Blackening chemicals for iron Blackening chemicals for iron are used to create a durable and attractive black oxide finish on iron and steel surfaces. This process not only improves the aesthetic appeal of the metal but also enhances its corrosion resistance. Several types of blackening chemicals and processes are commonly used: *Hot Black Oxide Chemicals: 1. Sodium Hydroxide (Caustic Soda): This is a key component in the hot blackening process, often combined with nitrates and nitrites. It creates a black magnetite (Fe3O4) coating on the metal surface. 2. Nitrate Salts: Sodium nitrate or potassium nitrate is used in conjunction with caustic soda to facilitate the blackening reaction. 3. Blackening Salts: Specific proprietary blends like the VCFERROUS hot blackening salts are used for consistent and reliable results​ (Dorsetware Limited)​​ (EPI)​.