JP2006291273A - Plating method for base material made from aluminum alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plating method for a base material made from an aluminum alloy, which does not use nitric acid and fluoric acid for a pretreatment liquid for plating, thereby reduces an environmental load, improves a working environment, reduces a chemical cost, reduces a waste liquid treatment cost and imparts adequate adhesiveness to a plated film. <P>SOLUTION: When plating the material made from the aluminum alloy, this plating method includes the pretreatment step of cathodically electrolyzing the aluminum alloy in an acidic solution, which has been treated in an alkali etching step, in order to remove insoluble components in the alloy formed in the etching step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plating method for performing wear-resistant plating on an aluminum alloy material, and more particularly, to a plating method for an aluminum alloy material that can reduce the environmental load in plating pretreatment.

  Conventionally, wear-resistant plating (iron plating 4) is applied to an aluminum alloy material, for example, a cylinder 1 for an internal combustion engine such as a Schnure scavenging type small air-cooled two-cycle gasoline engine as shown in FIG. As described in the following Patent Document 1, etc., the pretreatment (base treatment) is performed in order to improve the adhesion (biting property) of the plating 4 to the material surface 3 before the plating step. It is common to do it.

  Such plating pretreatment is performed, for example, in the order (process) and processing conditions as shown in Table 1 below. That is, the aluminum alloy material 1 is degreased, washed with water after the degreased material 1 is subjected to alkali etching, the alkali-etched material 1 is washed with water, and then generated in the alkali etching step. The insoluble components (smut: Si, Cu, Fe, Mn, etc.) in the raw material (aluminum alloy) 1 are dissolved and removed with a mixed solution of nitric acid, hydrofluoric acid and sulfuric acid (acid corrosion) ) Thereby, the material surface 3 is cleaned, and minute irregularities are formed on the material surface 3. Then, after washing with water, an anodizing process is performed. As a result, an oxide film is formed on the material surface 3, and holes are formed in portions corresponding to the minute irregularities in the oxide film. After the material 1 in which such holes are formed is washed with water, iron plating 4 is applied to the surface thereof. In this case, since the iron plating 4 (the lowermost layer portion) penetrates into the holes and the unevenness, a high anchor effect is obtained, and the adhesion (biting property) of the plating 4 is improved. .

Japanese Patent Laid-Open No. 3-191095

  However, the above-described conventional plating method has the following problems to be improved.

  That is, the insoluble component (smut) in the aluminum alloy generated in the alkali etching step is dissolved and removed (acid erosion) with a mixed solution of nitric acid, hydrofluoric acid, and sulfuric acid. Nitric acid used in Japan is a nitrogen regulation for the eutrophication problem of seawater, and hydrofluoric acid is a type 1 designated chemical substance designated by the PRTR method, and both are used to reduce environmental impact There is a strong demand for reduction, and there is an urgent need for measures that do not use nitric acid and hydrofluoric acid for plating (pretreatment) of aluminum alloy materials.

  Further, it is desired that nitric acid and hydrofluoric acid should not be used as much as possible from the viewpoint of the working environment, such as the safety of workers involved in the plating pretreatment, as well as the natural environmental problems.

  Furthermore, the desmutting treatment by erosion is low in stability and the etching depth involved in the adhesion of the plating varies, making it difficult to manage and sufficient anchor effect for plating applied to the aluminum alloy material. Was not obtained, and there were not a few cases where adhesion of plating was poor.

  In addition, the life of the chemical used for the acid corrosion (mixed solution of nitric acid, hydrofluoric acid and sulfuric acid) is relatively short, and waste water containing hydrofluoric acid has a great time and cost for detoxification treatment. For this reason, there is a dislike that the chemical cost and the wastewater treatment cost become high.

  The present invention has been made in view of the problems as described above. The object of the present invention is to avoid the use of nitric acid and hydrofluoric acid in the plating pretreatment, thereby reducing the environmental burden and improving the working environment. Another object of the present invention is to provide a plating method for an aluminum alloy material that can reduce chemical costs and wastewater treatment costs and that can obtain good plating adhesion.

  In order to achieve the above object, the method for plating an aluminum alloy material according to the present invention is basically an aluminum alloy produced by an alkali etching process as a pretreatment when plating an aluminum alloy material. In order to remove insoluble components in the alloy, cathodic acid electrolysis is performed.

  In a more preferred embodiment, the step of degreasing the material, the step of subjecting the material subjected to the degreasing treatment to alkali etching, the step of subjecting the material subjected to the alkali etching to cathodic acid electrolysis treatment, and the cathodic acid The process includes an anodizing process on the electrolytically treated material and a plating process on the anodized material.

