1. Identification inspection

2. Surface quality

3. Thickness of oxide film

4. Sealing quality

During on-site inspection, the acid immersion method is generally used, which involves scrubbing the surface of aluminum profiles with acetone to remove oil and dust. A volume ratio of 50% nitric acid is dropped onto the surface and gently scrubbed. After 1 minute, the nitric acid is washed off with clean water, and then dried. A drop of medical purple medicine water is dropped onto the surface. After 1 minute, the purple medicine water is wiped off and the surface is thoroughly cleaned. Carefully observe the traces left, and aluminum profiles with poor sealing will leave obvious marks, The heavier the trace, the worse the sealing quality.