JP3835888B2

JP3835888B2 - Electrodeposition surface treatment method

Info

Publication number: JP3835888B2
Application number: JP13086397A
Authority: JP
Inventors: 信介白川; 龍生吉田; 良一村上
Original assignee: Nippon Paint Co Ltd; Nippon Paint Holdings Co Ltd
Current assignee: Nippon Paint Co Ltd; Nippon Paint Holdings Co Ltd
Priority date: 1997-05-21
Filing date: 1997-05-21
Publication date: 2006-10-18
Anticipated expiration: 2017-05-21
Also published as: JPH10317191A

Description

【０００１】
【発明が属する技術分野】
本発明は電着塗装表面の処理方法に関し、特に基材の表面に形成されるカチオン電着塗料の電気析出被膜の表面を処理する方法に関する。
【０００２】
【従来の技術】
電着塗装は水性塗料を槽中に満たし同じ浴中にある被塗物に塗料成分を電気泳動させ、被塗面に電気析出させることで塗装を行う方法である。この塗装法は自動車車体の防食塗装を主な用途としており、産業上重要である。
【０００３】
電着塗装法では、電着直後、被塗物の表面に形成される電気析出被膜には水、溶剤、および未析出塗装液等が付着している。かかる余剰物を除去するため、一般に電気析出被膜は入念に水洗される。
【０００４】
実際、工業ラインでは多数回の水洗工程が設けられている。しかし、電気析出被膜の表面に付着した余剰物を完全に除去することは困難であり、作業効率を高めるためには水洗回数の増加にも限界がある。
【０００５】
かかる余剰物の除去が不完全である場合、焼付乾燥後、電気析出被膜上に水滴痕、又は水洗ムラが残る。また、水滴痕の上に塗膜を重ねた場合、水滴痕の円周部分にピンホールが発生し易い。
【０００６】
水洗後にエアーブローを行って水滴を除去して水滴痕の形成を防止する方法も一般に行われる。しかしながら、かかる方法でも、エアーの吹き付け角度や位置、基材の大きさや形状等が変化した場合、水滴が飛散して水滴痕が被膜上に残留する。
【０００７】
【発明が解決しようとする課題】
本発明は上記従来の問題を解決するものであり、その目的とするところは、電気析出被膜の表面に水洗ムラ、水滴痕を残さない電気析出被膜の表面処理方法を提供することにある。
【０００８】
【課題を解決するための手段】
本発明は、基材の表面にカチオン電着塗料を電気析出させる工程；電気析出被膜の表面を水で洗浄し、乾燥させる工程；電気析出被膜の表面を、３０〜３５ｄｙｎ／ｃｍの表面張力を有する界面活性剤を含む水溶液で洗浄する工程；および電気析出被膜を乾燥硬化させる工程；を包含する電着塗装表面の処理方法を提供するものであり、そのことにより上記目的が達成される。
【０００９】
本発明の方法では、まず、被塗物である基材の表面にカチオン電着塗料を電気析出させる。基材は特に限定されない。自動車の車体、二輪車のフレームおよびホイール等、通常電着塗装される被塗物を基材として用いうる。
【００１０】
基材の表面に電気析出させるカチオン電着塗料は従来用いられているいかなるものでもよい。例えば、特公昭５２−６３０６号公報に記載のエポキシウレタン硬化型塗料、同６３−１３９９０９号公報に記載のアクリル型塗料等が挙げられる。
【００１１】
基材の表面にカチオン電着塗料を電気析出させる方法も特に限定されず、従来用いられているいかなる電着塗装方法を用いてもよい。例えば、塗料浴温２０〜４０℃、印加電圧５０〜５００Ｖ、通電時間は被塗物が塗料浴中に完全に浸漬している状態で３０秒〜１０分間、のような条件で行う方法が挙げられる。
