Anodized aluminum refers to a layer of dense aluminum oxide coated on the surface of aluminum and aluminum alloys. In order to prevent further oxidation, its chemical properties are the same as aluminum oxide. But unlike ordinary oxide films, anodized aluminum can be dyed with electrolytic coloring.
The preparation principle of anodized aluminum is the anode effect (also known as anodizing).
The anode effect is a unique phenomenon of molten salt electrolysis, and the performance of electrolytic aluminum production is still obvious. When the anode effect occurs in production, the voltage of the electrolytic cell rises sharply, reaching 20-50V, sometimes even higher. Its occurrence has a great impact on the entire electrolysis series, reducing the current efficiency, affecting the technical indicators of electrolysis, and reducing the output and quality of aluminum, and destroying the smooth power supply of the entire electrolysis series. In terms of processing methods, nothing but
Anodized aluminum coil
Anodized aluminum coil
There are two kinds: using an effect rod (wooden rod) to extinguish, or lower the anode, and increase the amount of alumina to achieve the purpose of extinguishing the anode effect. No better treatment has been found.
The anode effect occurs because the oxygen-containing ions in the electrolyte gradually decrease with the progress of the electrolysis process. When it reaches a certain level, there will be fluorine precipitation and interact with the anode carbon to produce carbon fluoride. When the fluoride of carbon decomposes again, Precipitated fine carbon particles, which are attached to the surface of the anode, prevent the electrolyte from contacting with the anode, make the electrolyte not wet the anode well, just like water can not wet the oiled surface, so that the electrolyte-anode form a For a gas film with poor conductivity, the anode overvoltage increases, causing an anode effect. When new alumina is added, oxygen is precipitated on the anode, and the oxygen reacts with the carbon powder, gradually making the anode surface quiet, the resistance decreases, and the electrolysis process tends to normal.
Production process editing
1. Mechanical polishing;
2. Chemical treatment removes the copper component on the surface of certain alloys;
3. Cleaning and degreasing (for the anodized parts, if re-anodization is required, the original anodized surface layer is removed with alkali or special agent)
4. Put it in dilute sulfuric acid as an anode to conduct electricity to generate a surface oxide layer (it is porous and is a white translucent film);
6. Fix (heat or close the pores of the surface oxide layer with chromate solution).