One of the causes of surface corrosion of aluminum extrusion profiles

JE company uses 6063 aluminum ingots for aluminum materials. During the surface treatment process of 6063 aluminum alloy profiles, it is sometimes found that there are irregularly arranged point-like dark gray corrosion spots on the surface of the aluminum profiles. The resulting corrosion spots have completely different shapes, and appear intermittently during the production of aluminum profiles. Some people think that the reason is that the operator did not perform the correct surface treatment process; there are some harmful impurity ions in the bath; the material is not good and there are too many inclusions. In this regard, our JE company combines years of experience in aluminum extrusion production to analyze as follows:

Sometimes due to some reasons, the addition ratio of magnesium and silicon is not appropriate during the casting process, so that ω(Mg)/ω(Si) is in the range of 1.0-1.3, which is much smaller than the optimal ratio of 1.73 (generally controlled at 1.3-1.5 within the range). In this way, although the content of magnesium and silicon components is within the specified range (ω (Mg) = 0.45% to 0.9%, ω (Si) = 0.2% to 0.6%). However, there is a part of excess silicon, which will form a ternary compound in the aluminum alloy in addition to a small amount of silicon in a free state. When ω(Si)<ω(Fe), more α(Al12Fe3Si) phases are formed, which is a brittle compound; when ω(Si)>ω(Fe), more β(Al9Fe2Si12) phases are formed phase, which is a more brittle needle-like compound, is more detrimental than the alpha phase and tends to make the alloy prone to fracture along it. These insoluble impurity phases or free impurity phases formed in the alloy tend to gather on the grain boundaries, and at the same time weaken the strength and toughness of the grain boundaries [1-3], becoming the weakest link with the worst corrosion resistance, and the corrosion starts from there. produce.

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