【発明の詳細な説明】[Detailed description of the invention]
本発明は、めつき前処理方法の改良に関する。
一般に行われているめつき前処理方法は、研摩
→予備洗浄→水洗→脱脂→水洗→酸浸漬（活性
化）→水洗→中和→水洗→めつきの工程で行われ
ている。
ところで、被めつき物が非常に酸化し易い金
属、例えばチタニウム、モリブデン等の材料より
成る場合、前記のめつき前処理方法では水洗中に
被めつき物の金属面が酸化することがあり、その
ような時にはめつきの密着力が低下し、耐久性の
あるめつき被膜を得ることができなかつた。
本発明は、かかる問題を解消すべくなされたも
ので、酸浸漬からめつきに入るまで希薄酸浸漬を
複数回繰返し行い、さらに金属イオン不含希薄め
つき液浸漬を複数回行つて、酸浸漬からめつきに
入るまでの水洗を無くし、被めつき物の金属面の
酸化を防止することのできるめつき前処理方法を
提供せんとするものである。
本発明のめつき前処理方法は、２種以上の酸で
被めつき物を前処理する場合に急激な酸濃度の変
化により被めつき物が酸化する等の影響を及ぼす
ことをさけることと、異種の酸の持ち込み等によ
る混合を軽減させるもので、例えば被めつき物を
Ａの酸とＢの酸に浸漬して前処理する場合、被め
つき物をＡの酸に浸漬して活性化し、次いでＡの
酸の濃度を段階的に薄くした希薄酸浸漬を濃度の
濃い方から薄い方に順次行い、次にＢの酸の濃度
を段階的に濃くした希薄酸浸漬を濃度の薄い方か
ら濃い方に順次行うか、又はＢの希薄酸浸漬を複
数回行つた後、Ｂの濃い酸に浸漬し、次いでＢの
酸の希薄酸浸漬又は濃度を段階的に薄くした希薄
酸浸漬を濃度の濃い方から薄い方に順次行い、次
に金属イオン不含の希薄めつき液の濃度を段階的
に濃くした金属イオン不含の希薄めつき液の濃度
の薄い方から濃い方に順次浸漬するか、又は金属
イオン不含の希薄めつき液浸漬したのち金属イオ
ン不含のめつき液に浸漬し、さらに前記金属イオ
ン不含の希薄めつき液浸漬することを特徴とす
る。
本発明のめつき前処理方法に於いて、被めつき
物を酸浸漬して活性化した後めつきに入るまで、
希薄酸浸漬を複数回繰り返し行い、さらに金属イ
オン不含の希薄めつき液浸漬を複数回行う理由
は、水洗を無くして、被めつき物とりわけ非常に
酸化し易いチタニウム、モリブデン等の材料によ
り成る被めつき物の金属面を酸化しにくい状態の
ままにしてめつきする為で、これにより密着力の
高い耐久性のあるめつき被膜を得ることができる
からである。
希薄酸及び希薄めつき液の濃度は、最初の酸浸
漬の酸液、次の異なる濃い酸の酸浸漬の酸液又は
金属イオン不含めつき液に於ける濃度の1/5乃至
１／１００に希釈したものに相当する。
次に本発明によるめつき前処理方法の効果を明
瞭ならしめる為、具体的な実施例と従来例につい
て説明する。
〔実施例〕
工業的に純粋なチタニウム板にクエン酸系の金
めつき液で金めつきする場合、研摩、予備洗浄、
水洗を省略して、チタニウム板を脱脂し、水洗い
した後、40℃の５％フツ酸液に浸漬し酸処理して
活性化し、次に40℃の0.5％希釈フツ酸液に浸漬
して酸処理し、次いで40℃の0.05％極希釈フツ酸
液に浸漬して酸処理する。次に80℃の薄い５重量
％シユウ酸液に２回浸漬して酸処理し、次いで80
℃の濃い20重量％シユウ酸液に浸漬して酸処理
し、次に80℃の薄い１重量％シユウ酸液に浸漬し
て酸処理し、次いで100℃の１重量％クエン酸液
に浸漬して酸処理し、次に100℃の５重量％クエ
ン酸液に浸漬して酸処理し、次いで50℃の１重量
％クエン酸液に浸漬して酸処理し、然る後クエン
酸系金めつき液中でチタニウム板に金めつきし
た。
〔従来例〕
工業的に純粋なチタニウム板にクエン酸系の金
めつき液で金めつきする場合、研摩、予備洗浄、
水洗を省略して、チタニウム板を脱脂し、水洗し
30℃の１％フツ酸液に浸漬して酸化物を除去した
後、水洗し、次い100℃の20重量％シユウ酸液に
浸漬して酸処理し、水洗後クエン酸系金めつき液
中でチタニウム板に金めつきした。
然して実施例及び従来例の金めつきした各チタ
ニウム板各100枚の金めつき被膜の密着力を測定
した処、下記の表に示すような結果を得た。
The present invention relates to improvements in plating pretreatment methods. A commonly used plating pretreatment method includes the following steps: polishing → preliminary cleaning → water washing → degreasing → water washing → acid immersion (activation) → water washing → neutralization → water washing → plating. By the way, when the object to be plated is made of a metal that is highly oxidizable, such as titanium or molybdenum, the metal surface of the object to be plated may be oxidized during washing with water in the above plating pretreatment method. In such cases, the adhesion of plating deteriorates, making it impossible to obtain a durable plating film. The present invention has been made to solve this problem, and involves repeating dilute acid immersion multiple times from acid immersion to plating, and then performing immersion in dilute plating solution containing no metal ions multiple times. It is an object of the present invention to provide a plating pretreatment method that eliminates the need for washing with water before plating and can prevent oxidation of the metal surface of the object to be plated. The plating pretreatment method of the present invention is aimed at avoiding effects such as oxidation of the plating material due to sudden changes in acid concentration when pretreating the plating material with two or more types of acids. This is to reduce the mixing caused by bringing in different types of acids. For example, when pre-treating a coated object by immersing it in acid A and acid B, immersing the coated object in acid A and activating it. , then immersion in a dilute acid in which the concentration of acid A was gradually diluted from the highest concentration to the lowest concentration, and then immersion in a dilute acid in which the concentration of acid B was gradually increased in the direction of the lowest concentration. After immersion in dilute acid B several times, immerse in concentrated acid B, then immerse in dilute acid B, or immerse in dilute acid with gradually decreasing concentration. Then, the metal ion-free diluted plating solution is immersed in a diluted plating solution containing no metal ions, which has been gradually increased in concentration. Alternatively, it is characterized in that it is immersed in a dilute plating solution that does not contain metal ions, then immersed in a plating solution that does not contain metal ions, and then further immersed in the dilute plating solution that does not contain metal ions. In the plating pretreatment method of the present invention, after the object to be plated is immersed in acid to activate it, until plating is started,
