JP5614671B2 - Oxide film and method for forming the same - Google Patents
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本発明は、アルミニウム基材に形成される酸化被膜及びその形成方法に関する。 The present invention relates to an oxide film formed on an aluminum substrate and a method for forming the same.
従来、アルミニウム鋳造材等のアルミニウム基材に塗装を施す場合には、塗膜との密着性及び耐食性を確保するため、塗装の下地処理としてカチオン電着塗装を行い、その後に溶剤塗装を行っている。 Conventionally, when coating aluminum substrates such as cast aluminum, in order to ensure adhesion and corrosion resistance with the coating film, cationic electrodeposition coating is performed as a base treatment for coating, and then solvent coating is performed. Yes.
近年では、大気汚染防止法の改正により、揮発性有機化合物（ＶＯＣ）の排出の抑制が求められており、有機溶剤を使用する溶剤塗装に代えて有機溶剤を使用しない粉体塗装について検討されている。一方、粉体塗装を行う場合でもその塗膜のみでは密着性と耐食性とが不十分であり、またカチオン電着塗装ではＶＯＣが排出されるため、ＶＯＣを排出しない下地処理についても検討が進められている。 In recent years, due to amendments to the Air Pollution Control Law, there has been a demand for suppression of volatile organic compound (VOC) emissions, and powder coating that does not use organic solvents instead of solvent coating that uses organic solvents has been studied. Yes. On the other hand, even in the case of powder coating, adhesion and corrosion resistance are insufficient with only the coating film, and since VOC is discharged in cationic electrodeposition coating, investigations are also being made on a ground treatment that does not discharge VOC. ing.
このような下地処理としては、アルミニウム基材に陽極酸化処理を施してアルマイト（陽極酸化）被膜を形成することが提案されている（例えば、特許文献１参照）。この技術では、アルマイト被膜に半封孔処理を施した後、塗装を行うことにより、油分等の汚染物を孔内に入り難くすると共に、塗装用の塗料を孔内に入り込ませることによるアンカー効果および表面化学反応の活性化により、塗膜との密着性及び耐食性を向上させている。 As such a base treatment, it has been proposed to anodize an aluminum substrate to form an alumite (anodized) film (for example, see Patent Document 1). In this technology, after applying semi-sealing treatment to the anodized coating, it is difficult to get oil and other contaminants into the hole, and the anchor effect by allowing the paint for coating to enter the hole In addition, the adhesion to the coating film and the corrosion resistance are improved by the activation of the surface chemical reaction.
しかし、前記従来のアルマイト被膜では、耐食性に対して効果があるバリヤー層の厚みを厚く形成することができないため、使用条件によっては耐食性が不十分となる場合があった。そのため、耐食性を向上させるには、さらに封孔処理を必要としていた。 However, in the conventional alumite coating, the thickness of the barrier layer having an effect on the corrosion resistance cannot be formed thick, so that the corrosion resistance may be insufficient depending on the use conditions. Therefore, in order to improve the corrosion resistance, further sealing treatment is required.
アルマイト被膜の形成プロセスでは、陽極酸化処理工程の前後に脱脂処理工程や封孔処理工程等が必要になり、また陽極酸化処理自体における成膜速度も遅いため、アルマイト被膜を形成させるのに時間がかかり、製造コストが高くなるというも問題があった。 In the process of forming the anodized film, a degreasing process, a sealing process, etc. are required before and after the anodizing process, and the film forming speed in the anodizing process itself is slow, so it takes time to form the anodized film. The manufacturing cost is also high.
本発明は、上記課題に鑑みてなされたものであり、安価で、塗膜との密着性及び耐食性に優れる酸化被膜、及びその形成方法を提供することを目的とする。 This invention is made | formed in view of the said subject, It aims at providing the oxide film which is cheap, and is excellent in adhesiveness and corrosion resistance with a coating film, and its formation method.
上記目的を達成するための本発明に係る酸化被膜の第１特徴構成は、アルミニウム基材に形成され、塗膜の下地とする酸化被膜であって、非晶質のバリヤー層と、当該バリヤー層に積層され、複数の中空柱状のセルから構成される多孔質層とを備え、前記多孔質層は、γ相とα相とが混在しており、前記セルの平均セル径が２００〜８００ｎｍであり、厚みが１〜４μｍである点にある。 In order to achieve the above object, a first characteristic configuration of an oxide film according to the present invention is an oxide film formed on an aluminum base material and used as a base of the film, the amorphous barrier layer, and the barrier layer. And a porous layer composed of a plurality of hollow columnar cells, the porous layer is a mixture of γ phase and α phase, and the average cell diameter of the cells is 200 to 800 nm. And the thickness is 1 to 4 μm.
