HOT BLACKENING SALT - Hot blackening salt is a mixture of chemicals used in the hot blackening process, a method for blackening steel and iron surfaces to improve corrosion resistance and enhance appearance. The salts are typically composed of sodium hydroxide (NaOH), sodium nitrite (NaNO₂), and sodium nitrate (NaNO₃). *. How It Works 1. Cleaning: The metal is thoroughly cleaned to remove oil, rust, and scale. 2. Immersion in Hot Blackening Salt Bath: The metal is submerged in a heated (135–150°C) alkaline nitrate-nitrite solution, which induces a controlled oxidation reaction, forming a black oxide (Fe₃O₄) layer. 3. Water Rinse: The part is rinsed to remove excess salts. 4. Sealing with Oil or Wax: A post-treatment step involves applying oil, wax, or another sealant to improve corrosion resistance. * Common Uses Firearms (gun bluing) Automotive parts Industrial machinery # Hot Blackening Salt Manufacturer.