JP2947006B2 - Method for forming colorless chromate film on glittering aluminum wheels - Google Patents

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【産業上の利用分野】本発明は、アルミホイールの塗装
前処理方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pre-painting an aluminum wheel.

【０００２】[0002]

【従来の技術】アルミホイールについては、自動車技術
ハンドブック第２分冊「設計編」１９９１年３月１日社
団法人自動車技術会発行の第15頁〜第16頁の項目７．
４．１の(3) ｂ「アルミホイール」なる記述部分に紹介
されている。一方、アルミニウム又はアルミニウム合金
の表面処理方法としては、陽極酸化（アルマイト法）、
着色処理、化学皮膜処理（反応クロメート法、ＭＢＶ
法、ベーマイト法等）が一般に知られている。アルミホ
イールを塗装する場合、耐食性及び塗装密着性の向上の
ため塗装前処理として反応クロメート処理、ノンクロメ
ート処理（有機金属塩皮膜等）、陽極酸化皮膜処理が施
されている。2. Description of the Related Art For aluminum wheels, item 7 on pages 15 to 16 published by the Japan Society of Automotive Engineers on March 1, 1991, the second edition of the Automotive Technology Handbook, "Design".
Refer to 4.1 (3) b, “Aluminum wheel”. On the other hand, as a surface treatment method of aluminum or aluminum alloy, anodization (alumite method),
Coloring treatment, chemical coating treatment (reaction chromate method, MBV
Method, boehmite method, etc.) are generally known. When painting aluminum wheels, reactive chromate treatment, non-chromate treatment (organic metal salt film etc.), and anodic oxide film treatment are applied as pre-coating treatments to improve corrosion resistance and paint adhesion.

【０００３】アルミホイールの光輝性を生かしたクリヤ
ー塗装用前処理を考えた場合、ノンクロメート処理（有
機金属塩皮膜）では耐食性が不足しており、陽極酸化膜
では耐食性は良好であるが皮膜量が多く光沢がなくなる
ため、素材の光輝性を重視したクリヤー塗装用の前処理
としては不向きである。反応クロメート皮膜は優れた耐
食性を有しているが、無色の皮膜外観を求められた場
合、クロム付着量が１０ｍｇ／ｍ² 以下に制限されるた
め糸錆耐食性が不足する。糸錆とは、金属表面の塗膜を
通して水が金属表面に進入して局部的に電解腐蝕を起こ
し幅0.1 〜0.5 mm程度のミミズ這い状の錆が経時と共に
進行して行く状態を言う。[0003] Considering the pretreatment for clear coating utilizing the glitter of aluminum wheels, the non-chromate treatment (organic metal salt film) is insufficient in corrosion resistance, and the anodic oxide film has good corrosion resistance, but the amount of film is small. Therefore, it is not suitable as a pretreatment for clear coating, which emphasizes the glitter of the material. The reactive chromate film has excellent corrosion resistance, but when a colorless film appearance is required, the chromium adhesion amount is limited to 10 mg / m ² or less, resulting in insufficient rust corrosion resistance. Yarn rust refers to a state in which water enters the metal surface through a coating film on the metal surface, locally causes electrolytic corrosion, and worm-like rust having a width of about 0.1 to 0.5 mm progresses with time.

【０００４】[0004]

【発明が解決しようとする課題】以上のようにアルミホ
イールの素材の光輝性を保持し、且つ塗装後の耐食性並
びに密着性に満足できる前処理方法はまだ見いだされて
いない。本発明の目的はアルミホイール素材の光輝性を
保持し、且つ塗装後耐食性（特に糸錆耐食性）、密着性
に優れた前処理皮膜を形成する前処理方法を提供するこ
とにある。As described above, no pretreatment method has yet been found which can maintain the brilliancy of the material of the aluminum wheel and satisfy the corrosion resistance and adhesion after coating. SUMMARY OF THE INVENTION An object of the present invention is to provide a pretreatment method for forming a pretreatment film that retains the brilliancy of an aluminum wheel material, has excellent corrosion resistance after coating (particularly, rust corrosion resistance), and has excellent adhesion.

【０００５】[0005]

【課題を解決するための手段】本発明者らは上記目的を
達成する為に鋭意研究を重ねた結果、アルミホイールを
特定した濃度の６価クロムイオン、硫酸イオン、フッ素
を含有し、且つ特定したｐＨに調整した酸性水溶液中で
陰極電解処理することにより前記目的に適応した無色の
クロメート皮膜を得ることが出来ることを見いだし、且
つ該皮膜は特に100μｍＲmax 以下に機械加工したアル
ミホイール表面において塗装後糸錆耐食性、塗料密着性
に優れていることを見いだして本発明を完成するに至っ
た。Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have found that aluminum wheels contain hexavalent chromium ions, sulfate ions, and fluorine at a specified concentration and are specified. It has been found that a colorless chromate film suitable for the above purpose can be obtained by performing cathodic electrolysis in an acidic aqueous solution adjusted to the above-mentioned pH, and the film is obtained after coating, especially on an aluminum wheel surface machined to 100 μm Rmax or less. The inventors have found that the present invention has excellent rust corrosion resistance and paint adhesion, and have completed the present invention.

【０００６】すなわち、本発明は、アルミホイールの表
面を 100μｍＲmax 以下に機械加工した後、６価クロム
イオン２ｇ／リットル以上、硫酸イオン20〜2000ｐｐｍ
含有するｐＨ0.6 〜1.7 の酸性溶液を用い、0.5 〜15Ａ
／ｄｍ² の電流密度で陰極電解処理することを特徴とす
るアルミホイールの無色クロメート皮膜形成方法を提供
する。本発明の構成について具体的に説明する。That is, according to the present invention, after machining the surface of an aluminum wheel to 100 μm Rmax or less, hexavalent chromium ion is 2 g / liter or more, and sulfate ion is 20 to 2000 ppm.
Using an acidic solution having a pH of 0.6 to 1.7 and containing 0.5 to 15 A
The present invention provides a method for forming a colorless chromate film on an aluminum wheel, which is characterized by performing cathodic electrolytic treatment at a current density of / dm ² . The configuration of the present invention will be specifically described.

