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Petroleum and chemical products are often highly corrosive, such as acids, alkalis, solvents, etc., and require the use of valves made of corrosion- and chemical-resistant materials, such as stainless steel valves, fluorine-lined valves, etc. resistant materials, such as stainless steel valves, fluorine-lined valves, etc., and require the use of valves made of corrosion- resistant materials.