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What should I do if the oxide film is loose and pulverized and has poor corrosion resistance?

Release time:

2023-04-14 16:36

In the entire process of anodizing and oxidation of aluminum alloy profiles, the formation and dissolution of the oxide film are carried out together. The organic chemical dissolution of the oxide film will cause the oxide film to loosen, even loose into a powdery oxide film. The dissolution rate of the oxide film is higher than the temperature damage of the saturated solution, and with the saturated solutionTemperatureThe rise and acceleration. Therefore, such common problemsoften appear in the summer, Especially in a liquid tank without water cooling equipment.Under normal circumstances, the temperature should be adjusted to 18~22 ℃, the oxide film quality is good.If the temperature of the electrolyte is above 30°C, the oxide film will cause the layer to loosen and the film to deteriorate poorly. If it is more serious, it will cause "burning".

In addition, when the temperature of the electrolyte is stable, it is necessary to limit the anodic oxidation.current densityBecause the current density of anodic oxidation is too high, the temperature rises strongly, and the oxide film is easy to powder or sand, which is very unfavorable to the quality of the oxide film. Generally, the current density should not exceed 1.5 A/dm2, otherwise the oxide film will become loose and pulverized.

in addition,Long anodizing time and high solution concentrationIt will also cause loose anodic oxide film. When the current density is too large or the current is too large, the resulting Joule heat will heat the aluminum alloy parts, increase the temperature of the solution around the parts, accelerate the organic dissolution of the oxide film, and make the oxide film loose or produce powdery oxide film. Therefore, strict compliance with technical standards is the main factor to avoid the loosening of the anodic oxide film. In the whole process of aluminum anodic oxidation, water washing and other processes may produce chloride ions in the oxidation solution, and may also produce chloride ions in sulfuric acid, which will eventually lead to the increase of sulfate content in the oxidation solution, and then cause oxidation and loose film layer. When sulfuric acid is added to the anodic oxidation tank, the uneven mixing of the solution will also cause uneven oxidation of the parts of the same tank, some oxide films are too thin, some oxide films are loose, and there is powdery dust.

Specific measures to eliminate the above problems：

① The electrolyte temperature is too high, should think of some wayReduce temperature, Start the refrigeration equipment, turn on the compressed air stirring device, and run the temperature difference within (20±2)℃.

② oxidation solution time is too long, should beReduced anodization time.

③ If the current density is too high, you needReduce the current density.

④ When the sulfate content in the solution is too high, it can be passedDilute solution or partially replace solution to solve.

At the same time, strictly control the harmful residues in the electrolyte, and it is not suitable to treat the aqueous solution with sulfuric acid anodic oxidation, especially the groundwater with high content of magnesium, calcium, silica and Cl. When the Cl-component reaches 25 mg/L (including other halogen elements), the Cl-component in the electrolyte of the lithium battery is ≤ 15 mg/L, and the total mineral component is ≤ 50 mg/L; Oil stains, foam plastics and dissolved total solid residues generated during the whole oxidation process shall be immediately removed and other toxic residual components shall be decomposed, such as Cu2 content <0.02g/L and AI3 <20g/L. If the impurity content is too high, part or all of the sulfuric acid solution can be decomposed to ensure the quality of the anodic oxide film.