Why does the aluminum profile in the LED tube housing have corrosion spots?

According to JE's many years of production experience and the investigation of various process parameters in the production of aluminum profiles, as well as the follow-up investigation of the operator's implementation of the process, it is believed that the main reasons for the corrosion points of the aluminum profiles in the LED lamp shell are as follows:

(1) Sometimes for some reasons, the addition ratio of magnesium and silicon in the casting process is not appropriate, so that ω(Mg)/ω(Si) is in the range of 1.0 to 1.3, which is much smaller than the optimal ratio of 1.73 (generally controlled at 1.3 to 1.5 range). In this way, the content of magnesium and silicon components is within the prescribed 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 the free state. When ω(Si)<ω(Fe), more α(Al12Fe3Si) phase is formed, which is a brittle compound. When ω(Si)>ω(Fe), more β(Al9Fe2Si12) is formed The alpha phase, which is a more brittle needle-like compound, has a more detrimental effect than the alpha phase, tending to make the alloy prone to fracture along it. These insoluble impurity phases or free impurity phases formed in the alloy tend to aggregate on the grain boundaries, weaken the strength and toughness of the grain boundaries at the same time [1-3], and become the weakest link in corrosion resistance, where corrosion first starts from produce.

(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 local enrichment areas and depletion. Area. Because the solubility of silicon in aluminum is very small, the eutectic temperature is 1.65% at 577°C, but only 0.05% at room temperature. After casting the rod, the phenomenon of uneven composition occurs, which is directly reflected on the industrial aluminum profile products. , the presence of a small amount of free silicon in the aluminum matrix not only reduces the corrosion resistance of the alloy, but also coarsens the grains of the alloy [4].

(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. Magnesium and silicon do not completely become Mg2Si phase, but some free silicon exists.

JE is a factory specializing in the production of T12 tube housings, for more tube housings, please refer to:

https://www.jeledprofile.com/led-tube-housing

For more details, please contact: sales@jeledprofile.com

Tel/Whatsapp/Wechat: 0086 13427851163