it is unpreferable.

本発明では、下塗り塗膜４の中に所定量のリン酸マンガン、亜リン酸マンガンの１種以上を防錆顔料として存在させている。発明者らの検討によれば、この場合、屋外暴露環境のような比較的マイルドな腐食環境でも保護皮膜１１が従来よりも迅速に形成されるものと考えられ、結果的にエッジクリープ２０は１ｍｍ未満の成長量で止まり、目立ちにくい。その理由については現時点で必ずしも明らかではないが、１つには、下塗り塗膜４中に存在させたリン酸マンガンや亜リン酸マンガンは、従来の防錆顔料成分であるリン酸マグネシウム、リン酸亜鉛、変性シリカなどと比べ、雨水が当たりにくいマイルドな屋外環境においても溶出しやすいのではないかと考えられる。また、リン酸マンガンや亜リン酸マンガンから溶出したマンガンイオンは、めっき層２の溶出成分であるアルミニウムイオン等と結びついて形成される難溶性腐食生成物（リン酸アルミニウムや、Ａｌ、Ｚｎ等の水酸化物を主体とする物質）の付着性を向上させる作用があることも考えられる。いずれにしても、防錆顔料として配合させたリン酸マンガン、亜リン酸マンガンは、促進試験環境とは異なりマイルドな環境である屋外暴露環境において、迅速に保護皮膜１１を形成する上で極めて有効に作用し、エッジクリープの成長抑制効果に優れることがわかった。 In the present invention, a predetermined amount of one or more of manganese phosphate and manganese phosphite is present in the undercoat coating 4 as a rust preventive pigment. According to the study by the inventors, in this case, it is considered that the protective film 11 is formed more rapidly than in the conventional case even in a relatively mild corrosive environment such as an outdoor exposure environment. As a result, the edge creep 20 is 1 mm. It stops at less than the growth amount and is not conspicuous. The reason for this is not necessarily clear at the present time. For example, manganese phosphate and manganese phosphite present in the undercoat film 4 are magnesium phosphate and phosphoric acid, which are conventional antirust pigment components. Compared to zinc, modified silica, etc., it is thought that elution is likely to occur even in mild outdoor environments where rainwater is difficult to hit. In addition, manganese ions eluted from manganese phosphate and manganese phosphite are hardly soluble corrosion products (such as aluminum phosphate, Al, Zn, etc.) formed in combination with aluminum ions, etc., which are elution components of the plating layer 2. It is also conceivable that there is an effect of improving the adhesion of a substance mainly composed of hydroxide). In any case, manganese phosphate and manganese phosphite blended as rust preventive pigments are extremely effective in rapidly forming the protective coating 11 in an outdoor exposure environment that is a mild environment unlike the accelerated test environment. It was found that the effect of suppressing the growth of edge creep was excellent.

図２に、本発明の塗装鋼板の曲げ加工部における断面の腐食形態を模式的に示す。屋根材等の施工に際し、溶融Ｚｎ−Ａｌ系めっき塗装鋼板や、溶融Ａｌ系めっき塗装鋼板に曲げ加工を施すと、曲げの外側表面ではめっき層２およびその上の化成処理層３、下塗り塗膜４、上塗り塗膜５に不可避的にクラックが生じ、めっき層２および鋼素地１が外部に露出する。従来は特に屋外暴露環境などで、この部分での金属腐食が目立つことが問題となっていた。本発明によれば、これが顕著に抑制される。そのメカニズムについては前述の切断端面の場合と同様に、下塗り塗膜４中に配合させたリン酸マンガン、亜リン酸マンガンの溶出成分が、めっき層２から溶出するアルミニウムイオン等とともに迅速に難溶性の腐食生成物を形成し、金属露出部に保護皮膜１１を形成するものと考えられる。 In FIG. 2, the corrosion form of the cross section in the bending process part of the coated steel plate of this invention is shown typically. In the construction of roofing materials, etc., when bending work is performed on the hot-dip Zn-Al-plated coated steel sheet or hot-dip Al-plated coated steel sheet, the plated layer 2 and the chemical conversion treatment layer 3 on the outer surface of the bend, undercoat 4. Cracks are inevitably generated in the top coat film 5, and the plating layer 2 and the steel base 1 are exposed to the outside. Conventionally, metal corrosion in this part has become a problem, particularly in outdoor exposure environments. According to the present invention, this is remarkably suppressed. As for the mechanism, as in the case of the above-mentioned cut end face, the elution components of manganese phosphate and manganese phosphite mixed in the undercoat coating 4 are rapidly hardly soluble together with aluminum ions and the like eluted from the plating layer 2. It is considered that the corrosion product is formed and the protective film 11 is formed on the exposed metal portion.

