JP2012057223A

JP2012057223A - Plating pretreatment method

Info

Publication number: JP2012057223A
Application number: JP2010202568A
Authority: JP
Inventors: Yuki Furukawa; 雄貴古川; Nobuhiko Yoshimoto; 信彦吉本; Hitoshi Karasawa; 均唐澤
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2010-09-10
Filing date: 2010-09-10
Publication date: 2012-03-22

Abstract

PROBLEM TO BE SOLVED: To provide a plating pretreatment method in which the number of plating pretreatment applied to an aluminum alloy can be reduced.SOLUTION: A mixed acid comprising a phosphoric acid having the concentration of 10-20 vol% and a nitric acid having the concentration of 3-12 vol% is used as a treatment liquid for removing an altered layer and an aluminum alloy component.

Description

本発明は、シリンダブロックなどのアルミニウム合金製部材の表面のメッキ前処理方法に関する。 The present invention relates to a pretreatment method for plating a surface of an aluminum alloy member such as a cylinder block.

アルミニウム合金製シリンダブロックのピストン摺動面にはＮｉ−ＳｉＣメッキが施される。このメッキ前処理として亜鉛下地被膜が一般に形成される。この亜鉛下地被膜を形成するには、図２に示すように、シリンダブロック表面に付着している油膜を脱脂処理して除去し、次いで、シリンダブロック表面のＡｌ酸化膜、加工流動層或いは含油相などの変質層をアルカリ溶液でエッチングして除去し、更にシリンダブロック表面に残った合金成分を酸洗で除去し、この後、粗い亜鉛皮膜を形成し、この亜鉛皮膜を硝酸などで溶解させて亜鉛を含む不動態被膜とし、この不動態被膜をＺｎ−Ｏ−Ａｌからなる緻密な下地膜に置換するダブル亜鉛置換法が知られている。
上記の方法は、アルカリエッチング、酸洗、亜鉛皮膜置換、酸処理、亜鉛皮膜置換と工程数が多く、且つ各工程間に水洗工程が付加され、効率的ではない。 Ni-SiC plating is applied to the piston sliding surface of the aluminum alloy cylinder block. As this pretreatment for plating, a zinc undercoat is generally formed. In order to form this zinc undercoat, as shown in FIG. 2, the oil film adhering to the cylinder block surface is removed by degreasing, and then the Al oxide film, processed fluidized layer or oil-containing phase on the cylinder block surface is removed. Etch the denatured layer with an alkaline solution and remove the alloy components remaining on the cylinder block surface by pickling. Then, form a rough zinc film and dissolve this zinc film with nitric acid. There is known a double zinc replacement method in which a passive film containing zinc is used, and this passive film is replaced with a dense base film made of Zn—O—Al.
The above methods are not efficient because alkali etching, pickling, zinc film replacement, acid treatment, zinc film replacement and many processes are added, and a water washing process is added between the processes.

そこで、特許文献１には、上記のエッチングと酸洗に用いる処理液として、硝酸と硫酸と酸性フッ化アンモン(酸性フッ化アンモニウム)を混合した酸性エッチング液を用いることで、２工程を１工程で済ます提案がなされている。 Therefore, in Patent Document 1, an acidic etching solution obtained by mixing nitric acid, sulfuric acid, and acidic ammonium fluoride (acidic ammonium fluoride) is used as the processing solution used for the above-described etching and pickling, so that two processes are performed as one process. Proposals to be made are made.

特許文献２には、銀または銀合金からなる金属膜とＩＴＯなどの透明導電膜とを同時にエッチングする処理液として、銅イオン、硝酸及び酸性フッ化アンモニウム（ＮＨ_４Ｆ・ＨＦ）などのフッ素化合物を含有する処理液が提案されている。 Patent Document 2 discloses a fluorine compound such as copper ion, nitric acid, and acidic ammonium fluoride (NH ₄ F · HF) as a processing solution for simultaneously etching a metal film made of silver or a silver alloy and a transparent conductive film such as ITO. Has been proposed.

特開平１１−１９３４８１号公報Japanese Patent Laid-Open No. 11-193481 特開２００９−２０６４６２号公報JP 2009-206462 A

特許文献１に開示される酸性エッチング液は硝酸と硫酸を混合しており、酸性フッ化アンモニウムが含まれていても、酸化力が過度に強くアルミニウム合金表面に不動態膜が形成されエッチングが進行しにくくなる。 The acidic etching solution disclosed in Patent Document 1 is a mixture of nitric acid and sulfuric acid, and even when acidic ammonium fluoride is contained, the oxidizing power is excessively strong and a passive film is formed on the surface of the aluminum alloy and etching proceeds. It becomes difficult to do.