バリヤー層は緻密な非晶質層で構成される。このため、本構成のように、バリヤー層を設けることで、アルミニウム基材の耐食性を向上させることができる。
また、酸化被膜に塗装を施す場合には、多孔質層の表面が塗膜と化学反応して結合する。本構成によれば、多孔質層の平均セル径が２００〜８００ｎｍと、従来のアルマイト被膜に比べて大きく、塗膜との化学反応は酸化被膜のセルの全面で均一に起こるため、塗膜との密着性は向上する。
The barrier layer is composed of a dense amorphous layer. For this reason, the corrosion resistance of an aluminum base material can be improved by providing a barrier layer like this structure.
Moreover, when coating an oxide film, the surface of a porous layer chemically reacts and couple | bonds with a coating film. According to this configuration, the average cell diameter of the porous layer is 200 to 800 nm, which is larger than that of the conventional alumite coating, and the chemical reaction with the coating occurs uniformly over the entire surface of the oxide coating cell. The adhesion is improved.
本発明に係る酸化被膜の第２特徴構成は、前記バリヤー層の厚みを１００〜３００ｎｍとした点にある。 The second characteristic configuration of the oxide film according to the present invention is that the thickness of the barrier layer is 100 to 300 nm.
本構成によれば、バリヤー層としての十分な厚みを確保することができるため、耐食性をより向上させることができる。
本発明に係る酸化被膜の第３特徴構成は、前記多孔質層は、前記セル内に形成される微細孔を有し、前記微細孔は、前記バリヤー層に近づくに従って枝分かれする点にある。
According to this structure, since sufficient thickness as a barrier layer can be ensured, corrosion resistance can be improved more.
A third characteristic configuration of the oxide film according to the present invention is that the porous layer has micropores formed in the cell, and the micropores branch as they approach the barrier layer.
本発明に係る酸化被膜の形成方法の特徴手段は、アルミニウム基材に形成され、塗膜の下地とする酸化被膜の形成方法であって、シュウ酸チタンカリウムを含むｐＨ５〜６の電解液中において、前記アルミニウム基材を陽極とする２５０〜４５０Ｖの電圧と、前記アルミニウム基材を陰極とする４０〜１００Ｖの電圧とを交互に印加して行うプラズマ電解処理を行うことにより、前記アルミニウム基材の表面に、非晶質のバリヤー層と、前記バリヤー層に積層されてγ相とα相とが混在する多孔質層とを備える酸化被膜を形成する点にある。 The characteristic means of the method for forming an oxide film according to the present invention is a method for forming an oxide film formed on an aluminum base material and used as a base of the film, in an electrolyte having a pH of 5 to 6 containing potassium titanium oxalate. By performing plasma electrolysis treatment by alternately applying a voltage of 250 to 450 V using the aluminum base material as an anode and a voltage of 40 to 100 V using the aluminum base material as a cathode, An oxide film including an amorphous barrier layer and a porous layer laminated on the barrier layer and containing a γ phase and an α phase is formed on the surface.
本手段によれば、ｐＨ５〜６の電解液を用いて、プラズマ電解処理を行うだけで、アルミニウム基材にバリヤー層と多孔質層とを備えた酸化被膜を容易に形成することができる。また、耐食性はバリヤー層で確保されているため、多孔質層に対して封孔処理等を別途行う必要がなく、安価で簡便に酸化被膜を形成することができる。 According to this means, an oxide film comprising a barrier layer and a porous layer can be easily formed on an aluminum substrate simply by performing a plasma electrolysis treatment using an electrolytic solution having a pH of 5-6. Further, since the corrosion resistance is ensured by the barrier layer, it is not necessary to separately perform a sealing treatment or the like on the porous layer, and an oxide film can be easily formed at a low cost.
酸化被膜の多孔質層はある程度成長すると、電流が流れ難くなる。
本手段のように、アルミニウム基材を陽極とする正電圧と、アルミニウム基材を陰極とする負電圧とを交互に印加しながら行えば、負電圧が印加された時に多孔質層が溶かされ、電流が継続して流れるようになるため、多孔質層を継続して成長させることができる。
When the porous layer of the oxide film grows to some extent, it becomes difficult for current to flow.
If the positive voltage with the aluminum base as the anode and the negative voltage with the aluminum base as the cathode are alternately applied as in this means, the porous layer is dissolved when the negative voltage is applied, Since the current flows continuously, the porous layer can be continuously grown.
