Some of the protective tapes on the surface of the sheet material are transparent and can be identified by detecting whether the surface of the article is hydrophilic after chemical cleaning or alkaline etching. When these obstructions are identified, do not continue to etch in the strong alkaline solution to avoid excessive erosion of the adhesive-free areas, and at this time, the adhesive tape cannot be removed. As a result, the surface is uneven. If this happens, the parts should be fully cleaned in water, and then neutralized and cleaned. Carefully remove the protective tape from the edge of the part with a knife. (Prevent tearing and leave small parts.) Block, otherwise it is more difficult to strip), and finally clean cotton with a clean cotton stain rub twice, when rubbing to prevent the metal powder and contact with the end of the rub, this is because the surface of the material with protective tape surface requirements Are relatively high. In order to avoid excessive corrosion during etching in strong alkaline solution, after the gasoline evaporates, it must first be chemically cleaned in a slightly alkaline solution, and then in a strongly alkaline solution for a short period of time. After the work-up, oxidation treatment was performed again.