以下、本発明を特定する事項について説明する。
〔めっき鋼板〕
塗装原板となるめっき鋼板としては、溶融Ｚｎ−Ａｌ系めっき鋼板または溶融Ａｌ系めっき鋼板が採用される。これらは亜鉛めっき鋼板よりもめっき表面の耐食性に優れる。特に溶融Ｚｎ−Ａｌ系めっき鋼板は亜鉛による犠牲防食作用を併せ持つ。めっき基材の鋼板は用途に応じて従来一般的なものが使用できる。 Hereinafter, the matter which specifies this invention is demonstrated.
[Plated steel sheet]
As the plated steel sheet as the coating original sheet, a molten Zn—Al-based plated steel sheet or a molten Al-based plated steel sheet is employed. These are more excellent in corrosion resistance of the plated surface than the galvanized steel sheet. In particular, a hot-dip Zn—Al-based plated steel sheet also has a sacrificial anticorrosive action due to zinc. Conventional steel plates can be used as the plating substrate depending on the application.

本発明で対象とする溶融めっきは、質量％で、Ａｌ：５〜９５％を含有し、残部元素としてＺｎ：９５％以下、Ｍｇ：１０％以下：Ｓｉ：１２％以下の１種以上を含有し、Ａｌ、Ｚｎ、Ｍｇ、Ｓｉ以外の元素の合計含有量が３％以下（０％を含む）である溶融めっき浴に鋼板を浸漬することにより施されるめっきである。このうち、Ｚｎをめっき成分として含有するものを溶融Ｚｎ−Ａｌ系めっきと呼び、それ以外を溶融Ａｌ系めっきと呼んでいる。Ａｌはめっき層自体の耐食性を向上させる上で有効な成分である。Ａｌ含有量が５％未満の場合またはＺｎ含有量が９５％を超える場合は、亜鉛めっき鋼板に対して耐食性の向上効果が小さく、コストメリットに乏しい。Ａｌ含有量が９５％を超えるとめっき浴の融点が高くなり好ましくない。Ｍｇはめっき層表面に均一な腐食生成物を生成させて当該めっき鋼板の耐食性を著しく高める作用を呈する。Ｍｇ含有量が１０質量％を超えると平滑なめっき表面を実現することが難しくなる。Ｓｉは、Ａｌを含有する溶融めっきにおいて脆いＦｅ−Ａｌ系合金層の成長を抑制する作用がある。また、Ａｌ含有量が高い場合にはＳｉ添加によりめっき浴の融点を低下させることができる。Ｓｉ含有量が１２％を超えるとこれらの効果が十分に発揮されない。 The hot dip plating which is the subject of the present invention contains at least 5% by mass of Al: 5 to 95%, and the balance of Zn: 95% or less, Mg: 10% or less: Si: 12% or less as the remaining elements. In addition, the plating is performed by immersing the steel sheet in a hot dipping bath in which the total content of elements other than Al, Zn, Mg, and Si is 3% or less (including 0%). Among these, what contains Zn as a plating component is called molten Zn-Al-based plating, and the others are called molten Al-based plating. Al is an effective component for improving the corrosion resistance of the plating layer itself. When the Al content is less than 5% or the Zn content exceeds 95%, the effect of improving the corrosion resistance is small with respect to the galvanized steel sheet, and the cost merit is poor. When the Al content exceeds 95%, the melting point of the plating bath increases, which is not preferable. Mg exhibits the effect | action which produces | generates a uniform corrosion product on the surface of a plating layer, and raises the corrosion resistance of the said plated steel plate remarkably. If the Mg content exceeds 10% by mass, it becomes difficult to realize a smooth plating surface. Si has an action of suppressing the growth of a brittle Fe—Al-based alloy layer in hot-dip plating containing Al. Moreover, when Al content is high, melting | fusing point of a plating bath can be reduced by Si addition. If the Si content exceeds 12%, these effects are not sufficiently exhibited.

