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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

The inscriptions on metal plates, making scales and just drawings on a metal surface can be performed 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 rods, bolts and pins.

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

Aluminum and its alloys are better to etch 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 the metal can dissolve 1 mm .

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

Making inscriptions or drawings on the brass panel (in-depth image - chemical engraving). The metal panel is polished, washed with water and dried. Then it is heated to a temperature of 60–70 ° C and covered with a layer of paraffin, which, having melted, spreads evenly over the entire surface. On the coated with paraffin panel translate through carbon paper lettering or drawing. Next, with the tip of the needle and the tip of a penknife, carefully remove the layer of paraffin from the inscription or design, which should be in-depth (etched).

Along the edges of the softened paraffin panel, make a 8–10 mm high rim ( fig. ). After that, a 50% solution of nitric acid is poured onto the panel, which dissolves (herbal) the metal in the areas free from paraffin, forming an inscription or drawing. Having inclined the panel, it is possible to observe, whether the inscription or drawing was etched enough.

Attention! To poison the panel with nitric acid is possible only under the hood or in the open air.

When the etching is finished, the solution is poured, and the panel is washed thoroughly. The remaining paraffin is easy to remove, putting 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 coated with clear varnish.

Pickling solutions for chemical milling

Metal

Pickling solution

Brass and bronze

50% acid solution

Aluminum and duralumin

10–15% caustic soda solution

Copper

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

Zinc

8–12% alcoholic solution of hydrochloric acid