以下、本発明に係る酸化被膜の一実施形態について図面を参照して説明する。
本実施形態に係る酸化被膜は、図１，２に示すように、アルミニウム基材の表面に形成されるものであり、バリヤー層と、そのバリヤー層の表面に積層された多孔質層とを備えている。多孔質層は、複数の中空柱状のセルで構成されており、多孔質層の平均セル径は、従来のアルマイト被膜の平均セル径に比べてかなり大きく、２００〜８００ｎｍになっている。尚、多孔質層の平均セル径とは、図３に示すように、多孔質層の表面に観察されるセルの幅をセル径とし、これを複数のセルからサンプリングして平均したものである。サンプリングの際には、輪郭が明確なセルのみについて測定し、セルの形状を留めていないセルや、他のセルに比べてセル径が極端に小さいセルについては除外することとした。また、微細孔径は、セルに形成された孔の直径のうち最も長い直径を測定したものである。多孔質層の平均微細孔径は、特に制限はないが、例えば、１００〜１６０ｎｍ程度である。
Hereinafter, an embodiment of an oxide film according to the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the oxide film according to the present embodiment is formed on the surface of an aluminum substrate, and includes a barrier layer and a porous layer laminated on the surface of the barrier layer. ing. The porous layer is composed of a plurality of hollow columnar cells, and the average cell diameter of the porous layer is considerably larger than the average cell diameter of the conventional alumite coating, which is 200 to 800 nm. The average cell diameter of the porous layer is, as shown in FIG. 3, the cell width observed on the surface of the porous layer as the cell diameter, which is averaged by sampling from a plurality of cells. . At the time of sampling, only cells having a clear outline were measured, and cells that did not retain the shape of the cells and cells that had an extremely small cell diameter compared to other cells were excluded. The fine pore diameter is a value obtained by measuring the longest diameter among the diameters of the holes formed in the cell. The average fine pore diameter of the porous layer is not particularly limited, but is, for example, about 100 to 160 nm.
このような酸化被膜では、バリヤー層は緻密な非晶質層で形成され、多孔質層のセルではγ相とα相が混在して形成されている。このバリヤー層により、アルミニウム基材の耐食性が向上する。また、多孔質層に混在するγ相の表面化学反応が活性である性質により、密着性が向上する。また、α相が高強度である性質により、被膜自体の強度が向上する。バリヤー層の膜厚は、特に限定はされないが、ある程度の厚みを有することが好ましく、例えば、１００〜３００ｎｍが好ましい。尚、バリヤー層の膜厚は３００ｎｍより厚くなっても構わないが、耐食性はあまり変わらない。バリヤー層の膜厚は、例えば、プラズマ電解処理において印加する電圧の大きさ等によって制御することができる。このように、本発明に係る酸化被膜においては、バリヤー層によって耐食性を確保しているため、多孔質層に対して封孔処理等を施す必要はない。 In such an oxide film, the barrier layer is formed of a dense amorphous layer, and in the cell of the porous layer, a γ phase and an α phase are mixedly formed. This barrier layer improves the corrosion resistance of the aluminum substrate. In addition, the adhesiveness is improved by the property that the surface chemical reaction of the γ phase mixed in the porous layer is active. Moreover, the strength of the coating itself is improved due to the high strength of the α phase. Although the film thickness of a barrier layer is not specifically limited, It is preferable to have a certain amount of thickness, for example, 100-300 nm is preferable. The barrier layer may be thicker than 300 nm, but the corrosion resistance does not change much. The thickness of the barrier layer can be controlled by, for example, the magnitude of the voltage applied in the plasma electrolysis process. Thus, in the oxide film according to the present invention, since the corrosion resistance is ensured by the barrier layer, it is not necessary to perform a sealing treatment or the like on the porous layer.
多孔質層は塗装を施した場合の塗膜との密着性に影響を与える。塗膜の焼付け時には１８０℃で３０分間程度の熱処理を施すため、このとき、多孔質層中の不安定なＡｌ及びＡｌ2Ｏ3のγ相は、塗料成分中に含まれるＯＨ基との反応によりベーマイト化し、これに伴って塗膜と多孔質層の表面との間で化学反応が起こり、密着性が確保される。本発明に係る酸化被膜であれば、多孔質層は平均セル径が大きく、均一なセルの集合体であるため、塗膜との化学反応は酸化被膜のγ相で形成されたセルの全面で均一に起こり、密着性はより向上することになる。このため、多孔質層の膜厚は、塗膜と反応する多孔質層が存在していればよく、特に限定はされない。多孔質層の膜厚は、例えば１〜４μｍ程度に設定すればよい。多孔質層の膜厚は、例えば、プラズマ電解処理における電圧の印加時間等によって制御することができる。 The porous layer affects the adhesion with the coating film when the coating is applied. When the coating is baked, heat treatment is performed at 180 ° C. for about 30 minutes. At this time, unstable Al and Al 2 O 3 γ phases in the porous layer react with OH groups contained in the paint components. As a result, boehmite is formed and a chemical reaction occurs between the coating film and the surface of the porous layer, thereby ensuring adhesion. In the case of the oxide film according to the present invention, the porous layer has a large average cell diameter and is an aggregate of uniform cells. Therefore, the chemical reaction with the film occurs on the entire surface of the cell formed by the γ phase of the oxide film. It occurs uniformly and the adhesion is further improved. For this reason, the film thickness of a porous layer should just have the porous layer which reacts with a coating film, and is not specifically limited. What is necessary is just to set the film thickness of a porous layer to about 1-4 micrometers, for example. The film thickness of the porous layer can be controlled by, for example, the voltage application time in plasma electrolysis.
