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TECHNOLOGY ANODIATION OF ALUMINUM AND ITS ALLOYS
Glossary of terms
Parts and products made of aluminum and its alloys are oxidized in air, resulting in the formation of gray spots on the surface, which spoil the appearance.
Duraluminum (aluminum) will be more beautiful if it is subjected to anodization, as a result of which a delicate passive layer forms on the surface, which prevents further oxidation.
The anodized surface has a flattering gray paint. In addition, after anodizing, the aluminum product can easily be colored in any color with conventional aniline dyes.
First, separately prepare a pair of saturated solution - baking soda and sodium chloride - in boiled water at room temperature. To obtain a saturated solution, dissolution must be conducted no less than half an hour, periodically stirring the solution. After this, the solutions must stand for 15 minutes, and they must also be filtered.
Then, electrolyte is prepared by mixing the nine volume elements of the drinking soda solution plus one volume element of the salt solution (9: 1).
The electrolyte is mixed well in a glass bowl.
Before anodizing the part is carefully cleaned with a Fine sandpaper, degrease (it is possible in a hot detergent solution), plus it is washed in running water, after which it should not be touched by hands. Then the anodized part is immersed in the electrolyte solution, which is forced to be in an aluminum container. As a source of current, it is possible to use an adjustable 12 V rectifier also with a current of up to 2 A or a car battery.
The "plus" current source is connected to the part, "minus" - to the aluminum container with electrolyte. The current density should be about 15 mA / cm2. To fulfill this condition, the required current density must be multiplied by the surface area of the part in square centimeters. The current value calculated in this manner is maintained by adjusting the current source.
Anodization lasts about 90 minutes - until, until the part is covered with a bluish-gray coating. The anodizing process can be observed from the release of air bubbles and the appearance of a light gray coating on the surface of the anodized part.
After the anodization is completed, the part is washed in running water and is also cleaned with a cotton swab dipped in a solution of potassium permanganate, from the products of the electrochemical reaction. After that, the surface of the part is smooth, with a light gray tinge. The part is washed once more in running water and is also dried in air.
If desired, the part after anodizing can be stained in an aniline dye solution. The coloring solution contains 15 g of the dye also 1 ml of acetic acid per 1 liter of water.
Staining is performed in a heated solution up to 60 ... 80 ° C. The duration of aging in a solution depends on the required color saturation, and is usually 10 ... 15 min. to fix the color, the colored part is kept in boiling distilled water for 1 ... 1.5 min.
To protect the part from mechanical damage it is useful to paint it with colorless furniture varnish (NC).