1. The addition ratio of magnesium and silicon is not appropriate during the casting process. For example, some excess silicon exists. In addition to a small amount of free silicon, this part of excess silicon will form a ternary compound in the aluminum alloy at the same time. These insoluble impurity phases or free impurity phases formed in the alloy tend to gather on the grain boundary, weaken the strength and toughness of the grain boundary at the same time, and become the weakest link with the worst corrosion resistance, where corrosion first occurs. 

2. During the smelting process, although the addition ratio of magnesium and silicon is within the range specified by the standard, sometimes due to uneven and insufficient stirring, the distribution of silicon in the melt is uneven, and there are locally enriched and poor areas . It is directly reflected on aluminum profile products. When there is a small amount of free silicon in the aluminum matrix, it not only reduces the corrosion resistance of the alloy, but also coarsens the grains of the alloy.

 3. The control of various process parameters during extrusion, such as excessive preheating temperature of billet, improper control of metal extrusion flow rate, air cooling strength during extrusion, aging temperature and holding time, etc., will easily cause silicon segregation and dissociation, making magnesium And silicon does not completely become Mg2Si phase, but some free silicon exists. In short, if the surface of the aluminum profile is easy to corrode during use, it is caused by the low quality standard of the aluminum profile during production. Therefore, we should go to a regular manufacturer when choosing aluminum profiles, so that such aluminum profiles will be more secure