* Metal blackening process - Steps in Metal Blackening Process: 1. Cleaning and Surface Preparation: The metal surface must be thoroughly cleaned to remove oils, greases, dirt, and any other contaminants. This can be done using degreasers or alkaline cleaners followed by 2. rinsing and drying. Activation (Optional): Some metals, particularly stainless steels, require an activation step prior to blackening. This can involve treating the metal with a specific solution to promote oxide formation. Blackening Bath Preparation: Prepare the blackening solution or bath, which typically contains a mixture of oxidizing salts, such as sodium hydroxide (caustic soda) and sodium nitrite, along with other additives depending on the desired finish and metal type.