Abstract
The reflectivity of electro-polished aluminium sheet is generally decreased when it is anodized. This is due to the existance of thick film on the surface of it. The reflectivity is, therefore, dependent upon the state and quantity of separated constituents included. When these material is heat-treated so that these separated constituents dissolved are into solid solution, the reflectivity of the metal is improved.
Through the experiments, it was found out that the reflectivity of 70% or more on the electropolished and anodized surface can be obtained in the cases that pure aluminium contains following impurities respectively:
Fe content: 0.007% or less
Si content: 0.012% or less
Cu content: 0.01% or less
Mg2Si content: 0.27% or less
It was also found out that magnesium conbines silicon in the material and increases the reflectivity.
From the above, it can be confirmed that, as konwn, high purity aluminium or high purity aluminium containing a little Mg must be used for obtaining high reflectivity of electro-polished and anodized products.