溶融Ｚｎ−Ａｌ系めっき鋼板の代表例としては、Ｚｎ−５０〜６０％Ａｌ合金めっき鋼板、Ｚｎ−３〜２２％Ａｌ−２〜１０％Ｍｇ合金めっき鋼板が挙げられる。溶融Ａｌ系めっき鋼板としてはＡｌ−５〜１２％Ｓｉ合金めっき鋼板が挙げられる。本発明ではこれら公知の溶融めっき鋼板が広く使用でき、上記組成範囲を持つめっき鋼板である限り、その種類に特にこだわる必要はない。なお、めっき付着量は鋼板片面あたり３０〜２００ｇ／ｍ²程度の範囲とすればよい。 Typical examples of the hot-dip Zn—Al-based plated steel sheet include Zn-50 to 60% Al alloy plated steel sheet and Zn-3 to 22% Al-2 to 10% Mg alloy plated steel sheet. Examples of the molten Al-based plated steel sheet include Al-5 to 12% Si alloy plated steel sheet. In the present invention, these known hot-dip galvanized steel sheets can be widely used, and as long as they are galvanized steel sheets having the above composition range, there is no need to pay particular attention to their types. In addition, what is necessary is just to let the plating adhesion amount be the range of about 30-200 g / m < ² > per steel plate single side | surface.

〔化成処理層〕
溶融めっき鋼板を塗装原板として使用する場合には、多くの場合、下地処理として化成処理が施される。以前はクロメート処理が多用されていたが、最近では環境に配慮してクロムフリー処理が主流となっている。ただし、クロムフリー処理によりクロメート処理と同等以上の耐食性を安定して確保することは必ずしも容易ではなく、その意味でも後述の防錆顔料の配合が重要となる。クロムフリー処理としては、例えばエッチング作用のあるチタン化合物、フッ化物を有機樹脂に溶解した水溶液を用いて有機−無機複合皮膜を形成する処理等、種々のものが知られている。本発明では、これら公知の手法で形成した化成処理層を有するものが利用できる。特にチタン化合物、フッ化物を含有する無機−有機複合皮膜型のクロムフリー化成処理層を有するものが好適である。 [Chemical conversion treatment layer]
In the case of using a hot-dip plated steel sheet as a coating original sheet, in many cases, a chemical conversion treatment is performed as a base treatment. In the past, chromate treatment was often used, but recently, chromium-free treatment has become the mainstream in consideration of the environment. However, it is not always easy to stably secure the corrosion resistance equivalent to or higher than that of the chromate treatment by the chromium-free treatment. In that sense, the blending of the rust preventive pigment described later is important. Various chromium-free treatments are known, such as a treatment for forming an organic-inorganic composite film using an aqueous solution obtained by dissolving an etching titanium compound or fluoride in an organic resin. In this invention, what has the chemical conversion treatment layer formed by these well-known methods can be utilized. In particular, those having an inorganic-organic composite film type chromium-free chemical conversion treatment layer containing a titanium compound and fluoride are suitable.

〔下塗り塗膜〕
本発明では、下塗り塗膜（プライマー）中に顔料としてリン酸マンガン、亜リン酸マンガンの１種以上を配合させる。具体的には例えばリン酸第一マンガン；Ｍｎ(Ｈ₂ＰＯ₄)₂、リン酸第二マンガン；ＭｎＨ₃(ＰＯ₄)₂、亜リン酸マンガン；ＭｎＨＰＯ₃の１種以上を合計１０〜３５質量％配合させることができる。この含有量は乾燥塗膜中の質量％であり、塗料調合時には揮発成分の含有量を考慮して顔料の添加量を設定する。上記顔料の合計含有量が１０質量％未満では金属露出部へ保護皮膜を迅速に形成させる作用が小さく、結果的に従来の防錆顔料を添加した場合に対するメリットが十分に発揮されないことがある。下塗り塗膜の厚さが２〜５μｍ程度と比較的薄い場合は上記顔料の合計含有量を２０質量％以上とすることがより効果的である。一方、３５質量％を超えて多量に含有させても効果は飽和し不経済となり、また、塗布性や塗膜密着性を損なう要因となる。リン酸マンガン、亜リン酸マンガンの合計含有量は３０質量％以下とすることがより好ましく、２５質量％以下とすることが一層好ましい。配合させる顔料粉末は例えばレーザー回折式粒度分布測定装置を用いた体積平均粒子径Ｄ₅₀において２〜１０μｍ程度とすればよい。なお、他の顔料を複合して配合させても良いが、その場合は全ての顔料の合計量を３５質量％以下とすることがより好ましい。 [Undercoat]
In this invention, 1 or more types of manganese phosphate and manganese phosphite are mix | blended as a pigment in undercoat coating film (primer). Specifically, for example phosphoric acid _{_{manganous; Mn (H 2 PO 4)}} 2, manganic _{_{_{phosphate; MnH 3 (PO 4) 2}}} , phosphorous acid manganese; total 1 or more MnHPO ₃ 10~35 A mass% can be blended. This content is mass% in the dry coating film, and the amount of pigment added is set in consideration of the content of volatile components at the time of coating preparation. When the total content of the pigment is less than 10% by mass, the effect of rapidly forming a protective film on the exposed metal portion is small, and as a result, the merit with respect to the case where a conventional rust preventive pigment is added may not be sufficiently exhibited. When the thickness of the undercoat film is relatively thin, about 2 to 5 μm, it is more effective to set the total content of the pigment to 20% by mass or more. On the other hand, even if it is contained in a large amount exceeding 35% by mass, the effect is saturated and uneconomical, and the coating property and coating film adhesion are impaired. The total content of manganese phosphate and manganese phosphite is more preferably 30% by mass or less, and further preferably 25% by mass or less. The pigment powder to be blended may be, for example, about 2 to 10 μm in the volume average particle diameter D ₅₀ using a laser diffraction particle size distribution measuring device. In addition, although other pigments may be compounded and mixed, in that case, the total amount of all the pigments is more preferably 35% by mass or less.

