The most common harmful impurity in aluminum alloys is iron. In the production process of industrial aluminum profiles, when the iron content is more than 0.25%, normal color tone cannot be obtained. As the iron content increases, the gloss decreases and the hue shifts. Green and gray are hard to see. If the silicon content is high, the effect will be small because aluminum, iron, and silicon form elemental impurity intermetallic compounds. When the silicon content of the aluminum alloy is low, the effect of iron is more pronounced.

The main reason for the effect of iron on coloring is that iron and aluminum form sharp or rod-like structures ranging from a few microns to tens of microns. The electrode potential is different from aluminum, so it will affect the uniformity and continuity of oxidative coloring and make the oxide film shiny. Decreased transparency affects coloring effects.

Effect of Elemental Impurities on Oxidation Quality of Aluminum Profiles

Surface oxidation of aluminum profile

A small amount of copper contributes to the mechanical properties and surface brightness of the profile without reducing the corrosion resistance. However, when the copper content is high, the oxide film becomes black and can be seen with the naked eye.

A small amount of manganese can eliminate the harmful effects of AlFeSi structure to a certain extent and reduce the production of extrusion lines. However, when the manganese content is high, the oxide film becomes yellow. As the content of manganese increases, the color of the oxide film becomes darker, and the coloring effect becomes worse.

When the zinc content is high, the extrusion difficulty increases, the profile grains are coarse, and the mold release is also large. The oxide film is milky white, zinc ions are accumulated in the alkaline etching solution, and zinc is inverted in silicon. The contour produces a shiny pear. Skin spots.

Aluminum oxide tube

When the titanium content is more than 0.1%, the hue and color difference of the contour coloration are greatly affected, which is caused by the non-uniformity of titanium.

In short, the main factors affecting the surface oxidation quality of aluminum profiles are iron, copper, manganese, zinc and titanium. Therefore, in order to ensure the surface quality of the aluminum profile, the metal impurities in the aluminum alloy of the aluminum alloy profile must be strictly controlled. The iron content should be controlled below 0.25%, and the metal content of other impurities should be controlled below 0.1%.