How to know that aluminum profile belongs to inferior quality

The thickness of oxide film is thin. According to the national standard, the oxide film thickness of building aluminum profile shall not be less than 10um (μ m). The thickness is not enough, the surface of aluminum profile is easy to rust and corrosion. In the sampling inspection, for some aluminum profiles without production name, plant site, production license or qualification certificate, the thickness of oxide film is only 2-4um, and some of them do not even have oxide film. According to experts' estimation, for every 1um reduction of oxide film thickness, the power consumption cost per ton of profile can be reduced by more than 150 yuan.