下塗り塗膜用の塗料としては、従来のプライマーと同様の有機溶媒および樹脂成分を主体とするものを調合すれば良く、特にこだわる必要はない。塗装方法も従来一般的な手法が採用できる。下塗り塗膜の乾燥後の平均厚さは２〜２５μｍとすることが望ましい。薄すぎるとリン酸マンガン、亜リン酸マンガンの１種以上からなる防錆顔料成分の絶対量が不足し、迅速な保護皮膜の形成が十分に行われないおそれがある。ただし、２５μｍを超えるような厚い下塗り塗膜を形成させても効果は飽和し不経済となる。 As the paint for the undercoat film, a paint mainly composed of an organic solvent and a resin component similar to those of a conventional primer may be prepared, and it is not particularly required to be particular. Conventionally, a general method can be used as a painting method. The average thickness of the undercoat coating after drying is desirably 2 to 25 μm. If it is too thin, the absolute amount of the rust preventive pigment component comprising at least one of manganese phosphate and manganese phosphite may be insufficient, and a rapid protective coating may not be sufficiently formed. However, even if a thick undercoat film exceeding 25 μm is formed, the effect is saturated and uneconomical.

〔上塗り塗膜〕
上塗り塗膜は、従来から塗装鋼板に使用されている種々のものが適用対象となる。上塗り塗膜の乾燥後の平均厚さは１０〜４０μｍ程度である。塗装方法も従来一般的な手法が採用できる。 [Top coat]
Various top coating films that have been conventionally used for coated steel sheets are applicable. The average thickness of the top coat after drying is about 10 to 40 μm. Conventionally, a general method can be used as a painting method.

板厚０.５ｍｍの溶融Ｚｎ−５５％Ａｌ合金めっき鋼板を用意した。鋼板片面あたりのめっき付着量は７３ｇ／ｍ²である。めっき浴組成は、質量％でＡｌ：５５％、Ｓｉ：１.６％、残部Ｚｎおよび不可避的不純物である。この溶融めっき鋼板をアルカリ脱脂した後、以下の方法で両面に化成処理、下塗り塗装、上塗り塗装を施した。ここで、商品として外観に供する方の面を「上面」、その反対側の面を「裏面」と呼ぶ。 A hot-dip Zn-55% Al alloy-plated steel sheet having a thickness of 0.5 mm was prepared. The plating adhesion amount per one side of the steel plate is 73 g / m ² . The plating bath composition is Al: 55% by mass, Si: 1.6%, the balance Zn and inevitable impurities. After this hot-dip galvanized steel sheet was degreased with alkali, chemical conversion treatment, undercoating, and topcoating were performed on both sides by the following method. Here, the surface that is used for appearance as a product is referred to as “upper surface”, and the opposite surface is referred to as “back surface”.