【０００７】まず、酸性水溶液を構成する各成分につい
て説明する。６価クロムイオンとしては、無水クロム
酸、重クロム酸、及び重クロム酸のアルカリ金属塩類な
どがあげられ、それらの化合物から任意に１種又は２種
以上を選んで使用でき、その濃度範囲は２〜50ｇ／リッ
トルである。６価クロムイオン濃度が２ｇ／リットル未
満では、十分な耐食性を有するクロメート皮膜が得られ
ず、50ｇ／リットルを超えても性能上は問題ないが、排
水処理等の負担がかかり不経済である。また、電解処理
を行うにつれて、３価のクロムイオンが増加するが、本
発明を実施するに当り、皮膜性能上３価のクロムイオン
の濃度は影響が少ないので特に３価のクロムイオンにつ
いては限定範囲を設ける必要がない。First, each component constituting the acidic aqueous solution will be described. Hexavalent chromium ions include chromic anhydride, dichromic acid, and alkali metal salts of dichromic acid, and one or more of these compounds can be arbitrarily selected and used, and the concentration range is as follows. It is 2 to 50 g / liter. If the hexavalent chromium ion concentration is less than 2 g / l, a chromate film having sufficient corrosion resistance cannot be obtained. If the concentration exceeds 50 g / l, there is no problem in performance, but the burden of drainage treatment and the like is uneconomical. In addition, trivalent chromium ions increase as the electrolytic treatment is carried out. However, in carrying out the present invention, the concentration of trivalent chromium ions has little influence on the film performance. There is no need to set a range.

【０００８】硫酸イオンとしては、硫酸、硫酸のアルカ
リ金属塩類が使用でき、その濃度範囲は20〜2000ｐｐｍ
である。その濃度が20ｐｐｍ未満では、無色のクロメー
ト皮膜が形成されない。又、2000ｐｐｍを超えると、ク
ロム付着量が減少し耐食性が低下するので好ましくな
い。フッ素はフッ素イオン及び／又は、錯フッ素イオン
の形で存在し、フッ素イオンの供給源としては、例えば
フッ化水素酸、錯フッ素イオンの供給源としてはケイフ
ッ化水素酸、ジルコンフッ化水素酸、ホウフッ化水素酸
等から任意に選んで使用することができる。フッ素とし
ての濃度範囲は10〜４００ｐｐｍである。１０ｐｐｍ未
満では塗装後耐食性に優れたクロメート皮膜を形成せ
ず、４００ｐｐｍを超えると、電解によるクロメート皮
膜形成を抑制するので、所望するクロム付着量が得難く
なり、比較的に少ないクロム付着量でも皮膜が着色して
しまう為、クリヤー塗装用として不適当である。As sulfate ions, sulfuric acid and alkali metal salts of sulfuric acid can be used, and the concentration range is 20 to 2000 ppm.
It is. When the concentration is less than 20 ppm, a colorless chromate film is not formed. On the other hand, when the content exceeds 2,000 ppm, the amount of chromium adhering decreases and the corrosion resistance decreases, which is not preferable. Fluorine exists in the form of fluorine ions and / or complex fluoride ions. The source of the fluorine ions is, for example, hydrofluoric acid, and the supply source of the complex fluoride ions is hydrofluorosilicic acid, zircon hydrofluoric acid, It can be arbitrarily selected from hydrofluoric acid and the like. The concentration range as fluorine is 10 to 400 ppm. If it is less than 10 ppm, a chromate film having excellent corrosion resistance after coating is not formed, and if it exceeds 400 ppm, the formation of a chromate film by electrolysis is suppressed, so that it becomes difficult to obtain a desired amount of chromium coating. Is unsuitable for clear coating because of coloring.

【０００９】酸性水溶液のｐＨはその価を0.6 〜1.7 の
範囲に限定する。ｐＨをコントロールするためには、水
酸化アンモニウム、アルカリ金属水酸化物、アルカリ金
属炭酸化合物、クロム酸、硫酸、及び硝酸等より任意に
選んで水溶液に加えることが出来る。ｐＨが0.6 未満で
も塗装性能上は問題ないが、陰極電解処理することによ
り処理液のｐＨが上昇するため、工業生産上常時ｐＨ調
整が必要となり維持すること及びコントロールすること
が困難である。ｐＨが1.7 を超えるとクロメート皮膜付
着量が急激に減少し、適性クロム付着量を得るのが困難
となる。The pH of the acidic aqueous solution limits its value to the range of 0.6 to 1.7. In order to control the pH, it can be arbitrarily selected from ammonium hydroxide, alkali metal hydroxide, alkali metal carbonate, chromic acid, sulfuric acid, nitric acid and the like and added to the aqueous solution. If the pH is less than 0.6, there is no problem in coating performance. However, since the pH of the processing solution is increased by performing the cathodic electrolysis, it is necessary to constantly adjust the pH in industrial production, and it is difficult to maintain and control the pH. If the pH exceeds 1.7, the amount of chromate film adhered decreases sharply, making it difficult to obtain an appropriate amount of chromium film adhered.

【００１０】処理液の温度は特定するものではないが、
より好ましくは30°〜60°Ｃである。30°Ｃ以下では、
電解による発熱があるため温度維持に冷却が必要となり
工業生産的には不経済である。60°Ｃより高くしても、
生成する皮膜の特性に大きな変化はないが、電解処理
後、次の水洗工程での洗浄性を低下させるので好ましく
ない。Although the temperature of the processing solution is not specified,
More preferably, it is 30 ° -60 ° C. Below 30 ° C,
Since heat is generated by the electrolysis, cooling is required to maintain the temperature, which is uneconomical for industrial production. Even if it is higher than 60 ° C,
Although there is no significant change in the characteristics of the formed film, it is not preferable because the washing property in the next washing step after the electrolytic treatment is reduced.

【００１１】次に電解処理は被処理物を陰極とし、陽極
にはステンレス、チタン、白金、スズ、鉛合金等を用い
て電解処理を行う。電解処理の条件は、陰極における電
解電流密度を0.5 〜15Ａ／ｄｍ² の範囲で行う。電流密
度が０．５Ａ／ｄｍ² よりも低いときはクロメート皮膜
が形成され難く、又、15Ａ／ｄｍ² より高いと皮膜が着
色し、更に、皮膜の再溶解が起こり、本発明の目的であ
る無色のクロメート皮膜は得られない。Next, in the electrolytic treatment, an object to be treated is used as a cathode and the anode is subjected to electrolytic treatment using stainless steel, titanium, platinum, tin, a lead alloy or the like. The conditions for the electrolytic treatment are such that the electrolytic current density at the cathode is in the range of 0.5 to 15 A / dm ² . When the current density is lower than 0.5 A / dm ^2, it is difficult to form a chromate film. On the other hand, when the current density is higher than 15 A / dm ² , the film is colored and the film is redissolved. A colorless chromate film cannot be obtained.

【００１２】電解時間は、形成皮膜量（クロム付着量）
を所望の範囲とするためにコントロールされる。形成皮
膜量（クロム付着量）を変動される要因としては色々挙
げられるが、本発明の方法においては、処理液の各成分
の濃度、ｐＨ、温度、及び電流密度等を、夫々本発明の
好ましい条件に固定しておいても、電解時間を変えるこ
とにより所望のクロム付着量に制御することができる。
又、その逆に電解時間を固定して、電流密度を変えるこ
とによりクロム付着量を制御することもできる。The electrolysis time depends on the amount of the formed film (the amount of chromium adhered).
Is controlled to be within a desired range. There are various factors that can change the amount of the formed film (the amount of chromium adhering). In the method of the present invention, the concentration, pH, temperature, current density, and the like of each component of the processing solution are preferably used in the present invention. Even if the conditions are fixed, the desired amount of chromium can be controlled by changing the electrolysis time.
Conversely, the amount of chromium deposited can be controlled by fixing the electrolysis time and changing the current density.