尚、本実施形態に係る酸化被膜では、被膜の表面に水和物が形成されており、多孔質層の微細孔は被膜表面付近において塞がるような構造を有している。このため、微細孔に腐食液等が進入すること自体を抑制することができる。そして、塗装を施す場合には、多孔質層の表面において塗膜との接触面積が増大させることができると共に、塗装焼付け時に不安定なＡｌ及びＡｌ2Ｏ3のγ相が、塗料成分中に含まれるＯＨ基との反応によりベーマイト化するため、塗膜と反応させることができる。
また、多孔質層の微細孔は枝分かれ部を有している（図２において一部は横穴として観察できる）。この枝分かれ部は、バリヤー層に近づくに従って枝分かれしており、微細孔に腐食液等が進入した場合でもバリヤー層への浸透自体を抑制することができる。
In addition, in the oxide film which concerns on this embodiment, the hydrate is formed in the surface of a film, and it has a structure where the micropore of a porous layer is plugged up near the film surface. For this reason, it can suppress that corrosive liquid etc. approach into a micropore itself. When applying the coating, the contact area with the coating film can be increased on the surface of the porous layer, and the unstable γ phase of Al and Al 2 O 3 during coating baking is contained in the coating component. Since boehmite is formed by reaction with the contained OH group, it can be reacted with the coating film.
Moreover, the micropores of the porous layer have branch portions (a part of them can be observed as horizontal holes in FIG. 2). This branching portion branches as it approaches the barrier layer, and even when a corrosive liquid or the like enters the micropores, permeation into the barrier layer itself can be suppressed.
したがって、本発明に係る酸化被膜であれば、アルミニウム基材の耐食性を向上させることができる。また、アルミニウム基材に塗装を施す場合には、下地として塗膜との密着性を向上させることができる。 Therefore, if it is the oxide film which concerns on this invention, the corrosion resistance of an aluminum base material can be improved. Moreover, when apply | coating to an aluminum base material, adhesiveness with a coating film can be improved as a foundation | substrate.
アルミニウム基材としては、特に限定はされず、例えば、アルミニウム押出し材、アルミニウム鋳造材、アルミニウム鍛造材等を用いることができる。アルミニウムとしては、純アルミニウム、アルミニウム合金等を適用でき、特に制限はない。アルミニウム合金の種類は、銅、マンガン、ケイ素、マグネシウム、亜鉛、ニッケル、錫、鉛、チタン、クロム、ジルコニウム等の１種または複数種との合金が例示される。また、アルミニウム基材には、添加物や不純物等が含有していても何ら構わない。 The aluminum substrate is not particularly limited, and for example, an aluminum extruded material, an aluminum cast material, an aluminum forged material, or the like can be used. As aluminum, pure aluminum, aluminum alloy or the like can be applied, and there is no particular limitation. Examples of the aluminum alloy include alloys with one or more of copper, manganese, silicon, magnesium, zinc, nickel, tin, lead, titanium, chromium, zirconium and the like. The aluminum substrate may contain any additives, impurities, etc.
酸化被膜は、ｐＨ４〜９の電解液中に、アルミニウム基材を陽極として陰極と共に配置し、プラズマ電解処理を行うことによりアルミニウム基材の表面に形成することができる。アルミニウム基材にプラズマ電解処理を行う場合には、その前後の処理が必要なく、簡便に行えるため、製造コストを抑えることができる。 An oxide film can be formed on the surface of an aluminum substrate by placing the aluminum substrate as an anode together with a cathode in an electrolyte having a pH of 4 to 9, and performing plasma electrolysis treatment. When plasma electrolytic treatment is performed on an aluminum substrate, the treatment before and after that is not necessary and can be easily performed, so that the manufacturing cost can be reduced.
電解液は、ｐＨ４〜９の範囲にあるものを用いる。従来のプラズマ電解処理がｐＨ１０以上のアルカリ性の電解液を用いるのに対し、酸性〜弱アルカリ性、好ましくはｐＨ５〜６の弱酸性の電解液を用いてプラズマ電解処理を行うことにより、バリヤー層と多孔質層とを備える酸化被膜を形成することができる。このような電解液としては、例えば、プラズマ電解処理において、一般に用いられるピロリン酸塩の溶液をｐＨ４〜９にしたものが挙げられ、具体的には、ピロリン酸ナトリウムとシュウ酸チタンカリウムとを、水にそれぞれ５〜３０ｇ／Ｌで含有させたものが例示される。シュウ酸チタンカリウムは、後述の実施例で示すように、プラズマ電解処理条件によっては多孔質層の形成に影響を与える場合がある。このため、シュウ酸チタンカリウムを電解液に用いることは特に好ましい。電解液の温度は、特に限定はされないが、プラズマ電解処理の場合は、加わるエネルギーが大きく、発熱を伴うため、例えば、０〜１０℃の低温とすることが好ましい。 As the electrolytic solution, one having a pH in the range of 4 to 9 is used. Whereas the conventional plasma electrolytic treatment uses an alkaline electrolytic solution having a pH of 10 or more, the barrier layer and the porous layer are formed by performing the plasma electrolytic treatment using an acidic to weak alkaline, preferably a weakly acidic electrolytic solution having a pH of 5 to 6. An oxide film comprising a quality layer can be formed. As such an electrolytic solution, for example, in plasma electrolytic treatment, a solution of pyrophosphate generally used to pH 4 to 9 can be mentioned, specifically, sodium pyrophosphate and potassium potassium oxalate, What was made to contain at 5-30 g / L in water, respectively is illustrated. Titanium potassium oxalate may affect the formation of the porous layer depending on the plasma electrolytic treatment conditions, as shown in Examples described later. For this reason, it is particularly preferable to use potassium potassium oxalate as the electrolyte. The temperature of the electrolytic solution is not particularly limited. However, in the case of plasma electrolytic treatment, the applied energy is large and accompanied by heat generation.
