BLACKENING CHEMICALS FOR AUTOMOTIVE INDUSTRIES
What Are Blackening Chemicals?
1. Types of Blackening Processes:
- Hot Black Oxide: Involves submerging metal parts in a heated solution of alkaline salts and nitrates, typically at temperatures around 285-300°F (140-150°C). This process is used for ferrous metals and provides a durable black finish.
- Cold Black Oxide: Uses room temperature or mildly heated solutions containing selenium or copper-selenium compounds. This method is often used for touch-ups and smaller parts but does not provide the same level of protection as hot black oxide.
- Mid-Temperature Black Oxide: Operates at temperatures between 200-220°F (93-104°C) and is used for both ferrous and some non-ferrous metals. It’s a compromise between hot and cold processes, providing decent corrosion resistance with lower operational hazards.
- Black Phosphate: A conversion coating that creates a black phosphate layer on the metal surface. It is often used for steel parts to enhance lubrication and corrosion resistance.
