Appearance Inspection: Refer to the drawings, to confirm that the packaging and color meets the requirements, and then confirm the appearance of defects, no defects judged to be qualified, defects using a plug gauge, needle gauge or calipers to determine the status of defects, while referring to the standard to determine whether it meets the requirements. Defect description, convex, the product surface protruding part. Haze, the surface of the metal parts is cloudy fuzzy, unclear, not bright phenomenon. Watermark: The film-like or lump-like debris attached to the product surface caused by uncleanness or poor oxidation after plating and oxidation. Yellowing: When oxidizing, the surface is not cleaned or colorless chromate operation, the operation time and operation mode is not standardized, the surface of the product shows yellow marks. Different color, the same product, its color and brightness in different parts, showing obvious differences, such as the hole edge bright block. Color difference, the product surface color and brightness and the standard color and brightness samples show obvious differences or the same batch of products whose surface color and brightness there are obvious differences. Pits, due to defects in the surface of the substrate material itself or due to the processing process caused by the surface of the material appeared concave projectile defects, such as pressure injuries. Scratch impurities, etc.