【００１２】
ついで、基材の表面に形成された電気析出被膜の表面を水で洗浄し、乾燥させる。水はできるだけ不純物を含まないものが好ましい。一般には、限外ろ過水とイオン交換水等を用いる。
【００１３】
水洗は、電気析出被膜の表面に付着した余剰物をできるだけ除去するために長時間行う方が好ましい。一般には、電気析出被膜の表面の面積１ｍ²当り０．１〜１リットル／秒の流量でＶジェットノズル、パイプノズル、ワールジェットノズル等で３０秒〜１０分間行う。あまり長時間水洗を行うと作業効率が低下する。水洗を行わない場合、又は不十分である場合は、電着塗膜中に持出し塗料成分が残存する。その結果、持出し塗料による電着塗膜の溶解、持出塗料中の揮発成分の蒸発等により最終仕上がり塗膜の外観不良が起こる。
【００１４】
乾燥は、水洗後の基材を室温〜６０℃、好ましくは１０〜５０℃の雰囲気下に置くことにより行う。乾燥温度が室温を下回ると乾燥に長時間を要する。６０℃を上回ると塗膜が軟化フローし、塗膜の表面張力低下がおこることによってその後の水洗時水跡になりやすい。
【００１５】
乾燥時間は一般には３〜６０分であるが、特に限定されず、休憩、直間及びラインストップ時間等１〜７２時間の範囲で適宜調節できる。電気析出被膜のセッティングが３分以下で、水切れが不十分である場合、凹部に溜まった塗料が焼付工程中に表面に漏出する等により、焼付塗膜の外観不良を起こす（二次タレ）。
【００１６】
ついで、乾燥した電気析出被膜の表面を界面活性剤を含む水溶液で洗浄する。界面活性剤とは一分子中に親水性部と疎水性部を有し、溶液表面において表面活性を示し、かつ溶液内部において臨界ミセル濃度以上でミセルコロイドを形成する物質である。かかる界面活性剤を含む水溶液は界面張力の低下作用によって湿潤あるいは浸透作用が生じ、析出膜表面上に濡れ広がる。
【００１７】
すなわち、電着後の析出被膜表面が適当な界面活性剤を含む水溶液で処理することによってかかる被膜表面に残留する水は接触角の大きい水玉状態で存在しえず、被膜表面で均一に濡れ広がってしまい、その後の焼付工程を経ても水滴痕は残らない。
【００１８】
界面活性剤は適量を水に溶解させて界面活性剤を含む水溶液とし、本発明の方法に用いる。界面活性剤は、得られる水溶液の表面張力が３０〜３５ｄｙｎ／ｃｍとなる量で溶解させることが好ましい。
【００１９】
この量は、用いる界面活性剤の種類に依存して変化するが、一般に０．００５〜１．０重量％、好ましくは０．０１〜１．０重量％の範囲である。界面活性剤を含む水溶液の表面張力が３５ｄｙｎ／ｃｍを上回ると焼付乾燥後の塗膜に水滴痕、又は水洗ムラが残り易くなる。
【００２０】
界面活性剤を含む水溶液を用いる洗浄は、一般には、電気析出被膜の表面の面積１ｍ²当り０．０５〜０．５リットル／秒の流量でＶジェットノズル、パイプノズル、ワールジェットノズル等を用いて０．１〜１分間行う。
【００２１】
その後、電気析出被膜を乾燥硬化させる。電気析出被膜の乾燥は上述と同様にして行う。電気析出被膜の硬化の条件は用いる塗料の種類に依存して変化するが、一般には基材を約１４０〜２００℃の温度の雰囲気に１０〜４０分間置くことにより行う。
【００２２】
本発明に使用される界面活性剤としては従来公知のものが使用できるが、非イオン性界面活性剤が好ましい。これらは、焼付乾燥後の塗膜に残存した場合でも、塗膜性能を低下させないことが多いからである。
【００２３】
また、ＨＬＢ１０．５〜１４．０、好ましくは１０．５〜１２．０を有する界面活性剤が特に好ましい。界面活性剤のＨＬＢが１０．５を下回ると水溶性が乏しくなり、１４．０を上回ると水滴が残り易くなり、共に焼付乾燥後の電気析出被膜上に水滴痕、又は水洗ムラが残り易くなる。
【００２４】
更に、常温で造膜性を有しないもの、特に常温で液状のものが好ましい。常温で造膜性を有するものは、焼付乾燥後の塗膜に残存しやすく、残存した場合塗膜の耐水性の低下を引きおこすため、好ましくない。
【００２５】
好ましい界面活性剤は、式
