1. Observe the appearance of the metal: Observe whether there are problems such as color difference, scratches, blisters, peeling water marks, etc. on the surface of the color steel plate.
2. Identify the surface coloring process.
3. The quality of the film: The protective film of poor quality will be chalked up after a long time, and it will be difficult to tear it apart.
4. Distinguish raw materials: different raw materials, different corrosion resistance and different prices.