【００１３】クロム付着量は特定されるものではない
が、好ましいクロム付着量範囲は、50〜 250ｍｇ／ｍ²
である。クロム付着量50ｍｇ／ｍ² 未満では、塗装後耐
食性、特に糸錆性が劣り、また、 250ｍｇ／ｍ² を超え
るとクロメート皮膜が着色し、クリヤー塗装用に適さな
い。但し、有色塗装の場合は、250 ｍｇ／ｍ² 以上でも
使用できる。Although the chromium deposition amount is not specified, a preferable chromium deposition range is 50 to 250 mg / m ^2.
It is. If the chromium adhesion amount is less than 50 mg / m ² , the corrosion resistance after coating, particularly the thread rust resistance, is inferior. If it exceeds 250 mg / m ² , the chromate film is colored and is not suitable for clear coating. However, in the case of colored coating, 250 mg / m ² or more can be used.

【００１４】また、本酸性処理後にコロイダルシリカ、
乾式シリカ、珪酸アルカリ金属塩等の化合物を含有させ
ることにより、無色で比較的厚膜のクロメート皮膜を形
成させることもできる。また、より耐食性を向上させる
ためにはジルコニウムイオンを本酸性処理液に添加でき
る。ジルコニウムイオンとしては、ジルコニウムフッ化
水素酸及びナトリウム、カリウム、アンモニウム等の
塩、硫酸ジルコニウム等を挙げることができる。After the acid treatment, colloidal silica,
By containing a compound such as fumed silica or an alkali metal silicate, a colorless and relatively thick chromate film can be formed. In order to further improve the corrosion resistance, zirconium ions can be added to the present acidic treatment liquid. Examples of zirconium ions include zirconium hydrofluoric acid and salts of sodium, potassium, ammonium and the like, zirconium sulfate and the like.

【００１５】本発明により陰極電解されたアルミホイー
ルは、水洗した後乾燥して、塗装下地用として適用され
る。また、必要に応じて、前記水洗と乾燥の間に一般的
に用いられているクロメート水溶液、及び有機化合物な
どによる後処理を行うこともできる。本発明は鋳造法、
鍛造法いずれの方法で成形された１ピースタイプアルミ
ホイールに適用可能であり、また鋳造材、鍛造材、板材
のいずれかの組み合わせによる構成される２ピース、３
ピースタイプのアルミホイールにも適用可能である。The aluminum wheel subjected to the cathodic electrolysis according to the present invention is washed with water, dried and applied as a base material for coating. If necessary, a post-treatment with an aqueous chromate solution, an organic compound, and the like, which are generally used between the water washing and drying, can be performed. The present invention relates to a casting method,
Applicable to one-piece type aluminum wheels formed by any of the forging methods, and two-piece, three-piece, three-piece, or forged materials
It is also applicable to piece type aluminum wheels.

【００１６】上記アルミホイールの機械加工後の表面粗
さが本発明のようにＲmax100以下の場合、塗装後耐食
性、塗料密着性に著しく優れる。Ｒmax100より大きい
と、その他の本発明の条件を備えても反応クロメート処
理と比較して効果は小さい。また、アルミ材表面の機会
加工としては、研削加工、フライス加工、ブラスト加
工、研磨加工（バフ、ペーパー、グラインダー、サンダ
ー、ヤスリ、ラップ等）のいずれの機械加工でも適用可
能である。When the surface roughness of the aluminum wheel after machining is not more than Rmax100 as in the present invention, the corrosion resistance and paint adhesion after coating are remarkably excellent. When it is larger than Rmax100, the effect is small as compared with the reaction chromate treatment even when the other conditions of the present invention are provided. In addition, as the opportunity processing of the aluminum material surface, any mechanical processing such as grinding, milling, blasting, and polishing (buff, paper, grinder, sander, file, wrap, etc.) can be applied.

【００１７】[0017]

【実施例】次に、本発明を実施例と比較例を挙げて具体
的に説明する。試験板は、アルミニウム合金（ＪＩＳ記
号ＡＣ４Ｃ、ＡＣ４ＣＨ）をサイズ70×150 ×15mmに鋳
造成形し、熱処理を行い（Ｔ６処理）、その後表面を研
削により25μm Ｒmax に仕上げたものを、アルカリ脱脂
洗浄して表面を清浄にした後、電解処理に供した（実施
例１〜14及び比較例１〜８）。Next, the present invention will be specifically described with reference to examples and comparative examples. For the test plate, an aluminum alloy (JIS symbol AC4C, AC4CH) was cast into a size of 70 × 150 × 15 mm, heat-treated (T6 treatment), and then the surface was finished to 25 μm Rmax by grinding, followed by alkali degreasing and washing. After the surface was cleaned, the substrate was subjected to electrolytic treatment (Examples 1 to 14 and Comparative Examples 1 to 8).

【００１８】（実施例１〜６）６価クロムイオンを無水
クロム酸で20ｇ／リットル、硫酸イオンを硫酸で400pp
m、フッ化水素酸でフッ素を100ppm添加した酸性水溶液
のｐＨを水酸化アンモニウムを用いて表１に示した条件
（実施例１−ｐＨ0.6 〜実施例６−ｐＨ1.6 ）に調整し
た。試験板を前記酸性水溶液に浸漬し陰極とし、電流密
度を２Ａ／ｄｍ²で60秒通電した。この間水溶液温度は4
0°Ｃに循環しながら維持した。通電後、試験板を取り
出し水洗及び純水洗浄を行った後100 °Ｃの乾燥炉で５
分間乾燥した。次に試験板に熱硬化型アクリル樹脂クリ
ヤーを塗装し（膜厚30μ）１４０°Ｃ30分焼付け乾燥
後、耐食性試験（糸錆試験、塩水噴霧試験＝ＳＳＴ）を
実施した。結果を表１に示す。(Examples 1 to 6) Hexavalent chromium ions were added with chromic anhydride at 20 g / l and sulfate ions at 400 pp with sulfuric acid.
m, the pH of the acidic aqueous solution to which 100 ppm of fluorine was added with hydrofluoric acid was adjusted to the conditions shown in Table 1 (Example 1-pH 0.6 to Example 6-pH 1.6) using ammonium hydroxide. The test plate was immersed in the acidic aqueous solution to serve as a cathode, and a current density of 2 A / dm ² was applied for 60 seconds. During this time, the temperature of the aqueous solution was 4
Maintained while circulating at 0 ° C. After energization, the test plate is taken out, washed with water and pure water, and dried in a drying oven at 100 ° C for 5 minutes.
Dried for minutes. Next, a thermosetting acrylic resin clear was applied to the test plate (thickness: 30 μm), baked and dried at 140 ° C. for 30 minutes, and then subjected to a corrosion resistance test (fiber rust test, salt spray test = SST). Table 1 shows the results.

