Electrolytic Preparation

About Electrolytic Preparation

A fast and efficient method.

Electrolytic preparation is a fast and efficient method for metallographic preparation, providing a deformation-free surface, whereas mechanical grinding and polishing tends to leave a thin deformation layer at the surface.

Using the electrolytic polishing equipment, the specimen is configured as the anode in a suitable electrolyte, and material is removed by controlled dissolution of the surface of the specimen. Electrolytic polishing can be followed by an electrolytic etching process to bring forth contrasts in the microstructure of the specimen.

How to Do Electrolytic Preparation

To do electrolytic preparation, the right method needs to be selected. Struers’ equipment contains ten standard methods for different materials. If these standard methods do not fit the material, a correct electrolyte can be selected from the Selection of Electrolyte list. Having selected the correct electrolyte for your purpose, it is necessary to determine the polishing voltage. This is done using a scan function that is built into the electrolytic preparation equipment.

Correct application settings

After placing a specimen on the polishing table, a pre-defined voltage range is scanned to determine the current density curve. This curve is used to define the correct polishing voltage for the polishing or thinning process. The other parameters to be determined are polishing time and the flow rate. Once the correct application settings have been determined, they can be stored in the database and recalled for subsequent polishing tasks.

Safety is important.

Safety is a key word when dealing with electrolytes, and all users must be familiar with the relevant safety procedures.

How to do electrolytic preparation
How to Do Electrolytic Preparation

Selection of Electrolyte

Several materials can be polished/etched with more than one of the electrolytes.
The right choice depends on the composition of the material and what you want to see.

Electrolyte-tabel

Troubleshooting

Problem

Surface not polished or only  partly polished
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Cause:
Current density insufficient
Solution:
Adjust the voltage.

Cause:
The electrolyte is too old.
Solution:
Renew the electrolyte.

Cause:
Insufficient quantity of electrolyte.
Solution:
Add the electrolyte.
Spots that have not been  polished
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Cause:
Gas bubbles
Solution: 
- Adjust the flow rate.
- Check the electrolyte temperature.
- Decrease the voltage. 
Etching of the polished  surface
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Cause:
Chemical attack of grain  boundaries after switching of f the current. 
Solution:
- Remove the specimen  immediately when the curren t is switched off. 
- Choose a less corrosive  electrolyte.
Phases in relief
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Cause:
Polishing film is inadequate.
Solution:
- Increase the voltage.
- Improve the mechanical preparation of the specimen.

Cause:
The polishing time is too long.
Solution:
Reduce the polishing time.
Pitting
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Cause:
The polishing time is too long.
Solution:
- Improve the mechanical preparation.
- Decrease the time.

Cause:
The voltage is too high.
Solution:
Lower the voltage.

Cause:
Insufficient anodic layer.
Solution:
- Reduce the flow rate.
- Use a different electrolyte.
Attack at the edge of the  specimen.
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Cause:
The film is too viscous or too thin.
Solution:
- Decrease the voltage.
- Increase the flow rate.
The center of the specime n is deeply attacked or not polished at all.
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Cause:
Polishing the film did not for m in the center of the specimen.
Solution:
- Increase the voltage.
- Reduce the flow rate.
- Add more electrolyte.
Deposits on the surface
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Cause:
Insoluble reaction products.
Solution:
- Renew the electrolyte or try a different one.
- Increase the voltage.
Wavy surface or residual  deformation
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Cause:
The polishing time is too short.
Solution:
Increase the time.

Cause:
The flow rate is too high or too low.
Solution:
Change the flow rate.

Cause:
Rough surface after grinding.
Solution:
Improve the preparation prior to electrolytic polishing.

Cause:
The electrolyte is too old.
Solution:
Renew the electrolyte.

Cause:
Selective polishing because of potential differences in surface (heterogeneous material).
Solution:
Use another electrolyte with other polishing data or use a mechanical preparation instead.
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Helle Michaelsen

Helle Michaelsen

Global Business Solution & Application Manager
Struers Aps.
Ballerup, Denmark
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Birgitte Nielsen

Birgitte Nielsen

Metallographer,
Application Specialist
Struers ApS
Ballerup, Denmark
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Farouk Mouzafer

Farouk Mouzafer

Metallurgical and Materials Engineer,
Application Specialist
Struers ApS
Ballerup, Danmark
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Olafsson Olafur

Òlafur Magnús Òlafsson

PhD in Mechanical Engineering,
Application Specialist
Struers ApS
Ballerup, Denmark
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Patrick Toser

Patrik Tősér

MSc in Petroleum Engineering,
Application Specialist
Struers ApS, Denmark
Ballerup, Denmark
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Henry Udomon

Henry Udomon

PhD in Metallurgical Engineering,
Applications Manager
Struers Inc.
Cleveland, Ohio, US
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Kelsey Torboil

Kelsey Torboli

B.S. in Material Science,
Senior Applications Engineer
Struers Inc.
Cleveland, Ohio, US
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Brian Jones

Brian Jones

Applications Engineer
Struers Inc.
Cleveland, Ohio, US
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Caroline Horn

Caroline Horn

B.S. in Materials Science and Engineering,
Applications Engineer
Struers LLC, United States
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Reese Capo

Reese Capo

M.S. in Materials Science and Engineering,
Applications Engineer
Struers Inc.
Cleveland, Ohio, US
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Holger Schnarr

Holger Schnarr

Dr. Material Science,
Lab Manager
Struers GmbH
Willich, Germany
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Kinichi Ishikawa

Kinichi Ishikawa

M.S. in Materials Science,
Lab Manager
株式会社ストルアス
Tokyo, Japan
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Xiuping Jiang

Xiuping Jiang

PhD, MSc in Material Science,
Application and Laboratory Manager
Struers Ltd.
Shanghai, China
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