The reason why dipping in a dilute acid is repeated multiple times and then dipping in a dilute plating solution that does not contain metal ions multiple times is to eliminate the need for washing with water, and remove the plating material, especially materials that are extremely easily oxidized, such as titanium and molybdenum. This is because the metal surface of the object to be plated is left in a state where it is difficult to oxidize, and thereby a durable plating film with high adhesion can be obtained. The concentration of the dilute acid and dilute plating solution is 1/5 to 1/100 of the concentration in the first acid immersion, the subsequent acid immersion with a different strong acid, or the metal ion-free plating solution. It corresponds to a diluted version. Next, in order to clarify the effects of the plating pretreatment method according to the present invention, specific examples and conventional examples will be described. [Example] When gold plating an industrially pure titanium plate with a citric acid-based gold plating solution, polishing, pre-cleaning,
After omitting water washing, the titanium plate was degreased, washed with water, immersed in 5% hydrofluoric acid solution at 40°C for acid treatment, and then immersed in 0.5% diluted hydrofluoric acid solution at 40°C to activate the titanium plate. Then, it is immersed in a 0.05% extremely dilute hydrofluoric acid solution at 40°C for acid treatment. Next, it was acid-treated by immersing it twice in a dilute 5% oxalic acid solution at 80°C, and then at 80°C.
It was immersed in a strong 20% oxalic acid solution at 80°C for acid treatment, then in a thin 1% oxalic acid solution at 80°C for acid treatment, and then in a 1% citric acid solution at 100°C. Then, it was immersed in a 5% by weight citric acid solution at 100°C for acid treatment, then immersed in a 1% by weight citric acid solution at 50°C for acid treatment, and then citric acid-based gold plated. Gold plated a titanium plate in a dipping solution. [Conventional example] When gold plating an industrially pure titanium plate with a citric acid-based gold plating solution, polishing, pre-cleaning,
Skip water washing and degrease the titanium plate and wash it with water.
After immersing in 1% hydrofluoric acid solution at 30℃ to remove oxides, washing with water, then immersing in 20wt% oxalic acid solution at 100℃ for acid treatment, and after washing with water, remove oxides from citric acid-based gold plating solution. Inside, the titanium plate was plated with gold. However, when the adhesion of the gold-plated coatings of 100 gold-plated titanium plates of the example and the conventional example was measured, the results shown in the table below were obtained.
【表】
180℃に折り曲げ、曲げ部をセロテープで剥離
し、めつき被膜残存率を目視観察し％表示した。
上記の表で明らかなように実施例のチタニウム
板の金めつき被膜の密着力は、従来例のチタニウ
ム板の金めつき被膜の密着力に比べ、著しく高く
且つばらつきが少なく安定していることが判る。
これは従来例のめつき前処理方法が、水洗工程
で一部酸化が起きる為、金めつき被膜の密着力が
悪くなるのに対し、実施例のめつき前処理方法は
被めつき物の水洗を無くして希薄酸浸漬を複数回
繰返し行い、さらに希薄めつき液浸漬を複数回行
つて、被めつき物の金属面を酸化しにくくし、僅
かにエツチングして金めつき被膜の密着力を高め
ているからに他ならない。
以上詳記した通り本発明のめつき前処理方法に
よれば、被めつき物とりわけチタニウム、モリブ
デン等の非常に酸化し易い材料より成る被めつき
物の金属面を、酸浸漬後めつきに入るまで、酸化
を防止することができるので、被めつき物にめつ
きして得られるめつき被膜は密着力が極めて高い
耐久性のあるものにできるという効果を奏する。[Table] The product was bent at 180°C, the bent portion was peeled off with cellophane tape, and the residual rate of the plating film was visually observed and expressed as a percentage. As is clear from the above table, the adhesion force of the gold plating coating on the titanium plate of the example is significantly higher and stable with less variation than the adhesion force of the gold plating coating on the titanium plate of the conventional example. I understand. This is because in the conventional plating pre-treatment method, some oxidation occurs during the water washing process, which deteriorates the adhesion of the gold plating film, whereas the plating pre-treatment method in the example By removing water washing and repeating dipping in dilute acid several times, and then dipping in diluted plating solution multiple times, the metal surface of the object to be plated is made difficult to oxidize, and slightly etched to improve the adhesion of the gold plating film. This is because it increases the As described in detail above, according to the plating pretreatment method of the present invention, the metal surface of the plated object, particularly the metal surface of the plated object made of a highly oxidizable material such as titanium or molybdenum, can be plated after being immersed in an acid. Since oxidation can be prevented until the coating is applied, the plating film obtained by plating the object to be plated has extremely high adhesion and durability.