【００１９】（実施例７）６価クロムイオンを無水クロ
ム酸で５ｇ／リットル、硫酸イオンを硫酸で100ｐｐ
ｍ、フッ化水素酸でフッ素を30ｐｐｍ添加した酸性水溶
液のｐＨを水酸化アンモニウムを用いて１．０に調整
し、実施例１と同様の電解処理、塗装を行い、耐食性試
験を実施した。結果を表１に示す。(Example 7) Hexavalent chromium ions were added with chromic anhydride at 5 g / l and sulfate ions at 100 pp with sulfuric acid.
m, the pH of an acidic aqueous solution obtained by adding 30 ppm of fluorine with hydrofluoric acid was adjusted to 1.0 using ammonium hydroxide, and the same electrolytic treatment and coating as in Example 1 were performed, and a corrosion resistance test was performed. Table 1 shows the results.

【００２０】（実施例８）６価クロムイオンを無水クロ
ム酸で５０ｇ／リットル、硫酸イオンを硫酸で１ｇ／リ
ットル、フッ化水素酸でフッ素を400ppm、添加した酸性
水溶液のｐＨを水酸化アンモニウムを用いて１．０に調
整し、実施例１と同様の電解処理、塗装を行い、耐食性
試験を実施した。結果を表１に示す。Example 8 Hexavalent chromium ion was 50 g / l with chromic anhydride, sulfate ion was 1 g / l with sulfuric acid, 400 ppm of fluorine was added with hydrofluoric acid, and the pH of the added acidic aqueous solution was adjusted with ammonium hydroxide. It adjusted to 1.0 using it, performed the same electrolytic treatment and coating as Example 1, and performed the corrosion resistance test. Table 1 shows the results.

【００２１】（比較例１〜３）６価クロムイオンを無水
クロム酸で20ｇ／リットル、硫酸イオンを硫酸イオンを
硫酸で400ppm、フッ化水素酸でフッ素を100ppmという実
施例１〜実施例６と同一の条件で、添加した酸性水溶液
のｐＨを水酸化アンモニウムを用いて本発明の条件から
外れる表１に示した条件（比較例１−ｐＨ2.0 〜比較例
３−ｐＨ3.0 ）に調整し、実施例１と同様の電解処理、
塗装処理を行い、耐食性試験を実施した。結果を表１に
示す。(Comparative Examples 1 to 3) Comparative Examples 1 to 6 in which hexavalent chromium ion is 20 g / liter with chromic anhydride, sulfate ion is 400 ppm with sulfuric acid with sulfuric acid and 100 ppm with fluorine with hydrofluoric acid Under the same conditions, the pH of the added acidic aqueous solution was adjusted to the conditions shown in Table 1 (Comparative Example 1-pH 2.0 to Comparative Example 3-pH 3.0) which deviate from the conditions of the present invention using ammonium hydroxide. The same electrolytic treatment as in Example 1,
A coating treatment was performed and a corrosion resistance test was performed. Table 1 shows the results.

【００２２】以上の各実施例を比較例と比較して評価
(評価の方法については後述する) すると、表１に示さ
れるように、全ての実施例１〜８が、外観性, 耐食性
(糸錆試験, ＳＳＴ) を満たしており、特に、実施例５,
６は優れていた。これに対し、比較例１〜３につい
て、外観性は比較例１, ２では一応満たしているが、比
較例３はやや不良であり、また、耐食性については糸錆
試験結果は全て不良、ＳＳＴ結果は全てやや不良であっ
た。Each of the above embodiments was evaluated in comparison with a comparative example.
(The evaluation method will be described later.) Then, as shown in Table 1, all of Examples 1 to 8 show appearance and corrosion resistance.
(Yarn rust test, SST).
6 was excellent. On the other hand, in Comparative Examples 1 to 3, the appearance was satisfactory in Comparative Examples 1 and 2, but Comparative Example 3 was slightly poor. Were all somewhat poor.

【００２３】ここで、実施例１〜６と比較例１〜３につ
いては、他の条件は同一で水溶液のｐＨの条件のみを変
えているため、これらの相違は水溶液のｐＨの相違に起
因するものであり、クロム付着量の相違も水溶液のｐＨ
に起因することが明らかである。そこで、水溶液のｐＨ
とクロム付着量の関係をみてみると、図１に示すよう
に、ｐＨが本発明の条件から外れて2.0 以上の比較例の
場合は、クロム付着量が実施例１〜６に比較して著しく
小さくなっていることが判る。Here, in Examples 1 to 6 and Comparative Examples 1 to 3, the other conditions were the same and only the conditions of the pH of the aqueous solution were changed. Therefore, these differences were caused by the differences in the pH of the aqueous solution. The difference in the amount of chromium adhered also depends on the pH of the aqueous solution.
It is obvious that the Therefore, the pH of the aqueous solution
As shown in FIG. 1, when the pH deviates from the conditions of the present invention and the comparative example is 2.0 or more, the chromium deposition amount is remarkably higher than that of Examples 1 to 6. You can see that it is getting smaller.

【００２４】次に、電界処理、フッ素濃度, その他の添
加成分を本発明の条件内で変化させた各実施例９〜14
を、比較例として電界処理が本発明を条件から外れたも
の (比較例４, ５) 、硫酸イオン濃度が本発明を条件か
ら外れたもの (比較例６) 、その他処理方法が全く異な
るもの (比較例７〜９) を上げて比較した場合について
説明する。Next, Examples 9 to 14 in which the electric field treatment, the fluorine concentration, and other added components were changed within the conditions of the present invention.
As comparative examples, those in which the electric field treatment deviated from the conditions of the present invention (Comparative Examples 4 and 5), those in which the sulfate ion concentration deviated from the conditions of the present invention (Comparative Example 6), and those in which the treatment methods were completely different Comparative examples 7 to 9) will be described for comparison.

【００２５】（実施例９）６価クロムイオンを無水クロ
ム酸で20ｇ／リットル、硫酸イオンを硫酸で４００ｐｐ
ｍ、フッ化水素酸でフッ素を30ｐｐｍとなるように添加
した酸性水溶液のｐＨを水酸化アンモニウムを用いて
１．０に調整した。試験板を前記酸性水溶液に浸漬し陰
極とし、電流密度を０．５Ａ／ｄｍ² で 120秒間通電し
た。実施例１と同様の塗装を行い、耐食性試験を実施し
た。結果を表２に示す。EXAMPLE 9 Hexavalent chromium ions were converted to 20 g / liter with chromic anhydride and sulfate ions were converted to 400 pp with sulfuric acid.
m, the pH of the acidic aqueous solution to which fluorine was added to 30 ppm with hydrofluoric acid was adjusted to 1.0 using ammonium hydroxide. The test plate was immersed in the acidic aqueous solution to serve as a cathode, and a current density of 0.5 A / dm ² was supplied for 120 seconds. The same coating as in Example 1 was performed, and a corrosion resistance test was performed. Table 2 shows the results.