〔化成処理〕
以下の３種類の公知の方法で化成処理層を形成させた。
（化成処理Ａ）；ヘキサフルオロチタン酸：５５ｇ／Ｌ、ヘキサフルオロジルコニウム酸：１０ｇ／Ｌ、アミノメチル置換ポリビニルフェノール：７２ｇ／Ｌを含有する塗布型クロムフリー化成処理液をめっき層表面に常温で塗布し、水洗することなく１００℃で乾燥させた。上面、裏面とも下記の付着量とした。
Ｔｉ換算付着量：１０ｍｇ／ｍ²、Ｚｒ換算付着量：２.５ｍｇ／ｍ²、Ｆ換算付着量：２０ｍｇ／ｍ²、ポリビニルフェノール換算付着量：４０ｍｇ／ｍ² [Chemical conversion treatment]
The chemical conversion treatment layer was formed by the following three types of known methods.
(Chemical conversion treatment A): A coating-type chromium-free chemical conversion treatment solution containing hexafluorotitanic acid: 55 g / L, hexafluorozirconic acid: 10 g / L, aminomethyl-substituted polyvinylphenol: 72 g / L on the surface of the plating layer at room temperature It was applied and dried at 100 ° C. without washing with water. The following adhesion amounts were used for the upper surface and the back surface.
Ti equivalent deposit: 10 mg / m ² , Zr equivalent deposit: 2.5 mg / m ² , F equivalent deposit: 20 mg / m ² , Polyvinylphenol equivalent deposit: 40 mg / m ²

（化成処理Ｂ）；塗布型クロメート処理液（日本ペイント株式会社製；サーフコートＮＲ−Ｃ３００ＮＳ）をロールコーターで塗布し、水洗することなく１００℃で乾燥させた。上面、裏面とも付着量は、Ｃｒ換算付着量：４０ｍｇ／ｍ²とした。 (Chemical conversion treatment B): A coating type chromate treatment solution (manufactured by Nippon Paint Co., Ltd .; Surfcoat NR-C300NS) was applied with a roll coater and dried at 100 ° C. without washing with water. The adhesion amount on both the upper surface and the back surface was set to Cr conversion adhesion amount: 40 mg / m ² .

〔下塗り〕
リン酸第一マンガン（平均粒子径Ｄ₅₀；約６μｍ）、リン酸第二マンガン（平均粒子径Ｄ₅₀；約６μｍ）、亜リン酸マンガン（平均粒子径Ｄ₅₀；約６μｍ）の各粉末を顔料として用意した。その他の顔料として表１に示す各種公知の顔料を用意した。エポキシ樹脂をベースとし、表１に示す顔料を配合した下塗り塗料を調合し、バーコーター法により化成処理層の上に塗布し、２１５℃で乾燥・焼付けを行って下塗り塗膜を形成させた。上面、裏面とも乾燥塗膜の平均厚さが５μｍとなるようにした。表１中の組成は乾燥後の下塗り塗膜中における値である。〔undercoat〕
Phosphate manganous each powder; (about 6 [mu] m average particle size D ₅₀₎ (average particle diameter D _50;; about 6 [mu] m), phosphoric acid manganic (average particle diameter D ₅₀ of about 6 [mu] m), phosphorous acid manganese Prepared as a pigment. Various other known pigments shown in Table 1 were prepared as other pigments. An undercoat paint based on an epoxy resin and containing the pigments shown in Table 1 was prepared, applied onto the chemical conversion layer by a bar coater method, dried and baked at 215 ° C. to form an undercoat film. The average thickness of the dried coating film was set to 5 μm on both the upper surface and the back surface. The composition in Table 1 is a value in the undercoat film after drying.

〔上塗り〕
ポリエステル樹脂をベースとする上塗り塗料を調合し、バーコーター法により下塗り塗膜の上に塗布し、２１５℃で乾燥・焼付けを行って上塗り塗膜を形成させた。乾燥後の上塗り塗膜の平均厚さは、上面が１１μｍ、裏面が５μｍとなるようにした。 [Overcoat]
A top coat based on a polyester resin was prepared, applied onto the undercoat film by a bar coater method, and dried and baked at 215 ° C. to form a top coat film. The average thickness of the top coat after drying was 11 μm on the top surface and 5 μm on the back surface.

このようにして作製した塗装鋼板を用いて、下記の方法で塗膜密着性、促進耐食性、屋外暴露特性を調べた。 Using the coated steel sheet thus prepared, coating film adhesion, accelerated corrosion resistance, and outdoor exposure characteristics were examined by the following methods.

〔塗膜密着性〕
上面の上塗り塗膜が曲げの外側となるように常温で２ｔ密着曲げ加工を行い、曲げ加工部（曲げの外側表面）についてＪＩＳＺ１５２２に規定されるセロハン粘着テープを貼付した後、剥がす方法で塗膜剥離試験を行い、曲げ加工部の外側表面の面積に占める塗膜剥離が生じた面積の割合を測定し、以下の基準で塗膜密着性を評価した。○評価以上を合格と判定した。 [Coating film adhesion]
Perform 2t adhesion bending process at room temperature so that the top coating film on the upper surface is outside the bend, and apply the cellophane adhesive tape specified in JIS Z1522 on the bent portion (outer surface of the bend) and then peel off. A film peeling test was performed, the ratio of the area where the coating film peeling occurred in the area of the outer surface of the bent portion was measured, and the coating film adhesion was evaluated according to the following criteria. ○ Evaluation or higher was determined to be acceptable.

