JP5551636B2 - Judgment method of coating film deterioration - Google Patents
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- JP5551636B2 JP5551636B2 JP2011044976A JP2011044976A JP5551636B2 JP 5551636 B2 JP5551636 B2 JP 5551636B2 JP 2011044976 A JP2011044976 A JP 2011044976A JP 2011044976 A JP2011044976 A JP 2011044976A JP 5551636 B2 JP5551636 B2 JP 5551636B2
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Description
本発明は、腐食防止などのために鋼材に用いられる塗膜の劣化を判断する塗膜劣化の判断方法に関するものである。 The present invention relates to a coating film deterioration judging method for judging the deterioration of a coating film used for a steel material in order to prevent corrosion.
金属より構成された鋼材の防食として塗膜を利用することが行われる。大気中での金属の腐食は、表面を覆う水の膜中での電気化学的な反応と考えられている。従って、この電気化学的な反応を塗膜により絶縁することは、鋼材表面を腐食から防ぐことに有効である。ただし、実在の塗膜にはピンホールや顔料による短回路拡散領域などの欠陥が存在するので，これらの欠陥を通しての絶縁破壊があると、被覆している鋼材の腐食が進行する懸念がある。このような金属の腐食は、塗膜の下で進行し、結果として、塗膜の剥離を引き起こす場合がある。このような状態で適切な補修を行わないまま放置すると、鋼材の激しい腐食の進行を導くことになる。 Utilizing a coating film as an anticorrosion of a steel material made of metal is performed. Corrosion of metals in the atmosphere is considered to be an electrochemical reaction in a film of water covering the surface. Therefore, insulating this electrochemical reaction with a coating film is effective in preventing the steel surface from corrosion. However, since there are defects such as short circuit diffusion regions due to pinholes and pigments in the actual coating film, there is a concern that the corrosion of the coated steel material proceeds if there is a dielectric breakdown through these defects. Such corrosion of the metal proceeds under the coating film, and as a result, peeling of the coating film may be caused. If it is left without performing appropriate repairs in such a state, it will lead to the progress of severe corrosion of the steel material.
このような背景のもとに、剥離が生じる前に塗膜下での金属の腐食状態を非破壊または低侵襲で把握する手法が研究されている。例えば、インピーダンスを測定することで、塗膜を評価する方法が提案されている（非特許文献１参照）。この方法では、塗膜が形成されている金属と、塗膜表面に接触させたプローブとの間に交流電圧を印加することで、塗膜の膜厚方向のインピーダンスを測定し、この測定結果より塗膜の劣化を評価している。 Against this background, research has been conducted on techniques for grasping the corrosion state of a metal under a coating film in a non-destructive or minimally invasive manner before peeling occurs. For example, a method for evaluating a coating film by measuring impedance has been proposed (see Non-Patent Document 1). In this method, the impedance in the film thickness direction of the coating film is measured by applying an AC voltage between the metal on which the coating film is formed and the probe brought into contact with the coating film surface. The deterioration of the coating film is evaluated.
上述した塗膜の評価では、インピーダンスの測定を行うことによって、低侵襲で塗膜と金属の界面の腐食状況が理解でき、一定の効果をあげている。しかしながら、近年では、上塗りと下塗り、あるいは、これらの間に中塗りをするなど、塗装を複数層に重ねるようにしている。通常、金属に接触させて用いる下塗りには、金属との密着性が高い塗膜が用いられ、外部環境にさらされる上塗りには耐候性のよい塗膜が用いられる。これらの塗膜は、一般には、絶縁性の高い有機材料から構成されており、多層構造にするにつれて絶縁性が高くなる。 In the above-described evaluation of the coating film, by measuring the impedance, the corrosion state of the interface between the coating film and the metal can be understood with minimal invasiveness, and a certain effect is achieved. However, in recent years, the coating is made to overlap a plurality of layers, such as top coating and undercoating, or intermediate coating between them. Usually, a coating film with high adhesion to the metal is used for the undercoat used in contact with the metal, and a coating film with good weather resistance is used for the topcoat exposed to the external environment. These coating films are generally composed of an organic material having high insulation properties, and the insulation properties become higher as a multilayer structure is formed.