ＲＯ（ＣＨ₂ＣＨ₂Ｏ）_nＨ
【００２６】
［式中、Ｒは、炭素数８〜２０の直鎖状もしくは分枝鎖状のアルキル基又は炭素数８〜２０のモノアルキルフェニル基であり、ｎは３〜１５、好ましくは５〜１２の整数である。］
で示す構造を有するものである。
【００２７】
具体的には、分子量２００〜１０００のポリエチレンオキシド等が挙げられる。
【００２８】
【実施例】
以下に本発明をより具体的に説明するが、本発明はこれらの実施例により何ら制限されるものではない。
【００２９】
実施例１
常法により、縦１５ｃｍ、横７ｃｍ、厚さ８ｍｍの冷延鋼板（表裏）の表面上に日本ペイント社製カチオン電着塗料「パワートップＵ−８８０」を２０μmの厚さに電気析出させた。得られた電気析出被膜の表面を、水道水を用いて、０．０５リットル／秒の流量でＶジェットノズルを用いて０．５分間水洗した。その後、電気析出被膜が形成された冷延鋼板を３５℃で６０分間放置し、乾燥させた。
【００３０】
ＨＬＢ１０．５の旭電化工業社製ノニオン性界面活性剤「ＳＯ−１０５」を脱イオン水に０．０１重量％の量で含有させて、界面活性剤を含む水溶液を調製した。この水溶液の表面張力は３０．４ｄｙｎ／ｃｍであった。
【００３１】
この界面活性剤を含む水溶液を用いて、乾燥した電気析出被膜の表面を、０．０５リットル／秒の流量でＶジェットノズルを用いて０．５分間洗浄した。洗浄後、冷延鋼板を２５℃に１分間保つことにより電気析出被膜を乾燥させ、その後１８０℃で１０分間保つことにより電気析出被膜を硬化させた。
【００３２】
硬化した塗膜の表面を目視観察して水滴痕、水洗ムラの有無を調べ、以下の基準により水跡性として評価した。結果を表１に示す。
【００３３】
○：水跡無し
○△：水滴跡１〜３個
△：水滴跡４〜１０個
△×：水滴跡１１〜２０個
×：水滴跡２１個以上
【００３４】
また、以下の基準により塗膜外観を目視観察して評価した。結果を表１に示す。
【００３５】
○：ワキ（小さいブツ状跡）なし
△：一部ワキ有り
×：塗膜全体にワキ発生
【００３６】
実施例２
ＨＬＢ１１．９の旭電化工業社製ノニオン性界面活性剤「ＬＯ−７」を脱イオン水に０．０１重量％の量で含有させて、界面活性剤を含む水溶液を調製し、これを用いること以外は実施例１と同様にして硬化した塗膜を得、実施例１と同様にして評価した。結果を表１に示す。
【００３７】
実施例３
ＨＬＢ１２．０の旭電化工業社製ノニオン性界面活性剤「ＬＡ−８７５」を脱イオン水に０．０１重量％の量で含有させて、界面活性剤を含む水溶液を調製し、これを用いること以外は実施例１と同様にして硬化した塗膜を得、実施例１と同様にして評価した。結果を表１に示す。
【００３８】
実施例４
ＨＬＢ１４．０の旭電化工業社製ノニオン性界面活性剤「ＳＯ−１４５」を脱イオン水に０．０１重量％の量で含有させて、界面活性剤を含む水溶液を調製し、界面活性剤で洗浄後さらに水洗すること以外は実施例１と同様にして硬化した塗膜を得、実施例１と同様にして評価した。結果を表１に示す。
【００３９】
比較例１
界面活性剤を含む水溶液の代わりにイオン交換水を用いること以外は実施例１と同様にして硬化した塗膜を得、実施例１と同様にして評価した。結果を表２に示す。
【００４０】
比較例２
まず、実施例１と同様にして、冷延鋼板の表面上に電気析出被膜を形成した。
【００４１】
３０秒後、実施例１と同様にして調製した界面活性剤を含む水溶液を用いて、電気析出被膜の表面を、０．０５リットル／秒の流量でＶジェットノズルを用いて０．５分間洗浄した。洗浄後、冷延鋼板を３５℃に６０分間保つことにより電気析出被膜を水切りさせ、再び水洗(０．０５リットル／秒で０．５時間)した。その後１８０℃で１０分間保つことにより電気析出被膜を硬化させた。結果を表２に示す。
【００４２】
比較例３
実施例１で界面活性剤を脱イオン水に０．００１重量％の量で含有させる以外は、実施例１と同様にして硬化した塗膜を得、実施例１と同様にして評価した。結果を表２に示す。
【００４３】
【表１】