（塗膜密着性評価）
◎：塗膜剥離が認められない
○：塗膜剥離面積率：５％未満
△：〃：５％以上２０％未満
×：〃：２０％以上 (Coating adhesion evaluation)
◎: No peeling of coating film is observed ○: Coating film peeling area ratio: less than 5% △: 〃: 5% or more and less than 20% ×: 〃: 20% or more

〔促進耐食性〕
各塗装鋼板からせん断加工により切り出した板材を用いて、上記と同様の２ｔ密着曲げ加工を施した試験片を用意した。この試験片には曲げ加工部と切断端面があり、それらの箇所でめっき金属および鋼素地が露出している。酸性雨を模擬した試験液として、０.１％食塩水を硫酸でｐＨ＝４に調整した液を調製した。各試験片について、「上記試験液による塩水噴霧（３５℃×１ｈ）→乾燥（５０℃×４ｈ）→湿潤（相対湿度９８％、５０℃×３ｈ）」を１サイクルとする促進試験を３００サイクル実施した。 [Accelerated corrosion resistance]
Using a plate material cut out from each coated steel plate by a shearing process, a test piece subjected to the 2t contact bending process similar to the above was prepared. This test piece has a bent portion and a cut end surface, and the plated metal and the steel substrate are exposed at those portions. As a test solution simulating acid rain, a solution in which 0.1% saline was adjusted to pH = 4 with sulfuric acid was prepared. For each test piece, 300 cycles of the accelerated test with one cycle of “salt spray with the above test solution (35 ° C. × 1 h) → drying (50 ° C. × 4 h) → wet (relative humidity 98%, 50 ° C. × 3 h)” Carried out.

試験後の試験片の曲げ加工部の外側表面について、白錆評価および塗膜下腐食評価を行った。
白錆評価は、曲げ加工部の外側表面に占める白錆発生部分の面積率を測定することにより行った。
塗膜下腐食評価は、光学顕微鏡を用いて断面から曲げ加工部の下塗り塗膜下に生じている腐食箇所の面積を測定し、測定面積に占める腐食箇所（めっき金属の溶解が生じた部分）の面積率を求めることにより行った。
また、切断端面の上面塗膜部についてエッジクリープ長さ（図１のｘに相当する長さ）を測定した。切断端面の全域を調べて、最もエッジクリープ長さの長い部分の値を当該試験片のエッジクリープ長さの成績値として採用し、評価した。
各評価基準は以下のとおりとし、それぞれ○評価以上を合格と判定した。 The outer surface of the bent part of the test piece after the test was subjected to white rust evaluation and under-coating corrosion evaluation.
White rust evaluation was performed by measuring the area ratio of the white rust generation | occurrence | production part which occupies for the outer surface of a bending process part.
Under-coating corrosion evaluation uses an optical microscope to measure the area of the corroded area under the undercoat of the bent part from the cross-section, and the corroded area in the measured area (part where the plating metal has dissolved) This was done by determining the area ratio.
Further, the edge creep length (length corresponding to x in FIG. 1) was measured for the upper surface coating film portion of the cut end face. The entire area of the cut end face was examined, and the value of the portion with the longest edge creep length was adopted as the result value of the edge creep length of the test piece and evaluated.
Each evaluation standard was as follows, and each of the evaluations was evaluated as pass.

（白錆評価）
◎：白錆発生面積率：１０％未満
○：〃：１０％以上２０％未満
△：〃：２０％以上５０％未満
×：〃：５０％以上
（塗膜下腐食評価）
◎：腐食面積率：３％未満
○：〃：３％以上５％未満
△：〃：５％以上１０％未満
×：〃：１０％以上
（エッジクリープ評価）
◎：エッジクリープ長さ：１.０ｍｍ未満
○：〃：１.０ｍｍ以上２.０ｍｍ未満
△：〃：２.０ｍｍ以上３.０ｍｍ未満
×：〃：３.０ｍｍ以上 (White rust evaluation)
◎: White rust generation area ratio: less than 10% ○: 〃: 10% or more and less than 20% △: 〃: 20% or more and less than 50% ×: 〃: 50% or more (corrosion evaluation under coating film)
◎: Corrosion area ratio: less than 3% ○: 〃: 3% or more and less than 5% △: 〃: 5% or more and less than 10% ×: 〃: 10% or more (edge creep evaluation)
◎: Edge creep length: less than 1.0 mm ○: 〃: 1.0 mm or more and less than 2.0 mm △: 〃: 2.0 mm or more and less than 3.0 mm ×: 〃: 3.0 mm or more