陰極は、特に限定されないが、例えば、鉛板、ＳＵＳ板等を用い陽極としてのアルミニウム基材と対向するように配置して用いる。そして、両極間に、定電圧制御や定電流制御等によって通電を行うことにより、プラズマ電解処理を行うことができる。 Although a cathode is not specifically limited, For example, a lead plate, a SUS plate, etc. are used and it arrange | positions so that it may oppose the aluminum base material as an anode. And plasma electrolysis can be performed by energizing between both poles by constant voltage control, constant current control, etc.
プラズマ電解処理は、アルミニウム基材を陽極として通電することにより、アルミニウム基材に酸化被膜を形成することができ、特に制限はないが、アルミニウム基材を陽極とする正電圧と、アルミニウム基材を陰極とする負電圧とを交互に印加しながら行うことが好ましい。酸化被膜の多孔質層はある程度成長すると、電流が流れ難くなるため、途中で負電圧を印加して多孔質層を溶かしながら行うことで、電流が継続して流れ、多孔質層を成長させることができる。印加する正電圧は、バリヤー層の膜厚、多孔質層の形成に寄与するものである。バリヤー層は電圧値が低くなると膜厚が薄くなる、多孔質層は電圧値が低くなり過ぎても高くなり過ぎても形成され難くなる。このため、正電圧は２５０〜４５０Ｖが好ましい。負電圧は多孔質層を溶かして膜成長を助けるものであるため、４０〜１００Ｖが好ましい。正電圧と負電圧との印加条件は、交互に印加するものであれば特に制限はされず、周波数５０〜６０Ｈｚのパルス電圧が例示される。 Plasma electrolysis treatment can form an oxide film on the aluminum substrate by energizing the aluminum substrate as an anode. Although there is no particular limitation, a positive voltage using the aluminum substrate as an anode and an aluminum substrate It is preferable to carry out while alternately applying a negative voltage as a cathode. When the porous layer of the oxide film grows to some extent, it becomes difficult for the current to flow, so by applying a negative voltage in the middle and melting the porous layer, the current continues to flow and grow the porous layer Can do. The applied positive voltage contributes to the film thickness of the barrier layer and the formation of the porous layer. The barrier layer is thin when the voltage value is low, and the porous layer is difficult to be formed if the voltage value is too low or too high. For this reason, the positive voltage is preferably 250 to 450V. Since the negative voltage dissolves the porous layer and assists film growth, it is preferably 40 to 100V. The application conditions of the positive voltage and the negative voltage are not particularly limited as long as they are applied alternately, and a pulse voltage with a frequency of 50 to 60 Hz is exemplified.
以下に、本発明に係る酸化被膜を用いた実施例を示し、本発明をより詳細に説明する。但し、本発明はこれらの実施例に限定されるものではない。 Hereinafter, examples using the oxide film according to the present invention will be shown to explain the present invention in more detail. However, the present invention is not limited to these examples.
アルミニウム基材としてアルミニウム押出し材（Ａ６０６３−Ｔ５、１５０ｍｍ×５０ｍｍ×１２ｍｍ、表面積１．５ｄｍ2）を用い、これを陽極とする正電圧と、陰極とする
負電圧とのパルス電圧を、表１に示す条件により、印加してプラズマ電解処理を行い、酸化被膜を形成した。
Table 1 shows the pulse voltage of an aluminum extruded material (A6063-T5, 150 mm × 50 mm × 12 mm, surface area 1.5 dm 2 ) as an aluminum base, and a positive voltage using this as an anode and a negative voltage using a cathode. Under the conditions shown, plasma electrolysis was applied to form an oxide film.
