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Control and management of dyeing solution

Release time:

2020-11-27 13:35

1. Stirring of dyeing solution

Since the dye adsorption rate decreases with the continuation of the dyeing process, moderate stirring can make the dye concentration uniform throughout the whole tank, which can be circulated by compressed air, propeller or water pump.

2. Temperature of dyeing solution

The temperature should be within the appropriate range, the temperature is too high dye accumulation has not reached enough density will be terminated, so the heating system should be equipped with temperature control device and appropriate stirring, will make the dyeing liquid temperature uniform.

3. Dyeing time

Changing the time and interval of dyeing, sampling and inspection at regular intervals can make the oxide film defects caused by oxidation uniform to a certain extent during dyeing. In general, a dyed film dyed with an over-low concentration of dye (for a long time) has better durability than a dyed film dyed with a high concentration of dye (for a short time). The dyeing time of dark workpieces is short, and serious fading will occur in the sealing solution.

4. Dye concentration

The concentration of the dye must be selected so that the specified depth can be obtained under the process conditions. When selecting these working conditions, the aluminum material should be able to dye the specified standard at an absolute low dye concentration.

A, anodic oxide film thickness 3-5um (natural color, transparent color)

B, anodic oxide film thickness 4-6 um (light color system)

C, anodic oxide film thickness 8-12 um (darker color system)

D, anodic oxide film thickness 12-16 um (black, dark color system)

 

determination of dye concentration:

A, compare the dye concentration with the naked eye: dilute the standard solution used for control and the other used dyeing solution according to the same proportion, give identification with the naked eye inspection method, and then calculate the concentration difference of the dyeing solution with the volume of the two solutions.

B. Spectrophotometric determination of dye concentration: use a spectrophotometer. The sample solution of the dyeing solution is diluted to measure its absorption value, and then the control solution with the specified standard dye concentration is diluted in the same proportion to measure its absorption value, and then compare the two absorption values, and then calculate the actual dye concentration of the dyeing solution for production. Calculation method of dye concentration (g/L) = absorbance * dye coefficient * dilution factor

C, the method of regularly partially updating the dyeing liquid to adjust the dyeing force: regularly partially updating the dyeing liquid can also prolong the service life of the dyeing liquid. the method is to discharge a certain amount of bath liquid after a certain interval of time and replace it with a new liquid. the calculation of the new liquid should include the amount of dye taken away when flowing out, thus eliminating some impurities regularly, the dyeing solution can keep stable and produce uniform colored film for a long time.

 

5 Water quality

High purity water or deionized water should be used. Impure water quality has the following effects

A, metal ion water: iron, chromium, copper or silicon, etc., reduce the dyeing solution PH.

B. High hardness water is easy to dye unevenly.

C, negative ion water: phosphate, chloride or sulfide will affect the dyeing ability. Poor water quality leads to serious pigment diffusion (fading) in the closed liquid, and the result of dyeing desalination will also cause precipitation and turbidity of the liquid.

6. Dissolved impurities

The impurities dissolved in the dyeing solution in the form of ions will affect the dyeing process. The most common impurities are sulfate and aluminum salt. Because there is no feasible way to eliminate the interference of these ions, the dyeing solution must be partially or completely updated when the accumulated impurities have exceeded a certain limit. In order to prolong the service life of the dyeing solution, it is necessary to minimize the dirt brought into the dyeing solution, therefore, the work after anodizing must be thoroughly cleaned before dyeing.

 

7. Insoluble impurities

Such as oil particles will cause uneven cloud dyeing type form unqualified dyeing film, one thing is very important is that the compressed air used for dyeing liquid mixing must be oil-free compressed air.

 

8. Production of dye liquid mold

Under long-term low-temperature storage of organic dyes, molds will grow. Mold can decompose dyes and affect PH value, resulting in poor dyeing. Some molds have a great influence on dyes and cause difficulty in adjusting PH value of dyeing solution. Therefore, dyeing tank should be equipped with a cover, which should be covered when the tank liquid is stopped. If molds are found, they should be skimmed from the liquid level, and add anti-mold agent and regular part of the update or all the replacement of dyeing liquid.

 

9. PH value

The optimum pH for general dyeing is usually 5.0-6.0, and most dyes require a pH in the range of 5.0-6.0 in order to accumulate into the pores of the aluminum molecule and achieve satisfactory results.

Dyeing, dye, concentration, impurity, oxidation, ph, influence, temperature, anode, dyeing solution