Hot Blackening Salt VC FERROUS - Hot blackening salts for ferrous metals are used in a process known as hot blackening or black oxide coating. This technique involves immersing steel parts in a series of tanks containing heated alkaline solutions, usually at around 285°F to 310°F (140°C to 155°C), to produce a durable, corrosion-resistant black finish. The 'VC' in your query might refer to a specific product or grade, but here is a general overview of hot blackening salts and their use for ferrous metals: What is Hot Blackening Salt VC (Ferrous)? - Hot Blackening Salt VC (Ferrous) is a specialized chemical formulation used to create a black oxide coating on ferrous metals like mild steel, carbon steel, and cast iron. It is used in the hot blackening process, where metal parts are immersed in a heated salt bath to develop a uniform, dark black finish. #Hot Blackening Salt VC FERROUS Manufacturer.