得られた酸化被膜の断面及び表面を走査型電子顕微鏡（ＳＥＭ）で観察したところ、実施例１の酸化被膜は、図４〜６に示すようにバリヤー層と多孔質層とからなり、多孔質層が図７，８に示すように複数の中空柱状のセルで形成されていることが分かった。また、実施例２及び３の酸化被膜についても、それぞれ図９〜１２、及び図１３，１４に示すように、実施例１と同様の膜が形成されていた。実施例１〜３の酸化被膜の平均膜厚、成膜速度については、表２に示す通りであった。 When the cross section and surface of the obtained oxide film were observed with a scanning electron microscope (SEM), the oxide film of Example 1 was composed of a barrier layer and a porous layer as shown in FIGS. It was found that the layer was formed of a plurality of hollow columnar cells as shown in FIGS. In addition, as for the oxide films of Examples 2 and 3, the same film as that of Example 1 was formed as shown in FIGS. About the average film thickness of the oxide film of Examples 1-3, and the film-forming speed | rate, it was as showing in Table 2.
実施例１〜３の酸化被膜について、それぞれ図８，１２，１４に基づき、平均セル径及び平均微細孔径を測定した。その結果、表３に示すように、平均セル径が２００〜８００ｎｍの範囲にあることが確認できた。 About the oxide film of Examples 1-3, the average cell diameter and the average fine pore diameter were measured based on FIG. As a result, as shown in Table 3, it was confirmed that the average cell diameter was in the range of 200 to 800 nm.
実施例１と同条件で、印加電圧のみを変えた場合（実施例２，４，参考例）、及び実施例１とは電解液のピロリン酸ナトリウムの濃度を２倍（２０ｇ／Ｌ）にした場合（実施例５）に形成するバリヤー層の膜厚の変化を、図６（実施例１）、図１０（実施例２）、図１５（実施例４）、図１６（実施例５）、図１７（参考例）に基づき調べた。その結果、表４に示すように、バリヤー層の膜厚は１００〜３００ｎｍの範囲にあることが分かった。また、正電圧が２００Ｖの場合では、多孔質層が形成されず、バリヤー層は確認できなかった。
したがって、本実施例の場合では、印加する正電圧は２００Ｖより大きくすることが好ましい。
When only the applied voltage was changed under the same conditions as in Example 1 (Examples 2, 4 and Reference Examples), and in Example 1, the concentration of sodium pyrophosphate in the electrolyte was doubled (20 g / L). 6 (Example 1), FIG. 10 (Example 2), FIG. 15 (Example 4), FIG. 16 (Example 5), It investigated based on FIG. 17 (reference example). As a result, as shown in Table 4, it was found that the thickness of the barrier layer was in the range of 100 to 300 nm. Further, when the positive voltage was 200 V, the porous layer was not formed, and the barrier layer could not be confirmed.
Therefore, in the case of the present embodiment, it is preferable that the applied positive voltage is greater than 200V.
実施例１，２の条件において、電解液のみを変えた場合に形成する酸化被膜について調べた。電解液は、シュウ酸チタンカリウムは添加せず、ピロリン酸ナトリウム２０ｇ／Ｌを添加し、ｐＨ１０．２３、温度４．１℃としたものを用いた。その結果、図１８（比較例１）、図１９（比較例２）、表５に示すように、シュウ酸チタンカリウムを用いずにプラズマ電解処理した場合には、成膜速度が低下し、膜厚が薄くなっており、多孔質層が形成されていないことが分かった。したがって、本実施例の場合では、電解液には、シュウ酸チタンカリウムを含有させることが好ましい。 Under the conditions of Examples 1 and 2, the oxide film formed when only the electrolyte was changed was examined. As the electrolytic solution, a solution in which potassium potassium oxalate was not added, sodium pyrophosphate 20 g / L was added, and the pH was 10.23 and the temperature was 4.1 ° C. was used. As a result, as shown in FIG. 18 (Comparative Example 1), FIG. 19 (Comparative Example 2), and Table 5, when plasma electrolytic treatment was performed without using titanium potassium oxalate, the film formation rate decreased, and the film It was found that the thickness was reduced and no porous layer was formed. Therefore, in the case of the present Example, it is preferable to contain potassium titanium oxalate in electrolyte solution.
実施例３の酸化被膜について、一般にアルマイト被膜の封孔処理として行われる煮沸処理を行い、煮沸をしない場合と煮沸をした場合との酸化被膜表層の酸化物分析を行った。その結果を表６に示すように、煮沸を行うことによってＡｌＯ(ＯＨ)（ベーマイト）化していることが分かった。すなわち、アルミニウムは、一般に、７０℃を超えると不安定なγ相がベーマイト化することが知られており、プラズマ電解処理で形成した酸化被膜は、安定なα相と不安定なγ相とが混在していると推測される。このため、粉体塗装を施した場合には、塗装時の焼付け（１８０℃）の際にベーマイト化が起こり、表面に水酸基との化学反応が起こり、塗膜との密着性が確保されると考えられる。したがって、酸化被膜に塗装を施す場合には、煮沸を行うとベーマイト化が進み、不安定なＡｌ及びＡｌ2Ｏ3のγ相の比率が低下して塗膜との密着性が低下する虞があるため、煮沸は行わない方が好ましい。 About the oxide film of Example 3, the boiling process generally performed as a sealing process of an alumite film was performed, and the oxide analysis of the oxide film surface layer when not boiling and when boiling was performed. As shown in Table 6, it was found that AlO (OH) (boehmite) was formed by boiling. That is, it is known that aluminum generally has an unstable γ phase boehmite when the temperature exceeds 70 ° C., and an oxide film formed by plasma electrolytic treatment has a stable α phase and an unstable γ phase. Presumed to be mixed. For this reason, when powder coating is applied, boehmite formation occurs during baking (180 ° C.) during coating, a chemical reaction with hydroxyl groups occurs on the surface, and adhesion with the coating film is ensured. Conceivable. Therefore, when coating an oxide film, if it is boiled, boehmite formation proceeds, and the ratio of the unstable γ phase of Al and Al 2 O 3 may decrease, resulting in decreased adhesion to the coating film. For this reason, it is preferable not to boil.
