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Students of electrochemistry know that there exists a potential difference between iron and other metals and that a metal can be deposited by application of a suitable external potential. We have developed a simple and useful method of permanently labeling metallic items by the application of alternating current through a mask. The mechanism may be somewhat similar to that by which aluminum is “anodized” to make the oxide surface harder and more accepting of color (1). The method to print or engrave any black text on an iron or stainless steel surface is as follows: Cut a stencil with the label to be written from any dielectric material, such as thin plastic sheet or paper. Clean the surface to be engraved of any grease or dust. Place the stencil on the surface. On top of the stencil, place a cloth or tissue paper soaked in salt water. Place a sheet of copper on top of the dielectric material. Apply 12 V ac at 1 A between the copper and the iron or steel object. Within a few minutes (depending on the area being covered), the text is marked or engraved on the surface. Figure 1 depicts the arrangement for our method. Students may enjoy experimenting with the parameters to modify or improve the technique.
Figure 1. Schematic of layers to engrave a metal: (top) expanded view and (bottom) side view.
Literature Cited- Grotz, L. C. J. Chem. Educ. 1983, 60, 763.
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