【００２６】（実施例10）６価クロムイオンを無水クロ
ム酸で20ｇ／リットル、硫酸イオンを硫酸で 400ｐｐ
ｍ、フッ化水素酸でフッ素を30ｐｐｍ添加し、添加した
酸性水溶液のｐＨを水酸化アンモニウムを用いて1.0 に
調整した。試験板を前記酸性水溶液に浸漬し陰極とし、
電流密度を２Ａ／ｄｍ² で60秒通電した。実施例１と同
様の塗装を行い、耐食性試験を実施した。結果を表２に
示す。(Example 10) Hexavalent chromium ion was converted to 20 g / liter with chromic anhydride, and sulfate ion was converted to 400 pp with sulfuric acid.
m, 30 ppm of fluorine was added with hydrofluoric acid, and the pH of the added acidic aqueous solution was adjusted to 1.0 using ammonium hydroxide. A test plate was immersed in the acidic aqueous solution to form a cathode,
The current was passed at a current density of 2 A / dm ² for 60 seconds. The same coating as in Example 1 was performed, and a corrosion resistance test was performed. Table 2 shows the results.

【００２７】（実施例11）６価クロムイオンを無水クロ
ム酸で20ｇ／リットル、硫酸イオンを硫酸で 400ｐｐ
ｍ、フッ化水素酸でフッ素を 110ｐｐｍとなるように添
加した酸性水溶液のｐＨを水酸化アンモニウムを用いて
1.0に調整した。試験板を前記酸性水溶液に浸漬し陰極
とし、電流密度を10Ａ／ｄｍ² で30秒間通電した。実施
例１と同様の塗装を行い、耐食性試験を実施した。結果
を表２に示す。(Example 11) Hexavalent chromium ions were added with chromic anhydride at 20 g / liter and sulfate ions at 400 pp with sulfuric acid.
m, the pH of the acidic aqueous solution to which fluorine was added to be 110 ppm with hydrofluoric acid was adjusted using ammonium hydroxide.
Adjusted to 1.0. The test plate was immersed in the acidic aqueous solution to serve as a cathode, and a current density of 10 A / dm ² was supplied for 30 seconds. The same coating as in Example 1 was performed, and a corrosion resistance test was performed. Table 2 shows the results.

【００２８】（実施例12）６価クロムイオンを無水クロ
ム酸で20ｇ／リットル、硫酸イオンを硫酸で 400ｐｐ
ｍ、フッ化水素酸でフッ素を 110ｐｐｍとなるように添
加した酸性水溶液のｐＨを水酸化アンモニウムを用いて
1.0 に調整した。試験板を前記酸性水溶液に浸漬し陰極
とし、電流密度を15Ａ／ｄｍ² で30秒間通電した。実施
例１と同様の塗装を行い、耐食性試験を実施した。結果
を表２に示す。(Example 12) Hexavalent chromium ions were converted to 20 g / liter with chromic anhydride and sulfate ions were converted to 400 pp with sulfuric acid.
m, the pH of the acidic aqueous solution to which fluorine was added to be 110 ppm with hydrofluoric acid was adjusted using ammonium hydroxide.
Adjusted to 1.0. The test plate was immersed in the acidic aqueous solution to serve as a cathode, and a current density of 15 A / dm ² was supplied for 30 seconds. The same coating as in Example 1 was performed, and a corrosion resistance test was performed. Table 2 shows the results.

【００２９】（実施例13）６価クロムイオンを無水クロ
ム酸で20ｇ／リットル、硫酸イオンを硫酸で 400ｐｐ
ｍ、ジルコンフッ酸でフッ素を30ｐｐｍ、ジルコニウム
イオンを90ｐｐｍとなるように添加した酸性水溶液のｐ
Ｈを水酸化アンモニウムを用いて1.0 に調整した。試験
板を前記酸性水溶液に浸漬し陰極とし、電流密度を２Ａ
／ｄｍ² で60秒間通電した。実施例１と同様の塗装を行
い、耐食性試験を実施した。結果を表２に示す。(Example 13) Hexavalent chromium ion was converted to 20 g / liter with chromic anhydride and sulfate ion was converted to 400 pp with sulfuric acid.
m, p of acidic aqueous solution to which zircon hydrofluoric acid is added so that fluorine becomes 30 ppm and zirconium ion becomes 90 ppm.
H was adjusted to 1.0 with ammonium hydroxide. A test plate was immersed in the acidic aqueous solution to serve as a cathode, and the current density was 2 A.
/ Dm ² for 60 seconds. The same coating as in Example 1 was performed, and a corrosion resistance test was performed. Table 2 shows the results.

【００３０】（実施例14）６価クロムイオンを無水クロ
ム酸で20ｇ／リットル、硫酸イオンを硫酸で 400ｐｐ
ｍ、フッ化水素酸でフッ素を30ｐｐｍ添加し、シリカゾ
ルをコロイダルシリカ（日産化学製スノーテックス０）
で固形分濃度２ｇ／リットルとなるように添加した酸性
水溶液のｐＨを水酸化アンモニウムを用いて１．０に調
整した。試験板を前記酸性水溶液に浸漬し陰極とし、電
流密度を２Ａ／ｄｍ² で60秒通電した。実施例１と同様
の塗装を行い、耐食性試験を実施した。結果を表２に示
す。(Example 14) Hexavalent chromium ions were converted to 20 g / l with chromic anhydride and sulfate ions were converted to 400 pp with sulfuric acid.
m, adding 30 ppm of fluorine with hydrofluoric acid, and changing the silica sol to colloidal silica (Nissan Chemical Snowtex 0)
The pH of the acidic aqueous solution added was adjusted to 1.0 using ammonium hydroxide so that the solid content concentration became 2 g / liter. The test plate was immersed in the acidic aqueous solution to serve as a cathode, and a current density of 2 A / dm ² was applied for 60 seconds. The same coating as in Example 1 was performed, and a corrosion resistance test was performed. Table 2 shows the results.