実施例１の酸化被膜に、粉体塗装（塗料：日本ペイントビリューシア ＰＬ５６００ ５部艶黒）を施し、雰囲気温度１８０℃で３０分間焼付け処理を行った後、初期密着試験、耐水密着試験、耐食性試験を行った。また、比較例として、実施例１と同様のアルミニウム基材を用い、水酸化ナトリウム３ｇ／Ｌを含んだ電解液（ｐＨ１２．５５、５．０℃）を用いた場合（比較例３）、及びピロリン酸ナトリウム（リン換算で０．１ｍｏｌ／Ｌ）とＺｒ系金属イオン（ジルコニウム換算で０．５ｍｏｌ／Ｌ）を含んだ電解液（ｐＨ１０．１７、５．０℃）を用いた場合(比較例４)について、表７に示す条件で酸化被膜を形成し、粉体塗装、焼付け処理を行い、同様の試験を行った。 Powder coating (paint: Nippon Paint Bilucia PL5600, 5 parts gloss black) is applied to the oxide film of Example 1, and after baking for 30 minutes at an ambient temperature of 180 ° C., initial adhesion test, water resistance adhesion test, corrosion resistance test Went. Further, as a comparative example, the same aluminum base material as in Example 1 was used, and an electrolytic solution (pH 12.55, 5.0 ° C.) containing 3 g / L of sodium hydroxide was used (Comparative Example 3), and When using an electrolytic solution (pH 10.17, 5.0 ° C.) containing sodium pyrophosphate (0.1 mol / L in terms of phosphorus) and a Zr-based metal ion (0.5 mol / L in terms of zirconium) (Comparative Example) For 4), an oxide film was formed under the conditions shown in Table 7, powder coating and baking were performed, and the same test was performed.
初期密着試験は、碁盤目試験（ＪＩＳ Ｚ ８７０３）を実施し、各正方形内の塗膜の剥離を調べた。
耐水密着試験は、４０℃耐水試験法を用い、恒温水槽に蒸留水又は脱イオン水を入れ、４０＋１℃に保ち、２４０時間後において、しわ・割れ・ふくれ・剥がれの発生を調べた。
耐食性試験は、塩水噴霧試験（ＪＩＳ Ｚ ２３７１に規定する試験機を用いる）を行い、２４０時間後の状態を調べた。
In the initial adhesion test, a cross-cut test (JIS Z 8703) was performed to examine the peeling of the coating film in each square.
In the water-resistant adhesion test, a 40 ° C. water resistance test method was used. Distilled water or deionized water was placed in a constant temperature water bath and kept at 40 + 1 ° C., and after 240 hours, the occurrence of wrinkles, cracks, blisters, and peeling was examined.
In the corrosion resistance test, a salt spray test (using a test machine specified in JIS Z 2371) was performed, and the state after 240 hours was examined.
その結果、実施例１の酸化被膜では、初期密着試験（図２０（ａ））、耐水密着試験（図２０（ｂ））のいずれの場合も剥がれは発生せず、密着性は良好であった。また、耐食性については２４０時間後で問題がなく、４８０時間後についても調べたが問題はなかった。比較例３の酸化被膜では、初期密着試験（図２１（ａ））では剥がれは発生しなかったが、耐水密着試験（図２２（ｂ））では剥がれが発生し、密着性は不十分であった。比較例４の酸化被膜でも、比較例３と同様に、初期密着試験（図２３（ａ））では剥がれは発生しなかったが、耐水密着試験（図２３（ｂ））では剥がれが発生し、密着性は不十分であった。耐食性については比較例３，４の酸化被膜のいずれも２４０時間後では問題はなかった。 As a result, in the oxide film of Example 1, peeling did not occur in both the initial adhesion test (FIG. 20A) and the water resistance adhesion test (FIG. 20B), and the adhesion was good. . Further, there was no problem with the corrosion resistance after 240 hours, and after 480 hours were examined, there was no problem. In the oxide film of Comparative Example 3, peeling did not occur in the initial adhesion test (FIG. 21A), but peeling occurred in the water resistance adhesion test (FIG. 22B), and the adhesion was insufficient. It was. Even in the oxide film of Comparative Example 4, as in Comparative Example 3, peeling did not occur in the initial adhesion test (FIG. 23 (a)), but peeling occurred in the water resistance adhesion test (FIG. 23 (b)). Adhesion was insufficient. As for corrosion resistance, there was no problem after 240 hours in any of the oxide films of Comparative Examples 3 and 4.