  The cathodic acid electrolysis is preferably performed in a ferric sulfate solution using the aluminum alloy material as a cathode.

  Examples of the aluminum alloy material include a cylinder for an internal combustion engine (such as a small air-cooled two-cycle gasoline engine cylinder), and the piston sliding surface of the cylinder is plated.

  The cylinder for an internal combustion engine according to the present invention is obtained by iron-plating the piston sliding surface by the plating method described above.

  In the method for plating an aluminum alloy material according to the present invention, insoluble components (smuts: Si, Cu, and the like) generated in the alkaline etching process by cathodic acid electrolysis instead of the acid corrosion performed in the conventional plating pretreatment. Fe, Mn, etc.) are removed. More specifically, for example, cathodic acid electrolysis is performed in a ferric sulfate solution using the material as a cathode, and the insoluble components are physically removed using hydrogen gas generated during the treatment. To be. For this reason, it is not necessary to use nitric acid and hydrofluoric acid for the plating pretreatment. As a result, it is possible to reduce the environmental load and improve the working environment, and to reduce the chemical cost and the wastewater treatment cost.

  In addition, the etching depth involved in plating adhesion is determined by the processing conditions (concentration, temperature, and time of chemicals used (caustic soda, etc.) used in the alkaline etching process). In the cathodic acid electrolysis process, hydrogen gas is generated. Etching alone does not proceed, so that the etching depth can be managed easily and accurately. Therefore, a high anchor effect is obtained for the plating applied to the aluminum alloy material, and the adhesion (biting property) of the plating becomes good.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  One embodiment of the plating method according to the present invention is an aluminum alloy material, for example, a Schnure scavenging small air-cooled two-cycle gasoline engine used in a handheld portable working machine such as a brush cutter as shown in FIG. This is applied when wear-resistant plating (iron plating) 4 is applied to the sliding surface 3 of the piston 2 of the cylinder (die casting cylinder of the ADC 12), and in the order (process) and processing conditions as shown in Table 2 below. Done.

すなわち、まず、前記素材（シリンダ１のピストン２の摺動面４）に脱脂処理を施す。この脱脂処理は、前述した従来のめっき方法（表１参照）と同様に、例えば、カニング社製のボンダルクリーナ（苛性ソーダ）：２．５ｇ／Ｌ（リットル）を用いて、５０°Ｃで４５〜５５秒行う。該脱脂工程では、図１に図面代用写真（素材表面の脱脂後の走査電子顕微鏡写真：ＳＥＭ×１６００）で示される如くに、脱脂のみが行われ、エッチングは進行しない。

That is, first, the material (the sliding surface 4 of the piston 2 of the cylinder 1) is degreased. This degreasing treatment is performed at 45 ° C. at 50 ° C. using, for example, a bondal cleaner (caustic soda): 2.5 g / L (liter) manufactured by Canning, in the same manner as the above-described conventional plating method (see Table 1). Do ~ 55 seconds. In the degreasing step, only degreasing is performed, and etching does not proceed as shown in the drawing substitute photograph (scanning electron micrograph after degreasing the material surface: SEM × 1600) in FIG.

  After the degreased material 1 is washed with water, alkali etching is performed. This alkaline etching step is also performed for 45 to 55 seconds at 60 ° C. using, for example, a Bondal cleaner (caustic soda): 25 g / L manufactured by Canning, similarly to the above-described conventional plating method (see Table 1). .

  In the alkali etching step, as shown in FIG. 2 (photograph of scanning electron micrograph after alkali etching of the material surface: SEM × 1600), the surface of the material is etched by the caustic soda component, and the aluminum alloy contains Insoluble components (Si, Cu, Fe, Mn, etc.) remain on the surface layer as smut.

  Subsequently, after washing the material 1 subjected to the alkali etching with water, the insoluble components (smut: Si, Cu, Fe, etc.) in the material (aluminum alloy) 1 produced in the alkali etching step (residual on the surface layer) 1 Cathodic acid electrolysis is performed to remove Mn and the like. Specifically, FE agent (scale remover) made of Chuo Kagaku made of ferric sulfate, nonionic surfactant, and sulfuric acid as a component: 30%, and EBR agent (acid electrolysis additive): In a 3% aqueous solution (ferric sulfate solution), the material 1 is used as a cathode and a voltage of 6 to 12 V is applied at 25 to 60 ° C. for 30 to 90 seconds. In the cathodic acid electrolysis step, the smut is physically formed by hydrogen gas generated from the cathode, as shown in a drawing substitute photo (scanning electron micrograph after cathodic acid electrolysis of the material surface: SEM × 1600) in FIG. The fine irregularities that are optimal for improving the adhesion of the plating (improving the anchor effect) are formed on the surface of the material.

