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What is Electropolishing and what is it used for?

Electropolishing is a material removal process using an electrically powered chemical process called electrolysis. In this process the amount of material being removed is very small as it is done for polishing purposes only. A negatively charged copper electrode and positively charged workpiece are dipped into a solution of fast flowing electrolyte solution. When connected to the battery power the working surface starts to dissolve into the solution.

The process of Electropolishing

The electropolishing process involves the removal of material via diffusion from the workpiece into an electrolyte solution. The elements required are as follows:-

The power source is usually a direct current. The negative point is connected to two or more copper cathodes and the positive terminal to the workpiece. At this moment the workpiece is surrounded by copper cathodes. The system also contains a heating system as the electrolytes need to be at a high constant temperature. There is also a pump or stirrer to move the electrolytes during the process.

Material diffused in this process does not deposit onto the cathode. It simply remains in the electrolyte solution – a proper sludge tank and filter mechanism is also part of the system. The sludge tank takes input from main tank and the suction pump forces the fluid through the filter. After filtration the fluid moves to the heat exchanger where it is reheated before running back into the system. As this process is controlled by the direct current, the amount of material being removed depends on the current intensity.

The graph below shows the current intensity relation with anode potential. Between the area from zero to A only smoothing of a work piece can be done and between B and C the process of polishing occurs.

Applications for Electropolishing

Materials

Any material which can conduct electricity can benefit from this process. Some common materials are:-

Mechanical Design Guidelines

Electropolishing Process Variations

The process of electropolishing is basically controlled by seven different parameters which directly impact the results achieved. Those parameters are as follow:-

For a particular material which needs to be polished using this process there are some specific acids which can be used. The current and voltage density will be set as a consequence of the surface conditions.

Economics of the Process

Advantages of Electropolishing

Disadvantages of Electropolishing