Electrolytic Methods of Restoration

Electropolishing is a process where the specimen is made the anode in an electrochemical cell. When a current is applied, minute irregularities in the surface are dissolved, leaving a highly polished surface.

As the electrical properties of the stamped area are minutely altered due to the compressed crystalline structure, the dissolution of the compressed area will be different from that in the non -compressed area. This was first developed about 25 years ago (Arai and Shegio, 1953) and has proved to be a successful method for serial number restoration.

In this method, the specimen is made the anode, and a cotton swab containing the electrolytic solution becomes the cathode. An external variable DC voltage is applied and adjusted to be just greater than the minimum voltage necessary for the current to flow. This is called the critical voltage. For steel, the critical voltage is approximately 6 V, for brass 7 V and aluminium 7.5 V.

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