BLACKENING CHEMICAL FOR METAL 1. Cold Blackening: - Chemicals Used: Typically involve a mixture of copper selenide or copper sulfate solutions. - Process: . Clean the metal surface thoroughly to remove any oils, rust, or other contaminants. . Immerse the metal in the cold blackening solution for a specified period. . Rinse the metal with water and dry. . Apply a sealant or oil to enhance corrosion resistance and deepen the black color. . Applications: Suitable for small parts, tools, and hardware where a quick and relatively simple process is desired. 2. Hot Blackening: - Chemicals Used: Involves the use of caustic soda (sodium hydroxide), nitrates, and nitrites in a heated bath. - Process: . Clean the metal surface to remove contaminants. . Immerse the metal in a series of heated baths, including cleaning, blackening, and sealing baths. . The blackening bath typically operates at temperatures around 140-150°C (284-302°F). . Rinse and seal the metal to complete the process. . Applications: Commonly used in industrial settings for parts like fasteners, automotive components, and firearms due to the durable and uniform finish it provides.