〔屋外暴露特性〕
促進試験の場合と同様の２ｔ密着曲げ加工を施した試験片を用いて、１年間の大気暴露試験を行った。暴露地は千葉県市川市の海岸から５ｍの地点である。暴露角度は南向き３５°であり、傾斜の下部に曲げ加工部が位置するように試験片を設置した。
１年間の大気暴露後に、曲げ加工部について上記促進試験の場合と同様の方法で白錆評価および塗膜下腐食評価を行い、○評価以上を合格と判定した。
また、切断端面の上面塗膜部について上記促進試験の場合と同様の方法でエッジクリープ長さを求め、下記の基準で評価して、○評価以上を合格と判定した。 [Outdoor exposure characteristics]
A one-year atmospheric exposure test was performed using a test piece that had been subjected to 2t adhesion bending as in the case of the accelerated test. The exposed area is 5m from the coast of Ichikawa City, Chiba Prefecture. The exposure angle was 35 ° southward, and the test piece was placed so that the bent portion was located at the bottom of the slope.
After exposure to the atmosphere for one year, white rust evaluation and under-corrosion evaluation were performed on the bent portion by the same method as in the case of the above-described accelerated test.
Moreover, the edge creep length was calculated | required by the method similar to the case of the said acceleration test about the upper surface coating-film part of a cutting | disconnection end surface, it evaluated by the following reference | standard, and evaluated more than (circle) evaluation as the pass.

（大気暴露でのエッジクリープ評価）
◎：エッジクリープ長さ：０.５ｍｍ未満
○：〃：０.５ｍｍ以上１.０ｍｍ未満
△：〃：１.０ｍｍ以上１.５ｍｍ未満
×：〃：１.５ｍｍ以上
これらの結果を表２に示す。 (Evaluation of edge creep under atmospheric exposure)
◎: Edge creep length: less than 0.5 mm ○: 〃: 0.5 mm or more and less than 1.0 mm △: 〃: 1.0 mm or more and less than 1.5 mm ×: 〃: 1.5 mm or more These results are shown in Table 2. Show.

表１、表２から判るように、顔料としてリン酸マンガン、亜リン酸マンガンの１種以上が合計１０質量％以上含有されている下塗り塗膜を有する本発明例のものはいずれも、促進耐食性、屋外暴露特性とも良好であった。また、塗膜密着性も良好であった。 As can be seen from Tables 1 and 2, all of the examples of the present invention having an undercoat film containing at least 10 mass% of one or more of manganese phosphate and manganese phosphite as pigments are accelerated corrosion resistance. The outdoor exposure characteristics were also good. The coating film adhesion was also good.

これに対し、比較例Ｎｏ.９は特許文献１の技術に相当する従来例であり、促進耐食性は良好であるものの、１年間という長期の大気暴露を行うと本発明例のものより耐食性に劣った。このことから、本発明で採用したリン酸マンガン系の顔料は、比較例Ｎｏ.９のリン酸マグネシウム系の顔料と比べ、大気暴露等の比較的マイルドな環境でも迅速に溶出することができ、Ａｌを含有するめっき層の溶出成分と早期に結びついて強固な保護皮膜を形成するものと推察される。なお、ここではＺｎ−５０〜６０％Ａｌ合金めっき鋼板を原板に使用したが、Ｚｎ−３〜２２％Ａｌ−２〜１０％Ｍｇ合金めっき鋼板や、Ａｌ−５〜１２％Ｓｉ合金めっき鋼板を原板とした場合でも、本発明を適用すれば上記のような耐食性改善効果が認められることを別途確認している。Ｎｏ.１０〜１２は促進耐食性、屋外暴露特性がともに良好ではなかった。Ｎｏ.１３はクロメート処理層と、クロム系の顔料を配合する下塗り塗膜を有するものであり、各特性は良好であるが、環境問題に適合できない。 On the other hand, Comparative Example No. 9 is a conventional example corresponding to the technique of Patent Document 1, and although the accelerated corrosion resistance is good, the corrosion resistance is inferior to that of the present invention example when subjected to long-term atmospheric exposure for one year. It was. From this, the manganese phosphate pigment employed in the present invention can be rapidly eluted even in a relatively mild environment such as atmospheric exposure, compared with the magnesium phosphate pigment of Comparative Example No. 9. It is presumed that a strong protective film is formed by combining with the elution component of the plating layer containing Al at an early stage. In addition, although Zn-50-60% Al alloy plating steel plate was used for the original plate here, Zn-3-22% Al-2-10% Mg alloy plating steel plate and Al-5-12% Si alloy plating steel plate were used. It has been separately confirmed that even when the original plate is used, the above-described corrosion resistance improving effect is recognized if the present invention is applied. Nos. 10-12 were not good in both accelerated corrosion resistance and outdoor exposure characteristics. No. 13 has a chromate-treated layer and an undercoat coating film containing a chromium-based pigment. Although each characteristic is good, it cannot be adapted to environmental problems.

