What is Electropolishing, Electrotyping, Electrofacing, Electrometallisation and Anodizing

Closely allied to bright dipping is electropolishing, which utilises anodic treatment in specially formulated electrolytes to bring up a polished surface on such metals as stainless steel. Electropolishing is also useful as a tool in preparing metallic surfaces for microscopic examination. Both bright dipping and electropolishing depend on the more rapid eating away by the solution of micro-projections on the metal, so that a smoother surface results.

Electropolishing has one advantage over buffing. Unlike buffing electropolished surfaces are free from cold worked surface cemented layer embedding abrasive particles of mop in the metal.

The process of polishing, in principle, consists of making the work as anode in a suitable electrolytic solution. This develops insoluble compounds that are broken down by more anodic action on the hills than on valleys of surface. Thus smooth surface is produced.

Electrotyping

This is a special application of electroforming and it is used to reproduce printers type, engraving and medals etc. The process is same as for electroforming.

Electrofacing

It is a process of coating of metallic surface with a harder metal by electrodeposition in order to increase its durability.

Electrometallisation

It is a process of depositing metal on conducting base for protection and decoration. Non-conductive base is made conductive by a coating of graphite employed as cathode.

Electrodeposition of Rubber

Rubber latex, as obtained from the tree, consists of very fine colloidal particles of rubber suspended in water. Like other colloidal solutions, particles of rubber are negatively charged. On electrolysis of the solution the rubber particles migrate towards the anode and deposit on it. Current density of roughly 100 A/m² is used.

Anodizing

Anodizing is a process of anodic oxidation in which a thin uniform passive (tough thin, uniform and impermeable) film is produced artificially by the passage of electric current. Passive film is formed to protect the base metal from further corrosion. In the process of anodizing electric current of 10 to 30 amperes per square metre is passed through an electrolyte of 3% solution of chromic acid for a period of half an hour to one hour, the article to be anodized is thoroughly cleaned and made anode and carbon rod is made cathode. Aluminium and magnesium have capacity of producing such passive films and, therefore, anodizing is applicable to them. In case of aluminium great feature of these coatings is their submicroscopic porosity. This makes the passive films to take dyes which are absorbed and affect the entire firm length.