Aluminium alloy aluminum surface anodized coloring sealing hole processing technology sharing
[China Aluminum Industry Network] Aluminium has a large number of holes in its anodic oxide film, and its surface is very strong in adsorption, and its hand touch has a sticky feel. In order to improve the antifouling and anti-corrosion performance of the oxide film, sealing is an essential step. Aluminium anodic oxidation membrane sealing holes are mainly heat sealing and cold sealing holes. At present, China basically uses cold sealing holes. As the film thickness increases and the quality of the plugging increases. The consumption of cold sealing agent per ton of aluminum profiles increased from 0.8 to 1.2 kg to 1.5 to 2.0 kg. Nickel fluoride is the main component of the cold sealing agent at present, so the quality of the cold sealing agent is determined by the quality of the nickel fluoride. Nickel fluoride in iron, zinc, copper and other impurities, the impact of the new distribution tank is not obvious, but after a period of production, sealing quality is difficult to guarantee.
The pH of the cold-sealed pores was previously thought to be 5.5 to 6.5, which should in fact be determined based on the formulation characteristics of the cold-sealing agent. The pH value of the new bath solution is generally 5.3 to 7.0. However, for the old baths that use ammonium fluoride or ammonium hydrogen fluoride to regulate fluoride ions, the pH should be controlled at 6.5 to 7.1 due to the influence of ammonium ions. At this time, the sealing hole speed is fast, the fluorine consumption is small, and there is no “whitehead†phenomenon. Ammonium ions in plugging tanks are less prone to dusting than sodium ions, but the sealing rate is slower. In order to ensure the quality of sealing, the key points of the process are as follows:
(1) The anodizing temperature is generally less than 23°C, the temperature is too high, the cold sealing agent consumes large amounts, and the surface is "green".
(2) After anodizing, it should be washed in time, and staying in the oxidation tank will affect the subsequent sealing. Washing is not easy to cause pollution of phlegm, increase the fluorine consumption of the sealing slot.
(3) The aluminum and aluminum wires that have fallen off in the sealing groove should be promptly taken out, otherwise the pH rise and fluorine consumption will be accelerated.
(4) After sealing the bath with fluorine fluoride, after passing 20t aluminum material per cubic meter, it should be cleaned at the bottom.
(5) Sealing troughs with fluoride adjusted by hydrofluoric acid should be produced after 5 to 10 minutes after addition, preferably in the form of a 10% dilute solution.
(6) In order to improve the sealing quality and speed up the drying, after cold sealing, it is recommended to wash with hot water at 55±5°C for 10～15min, also called post-treatment after cold sealing.
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