このような塗膜の構造では、前述したようなインピーダンス測定を行うだけの電流を計測することができなくなり、塗膜を評価しにくくなると言う問題を発生させている。特に、相対的に、上塗り塗料の絶縁性が高く、下塗り塗料の絶縁性が低い場合には、上塗り塗料が健全なうちは、高い絶縁性からインピーダンスの測定が難しく腐食に対する抵抗性も高いが、インピーダンス測定が可能になるような状態に劣化した段階では、急激に絶縁性が落ちて塗膜下での腐食を生じるようになる。このため、多層構造の塗膜においては、前述したようなインピーダンス測定では、塗膜劣化の兆しをつかむことが容易ではなく、適正な劣化の判断ができないという問題があった。 With such a coating film structure, it becomes impossible to measure a current sufficient to perform impedance measurement as described above, which causes a problem that it becomes difficult to evaluate the coating film. In particular, when the insulation of the top coat is relatively high and the insulation of the base coat is low, while the top coat is healthy, it is difficult to measure impedance due to high insulation, and the resistance to corrosion is also high. At the stage where the impedance is measured so that it can be measured, the insulation properties drop rapidly and corrosion under the coating film occurs. For this reason, in the coating film having a multilayer structure, there is a problem that it is not easy to grasp a sign of coating film deterioration by impedance measurement as described above, and proper deterioration cannot be determined.
本発明は、以上のような問題点を解消するためになされたものであり、インピーダンス測定により、多層構造の塗膜の適切な劣化の判断ができるようにすることを目的とする。 The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to judge appropriate deterioration of a multilayer-structured coating film by impedance measurement.
本発明に係る塗膜劣化の判断方法は、金属表面に接して形成された第１塗膜と、第１塗膜の上の表面側に形成されて絶縁性が第１塗膜以下の第２塗膜とを備え、金属表面に形成された塗膜全体の膜厚方向の抵抗率が１ＧΩｍ以下とされた塗膜のインピーダンスを測定し、この測定の検出限界を超える測定電流が得られたことにより前記塗膜の劣化を判断する。 The coating film deterioration judging method according to the present invention includes a first coating film formed in contact with the metal surface, and a second coating film formed on the surface side of the first coating film and having an insulation property equal to or lower than the first coating film. The impedance of the coating film having a coating film thickness and resistivity of the entire coating film formed on the metal surface was 1 GΩm or less, and a measurement current exceeding the detection limit of this measurement was obtained. To determine the deterioration of the coating film .
以上説明したように、本発明によれば、表面側の第２塗膜は、絶縁性が金属に接する第１塗膜以下とし、塗膜全体の膜厚方向の抵抗率を１ＧΩｍ以下としたので、インピーダンス測定により、多層構造の塗膜の適切な劣化の判断ができるようになるという優れた効果が得られる。 As described above, according to the present invention, the second coating film on the surface side has an insulating property of not more than the first coating film in contact with the metal, and the resistivity in the film thickness direction of the entire coating film is set to 1 GΩm or less. The impedance measurement can provide an excellent effect that it is possible to judge appropriate deterioration of the coating film having a multilayer structure.
以下、本発明の実施の形態について図１を参照して説明する。図１は、本発明の実施の形態における塗膜の構成を示す断面図である。この塗膜は、金属１０１の表面に接して形成された第１塗膜１０２と、第１塗膜１０２の上の表面側に形成されて絶縁性が第１塗膜１０２以下の第２塗膜１０３とを備える。また、この塗膜は、金属１０１の表面に形成された塗膜全体の膜厚方向の抵抗率が１ＧΩｍ以下とされている。
Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing the configuration of a coating film according to an embodiment of the present invention. The coating film includes a
このような多層の塗膜では、金属に接触して形成される下塗塗膜においては、従来求められていたのは金属との密着性であるため、エポキシ樹脂塗料などが用いられいる。本実施の形態では、これらの場合と同様に、金属１０１に接して形成される第１塗膜１０２は、例えば、エポキシ樹脂から構成し、膜厚１００μｍ程度とする。この場合、第１塗膜１０２は、電気抵抗２００Ω／ｍ2となる。
In such a multilayer coating film, an epoxy resin coating or the like is used in an undercoating film formed in contact with a metal because it has been conventionally required to have adhesion to the metal. In the present embodiment, as in these cases, the
一方、このような多層の塗膜では、表面側の上塗塗料は、耐候性および美観という外界からの刺激・外部からの視覚的様相という点が求められ、絶縁性が高く、酸素や水の遮断能は高ければ高いほどよいとされている。これに対し、本実施の形態では、第２塗膜１０３は、エポキシ樹脂塗膜と同程度のものとする。具体的には、例えば、シリコーン樹脂から第２塗膜１０３を構成し、膜厚１００μｍ程度とする。この場合、第２塗膜１０３は、電気抵抗２００Ω／ｍ2となり、エポキシ樹脂より構成する第１塗膜１０２とほぼ同様とする。
On the other hand, in such a multi-layer coating film, the surface side top coat paint is required to have weather resistance and aesthetic appearance from the outside world and the external visual aspect, and has high insulation properties, blocking oxygen and water. The higher the performance, the better. On the other hand, in this Embodiment, the
以下、多層塗膜におけるインピーダンス測定による測定電流の挙動について説明する。高い絶縁性の材料から表面側の上塗塗膜を構成している場合、塗膜を形成した初期においては、測定される電流は、図２の点線のＡ１に示すような挙動となる。これは、塗膜を形成した初期においては、極めて高い絶縁性の上塗塗膜の存在により、一定の測定電圧に対して得られる測定電流がきわめて小さく、検出できないことを示している。 Hereinafter, the behavior of the measurement current by impedance measurement in the multilayer coating film will be described. When the surface-side top coat film is composed of a highly insulating material, at the initial stage when the coat film is formed, the measured current behaves as shown by the dotted line A1 in FIG. This indicates that at the initial stage of forming the coating film, the measurement current obtained for a certain measurement voltage is extremely small and cannot be detected due to the presence of the extremely high insulating top coating film.
