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Electro Polishing

Electrolytic polishing effective for high hygiene control and stability of product composition

Electro polishing removes fine burrs and particles in objects and forms a chromium-rich passivation film with excellent corrosion resistance. It is very effective for high hygiene management and stability of product composition that can be found in manufacturing facilities such as chemicals, medicine, semiconductors and beverages plants. We manufacture jigs and electrodes according to various shapes and sizes, and also perform electrolytic polishing of fine piping.

In particular, our Sasayama Factory has been working as a specialized factory of Electro Polishing (EP) for more than 30 years since 1985 to study electropolishing technology and accumulate know-how. We have received high evaluations from customers on the variety of the polished products and quality of product finish.

EP(Electrolytic polishing)

Nissho Astec’s Electro Polishing (EP) is effective in producing sanitary products and stable process piping and tanks!

EP forms a passivated film that has a high level of chromium concentration on the surface of stainless steel by an electrolytic reaction. This passivated film is very strong in terms of corrosion resistance, etc., and produces a smooth glossy surface. However, high technology is required to form a uniform film layer on the inside surface of stainless steel tubes and products with complicated shapes. Since its commercialization in 1985, Nissho Astec Co., Ltd. has been working to improve the quality of electropolishing variations and other processes.

Benefits and Features of Electro Polishing

Features of Electrolytic Polishing

  • The treated surface is extremely smooth (lubricant)

  • Existence of a dense passivation film

  • Existence of a highly-condensed chromium layer with great corrosion resistance


  • Improvement of Washing Efficiency

  • Difficult-to-adhere for fine powder

  • Strong rust prevention effect

  • Improvement of chemical resistance

  • No work-affected layer

Installation of Electro Polishing Anode Cathode

Electro Polishing (EP) is the process of putting certain materials into the electrolytic liquid and let electric current passes through that liquid.

For materials with complicated shapes, the finish after being electrolytic polished will change depending on the shape and arrangement of the electrodes.

EP is the electrochemical process used for treating micro irregularities, not for removing large irregularities.

It is necessary to pre-treat the stainless steel material beforehand by, for example, buffing.

Principal of Electro Polishing (EP)

Characteristics of the Mucus Layer:

1. Creation of an initial oxidizing zone with a viscous surface in electrolyte

2. The interface formed between polished surface and electrolyte becomes an almost-flat surface

3. The Mucus layer has electrical resistance larger than almost a digit than that of electrolyte

The top part which allows electric to easily pass through is dissolved, which later results in a flat surface.

Chromium-enriched Surface:

1. Easy-to-electrolyte iron will have a layer with high chromium concentration after being eluted

2. Thickness: 10~20Å, colorless and transparent

3. Chromium oxidizes faster than iron

Formation of passive state film
A strong passive state film of chromium oxide is formed due to chromium enrichment of the stainless steel surface.

Before-and After-Electro Polishing Photos of Sanitary Pipe

State of surface of stainless steel material after chromium-enrich Electro Polishing

Example of measurement of sample polished products

Explanation of Technical Symbol

Å (Angstrom)
1 Å = 10^-10 meters

Angstrom (Å), unit of length used chiefly in measuring wavelengths of light, equal to 10−10 metre, or 0.1 nanometer. It is named for the 19th-century Swedish physicist Anders Jonas Ångström. The angstrom and multiples of it, the micron (104 Å) and the millimicron (10 Å), are also used to measure such quantities as molecular diameters and the thickness of films on liquids. (According to Britannica Encyclopedia)

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