Hello, the chromium plating project needs pretreatment from raw materials to finished products: cutting, shaping and pickling. Cutting raw materials will produce dust and welding smoke. Acid cleaning and rust removal of raw materials will produce sulfuric acid mist; Parts can be directly plated with black chromium after pretreatment, and high-grade products can be plated with nickel as the bottom layer first, and then plated with black chromium, which has better protection and decoration effect. After the parts of electroplated black chromium products are cleaned and dried, the protection and decoration effect will be further improved if they are soaked in hot oil and sealed, and the protection and decoration effect will be greatly improved if they are sprayed with organic transparent paint, but this post-treatment process will also produce volatile organic compounds VOCs；; Electroplating wastewater is the most important pollutant in chromium plating project, which contains heavy metals such as chromium, nickel and zinc. The waste gas produced is mainly sulfuric acid mist and volatile organic compounds mentioned above. Because sulfuric acid is used in the pretreatment of parts, chromium plating process is not used, so chromic acid fog will not be generated, only sulfuric acid fog will be formed.