[China Aluminum Industry Network] Aluminium anodic oxidation membranes are more often closed by boiling water and nickel acetate closure process. The disadvantage of these two commonly used closed processes is that after the oxide film is closed, the surface of the oxide film is prone to produce disagreeable white or gray powder, and the industry calls it a closed “cream†or “closed Chinaâ€. Studies have shown that a variety of impurity ions blocking the treatment solution will promote the production of "cream", in which the existence of Al3 + plasma is more obvious. This shows that the alkaline earth metal ions Ca2+ and Mg2+ are detrimental to the traditional boiling water sealing process and nickel acetate sealing process, so it goes without saying that they are used to prepare the sealing treatment liquid.
After the oxide film is dyed, it should be sealed to increase the lightfastness and corrosion resistance of the color. The earlier sealing technique was to use pure water to boil, but the quality of the seal was deteriorated, and the need for frequent replacement of pure water was required.
The addition of nickel acetate or cobalt acetate salt in pure water is hydrolyzed in hot water, and hydroxide precipitates in the pores of the oxide film, also acting as a sealing effect. Such a closed process can be performed at slightly lower temperature conditions. The bath life is longer than the boiling water, and the closed quality is better. This kind of closed process is still very popular in the industry. The nickel acetate or cobalt acetate sealing process has an environmental problem, that is, the enclosed wastewater contains a large amount of heavy metal nickel. With cobalt, heavy metal ions can cause serious damage to the environment. In order to protect the environment, complex and expensive waste water treatment devices need to be used.
Alkali metal and alkaline earth metal are widely found in the soil and sea water of nature. Their toxicity to organisms is very small. The treatment of industrial waste water is relatively simple and inexpensive. US researchers have done a lot of research and studied that there is no heavy metal nickel. The composition of (Ni) and cobalt (CO) blocking agents, as well as formulations using alkali metal salts as blocking agents, but these two patents have adopted macromolecules and surfactants containing benzene rings, these organic compounds in nature The degradation rate is slow, long-term use is easy to accumulate in the environment, causing damage to the ecology.
On the basis of this, the relevant domestic institutions invented the medium temperature sealing agent and sealing process for aluminum anode oxidized film, and it belongs to the technical field of sealing and post-treatment of aluminum and aluminum alloy anodic oxide film. The sealing agent is made of alkali metal or alkaline earth metal. An aqueous solution composed of salt, complexing agent and pH buffering agent, in which the alkali metal or alkaline earth metal salt is 5 to 15 g/L, the complexing agent is 10 to 20 g/L, the pH buffering agent is 0 to 10 g/L, and the balance is Water, the pH value of the aqueous sealer solution is 5-6. The aluminum oxide film is sealed and sealed according to the sealer. The temperature of the aqueous solution of the sealer is 75-90° C., and the impregnation time is 20-30 min. The sealer uses a wide range of resources and low cost alkali. The metal salt or alkaline earth metal salt replaces the prior art heavy metal nickel salt or cobalt salt; the organic complexing agent adopting simple molecule with low biodegradation price is used instead of the macromolecular prior art benzene ring-containing surfactant and is closed according to the present invention. The treated aluminum anodic oxidation film obtains excellent anti-crease properties, and comprehensively improves the corrosion resistance and anti-pollution performance of the anodized films of aluminum and aluminum alloys.
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