特許文献２に開示されるエッチング液は、硝酸と酸性フッ化アンモニウムを含んでいるが、アルミニウム合金の表面に前記同様に不動態膜を形成してしまう。 The etching solution disclosed in Patent Document 2 contains nitric acid and acidic ammonium fluoride, but forms a passive film on the surface of the aluminum alloy as described above.

また、酸性フッ化アンモニウムなどのフッ化物は、廃水処理コストが高く、取り扱いについても高度の安全対策が要求される。 In addition, fluorides such as acidic ammonium fluoride have a high wastewater treatment cost and require advanced safety measures for handling.

上記課題を解決すべく本願発明は、アルミニウム合金表面を脱脂した後、表面の変質層の除去とアルミニウム合金成分の除去を行い、この後表面に下地皮膜を形成するメッキ前処理方法において、前記変質層の除去とアルミニウム合金成分の除去の処理液として、濃度が１０vol％以上２０vol％以下のリン酸と、濃度が３vol％以上１２vol％以下の硝酸との混酸を用いることで、１工程で前記変質層の除去とアルミニウム合金の除去を行うようにした。 In order to solve the above-mentioned problems, the present invention provides a plating pretreatment method in which the surface of the aluminum alloy is degreased, the altered layer on the surface is removed and the aluminum alloy component is removed, and then a base film is formed on the surface. By using a mixed acid of phosphoric acid having a concentration of 10 vol% or more and 20 vol% or less and nitric acid having a concentration of 3 vol% or more and 12 vol% or less as the treatment liquid for removing the layer and the aluminum alloy component, the alteration is performed in one step. Layer removal and aluminum alloy removal were performed.

本発明において、リン酸または硝酸の濃度（vol％）は９８％リン酸または９８％硝酸を水で希釈したもので、例えば１０vol％とは、９８％リン酸１００ｍｌに対し水９００ｍｌを加えたことを示す。
また、リン酸と硝酸の配合割合はリン酸１に対し硝酸を０．５〜２．０添加するのが好ましい。 In the present invention, the concentration (vol%) of phosphoric acid or nitric acid is 98% phosphoric acid or 98% nitric acid diluted with water. For example, 10 vol% means that 900 ml of water was added to 100 ml of 98% phosphoric acid. Indicates.
The mixing ratio of phosphoric acid and nitric acid is preferably 0.5 to 2.0 nitric acid added to phosphoric acid 1.

本発明によれば、従来アルカリエッチング液による変質層除去とアルミニウム合金成分の除去を２つの工程に分けて行っていたが、これを１工程で行うことが可能になった。その結果、メッキ前処理のサイクルタイムが短縮され効率が大幅に向上する。また、工程数削減に伴って専用及び汎用設備の投資削減ができる。 According to the present invention, the removal of the deteriorated layer and the removal of the aluminum alloy component by the alkali etching solution are conventionally performed in two steps, but this can be performed in one step. As a result, the cycle time of the plating pretreatment is shortened and the efficiency is greatly improved. In addition, investment in dedicated and general-purpose facilities can be reduced with the reduction in the number of processes.

本発明に係るメッキ前処理工程の概略図Schematic of plating pretreatment process according to the present invention 従来のメッキ前処理工程の概略図Schematic diagram of conventional plating pretreatment process 密着性の試験方法を説明した図Illustration explaining the adhesion test method

以下に本発明の実施の形態を添付図面に基づいて説明する。図１に示すように本実施例にあっては、変質層の除去とアルミニウム合金成分の除去（スマットの溶解も含む）を１工程で行うとともに、亜鉛下地皮膜の形成も１工程で行うようにしている。 Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, in this embodiment, the removal of the deteriorated layer and the removal of the aluminum alloy component (including dissolution of the smut) are performed in one step, and the formation of the zinc undercoat is also performed in one step. ing.

またこの実施例にあっては、前記亜鉛下地皮膜の形成は同一溶液内での電解、即ち、粗い亜鉛皮膜を陽極電解し、電解で発生した活性な酸素によって、Ｚｎ元素とＡｌ元素を結合して緻密なＺｎ−Ｏ−Ａｌ膜を形成するようにしている。 In this embodiment, the formation of the zinc undercoat is performed by electrolysis in the same solution, that is, by anodic electrolysis of a rough zinc coat and bonding Zn element and Al element by active oxygen generated by the electrolysis. And a dense Zn—O—Al film is formed.