比較例３の酸化被膜の断面及び表面をＳＥＭで観察したところ、図２３，２４に示すように、実施例１の酸化被膜とは異なり、バリヤー層のみが形成され、表面もセルはなく、均一ではなかった。比較例４の酸化被膜についても、図２５に示すように、同様であった。これらの酸化被膜では凹凸が形成されているものの、塗装焼付け時に塗料が凹凸の細部にまで流れ込まず、内部に形成されたポーラスに閉じ込められた空気が塗膜を押し上げることになり、アンカー効果が得られなくなるものと推測できる。さらには、これらの酸化被膜では、従来のエネルギーが高いプラズマ電解処理が行われているため、安定なα相が多くなっており、塗膜との化学反応が起こらず、密着性が不十分であったと考えられる。
また、従来のアルマイト被膜についても、断面及び表面をＳＥＭで観察したところ、図２６（ａ）に示すように複数のセルを有するものの、図２６（ｂ）に示すように、平均セル径は小さく、実施例１の酸化被膜とは大きく異なっていることが確認できた。
When the cross section and the surface of the oxide film of Comparative Example 3 were observed with an SEM, as shown in FIGS. 23 and 24, unlike the oxide film of Example 1, only the barrier layer was formed, and the surface was uniform with no cells. It wasn't. The oxide film of Comparative Example 4 was the same as shown in FIG. Although these oxide coatings have irregularities, the paint does not flow into the details of the irregularities during paint baking, and the air trapped in the porous formed inside pushes up the coating, resulting in an anchor effect. It can be assumed that it will not be possible. Furthermore, since these oxide films have been subjected to conventional plasma electrolytic treatment with high energy, there are many stable α phases, no chemical reaction with the paint film, and insufficient adhesion. It is thought that there was.
In addition, when the cross section and the surface of the conventional anodized film were observed with an SEM, the average cell diameter was small as shown in FIG. 26 (b) although it had a plurality of cells as shown in FIG. 26 (a). It was confirmed that the oxide film of Example 1 was significantly different.
本発明に係る酸化被膜は、塗膜との密着性や耐食性に優れるため、例えば、自動車部品や建材等に用いるアルミニウム基材の塗装前の下地に適用することができる。 Since the oxide film according to the present invention is excellent in adhesion and corrosion resistance with the paint film, it can be applied, for example, to a base before coating of an aluminum base material used for automobile parts, building materials and the like.
Claims (4)
非晶質のバリヤー層と、
当該バリヤー層に積層され、複数の中空柱状のセルから構成される多孔質層とを備え、
前記多孔質層は、γ相とα相とが混在しており、前記セルの平均セル径が２００〜８００ｎｍであり、厚みが１〜４μｍである酸化被膜。 An oxide film formed on an aluminum substrate and used as a base of a coating film,
An amorphous barrier layer;
A porous layer laminated on the barrier layer and composed of a plurality of hollow columnar cells;
The porous layer is an oxide film in which a γ phase and an α phase are mixed, the average cell diameter of the cells is 200 to 800 nm, and the thickness is 1 to 4 μm.
前記微細孔は、前記バリヤー層に近づくに従って枝分かれする請求項１又は２に記載の酸化被膜。 The porous layer has micropores formed in the cell,
3. The oxide film according to claim 1, wherein the micropores branch as they approach the barrier layer.
シュウ酸チタンカリウムを含むｐＨ５〜６の電解液中において、前記アルミニウム基材を陽極とする２５０〜４５０Ｖの電圧と、前記アルミニウム基材を陰極とする４０〜１００Ｖの電圧とを交互に印加して行うプラズマ電解処理を行い、非晶質のバリヤー層と、前記バリヤー層に積層されてγ相とα相とが混在する多孔質層とを備える酸化被膜を形成する酸化被膜の形成方法。 A method of forming an oxide film formed on an aluminum substrate and used as a base of a coating film,
In an electrolyte having a pH of 5 to 6 containing potassium potassium oxalate, a voltage of 250 to 450 V using the aluminum base as an anode and a voltage of 40 to 100 V using the aluminum base as a cathode are alternately applied. A method for forming an oxide film, comprising: performing an electrolytic plasma treatment to form an oxide film comprising an amorphous barrier layer and a porous layer laminated on the barrier layer in which a γ phase and an α phase are mixed.
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| JP6352087B2 (en) * | 2014-07-12 | 2018-07-04 | 株式会社Uacj | Surface-treated aluminum material and method for producing the same |
| JP2016156036A (en) * | 2015-02-23 | 2016-09-01 | 株式会社栗本鐵工所 | Coating formation method |
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