Aluminum alloys contain alloying elements and impurities, generally not a single solid solution alloy. For example, iron and silicon are the most common impurities in industrial pure aluminum and aluminum alloys. It is impossible to avoid the presence of iron-rich second group in aluminum and aluminum alloys, ALFESi. The precipitated ions of the phase. Even with 99.99% high-purity aluminum, the "unclean" grain boundary can be observed under the microscope. 1100 is used as industrial pure aluminum. The allowable value of iron-silicon is 0.95%. Obvious second phase can be observed under the optical microscope. Precipitation, because the electrode phase of the second phase formed by the alloying element is different from that of the aluminum matrix, the anodizing behavior and mechanism of the aluminum alloy are much more complicated than that of pure aluminum, and the anodized film composition of the aluminum alloy is not only the alumina but the anion in the solution. There must be some alloying elements in the aluminum alloy, which are all in a state of state or metal parts.
Among the most commonly used 5000 series and 6000 series aluminum alloys, elements such as iron, silicon, manganese, copper, magnesium, and chromium are often added alloying components, except for solid solution i, which is a simple or metallic compound. The second phase form is present in the aluminum alloy. When the aluminum is anodized, the elements of the melt are generally converted into oxides, and the intermetallic compounds such as ALFESI or silicon are generally not oxidized, but the elemental silicon or metal. The form of the inter-compound is directly left in the oxide film or oxidized, and if it is a cathode, it may directly enter the oxide film. The second phase intermetallic compounds commonly used in aluminum alloys, their sulfuric acid oxidation behavior is as follows: silicon. . . . Usually they are random, they have a positive electrode potential in sulfuric acid than an aluminum matrix, so they are not preferentially oxidized or dissolved and can be directly incorporated into the anodized film.