変質層の除去とアルミニウム合金成分の除去を１工程で行う処理液としては、リン酸と硝酸に着目し、これらを組み合わせて好適な範囲を検証した。因みに、リン酸のみでは酸化力が不足して変質層の除去が行えず、硝酸のみでは酸化力が強すぎて不動態膜を形成してしまう。 As a treatment liquid for removing the deteriorated layer and the aluminum alloy component in one step, attention was paid to phosphoric acid and nitric acid, and a suitable range was verified by combining them. In this connection, phosphoric acid alone is insufficient in oxidizing power to remove the deteriorated layer, and nitric acid alone is too strong in oxidizing power to form a passive film.

好適か否かの判断はＮｉ−ＳｉＣメッキ膜の密着性を基準として判断した。また、検証は図３に示すＪＩＳ−Ｈ８５０４−１１（押出し試験方法）によって行った。
押出し試験方法は、先ずめっき面に対し裏側から底厚１．５ｍｍを残しφ６．５ｍｍの平底の穴をあけ、次いで、φ２５ｍｍの穴があいた受台の上に試料を乗せ、φ６．３ｍｍのピンを前記平底の穴に刺し込み、打ち抜く。
打ち抜かれた破片部のめっきの状態変化を調べ密着性◎○×の判定を行った。
◎はめっきの剥がれが全く観られない、○は一部にめっきの剥がれが観られる、×は全周にめっきの剥がれが観られる、を表す。
以下の表に検証の結果を示す。 The determination as to whether or not it was suitable was made based on the adhesion of the Ni—SiC plating film. Moreover, verification was performed by JIS-H8504-11 (extrusion test method) shown in FIG.
For the extrusion test method, a flat bottom hole with a diameter of φ6.5 mm was left from the back side with respect to the plated surface, and then a sample was placed on a cradle with a hole with a diameter of φ25 mm, and a pin with a diameter of φ6.3 mm Is inserted into the hole in the flat bottom and punched out.
A change in the state of plating on the punched piece part was examined, and adhesion ◎ ○ × was determined.
◎ indicates that no peeling of the plating is observed, ○ indicates that peeling of the plating is partially observed, and × indicates that peeling of the plating is observed on the entire circumference.
The following table shows the results of verification.

上記した(表１)〜（表６）から明らかなように、リン酸と硝酸との混酸を使用する場合、リン酸については濃度を１０vol％以上２０vol％以下、硝酸については濃度を３vol％以上１２vol％以下とした混酸が好ましく、リン酸については１２vol％以上１８vol％以下の濃度とするのが更に好ましい。 As is clear from the above (Table 1) to (Table 6), when using a mixed acid of phosphoric acid and nitric acid, the concentration of phosphoric acid is 10 vol% or more and 20 vol% or less, and the concentration of nitric acid is 3 vol% or more. A mixed acid of 12 vol% or less is preferable, and phosphoric acid has a concentration of 12 vol% or more and 18 vol% or less.

但し、上記の範囲を検証したリン酸と硝酸の配合割合は、リン酸１に対し硝酸０．５〜２．０である。
尚、検証において液温については７０℃、処理時間は６０秒としたが、液温については５０℃まで下げ、処理時間については３０まで短縮しても同様の結果が得られた。 However, the mixing ratio of phosphoric acid and nitric acid for which the above range was verified is 0.5 to 2.0 nitric acid with respect to phosphoric acid 1.
In the verification, the liquid temperature was set to 70 ° C. and the processing time was set to 60 seconds. However, the same result was obtained even when the liquid temperature was reduced to 50 ° C. and the processing time was reduced to 30.

本発明に係るメッキ前処理工程は、例えばエンジンのシリンダブロックなどのアルミニウム合金製部材に施すメッキの前処理として利用することができる。
The plating pretreatment process according to the present invention can be used as a pretreatment for plating applied to an aluminum alloy member such as an engine cylinder block.

Claims

After degreasing the surface of the aluminum alloy, removal of the altered layer on the surface and removal of the aluminum alloy component are carried out. Thereafter, in the pre-plating treatment method for forming a base film on the surface, removal of the altered layer and removal of the aluminum alloy component By using a mixed acid of phosphoric acid having a concentration of 10 vol% or more and 20 vol% or less and nitric acid having a concentration of 3 vol% or more and 12 vol% or less as the treatment liquid, the deteriorated layer and the aluminum alloy are removed in one step. The plating pretreatment method characterized by the above-mentioned.