【００４４】
【表２】

【００４５】
【発明の効果】
電気析出被膜の表面に水洗ムラ、水滴痕を残さない電気析出被膜の表面処理方法が提供された。[0001]
[Technical field to which the invention belongs]
The present invention relates to a method for treating an electrodeposition coating surface, and more particularly to a method for treating the surface of an electrodeposited coating of a cationic electrodeposition coating formed on the surface of a substrate.
[0002]
[Prior art]
Electrodeposition coating is a method in which an aqueous coating material is filled in a tank, a coating component is electrophoresed on an object to be coated in the same bath, and electrodeposition is performed on the surface to be coated. This coating method is mainly used for anti-corrosion coating of automobile bodies and is industrially important.
[0003]
In the electrodeposition coating method, immediately after electrodeposition, water, a solvent, an undeposited coating liquid, and the like are attached to an electrodeposited film formed on the surface of an object to be coated. In order to remove such surplus, the electrodeposited coating is generally carefully washed with water.
[0004]
In fact, many water washing steps are provided in the industrial line. However, it is difficult to completely remove the surplus adhering to the surface of the electrodeposited coating, and there is a limit to the increase in the number of water washings in order to improve the working efficiency.
[0005]
When the removal of such surplus is incomplete, after baking and drying, water drop marks or uneven washing remains on the electrodeposited film. Moreover, when a coating film is piled up on a water drop trace, a pinhole is easy to generate | occur | produce in the circumferential part of a water drop trace.
[0006]
In general, a method of removing water droplets by air blowing after washing to prevent formation of water droplet traces is also performed. However, even with this method, when the air blowing angle and position, the size and shape of the base material, and the like are changed, water droplets are scattered and water droplet traces remain on the film.
[0007]
[Problems to be solved by the invention]
The present invention solves the above-described conventional problems, and an object of the present invention is to provide a surface treatment method for an electrodeposited coating that does not leave unevenness of washing and water droplets on the surface of the electrodeposited coating.
[0008]
[Means for Solving the Problems]
The present invention includes a step of electrodepositing a cationic electrodeposition coating on the surface of a substrate; a step of washing and drying the surface of the electrodeposition coating with water; and a surface tension of 30 to 35 dyn / cm on the surface of the electrodeposition coating. A method for treating the surface of an electrodeposited coating, comprising: a step of washing with an aqueous solution containing a surfactant having; and a step of drying and curing the electrodeposited film, whereby the above object is achieved.
[0009]
In the method of the present invention, first, a cationic electrodeposition paint is electrodeposited on the surface of a substrate that is an object to be coated. The substrate is not particularly limited. An object to be coated which is usually electrodeposited such as a car body of a car, a frame and a wheel of a motorcycle can be used as a base material.
[0010]
The cationic electrodeposition coating material that is electrodeposited on the surface of the substrate may be any conventionally used one. For example, an epoxy urethane curable paint described in JP-B-52-6306, an acrylic paint described in JP-A-63-139909, and the like can be mentioned.
[0011]
The method for electrodepositing a cationic electrodeposition paint on the surface of the substrate is not particularly limited, and any conventionally used electrodeposition coating method may be used. For example, the coating bath temperature is 20 to 40 ° C., the applied voltage is 50 to 500 V, and the energization time is 30 seconds to 10 minutes in a state where the object to be coated is completely immersed in the coating bath. It is done.
[0012]
Next, the surface of the electrodeposited film formed on the surface of the substrate is washed with water and dried. Water is preferably as free from impurities as possible. In general, ultrafiltered water and ion-exchanged water are used.
[0013]
Washing with water is preferably performed for a long time in order to remove as much as possible the extraneous matter adhering to the surface of the electrodeposited film. In general, the deposition is performed at a flow rate of 0.1 to 1 liter / ^second per 1 m ² of the surface area of the electrodeposited film for 30 seconds to 10 minutes using a V jet nozzle, pipe nozzle, whirl jet nozzle or the like. If it is washed for too long, the work efficiency will be reduced. When washing with water is not performed or when it is insufficient, the carried paint component remains in the electrodeposition coating film. As a result, an appearance defect of the final finished coating film occurs due to dissolution of the electrodeposition coating film by the carry-out paint, evaporation of volatile components in the carry-out paint, and the like.