【００３１】（比較例４）６価クロムイオンを無水クロ
ム酸で20ｇ／リットル、硫酸イオンを硫酸で 400ｐｐ
ｍ、フッ化水素酸でフッ素を 110ｐｐｍとなるように添
加した酸性水溶液のｐＨを水酸化アンモニウムを用いて
1.0 に調整した。試験板を前記酸性水溶液に浸漬し陰極
とし、電流密度を20Ａ／ｄｍ² で30秒間通電した。実施
例１と同様の塗装を行い、耐食性試験を実施した。結果
を表２に示す。(Comparative Example 4) Hexavalent chromium ions were converted to 20 g / liter with chromic anhydride and sulfate ions to 400 pp with sulfuric acid.
m, the pH of the acidic aqueous solution to which fluorine was added to be 110 ppm with hydrofluoric acid was adjusted using ammonium hydroxide.
Adjusted to 1.0. The test plate was immersed in the acidic aqueous solution to serve as a cathode, and a current density of 20 A / dm ² was supplied for 30 seconds. The same coating as in Example 1 was performed, and a corrosion resistance test was performed. Table 2 shows the results.

【００３２】（比較例５）６価クロムイオンを無水クロ
ム酸で20ｇ／リットル、硫酸イオンを硫酸で 400ｐｐ
ｍ、フッ化水素酸でフッ素を 110ｐｐｍとなるように添
加した酸性水溶液のｐＨを水酸化アンモニウムを用いて
1.0 に調整した。試験板を前記酸性水溶液に浸漬し陰極
とし、電流密度を30Ａ／ｄｍ² で30秒間通電した。実施
例１と同様の塗装を行い、耐食性試験を実施した。結果
を表２に示す。(Comparative Example 5) Hexavalent chromium ions were converted to 20 g / l with chromic anhydride and sulfate ions were converted to 400 pp with sulfuric acid.
m, the pH of the acidic aqueous solution to which fluorine was added to be 110 ppm with hydrofluoric acid was adjusted using ammonium hydroxide.
Adjusted to 1.0. The test plate was immersed in the acidic aqueous solution to serve as a cathode, and a current density of 30 A / dm ² was supplied for 30 seconds. The same coating as in Example 1 was performed, and a corrosion resistance test was performed. Table 2 shows the results.

【００３３】（比較例６）６価クロムイオンを無水クロ
ム酸で10ｇ／リットル、リン酸イオンをリン酸で15ｇ／
リットル、硫酸イオンを硫酸ナトリウムで３ｇ／リット
ルとなるよう添加した酸性水溶液に浸漬し陰極とし、電
流密度を 0.5Ａ／ｄｍ² で３分間通電した。実施例１と
同様の塗装を行い、耐食性試験を実施した。結果を表２
に示す。(Comparative Example 6) Hexavalent chromium ions were 10 g / liter with chromic anhydride and phosphate ions were 15 g / liter with phosphoric acid.
A liter of the solution was immersed in an acidic aqueous solution in which sulfate ions were added with sodium sulfate at a concentration of 3 g / liter to form a cathode, and a current density of 0.5 A / dm ² was applied for 3 minutes. The same coating as in Example 1 was performed, and a corrosion resistance test was performed. Table 2 shows the results
Shown in

【００３４】（比較例７）試験板をアルカリ脱脂洗浄し
て表面を清浄にした後、反応型クロメート処理（日本パ
ーカライジング製アルクロム３７０３使用）し、水洗及
び純水洗浄を行った後 100°Ｃの乾燥炉で５分間乾燥し
た。次に試験板に熱硬化型アクリル樹脂クリヤーを塗装
し（膜厚30μ） 140°Ｃ30分焼付け乾燥後、耐食性試験
（糸錆試験、塩水噴霧試験）を実施した。結果を表２に
示す。(Comparative Example 7) A test plate was cleaned with alkali degreasing to clean the surface, then subjected to a reactive chromate treatment (using Alchrome 3703 manufactured by Nippon Parkerizing), washed with water and pure water, and then washed at 100 ° C. It was dried for 5 minutes in a drying oven. Next, a thermosetting acrylic resin clear was applied to the test plate (thickness: 30 μm), baked and dried at 140 ° C. for 30 minutes, and then subjected to a corrosion resistance test (a rust test and a salt spray test). Table 2 shows the results.

【００３５】（比較例８）試験板をアルカリ脱脂洗浄、
苛性ソーダエッチング、デスマット処理して表面を清浄
にした後、一般的に使用されているアルマイト処理（硫
酸 180ｇ／リットル、溶存アルミニウム５ｇ／リット
ル、浴温25°Ｃ、電流密度１Ａ／ｄｍ² の条件で15分間
陽極酸化処理を行う）し、水洗及び純水洗浄を行った後
100°Ｃの乾燥炉で５分間乾燥した。次に試験板に熱硬
化型アクリル樹脂クリヤーを塗装し（膜厚30μ）、140
°Ｃで30分焼付け乾燥後、耐食性試験（糸錆試験、塩水
噴霧試験）を実施した。結果を表２に示す。(Comparative Example 8) A test plate was subjected to alkaline degreasing and washing,
After cleaning the surface by caustic soda etching and desmutting, alumite treatment (180 g / l sulfuric acid, 5 g / l dissolved aluminum, bath temperature 25 ° C, current density 1 A / dm ² ) is used. After performing anodizing treatment for 15 minutes), washing with water and pure water
It was dried for 5 minutes in a drying oven at 100 ° C. Next, a thermosetting acrylic resin clear was applied to the test plate (film thickness 30μ),
After baking and drying at 30 ° C. for 30 minutes, a corrosion resistance test (yarn rust test, salt spray test) was performed. Table 2 shows the results.

【００３６】（比較例９）試験板をアルカリ脱脂洗浄し
て表面を清浄にした後、 100°Ｃの乾燥炉で５分間乾燥
した。次に試験板に熱硬化型アクリル樹脂クリヤーを塗
装し（膜厚30μ）、140 °Ｃで30分焼付け乾燥後、耐食
性試験（糸錆試験、塩水噴霧試験）を実施した。結果を
表２に示す。(Comparative Example 9) A test plate was cleaned by alkali degreasing to clean the surface, and then dried in a drying oven at 100 ° C for 5 minutes. Next, a thermosetting acrylic resin clear was applied to the test plate (thickness: 30 μm), baked and dried at 140 ° C. for 30 minutes, and then subjected to a corrosion resistance test (fiber rust test, salt spray test). Table 2 shows the results.

【００３７】表２で判るように、比較例４, ５のように
電流密度を大きくしすぎると、外観性, 糸錆試験結果,
ＳＳＴ試験結果の順で悪影響を及ぼし、硫酸濃度が高す
ぎる比較例６では、外観性, 耐食性共に評価基準を満た
せない。また、反応型クロメート処理を行う比較例７や
アルカリ脱脂処理のみを行う比較例９では外観性は充分
良好であるが、耐食性に問題があり、逆にアルマイト処
理を行う比較例８では耐食性には優れるが、光沢が無く
なり外観性を満たせないことが判る。As can be seen from Table 2, when the current density was too high as in Comparative Examples 4 and 5, the appearance, the rust test results,
In the comparative example 6 in which the sulfuric acid concentration is too high, the external appearance and the corrosion resistance cannot satisfy the evaluation criteria. In Comparative Example 7 in which the reactive chromate treatment was performed and in Comparative Example 9 in which only the alkali degreasing treatment was performed, the appearance was sufficiently good, but there was a problem in the corrosion resistance. In contrast, in Comparative Example 8 in which the alumite treatment was performed, the corrosion resistance was poor. Although it is excellent, it turns out that glossiness is lost and external appearance cannot be satisfied.