１鋼素地
２めっき層
３化成処理層
４下塗り塗膜
５上塗り塗膜
６切断端面
１０腐食箇所
１１保護皮膜
２０エッジクリープ DESCRIPTION OF SYMBOLS 1 Steel substrate 2 Plating layer 3 Chemical conversion treatment layer 4 Undercoat film 5 Topcoat film 6 Cutting end face 10 Corrosion spot 11 Protective film 20 Edge creep

Claims

質量％で、Ａｌ：５〜９５％を含有し、残部元素としてＺｎ：９５％以下、Ｍｇ：１０％以下：Ｓｉ：１２％以下の１種以上を含有し、Ａｌ、Ｚｎ、Ｍｇ、Ｓｉ以外の元素の合計含有量が３％以下（０％を含む）である溶融めっき浴を用いてＡｌ含有めっき層を形成しためっき鋼板の、当該めっき層の上に、化成処理皮膜（ただし、リン酸塩処理皮膜の場合は除く）、下塗り塗膜、上塗り塗膜を有する塗装鋼板において、前記下塗り塗膜中に顔料としてリン酸マンガン、亜リン酸マンガンの１種以上が合計１０〜３５質量％含有されていることを特徴とする塗装鋼板。 In mass%, Al: 5 to 95% is contained, Zn: 95% or less, Mg: 10% or less: Si: 12% or less as the remaining elements, other than Al, Zn, Mg, Si The chemical conversion treatment film (however, phosphoric acid is formed on the plating layer of the plated steel sheet in which the Al-containing plating layer is formed using a hot dipping bath having a total content of 3% or less (including 0%). In the case of a coated steel sheet having an undercoating film and an overcoating film, a total of 10 to 35% by mass of at least one of manganese phosphate and manganese phosphite as pigments is contained in the undercoating film. Painted steel sheet characterized by being made.

質量％で、Ａｌ：５〜９５％を含有し、残部元素としてＺｎ：９５％以下、Ｍｇ：１０％以下：Ｓｉ：１２％以下の１種以上を含有し、Ａｌ、Ｚｎ、Ｍｇ、Ｓｉ以外の元素の合計含有量が３％以下（０％を含む）である溶融めっき浴を用いてＡｌ含有めっき層を形成しためっき鋼板の、当該めっき層の上に、チタン化合物およびフッ化物を有機樹脂に溶解した水溶液を用いて形成したクロムフリー化成処理皮膜、下塗り塗膜、上塗り塗膜を有する塗装鋼板において、前記下塗り塗膜中に顔料としてリン酸マンガン、亜リン酸マンガンの１種以上が合計１０〜３５質量％含有されていることを特徴とする塗装鋼板。 In mass%, Al: 5 to 95% is contained, Zn: 95% or less, Mg: 10% or less: Si: 12% or less as the remaining elements, other than Al, Zn, Mg, Si A titanium compound and a fluoride are formed on the plated layer of a plated steel sheet in which an Al-containing plated layer is formed using a hot dipping bath having a total content of 3% or less (including 0%). In a coated steel sheet having a chromium-free chemical conversion film, an undercoat film, and an overcoat film formed using an aqueous solution dissolved in the solution, a total of one or more of manganese phosphate and manganese phosphite as pigments in the undercoat film A coated steel sheet characterized by containing 10 to 35% by mass.

下塗り塗膜の平均厚さが２〜２５μｍである請求項１または２に記載の塗装鋼板。 The coated steel sheet according to claim 1 or 2 , wherein the average thickness of the undercoat coating film is 2 to 25 µm.

請求項１または２に記載の塗装鋼板を素材として成形され、切断端面の金属露出部および曲げ加工部の金属露出部の少なくとも一方を持つ建築物の外装部材。 An exterior member for a building which is formed using the coated steel sheet according to claim 1 or 2 as a raw material and has at least one of a metal exposed portion of a cut end surface and a metal exposed portion of a bent portion.