[0014]
Drying is performed by placing the substrate after washing in an atmosphere of room temperature to 60 ° C, preferably 10 to 50 ° C. If the drying temperature falls below room temperature, drying takes a long time. When the temperature exceeds 60 ° C., the coating film softens and flows, and the surface tension of the coating film is lowered, which easily causes water marks during subsequent washing.
[0015]
The drying time is generally 3 to 60 minutes, but is not particularly limited, and can be appropriately adjusted within a range of 1 to 72 hours such as a break, a direct interval, and a line stop time. When the setting of the electrodeposited film is 3 minutes or less and the water drainage is insufficient, the appearance of the baked coating film is deteriorated due to leakage of the paint accumulated in the recesses to the surface during the baking process (secondary sagging).
[0016]
Next, the surface of the dried electrodeposition coating is washed with an aqueous solution containing a surfactant. A surfactant is a substance having a hydrophilic part and a hydrophobic part in one molecule, showing surface activity on the surface of the solution, and forming a micelle colloid at a critical micelle concentration or more inside the solution. An aqueous solution containing such a surfactant is wetted or penetrated by the action of reducing the interfacial tension, and spreads on the surface of the deposited film.
[0017]
That is, when the surface of the deposited film after electrodeposition is treated with an aqueous solution containing an appropriate surfactant, water remaining on the surface of the film cannot exist in a polka dot state with a large contact angle and spreads uniformly on the surface of the film. As a result, no trace of water droplets remains even after the subsequent baking process.
[0018]
A suitable amount of the surfactant is dissolved in water to form an aqueous solution containing the surfactant, and used in the method of the present invention. The surfactant is preferably dissolved in such an amount that the surface tension of the resulting aqueous solution is 30 to 35 dyn / cm.
[0019]
This amount varies depending on the type of surfactant used, but is generally in the range of 0.005 to 1.0% by weight, preferably 0.01 to 1.0% by weight. If the surface tension of the aqueous solution containing the surfactant exceeds 35 dyn / cm, water droplet marks or uneven washing easily remain in the coating film after baking and drying.
[0020]
Cleaning using an aqueous solution containing a surfactant generally uses a V jet nozzle, pipe nozzle, whirl jet nozzle or the like at a flow rate of 0.05 to 0.5 liter / ^second per 1 m ² of the surface area of the electrodeposited film. For 0.1 to 1 minute.
[0021]
Thereafter, the electrodeposited film is dried and cured. The electrodeposition coating is dried in the same manner as described above. The conditions for curing the electrodeposited film vary depending on the type of paint used, but are generally performed by placing the substrate in an atmosphere at a temperature of about 140 to 200 ° C. for 10 to 40 minutes.
[0022]
As the surfactant used in the present invention, conventionally known surfactants can be used, but nonionic surfactants are preferred. This is because even when they remain in the paint film after baking and drying, the performance of the paint film is often not deteriorated.
[0023]
Also particularly preferred are surfactants having HLB of 10.5 to 14.0, preferably 10.5 to 12.0. When the HLB of the surfactant is less than 10.5, the water solubility becomes poor, and when it exceeds 14.0, water droplets are likely to remain, and both water droplet marks or uneven washing are likely to remain on the electrodeposition coating after baking and drying. .
[0024]
Further, those having no film-forming property at normal temperature, particularly those which are liquid at normal temperature are preferred. Those having film-forming properties at room temperature are not preferable because they tend to remain in the coating film after baking and drying, and if left, the water resistance of the coating film is lowered.
[0025]
A preferred surfactant is the formula RO (CH ₂ CH ₂ O) _n H
[0026]
[In the formula, R is a linear or branched alkyl group having 8 to 20 carbon atoms or a monoalkylphenyl group having 8 to 20 carbon atoms, and n is 3 to 15, preferably 5 to 12. It is an integer. ]
It has a structure shown by.
[0027]
Specific examples include polyethylene oxide having a molecular weight of 200 to 1000.
[0028]
【Example】
The present invention will be described more specifically below, but the present invention is not limited to these examples.
[0029]
Example 1