【００３８】次に、表面粗さを本発明の条件の範囲内で
変化させた各実施例15〜18を、表面粗さ以外の条件は実
施例15〜18と同一で表面粗さを本発明の範囲外とした比
較例10, 11及び処理方法が本発明と基本的に異なり表面
粗さが本発明の範囲内の比較例12〜15、同じく表面粗さ
が本発明の範囲外の比較例16, 17と比較して説明する。Next, each of Examples 15 to 18 in which the surface roughness was changed within the range of the conditions of the present invention was used. Comparative Examples 10 and 11 and the treatment method were basically different from those of the present invention, and Comparative Examples 12 to 15 in which the surface roughness was within the range of the present invention, and Comparative Examples in which the surface roughness was also out of the range of the present invention. This will be described in comparison with 16, 17.

【００３９】（実施例15〜18）試験板としてアルミニウ
ム合金（ＪＩＳ記号；ＡＣ４ＣＨ）をサイズ70× 150×
15mmの大きさに鋳造成形し熱処理（Ｔ６処理）を行った
後、表面を研作加工により1.6 、25、50、100 、200 、
300 μｍＲmax に仕上げた。６価クロムイオンを無水ク
ロム酸で20ｇ／リットル、硫酸イオンを硫酸で400ppm、
フッ化水素酸でフッ素を30ｐｐｍ添加した酸性水溶液の
ｐＨを水酸化アンモニウムを用いてｐＨ1.0 に調整し
た。各種表面粗さに仕上げた試験板をアルカリ脱脂洗浄
をして表面を清浄にした後、前記酸性水溶液に浸漬し陰
極とし、電流密度を２Ａ／ｄｍ² で60秒通電した。この
間水溶液温度は40°Ｃに循環しながら維持した。通電
後、試験板を取り出し水洗及び純水洗浄を行った後 100
°Ｃの乾燥炉で５分間乾燥した。次に試験板に熱硬化型
アクリル樹脂クリヤーを塗装し（膜厚30μ）１４０°Ｃ
30分焼付乾燥後、耐食性試験（糸錆試験）を実施した。
結果を表３に示す。また、表面粗さと耐食性（糸錆び長
さ）の関係を図２に示す。(Examples 15-18) An aluminum alloy (JIS symbol: AC4CH) having a size of 70 × 150 ×
After casting and heat treatment (T6 treatment) to a size of 15mm, the surface is polished to 1.6, 25, 50, 100, 200,
Finished to 300 μm Rmax. Hexavalent chromium ion with chromic anhydride 20g / l, sulfate ion with sulfuric acid 400ppm,
The pH of the acidic aqueous solution to which 30 ppm of fluorine was added with hydrofluoric acid was adjusted to pH 1.0 using ammonium hydroxide. After the test plates finished to various surface roughnesses were cleaned by alkali degreasing and cleaning, the surfaces were immersed in the above-mentioned acidic aqueous solution to form a cathode, and a current density of 2 A / dm ² was supplied for 60 seconds. During this time, the temperature of the aqueous solution was maintained while circulating at 40 ° C. After energization, remove the test plate and wash with water and pure water.
It was dried for 5 minutes in a drying oven at ° C. Next, a thermosetting acrylic resin clear was applied to the test plate (thickness: 30μ) at 140 ° C.
After baking and drying for 30 minutes, a corrosion resistance test (yarn rust test) was performed.
Table 3 shows the results. FIG. 2 shows the relationship between the surface roughness and the corrosion resistance (yarn rust length).

【００４０】（比較例10, 11）前記実施例15〜18と表面
粗さ以外の条件は同一で、表面粗さを本発明の範囲外の
値として、200 、300 μｍＲmax に仕上げた。結果を表
３に示す。また、表面粗さと耐食性（糸錆び長さ）の関
係を図２に示す。 (比較例12〜15)実施例15〜18にて供した各種表面粗さに
仕上げた試験板をアルカリ脱脂洗浄して表面を清浄にし
た後、反応型クロメート処理（日本パーカライジング製
アルクロム３７０３使用）し、水洗及び純水洗浄を行っ
た後 100°Ｃの乾燥炉で５分間乾燥した。次に試験板に
熱硬化型アクリル樹脂クリヤーを塗装し（膜厚３０μ）
140 °Ｃ30分焼付乾燥後、耐食性試験（糸錆試験）を実
施した。結果を表３に示す。また表面粗さと耐食性（糸
錆び長さ）の関係を図２に示す。(Comparative Examples 10 and 11) The conditions other than the surface roughness were the same as those of Examples 15 to 18, and the surface roughness was set to a value outside the range of the present invention to 200 or 300 μm Rmax. Table 3 shows the results. FIG. 2 shows the relationship between the surface roughness and the corrosion resistance (yarn rust length). (Comparative Examples 12 to 15) After the test plates finished in various surface roughnesses provided in Examples 15 to 18 were cleaned with alkali degreasing to clean the surface, a reactive chromate treatment (using Alchrome 3703 manufactured by Nippon Parkerizing) was used. Then, after washing with water and pure water, drying was performed in a drying oven at 100 ° C. for 5 minutes. Next, a thermosetting acrylic resin clear was applied to the test plate (thickness 30 μm).
After baking and drying at 140 ° C for 30 minutes, a corrosion resistance test (yarn rust test) was performed. Table 3 shows the results. FIG. 2 shows the relationship between the surface roughness and the corrosion resistance (yarn rust length).

