Metal surface treatment - metal finishing

Japanese: 金属表面処理 - きんぞくひょうめんしょり（英語表記）metal finishing

A general term for methods of processing the surface of metal materials to improve the metal's corrosion resistance or to give it new properties or functions. The chemical and physical properties of metal materials depend heavily on the condition of their surface, and changing the condition of the surface can greatly change these properties. For this reason, surface treatment techniques are used to give materials high corrosion resistance, heat resistance, beautiful appearances, or special functions that cannot be achieved with a single material. Industrial surface treatment techniques include surface cleaning, polishing, etching, electrodeposition, chemical conversion coating, vapor deposition, fusion coating, diffusion penetration, lining (attaching another material to the surface of an item), coating, etc.

[Katsuhisa Sugimoto]

Surface Cleaning

It is used as a pretreatment for all surface treatments. For rust removal, pickling or immersion in a molten salt bath is used. For degreasing, cleaning with organic solvents, alkali, emulsion, etc., electrolytic degreasing in an alkaline aqueous solution, ultrasonic cleaning in an organic solvent, etc. are used.

[Katsuhisa Sugimoto]

Polishing

Polishing is done to smooth and polish the surface of a material. There are various types of polishing: mechanical polishing using a polishing machine and abrasives, electrolytic polishing in which metal is electrolyzed in an electrolyte using the metal as the anode, and chemical polishing that uses the dissolving action of chemicals.

[Katsuhisa Sugimoto]

etching

This is done to chemically dissolve and remove part of the metal surface. Examples include shallow etching with acid to remove layers that have been affected by machining, or to draw special patterns on the surface. When deep etching is used to create molded products, it is called chemical milling.

[Katsuhisa Sugimoto]

Electroplating

A method of forming a metal coating by electrodepositing a metal from an electrolytic solution. There are two types of plating: electroplating, in which an external power source is used to electrolyze the plating bath and deposit the metal on the cathode, and chemical plating, in which a chemical with a strong reducing effect is added to the plating bath, which reduces the metal ions and deposits the metal.

[Katsuhisa Sugimoto]

Chemical Treatment

A treatment method that uses chemical or electrochemical reactions to form a non-metallic coating on a metal surface. Examples include anodizing, in which aluminum is used as the anode in various acid solutions and electrolysis is performed to form a thick aluminum oxide film, phosphate treatment, in which steel is immersed in a phosphate solution to form a phosphate film, and chromate treatment, in which zinc or aluminum is immersed in a chromate solution to form a chromium oxide film.

[Katsuhisa Sugimoto]

Evaporation

A method of obtaining a metallic or nonmetallic coating by precipitating the target substance from the vapor of a metallic or nonmetallic substance. There are physical vapor deposition (PVD) methods that use physical techniques such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition (CVD) methods that form coatings using chemical reactions between gaseous substances or between a gaseous substance and a metal substrate.

[Katsuhisa Sugimoto]

Melt Coating

There are two methods: hot-dip plating, in which steel is immersed in a molten metal bath to form a coating, and thermal spraying, in which molten metal is sprayed onto the steel surface to form a coating. Molten coatings used include zinc, tin, aluminum, and lead.

[Katsuhisa Sugimoto]

Diffusion and penetration

This is a method of heating steel in a powder or gas of another metal, and diffusing and penetrating the metal into the steel to form an alloy layer on the surface that has excellent heat resistance, corrosion resistance, and wear resistance. Diffusion and penetration of aluminum, chromium, zinc, etc. is used.

[Katsuhisa Sugimoto]

Linings and Coatings

A method of forming a coating by attaching a plate-shaped nonmetallic material to a metal surface or by spreading a thin layer of a liquid nonmetallic material on the surface. Coatings such as rubber, plastic, glass, enamel, ceramics, and inorganic and organic paints are made using this method.

[Katsuhisa Sugimoto]

[Reference items] | Polishing | Vapor deposition | Plating | Hot-dip plating

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

金属材料の表面に加工を施して、金属の耐食性などを向上させたり、新たな性質や機能を与える方法の総称。金属材料の化学的あるいは物理的性質はその表面の状態に大きく依存しており、表面の状態を変えることによってこれらの性質を大きく変えられる。このため、表面処理技術により、単独の材料では望めない高い耐食性や耐熱性、美しい外観、あるいは特殊な機能を材料に付与することが行われる。工業的表面処理技術には、表面清浄化、研摩、エッチングetching、電着、化成処理、蒸着、溶融被覆、拡散浸透、ライニングlining（品物の面に他材料を張り付けること）、コーティングなどの技術が含まれる。

［杉本克久］

表面清浄化

あらゆる表面処理の前処理としてなされる。除錆(じょせい)のためには酸洗い（ピックリングpickling）や溶融塩浴浸漬(しんし)処理などが行われる。脱脂のためには有機溶剤、アルカリ、エマルジョンなどによる洗浄、アルカリ水溶液中での電解脱脂、有機溶剤中での超音波洗浄などがある。

［杉本克久］

研摩

材料表面の平滑化と光沢化とのために行われる。研摩機と研摩材とを用いる機械的研摩、電解液中で金属を陽極にして電解する電解研摩、化学薬品の溶解作用を利用する化学研摩などがある。

［杉本克久］

エッチング

金属表面の一部分を化学的に溶解除去するために行われる。機械加工で生じた変質層を除いたり、あるいは表面に特殊な図案を描くためになされる酸による浅い食刻がこれに相当する。深い食刻によって成形品をつくる場合にはケミカルミリングchemical millingとよばれる。

［杉本克久］

電着

電解液中から金属を電析させて金属被覆を形成する方法。外部電源を用いてめっき浴を電解し陰極上に金属を析出させる電気めっき法と、めっき浴中に還元作用の大きな薬剤を添加し、これによって金属イオンを還元し金属を析出させる化学めっき法とがある。

［杉本克久］

化成処理

化学的あるいは電気化学的反応を利用して金属表面に非金属被覆を形成する処理法。各種の酸溶液中でアルミニウムを陽極にして電解し厚い酸化アルミニウム皮膜を形成させる陽極酸化処理、鉄鋼をリン酸塩溶液中に浸漬してリン酸塩皮膜を形成させるリン酸塩処理、亜鉛やアルミニウムをクロム酸塩溶液中に浸漬してクロム酸化物皮膜を形成させるクロメート処理などがある。

［杉本克久］

蒸着

金属あるいは非金属物質の蒸気から目的物質を析出させて金属あるいは非金属の被覆を得る方法。真空蒸着、スパッタリングspattering、イオンプレーティングionplatingなどの物理的な手法を使う物理蒸着法（PVD法）と、気体状物質どうしあるいは気体状物質と金属基板との化学反応を利用して被覆を形成する化学蒸着法（CVD法）とがある。

［杉本克久］