  Subsequently, after rinsing with water, an anodic oxidation treatment is performed. This anodic oxidation step is performed for 50 seconds by applying a voltage of 6 to 12 V at 55 ° C. using 50 g / L of phosphoric acid in the same manner as the above-described conventional plating method (see Table 1). As a result, an oxide film is formed on the material surface 3, and holes are formed in portions corresponding to the minute irregularities in the oxide film.

  After the material 1 in which such holes are formed is washed with water, iron plating 4 is applied to the surface thereof. In this case, as shown in FIG. 4 which is a drawing substitute photograph (scanning electron micrograph of the surface layer of the plated material: SEM × 1150), the iron plating 4 (the lowermost layer portion) fills the holes and irregularities. So that it has invaded it. Therefore, it was confirmed that a high anchor effect was obtained for the plating 4 and the adhesion (biting property) of the plating 4 was good.

  In the plating method of the present embodiment, insoluble components (smut: Si, Cu, Fe, Mn, etc.) generated in the alkali etching process by cathodic acid electrolysis instead of the acid corrosion performed in the conventional plating pretreatment. To be removed. More specifically, cathodic acid electrolysis is performed in a ferric sulfate solution using the material 1 as a cathode, and the insoluble components are physically removed using hydrogen gas generated during the treatment. Is done. For this reason, it is not necessary to use nitric acid and hydrofluoric acid for the plating pretreatment. As a result, it is possible to reduce the environmental load and improve the working environment, and to reduce the chemical cost and the wastewater treatment cost.

  In addition, the etching depth involved in plating adhesion is determined by the processing conditions (concentration, temperature, and time of chemicals used (caustic soda, etc.) used in the alkaline etching process). In the cathodic acid electrolysis process, hydrogen gas is generated. Etching alone does not proceed, so that the etching depth can be managed easily and accurately. Therefore, a high anchor effect is obtained for the plating applied to the aluminum alloy material, and the adhesion (biting property) of the plating becomes good.

  As mentioned above, although one Embodiment of this invention was explained in full detail, this invention is not necessarily limited to the said embodiment, Processing conditions, such as a kind and quantity of the chemical | medical agent used at each process, are required plating. Of course, various changes can be made according to the specifications and the like.

The scanning electron micrograph which shows the raw material surface after degreasing in one Embodiment of the plating method of the aluminum alloy raw material which concerns on this invention. The scanning electron micrograph which shows the raw material surface after the alkali etching in one Embodiment of the plating method of the aluminum alloy raw material which concerns on this invention. The scanning electron micrograph which shows the raw material surface after cathodic acid electrolysis in one Embodiment of the plating method of the aluminum alloy raw material which concerns on this invention. The scanning electron micrograph which shows the raw material surface layer cross section after plating in one Embodiment of the plating method of the aluminum alloy raw material which concerns on this invention. The longitudinal cross-sectional view of the cylinder for internal combustion engines as an aluminum alloy raw material which applies one Embodiment of the plating method of the aluminum alloy raw material which concerns on this invention.

Claims (5)

  In performing the plating (4) on the aluminum alloy material (1), as a pretreatment, cathodic acid electrolysis is performed to remove insoluble components in the aluminum alloy generated in the alkali etching step. Plating method for aluminum alloy material.   A method of plating an aluminum alloy material (1), the step of degreasing the material (1), the step of performing alkali etching on the material (1) subjected to the degreasing treatment, and the step of performing the alkali etching. The step of subjecting the material (1) to cathodic acid electrolysis treatment, the step of subjecting the material (1) subjected to cathodic acid electrolysis treatment to anodization treatment, and plating the material (1) subjected to this anodization treatment ( The method for plating an aluminum alloy material according to claim 1, comprising the step of 4).   3. The method for plating an aluminum alloy material according to claim 1, wherein the cathodic acid electrolysis is performed in a ferric sulfate solution using the aluminum alloy material (1) as a cathode.   The aluminum alloy material is an internal combustion engine cylinder (1), and the piston sliding surface (3) of the cylinder (1) is plated (4). The method for plating an aluminum alloy material according to the item.   A cylinder for an internal combustion engine, wherein the piston sliding surface (3) is subjected to iron plating (4) by the plating method according to claim 4.

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