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Ways of drawing convex and concave inscriptions and drawings on metal

Ways of drawing convex and concave inscriptions and drawings on metal

Labels on metal plates, making scales and simply drawings on a metal surface can be made by etching (chemical milling, engraving).

Chemical milling can also be used to reduce the thickness of the metal walls of parts, increase the diameter of the holes or reduce the diameter of the rods, bolts and pins.

Making an inscription or a picture on an aluminum panel (convex image - chemical milling). The surface of the metal is polished, washed with water and dried. Then it is labeled or patterned with any alcohol varnish, after which the panel is etched in alkali. Metal, protected by varnish, alkali, is not etched, and the inscriptions are convex.

Aluminum and its alloys are best etched with 10-15% sodium hydroxide solution. It should be remembered that such milling is very slow. When the solution is heated to 60-80 ° C in 20 minutes, a metal can dissolve 1 mm .

After etching, the panel is thoroughly washed with water and polished.

Making an inscription or a picture on a brass panel (depth image - chemical engraving). The metal panel is polished, washed with water and dried. Then warm up to a temperature of 60-70 ° C and cover with a layer of paraffin, which, melting, smoothly spreads over the entire surface. On the paraffin-covered panel, an inscription or figure is translated through a carbon paper. Further, with the tip of the needle and the tip of the penknife, carefully remove the paraffin layer from the inscription or drawing, which must be deepened (etched).

At the edges of the panel of softened paraffin, make a bead 8-10 mm high ( Fig. ). After that, a 50% solution of nitric acid is poured onto the panel, which dissolves (etches) the metal in paraffin-free places, forming an inscription or picture. By tilting the panel, you can see whether the inscription or drawing has been etched out enough.

Attention! The panel can be etched with nitric acid only under the hood or outdoors.

When the etching is complete, the solution is poured and the panel is thoroughly washed. The remaining wax is easily removed by placing the panel in hot water heated to a temperature of 90 ° C , and wiping it with a dry rag with chalk. To protect the panel from oxidation, it is covered with a clear varnish.

Pickling solutions for chemical milling

Metal

Pickling solution

Brass and bronze

50% acid solution

Aluminum and duralumin

10-15% solution of caustic soda

Copper

70% solution of ferric chloride with the addition of 0.3-0.35% hydrochloric acid

Zinc

8-12% alcohol solution of hydrochloric acid