Aluminum plate before the reaction principle and process

Commercially available aluminum surfaces often have many scratches, irregularities, and poor smoothness. Before the nameplate is produced, it needs to be polished to improve the finish. Aluminum polishing is commonly used in tri-acid polishing solutions (70% phosphoric acid, 20% sulfuric acid, and 10% nitric acid). Due to the presence of nitric acid components, a large amount of nitrogen oxide compounds are precipitated during the polishing process. The yellow-brown smoke seriously pollutes the air. Operators are healthy, so many chemical plants have developed acid mist inhibitors, but the effect is not satisfactory.

Aluminum is an amphoteric metal that reacts with both acid and alkali, while the alkaline polishing solution overcomes the shortcomings of yellow smoke produced by the tri-acid polishing solution and effectively eliminates scratches (triacid polishing fluid does not eliminate scratches. ), The aluminum surface is bright and smooth, and the aluminum alloy has a sand surface effect.

First, the reaction principle

The chemical polishing reaction process is a self-dissolution process of a metal in an electrolyte solution. Since the dissolution rate of the microscopic convex portion of the metal surface is faster than the dissolution rate of the concave portion? On the one hand, the activity of the metal atoms in the microprotrusions is greater than that of the metal atoms in the recesses, so that the dissolution rate of the convex portions is faster than that of the concave portions. On the other hand, due to the reaction process, The colloidal compound is produced. It deposits in the concave portion and inhibits dissolution of the metal in the concave portion. Therefore, the dissolution rate of the microscopic convex portion is faster than that of the concave portion. On the other hand, due to the microscopic convex portion and the When the electrolyte solution is fully contacted, the reactants can rapidly diffuse into the solution, so that the microscopic convex portion dissolves faster than the concave portion.

Second, the process

1. Aluminum parts to oil formulation: trisodium phosphate 50~60g/L
Sodium carbonate 30~40 g/L
Sodium silicate 10~15g/L
Temperature room temperature 30~60S (seconds)

2. Pickling formula: Nitric acid 100~150ml/L
Water 90~850 ml/L
Temperature room temperature 5-10S

3. Basic polishing formula: sodium hydroxide 150~200g/L
Sodium nitrite 145~200 g/L
Sodium nitrate 155~200g/L
Trisodium phosphate 100~150 g/L
Temperature 90~100°C
Time 30~60S

4. Preparation of the polishing solution First dissolve the sodium hydroxide with distilled water, and then dissolve the sodium nitrite and sodium nitrate in distilled water of about 60°C, and dissolve the trisodium phosphate with distilled water at 100°C. Finally, mix and add distilled water to the prepared volume. . Polishing solution should be in a stainless steel tank or beaker. Each use must be heated to 90~100°C.

Third, the conclusion

After the aluminum material is polished by the liquid before screen printing, the scratches can be well eliminated, the smoothness can be improved, and the quality of the screen printing nameplate can be improved.