【００４１】(比較例16, 17)前記比較例12〜15と同一の
処理を行い、表面粗さを本発明の範囲外の値として、20
0 、300 μｍＲmax に仕上げた。結果を表３に示す。ま
た、表面粗さと耐食性（糸錆び長さ）の関係を図２に示
す。図２から判るように、表面粗さを除き本発明の条件
で処理した場合でも、表面粗さが本発明の範囲外の200,
300 μｍＲmax の比較例の場合は、表面粗さが本発明の
範囲である100 μｍＲmax 以内の実施例15〜18に比較し
て糸錆長さが略２倍の長さとなってやや不良となってし
まう。また、基本的に処理方法の異なる比較例12〜17に
ついては、糸錆長さが６mm以上となって全て不良である
が、表面粗さが100 μｍＲmax 以内の小さいときの方
が、200,300 μｍＲmax と表面粗さが大きいときより糸
錆長さが大きくなるという本発明の処理の場合とは逆の
傾向となる。(Comparative Examples 16 and 17) The same treatment as in Comparative Examples 12 to 15 was performed, and the surface roughness was set to a value outside the range of the present invention.
Finished at 0, 300 μm Rmax. Table 3 shows the results. FIG. 2 shows the relationship between the surface roughness and the corrosion resistance (yarn rust length). As can be seen from FIG. 2, even when the treatment was performed under the conditions of the present invention except for the surface roughness, the surface roughness was out of the range of the present invention.
In the case of the comparative example of 300 μmRmax, the thread rust length was almost twice as long as that of Examples 15 to 18 in which the surface roughness was within 100 μmRmax, which is the range of the present invention. I will. Further, in Comparative Examples 12 to 17 having basically different treatment methods, the thread rust length was 6 mm or more and all were defective, but when the surface roughness was smaller than 100 μmRmax, the results were 200,300 μmRmax. This is opposite to the case of the treatment of the present invention in which the length of the thread rust is longer than when the surface roughness is large.

【００４２】最後に、上記試験片の表面仕上げ方法と評
価試験方法について以下に示す。 （試験片の表面仕上げ方法）ＪＩＳ Ｂ０６０１−１９
８２に従い基準長さ0.25mmにて各最大高さ（Ｒmax）に
なるよう表面を仕上げた。 （評価試験方法） １）皮膜外観 無処理サンプルを基準として色差計によりＪＩＳ−Ｚ８
７３０に規定されている色差を測定して下記のランクに
分けて評価した。Finally, the surface finishing method and the evaluation test method of the test piece will be described below. (Surface finishing method of test piece) JIS B0601-19
According to No. 82, the surface was finished to a maximum length (Rmax) at a reference length of 0.25 mm. (Evaluation test method) 1) Coating appearance JIS-Z8 using a color difference meter based on an untreated sample
The color difference specified in 730 was measured and evaluated according to the following ranks.

【００４３】 ◎ 色差 ０ 〜3.2 （目視では変色が確認され
ず） 〇 色差 3.2 〜6.5 （僅かに変色が認められる） △ 色差 6.5 〜13 （明らかに変色が認められ
る） × 色差 13以上 （強く変色が認められる） ２）クロム付着量 蛍光Ｘ線分析装置により測定。◎ Color difference 0 to 3.2 (discoloration is not visually observed) 〇 Color difference 3.2 to 6.5 (slight discoloration is observed) △ Color difference 6.5 to 13 (discoloration is clearly observed) × color difference 13 or more (strongly discolored) 2) Chromium adhesion amount Measured with a fluorescent X-ray analyzer.

【００４４】３）糸錆試験 塗装した試験板にＮＴカッターで素地まで達するカット
傷をつけた後腐蝕液（１規定塩酸と５％過酸化水素水の
混液）に１分浸漬後常温で乾燥し24時間経時する。温潤
試験（温度50°Ｃ、湿度80％）を1000時間行った後、カ
ット傷より発生した糸錆の長さを測定する。3) Yarn rust test A coated test plate was cut with a NT cutter to reach the substrate, then immersed in a corrosive solution (a mixture of 1N hydrochloric acid and 5% hydrogen peroxide solution) for 1 minute, and dried at room temperature. Allow 24 hours for aging. After a heat and moisture test (temperature of 50 ° C., humidity of 80%) for 1000 hours, the length of the thread rust generated from the cut scratch is measured.

【００４５】 ◎ 最大糸錆び長さ ２mm以内 〇 〃 ３mm以内 △ 〃 ５mm以内 × 〃 ５mmより大 ※実施例15〜20，比較例10〜15は、数値で表示。◎ Maximum thread rust length 2 mm or less 〇 ３ 3 mm or less △ 以内 5 mm or less × 大 Greater than 5 mm * Examples 15 to 20 and Comparative Examples 10 to 15 are indicated by numerical values.

【００４６】４）塩水噴霧試験（ＳＳＴ） 塗装した試験板にＮＴカッターで素地まで達するカット
傷をつけた後ＪＩＳ−Ｚ２３７１に基づいて1000時間行
った後、カット傷からの錆やフクレの最大幅を測定す
る。 ◎ 最大フクレ錆幅 １mm以内 〇 〃 ２mm以内 △ 〃 ３mm以内 × 〃 ３mmより大4) Salt Spray Test (SST) After making a cut on the coated test plate to reach the substrate with an NT cutter, performing the test for 1000 hours according to JIS-Z2371, and then measuring the maximum width of rust and blisters from the cut. Is measured. ◎ Maximum blister rust width: Within 1 mm 〇 〃 Within 2 mm △ 以内 Within 3 mm × 大 Larger than 3 mm

【００４７】[0047]

【発明の効果】本発明によれば、アルミホイール素材の
光輝性を保持し、且つ塗装後耐食性、密着性に優れた無
色クロムメート皮膜を形成させることができ、クリヤー
塗装前処理として、従来問題となっていた耐食性、特に
耐糸錆性を向上させることができる。According to the present invention, it is possible to form a colorless chromium film having good brilliancy of an aluminum wheel material and excellent corrosion resistance and adhesion after coating, which is a problem in the prior art for clear coating. The corrosion resistance, especially the thread rust resistance, can be improved.

【００４８】[0048]

【表１】 [Table 1]

【００４９】[0049]

【表２】 [Table 2]

【００５０】[0050]

【表３】 [Table 3]

【図面の簡単な説明】[Brief description of the drawings]

【図１】電解液のｐＨとクロム付着量の関係を示す図。FIG. 1 is a graph showing the relationship between the pH of an electrolytic solution and the amount of chromium deposited thereon.

【図２】アルミ材表面粗さと耐食性（糸錆び長さ）の関
係を示す図。FIG. 2 is a diagram showing a relationship between aluminum material surface roughness and corrosion resistance (yarn rust length).

Claims (1)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】 アルミホイールの表面を100 μｍＲmax
以下に機械加工した後、６価クロムイオン２ｇ／リット
ル以上、硫酸イオン 20 〜2000ｐｐｍ、フッ素10〜 400
ｐｐｍを含有するｐＨ0.6 〜1.7 の酸性溶液を用い、0.
5 〜15Ａ／ｄｍ² の電流密度で陰極処理することを特徴
とするアルミホイールの無色クロメート皮膜形成方法。1. An aluminum wheel having a surface of 100 μm Rmax
After machining below, hexavalent chromium ion 2 g / l or more, sulfate ion 20-2000 ppm, fluorine 10-400
Use an acidic solution with a pH of 0.6 to 1.7 containing
Colorless chromate film formation method of the aluminum wheel, characterized in that 5 at a current density of to 15A / dm ² to cathodic treatment.