この後、屋外での厳しい環境で上塗塗料が劣化して下塗塗膜が出現すると、劣化は急速に進行し、図２の点線のＡ２に示すように、測定される電流値が急激に増加する。この場合、電気測定による検出限界Ｘを超えて劣化が検出できた時点での劣化速度は極めて大きく、補修する十分な時間的余裕もない状況で、塗膜の剥がれが発生し、図２のＡ３に示すように、電気抵抗が小さく測定電流が大きい状態となる。 Thereafter, when the overcoat paint deteriorates and the undercoat film appears in a harsh environment outdoors, the deterioration progresses rapidly, and the measured current value increases rapidly as indicated by the dotted line A2 in FIG. . In this case, when the deterioration is detected exceeding the detection limit X by electrical measurement, the deterioration rate is extremely large, and there is no sufficient time for repair, and the coating film peels off, and A3 in FIG. As shown in FIG. 5, the electric resistance is small and the measurement current is large.
これらの変化に対し、本実施の形態によれば、塗膜を形成した初期の段階より、第２塗膜１０３は劣化が始まる。このため、上述した場合では電流が測定されない期間においても、図２の実線のＢ１に示すように、検出限界Ｘを超える測定電流が得られる。この結果、第１塗膜１０２の劣化が激しくならないうちに、塗膜劣化の状況が把握でき、対策を行う期間が得られる。現実の測定器では、インピーダンスの測定限界は１ＧΩ程度であるから、第１塗膜１０２から第２塗膜１０３までの合計の塗膜の抵抗率を１ＧΩｍ以下とすれば、有効に測定を行うことができる。このように、本実施の形態によれば、インピーダンス測定により、多層構造の塗膜の適切な劣化の判断ができるようになる。
In response to these changes, according to the present embodiment, the
なお、本発明は以上に説明した実施の形態に限定されるものではなく、本発明の技術的思想内で、当分野において通常の知識を有する者により、多くの変形および組み合わせが実施可能であることは明白である。例えば、上述では、エポキシ樹脂およびシリコーン樹脂の組み合わせとしたが、これに限るものではない。塗装材料として利用可能な範囲内で、第２塗膜は、絶縁性が第１塗膜以下となっていれば、どの様な材料を組み合わせて用いてもよい。 The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, in the above description, a combination of an epoxy resin and a silicone resin is used, but the present invention is not limited to this. The second coating film may be used in combination with any material as long as the insulating property is not more than the first coating film as long as it can be used as a coating material.
１０１…金属、１０２…第１塗膜、１０３…第２塗膜。 101 ... metal, 102 ... first coating film, 103 ... second coating film.
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| JPS62229056A (en) * | 1986-03-31 | 1987-10-07 | Nippon Steel Corp | Quantitative diagnosis of deterioration degree of coating of painted metal and device therefor |
| JPS63107783A (en) * | 1986-05-07 | 1988-05-12 | Jgc Corp | Heat and acid resistance processing method of metallic material |
| JPH02102446A (en) * | 1988-10-08 | 1990-04-16 | Nippon Steel Corp | Method for evaluating corrosion resistance of painted metallic material |
| JPH11314309A (en) * | 1998-05-08 | 1999-11-16 | Nippon Steel Corp | Galvanic corrosion-proof coating and method |
| JP2003194757A (en) * | 2001-12-27 | 2003-07-09 | Toshiba Corp | Deterioration diagnosing device for paint film |
| JP5152952B2 (en) * | 2006-09-27 | 2013-02-27 | 公益財団法人鉄道総合技術研究所 | Coating film for conductive wiring |
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