QUALANOD aluminum anodizing: equipment requirements
QUALANOD - this authoritative international organization, which certifies producers of anodic oxide coatings on aluminum products for construction application, i.e. sulfate aluminum anodizing. I present for review an overview of the requirements of QUALANOD for equipment manufacturers of anodized products, who are certified by QUALANOD or qualify for it. For some reason, I have not seen QUALANOD instructions in Russian on the Web. At the same time, for a detailed study of these requirements, you need to refer to the latest edition of the document QUALANOD SPECIFICATIONS directly on the site [1].
Bathtubs
Material and lining. Materials for the manufacture of bathtubs or their lining should eliminate any contamination of solutions – workers and flushing.
Capacity and design of bathtubs. The volume of the anodizing baths should be related to the maximum current strength of the rectifier., to provide the required current density on the products and maintain the desired electrolyte temperature.
Anodizing bath electrolyte cooling
Cooling capacity. The cooling capacity of the electrolyte cooling system must ensure that all heat is absorbed., formed during the electrolytic process at maximum use of installed power and at its maximum speed. The required cooling capacity is estimated using the following formula:
K = 0,86 × I × (V + 3),
Where
K - cooling capacity of the system, kcal / h,
I - maximum current, A,
V - maximum voltage, In.
When calculating the total cooling capacity, the local conditions must also be taken into account., for example, too high air temperature in the workshop in the summer.
Stirring electrolyte
Good mixing of the electrolyte is essential to maintain a constant temperature in the bath and remove heat, formed on the surface of aluminum during the anodizing process.
Air mixing (bubbling) is very important for the treatment of the charge. If bubbling is insufficient around a part of the surface of the product, then this will inevitably lead to poor quality anode coatings on this surface. At least compressed air must be supplied. 5 m3/h to m2 bath mirrors (rotameter). Recommended value - 12 m3/h to m2 bath mirrors.
The air supply must ensure uniform mixing of the electrolyte over the entire surface of the bath. This is best achieved by supplying a large volume of air at low pressure., better from blower, not from the compressor. If a compressor is used, then the dimensions of the pipes and the holes in them must be selected so, to ensure uniform mixing.
With cage anodizing technology, mixing the electrolyte only with a pump is insufficient to ensure proper temperature control of the bath.
Heat
Heating power. The heating power of the heated baths should provide temperatures, which should be supported in them at various stages of processing. In particular, it is necessary to ensure that the temperature of the filling baths is not lower than 96 ºС during the filling process.
Current source
Rectifier. Electrical equipment (rectifiers and busbars) must be capable of providing the required current density for the hitch at the maximum installed power of the rectifier. Usually specialized rectifiers are used., which have the necessary accuracy of voltage regulation, accuracy of current and voltage measurements, as well as automatic control of increase or decrease voltage.
Contacts. The voltage drop at the contact of the bus with the anode beam should not be more 0,3 volt, and the temperature at the contact must not exceed the ambient temperature by more than 30 oC.
Hitch
Cross section of hinge rods. Cross section of aluminum rods, which transmit current from the anode beam to the hinge, must be no less than 0,2 mm2/A. Titanium hinges, whose electrical resistance is greater, must have a larger cross-sectional area.
Contacts. The number and size of contacts should be sufficient for uniform supply of current to all processed cage products and over the entire surface of each product. The pressure at the contacts must be high enough to prevent oxidation of the contact points and any displacement of the products during the anodizing process..
Hitching products. Profiles should be mounted in this way., to minimize the variation in thickness of the anode coating. A very dense suspension of profiles or several rows of profiles without intermediate cathodes can lead to an increase in the heterogeneity of the thickness of the anode coating. It is recommended to use systems with central cathodes between the rows of products.
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