By a conventional method, a cationic electrodeposition paint “Power Top U-880” manufactured by Nippon Paint Co., Ltd. was electrodeposited to a thickness of 20 μm on the surface of a cold rolled steel sheet (front and back) having a length of 15 cm, a width of 7 cm, and a thickness of 8 mm. The surface of the obtained electrodeposited film was washed with tap water for 0.5 minutes using a V jet nozzle at a flow rate of 0.05 liter / second. Thereafter, the cold-rolled steel sheet on which the electrodeposited film was formed was left at 35 ° C. for 60 minutes and dried.
[0030]
Nonionic surfactant “SO-105” manufactured by Asahi Denka Kogyo Co., Ltd. with HLB 10.5 was added to deionized water in an amount of 0.01% by weight to prepare an aqueous solution containing the surfactant. The surface tension of this aqueous solution was 30.4 dyn / cm.
[0031]
Using the aqueous solution containing the surfactant, the surface of the dried electrodeposited film was washed for 0.5 minutes using a V jet nozzle at a flow rate of 0.05 liter / second. After washing, the electrodeposited film was dried by keeping the cold rolled steel sheet at 25 ° C. for 1 minute, and then the electrodeposited film was cured by keeping it at 180 ° C. for 10 minutes.
[0032]
The surface of the cured coating film was visually observed to examine the presence or absence of water droplet traces and water washing unevenness, and evaluated as water traceability according to the following criteria. The results are shown in Table 1.
[0033]
◯: No water mark △: Water drop trace 1 to 3 △: Water drop trace 4 to 10 △ ×: Water drop trace 11 to 20 ×: Water drop trace 21 or more [0034]
Further, the appearance of the coating film was visually observed and evaluated according to the following criteria. The results are shown in Table 1.
[0035]
○: There is no armpit (small small trace) △: Some armpit exists ×: Armpit occurs on the entire coating film [0036]
Example 2
A nonionic surfactant “LO-7” manufactured by Asahi Denka Kogyo Co., Ltd. with HLB 11.9 is contained in deionized water in an amount of 0.01% by weight to prepare an aqueous solution containing the surfactant, and to use this Except for the above, a cured coating film was obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0037]
Example 3
A nonionic surfactant “LA-875” manufactured by Asahi Denka Kogyo Co., Ltd. with HLB 12.0 is contained in deionized water in an amount of 0.01% by weight to prepare an aqueous solution containing the surfactant, and use this Except for the above, a cured coating film was obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0038]
Example 4
A nonionic surfactant “SO-145” manufactured by Asahi Denka Kogyo Co., Ltd. with HLB 14.0 is contained in deionized water in an amount of 0.01% by weight to prepare an aqueous solution containing the surfactant. A cured coating film was obtained in the same manner as in Example 1 except that it was further washed with water, and evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0039]
Comparative Example 1
A cured coating film was obtained in the same manner as in Example 1 except that ion-exchanged water was used instead of the aqueous solution containing the surfactant, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.
[0040]
Comparative Example 2
First, in the same manner as in Example 1, an electrodeposited film was formed on the surface of the cold rolled steel sheet.
[0041]
After 30 seconds, the surface of the electrodeposited film was washed for 0.5 minutes using a V jet nozzle at a flow rate of 0.05 liter / second using an aqueous solution containing a surfactant prepared in the same manner as in Example 1. did. After washing, the cold-rolled steel sheet was kept at 35 ° C. for 60 minutes to drain the electrodeposited film and washed again with water (0.05 liter / second for 0.5 hour). Thereafter, the electrodeposited film was cured by maintaining at 180 ° C. for 10 minutes. The results are shown in Table 2.
[0042]
Comparative Example 3
A cured coating film was obtained in the same manner as in Example 1 except that the surfactant was contained in deionized water in an amount of 0.001% by weight in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 2.
[0043]
[Table 1]

[0044]
[Table 2]

[0045]
【The invention's effect】
Provided is a surface treatment method for an electrodeposited coating that does not leave water washing unevenness and water droplet traces on the surface of the electrodeposited coating.

Claims

Electro-depositing a cationic electrodeposition paint on the surface of the substrate;
Washing the surface of the electrodeposited film with water and drying;
Washing the surface of the electrodeposited film with an aqueous solution containing a surfactant having a surface tension of 30 to 35 dyn / cm; and drying and curing the electrodeposited film;
A method for treating an electrodeposition coating surface including the order of descriptions .

The electrodeposition coating surface treatment method according to claim 1, wherein the surfactant has an HLB of 10.5 to 14.0.

The surfactant is of the formula RO (CH ₂ CH ₂ O) _n H
[In formula, R is a C8-C20 alkyl group or a C8-C20 monoalkylphenyl group, and n is an integer of 3-15. ]
The electrodeposition coating surface treatment method according to claim 1, which has a structure represented by: